担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

DOI： 10.7567/JJAPCP.8.011004

記述言語：英語   掲載種別：研究論文（学術雑誌）

We grew 500-nm-thick lightly As-doped n-BaSi2 epitaxial films at 600 °C by molecular beam epitaxy, and supplied atomic H in durations (t BaSi:H) of 0-30 min, followed by capping with a 3-nm-thick amorphous Si layer at 180 °C. The photoresponsivity of the BaSi2 films was enhanced by approximately five times by As doping. Deep-level transient spectroscopy measurement revealed the disappearance of two previously reported electron traps. The photoresponsivity was further enhanced by approximately six times after H supply. It reached a maximum at t BaSi:H = 1-10 min, owing to the reduction of defects.

DOI： 10.35848/1882-0786/ab8725

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記述言語：英語   掲載種別：研究論文（学術雑誌）

n-Mg2Si/p-Si heterojunction solar cell with a 1.4 µm thick unintentionally doped (n = 3 × 1017 cm−3) silicide epitaxial layer on p-Si(1 1 1) (p = 5 × 1014 cm−3) was grown by low temperature (250 °C) molecular beam epitaxy. Heterojunction demonstrated clear rectification and zero bias photoresponse in the (400–1400) nm wavelength range at room temperature. Under AM 1.5 illumination, an open-circuit voltage of 0.21 V, a short-circuit current density of 3.3 mA/cm2, fill factor of 0.36 were obtained while the conversion efficiency reached 0.24%, which is the pioneering demonstration of Mg2Si-based solar cell operation. Combined minority-carrier lifetime, Raman and AFM mapping together with TEM and XRD data revealed that carrier dynamics and photovoltaic performance are limited by the presence of non-epitaxial Mg2Si grains in the upper silicide film layer. However, minority-carrier lifetime up to 7.3 µs for Mg2Si demonstrates its great potential as absorbing material for Si-based solar cells.

DOI： 10.1016/j.solener.2020.09.085

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Photoluminescence (PL) properties of β-FeSi2 polycrystalline thin films and Si/β-FeSi2/Si doublehetero (DH) structure samples grown by an RF magnetron sputtering method were investigated. In the thin films, the PL intensity at 1.54 μm was increased in B-doped β-FeSi2 films. In the Si/B-doped β-FeSi2/Si DH samples, the PL intensity became much larger than the B-doped thin films. In the dependence of PL intensity on β-FeSi2-thickness, the PL intensity strongly depended on the β-FeSi2 thickness and showed a maximum at 2.5 nm. In the measurements of PL lifetime, the PL lifetimes were constant in the DH samples with different thickness of β-FeSi2. These results showed that the confinement of photoexcited carriers in the β-FeSi2 layer decreased as the β-FeSi2 thickness increased.

DOI： 10.7567/1347-4065/ab656e

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Photoluminescence (PL) measurements were carried out on 0.5-μm thick BaSi2 epitaxial films grown on Si(111) substrates with various Ba-to-Si deposition rate ratios (RBa /RSi ) in the range of 1.7–5.1. The samples were excited from both the frontside (BaSi2 ) and the backside (Si substrate), at temperatures in the range of 8–50 K. These measurements have highlighted the existence of localized states within the bandgap that result from defects in the BaSi2 films. The PL intensity is highly dependent on the excitation power, temperature, and RBa/RSi . Of those studied, the BaSi2 film at RBa /RSi =4.0 showed the most intense PL and weak photoresponsivity, whereas the PL intensity was weaker for the other samples. Therefore, we chose this sample for a detailed PL investigation. Based on the results we determined the energy separation between localized states, corresponding to PL peak energies. The difference in PL spectra excited from the BaSi2-side and Si-side is attributed to the difference in kinds of defects emitting PL. The photoresponsivity of the BaSi2 was drastically enhanced by atomic hydrogen passivation, and the PL intensity of the sample decreased accordingly.

DOI： 10.1088/2399-6528/ab2fa1

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Author(s). Polarized Raman spectra of a β-FeSi2(100)//Si(001) epitaxial film grown by molecular beam epitaxy were measured to identify the Raman mode of the observed Raman active lines. Twelve of the observed 18 Raman lines showed a clear dependence of the Raman intensity on the crystal rotation angle. By factor group analysis using the orthorhombic symmetry D2h18 of β-FeSi2, five Raman lines (193, 200, 249, 401, 494 cm-1) and seven lines (175, 277, 284, 298, 327, 410, 442 cm-1) were completely assigned to the Ag and B3g modes, respectively. The depolarization ratio of Raman scattering intensities was obtained from polarized Raman spectra measured in two polarization configurations. The values of the depolarization ratio also support the assignment of the Ag and B3g modes in β-FeSi2.

DOI： 10.1063/1.5042801

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 Author(s). We fabricate BaSi2 epitaxial films on Si(111) substrates by molecular beam epitaxy and investigate point defects inside the films using Raman spectroscopy with the help of first-principles calculation. Point defects such as Ba substituted for Si antisites, Si vacancies, and Si interstitials are considered as candidates for native point defects in BaSi2. Vibration analysis based on first-principles calculation suggests that local vibrational modes caused by these point defects appear at around 430, 480, and 560 cm−1, respectively, and are in good agreement with Raman peak positions. Comparing calculations with Raman spectra of the films formed with different Ba to Si deposition rate ratios RBa/RSi from 1.0 to 5.1, we conclude that the density of point defects reaches a minimum at RBa/RSi = 2.2. Furthermore, the position of Raman peaks at approximately 490 cm−1 shifts to a lower wavenumber, depending on RBa/RSi and thereby the density of point defects.

DOI： 10.1063/1.5029320

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2018 Trans Tech Publications, Switzerland Semiconducting ruthenium silicide (Ru2Si3) polycrystalline thin films were grown by solid phase epitaxy using Ru-Si amorphous layers on Si substrates. The formation of Ru2Si3 phase was confirmed by XRD and Raman measurements when the amorphous layers were annealed at 600− 900 °C in a vacuum. The Ru2Si3 thin films showed a low electron concentration of 1 × 1016 cm-3 with a high mobility of 430−940 cm2V-1s-1. Photoluminescence (PL) at ~0.8 eV was observed in the Ru2Si3 films.

DOI： 10.4028/www.scientific.net/DDF.386.33

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2018 Trans Tech Publications, Switzerland Infrared (IR) absorption and polarized Raman spectra were measured in BaSi2 epitaxial films to investigate the vibrational modes and the symmetry of Si4 cluster in BaSi2. By an analysis based on Raman and/or IR activity in the spectra, the symmetry of Si4 cluster was determined as Th-symmetry and the observed Raman lines and IR peaks were assigned to Ag, Eg, Fg, and Fu, respectively. In the three Raman lines of Fg-mode, one LO phonon line and two TO phonon lines were classified by the depolarization ratio of polarized Raman intensities.

DOI： 10.4028/www.scientific.net/DDF.386.43

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2018 Trans Tech Publications, Switzerland Sb-doped β-FeSi2 epitaxial films on Si(111) were grown by molecular beam epitaxy to control an electron density of β-FeSi2. After an optimization of donor activation conditions in the Sb-doped β-FeSi2, the electron density of 6 × 1018 cm-3 at 300 K was achieved by thermal annealing in a N2 ambient. In the temperature dependence of carrier density, the n-type conduction was changed to p-type conduction at low temperatures in the film annealed at high temperature (600 °C). Raman spectra of the annealed films showed that both Fe and Si sites were substituted by the doped Sb in β-FeSi2 lattice.

DOI： 10.4028/www.scientific.net/DDF.386.38

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2017 Author(s). Embedded in silicon β-FeSi 2 nanocrystals (NCs) were grown on Si(111) by solid phase epitaxy of a thin iron film followed by Si molecular beam epitaxy. After solid phase epitaxy, a mixture of β-FeSi 2 and ϵ-FeSi nanocrystals is formed on the surface, sometimes β and ϵ phases coexist inside one nanocrystal. During initial stage of Si molecular beam epitaxy all ϵ-FeSi transforms into β-FeSi 2 . β-FeSi 2 nanocrystals tend to move following Si growth front. By adjusting growth condition, we manage to prevent the nanocrystals from moving and to fabricate 7-layer n-Si(111)/β-FeSi 2 -NCs/p + -Si silicon heterostructure with embedded β-FeSi 2 NCs. An epitaxial relationship and a stress induced in the nanocrystals by silicon matrix were found to be suitable for indirect to direct band gap transition in β-FeSi 2 . Of the heterostructure, a n-i-p avalanche photodetector and a light-emitting diode were formed. They have shown relatively good performance: ultrabroadband photoresponse from the visible (400 nm) to short-wavelength infrared (1800 nm) ranges owing to quantum-confined Stark effect in the nanocrystals and optical emission power of up to 25 μW at 9 A/cm 2 with an external quantum efficiency of 0.009% at room temperature owing to a direct fundamental transition in stressed β-FeSi 2 nanocrystals.

DOI： 10.1063/1.4998036

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2017 Author(s). Two-layer heterostructure with GaSb nanocrystals formed by solid phase epitaxy and embedded into the silicon was investigated using low-temperature (10-140 K) photoluminescence and time-resolved photoluminescence spectroscopies. Two characteristic luminescence bands with a maximum of about 0.82 and 0.87 eV were observed. It was found that low-energy peak is associated with D1 dislocation-related luminescence in silicon. Analysis of the decay components together with temperature and power dependencies of the photoluminescence for the high-energy maximum revealed that emission is more likely originated from the combined D2 dislocation centers in silicon and radiative recombination in type-II band alignment Si/GaSb nanocrystals/Si heterostructure. A nonradiative recombination dominates in all temperature range studied.

DOI： 10.1063/1.4998044

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

DOI： 10.7567/JJAPCP.5.011204

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

DOI： 10.7567/JJAPCP.5.011106

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The determination of Raman modes in the range between 280 and 500 cm-1 for a BaSi2(100) epitaxial film on a Si(001) substrate has been accomplished by polarized Raman measurements using a crystal rotation method. The six Raman lines from Si clusters in BaSi2 were observed in the range. In the analysis of their intensity changes as a function of crystal rotation angle based on the Raman tensors of the Si cluster, the six Raman internal modes of A1 (1), E (2), and F2 (3) were completely assigned to the observed Raman lines.

DOI： 10.7567/JJAP.56.05DD02

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The structural and electrical properties of β-FeSi2 polycrystalline films grown by RF magnetron sputtering were investigated. In the optimization of growth conditions, single-phase β-FeSi2 films were reproducibly grown when the initial rate of temperature increase (Tr) to 800°C for silicidation reaction was set at Tr = 1 min. Undoped β-FeSi2 films showed an n-type conduction with a low electron density of ∼2 × 1016 cm-3 and a high electron mobility of >800 cm2V-1s-1 at room temperature. In the temperature dependence of electrical properties in the β-FeSi2 films, a change of the conduction mechanism from a band conduction to a localized conduction was observed. The transition temperature was systematically reduced by increasing the annealing time at 800°C.

DOI： 10.7567/JJAP.56.05DD03

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

This article describes the development of an Si-based light-emitting diode with β-FeSi2 nanocrystals embedded in the active layer. Favorable epitaxial conditions allow us to obtain a direct band gap type-I band alignment Si/β-FeSi2 nanocrystals/Si heterostructure with optical transition at a wavelength range of 1500-1550 nm at room temperature. Transmission electron microscopy data reveal strained, defect-free β-FeSi2 nanocrystals of diameter 6 and 25 nm embedded in the Si matrix. Intense electroluminescence was observed at a pumping current density as low as 0.7 A/cm2. The device reached an optical emission power of up to 25 μW at 9 A/cm2 with an external quantum efficiency of 0.009%. Watt-Ampere characteristic linearity suggests that the optical power margin of the light-emitting diode has not been exhausted. Band structure calculations explain the luminescence as being mainly due to radiative recombination in the large β-FeSi2 nanocrystals resulting from the realization of an indirect-to-direct band gap electronic configuration transformation arising from a favorable deformation of nanocrystals. The direct band gap structure and the measured short decay time of the luminescence of several tens of ns give rise to a fast operation speed for the device. Thus a method for developing a silicon-based photonic integrated circuit, combining complementary metal-oxide-semiconductor technology functionality and near-infrared light emission, is reported here.

DOI： 10.1063/1.4978372

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>We have evaluated β-FeSi₂ (110), (101) planes epitaxially grown on Si(111) by using ion beam analysis. Unexpected large displacements were deduced from analysis based on single ion scattering. We have discussed multiple ion scattering caused inside the film and obtained the comparatively reasonable atomic displacement of Δ<i>x</i> = 0.04 nm that is close to one sixth of one step height of six domains stacking on the (111) planes. This result suggests that multiple scattering may be attributed to the atomic displacement due to the domain stacking faults.</p>

DOI： 10.56646/jjapcp.5.0_011104

CiNii Research

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>Direct transition energy (<i>E</i>_g) of β-FeSi₂/Si(111) epitaxial films grown at different growth temperatures (<i>T</i>_s) was investigated by photoreflectance (PR) measurements. In Raman spectra, the wavenumber of A_g-mode in Fe–Fe and Si–Si vibrations shifted to higher wavenumber with decrease of <i>T</i>_s. The estimated Si/Fe composition ratio of the epitaxial layer became small (Si-poor) in the films grown at lower <i>T</i>_s. In PR spectra, <i>E</i>_g shifted to higher energy with decrease of <i>T</i>_s. These results show that the modification of electronic structure by a strain induced at β-FeSi₂/Si hetero-interface is suppressed by an increase of Si vacancies in β-FeSi₂.</p>

DOI： 10.56646/jjapcp.5.0_011106

CiNii Research

担当区分：最終著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>β-FeSi₂ polycrystalline films with p-type conduction were grown by RF magnetron sputtering using a B-doped p⁺-Si target with Fe chips. The hole density and mobility were 2 × 10¹⁷ cm⁻³ and 71 cm² V⁻¹ s⁻¹ at RT, respectively. The acceptor levels formed by the B-doping were obtained to be 10 and 245 meV. In the temperature dependence of electrical properties, the p-type β-FeSi₂ film showed the impurity-band conduction at 77–350 K.</p>

DOI： 10.56646/jjapcp.5.0_011204

CiNii Research

担当区分：責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）

Si(111)上にエピタキシャル成長した等価ドメインをもつβ-FeSi₂薄膜の多重イオン散乱解析を行った。このエピタキシャル成長では６つの等価なドメイン成長が可能で、Si(111)面上のそれらの積層欠陥が軸方向の原子列のランダムな変位を起こし、非チャネリング因子になっていることを、多重イオン散乱によるチャネリングデータの解析から突き止めた。

DOI： 10.14886/sssj2008.36.0_134

CiNii Article

CiNii Research

担当区分：責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）

イオンと同じ荷電粒子でありながら光電子で飛行時間型測定が実現しなかったのは、光電子がイオンに比べ質量が微量なため、外乱に妨げられるためとされていた。我々は磁気ボトル方式を採用することにより光電子を効率よく収集して検出器に導くことに成功し、パルスレーザーを励起源としてオシロスコープに飛行時間を表出することにより、仕事関数測定を可能にした。

DOI： 10.14886/sssj2008.36.0_337

CiNii Article

CiNii Research

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Temporal decay characteristics of 1.54μm photoluminescence (PL) were investigated in β-FeSi2 and Si-implanted Si samples grown by ion-beamsynthesis (IBS). In the samples, the band-edge PL of β-FeSi2 (A-band) and the dislocation-related PL (D1-band) of Si were both observed at >0.8 eV. Regarding the dependence of the PL decay curves on excitation power density (P), PL decay curves without extrinsic effects were obtained at a low P of P≤: 4.3mW/cm2. The PL decay times obtained at a low P showed clear differences between the A-band and the D1-line. The result showed that the band-edge PL of β-FeSi2 was distinguished from the dislocation-related PL of Si by the PL decay times. The intrinsic PL decay times of β-FeSi2 were determined to be τ1 = 70-100 ns and τ2 = 550-670 ns at 5 K.

DOI： 10.7567/JJAP.54.07JB05

Scopus

CiNii Article

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：記事・総説・解説・論説等（大学・研究所紀要）

DOI： 10.7567/JJAP.54.07J001

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2014 Elsevier B.V. All rights reserved.We have succeeded in situ Eu doping into AlxGa1-xN grown by organometallic vapor phase epitaxy and investigated the effects of the growth pressure and Al composition on the photoluminescence (PL) properties of Eu3+ ions. The intensity of red emission due to the 5D0-7F2 transition of Eu3+ ions decreased with increasing Al content in the case of growth at atmospheric pressure. The effect of the reactor pressure on the Eu concentration and Eu3+ PL properties showed that low-pressure growth is effective in increasing the Eu doping concentration and luminescence efficiency. The PL intensity increased with the Al composition and reached a maximum intensity at approximately x = 0.24. At Al compositions of higher than 0.24, X-ray absorption near-edge structure analysis revealed that the concentration of Eu2+ ions increased with increasing Al composition, leading to a reduction in the concentration of optically active Eu3+ ions.

DOI： 10.1016/j.optmat.2014.11.005

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We have grown Yb-doped ZnO (ZnO:Yb) on c-plane sapphire substrates by sputtering-assisted metal-organic chemical vapor deposition (SA-MOCVD). X-ray diffraction (XRD) revealed that these ZnO:Yb films exhibit a c-axis orientation and that the lattice constant increases with Yb concentration. After annealing the samples at 600 °C for 0.5 h in O2, they showed a clear 980 nm emission due to the intra-4f shell transitions of 2F5/2-2F7/2in Yb3+ ions. It turns out that Yb lu-minescent centers with different local structures coexist, which exhibit different energy transfer processes from the ZnO host. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssc.201300614

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

The electrical transport properties of β-FeSi2 epitaxial films grown on Si(001) or Si(111) substrates were investigated to clarify the growth-orientation dependence of the electrical conduction mechanism in the β-FeSi2 epitaxial films with low electron density of ~1016 cm-3. As temperature was decreased, the transition from band conduction to hopping conduction was observed in both the epitaxial films. The β-FeSi2 on Si(111) film showed the transition at higher temperature than the β-FeSi2 on Si(001). When the epitaxial films were annealed, the transition temperature shifted to lower temperature. The β-FeSi2 on Si(001) film annealed at 800oC showed the largest electron mobility of 14800 cm2/V·s at 70 K. These results were understood by the conduction through the defect levels in the β-FeSi2 epitaxial films. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssc.201300342

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The photoluminescence (PL) and electrical properties of Eu-doped ZnO (ZnO:Eu) grown by sputtering-assisted metalorganic chemical vapor deposition (SA-MOCVD) were investigated. Sharp PL lines due to intra-4f transition in Eu3+ ions were observed when ZnO:Eu was annealed at temperatures (Ta) higher than 500 °C in O2 ambient. In Hall measurements, the as-grown ZnO:Eu showed a high electron density of 3 × 1019 cm-3, indicating that the doped Eu ions act as a donor in ZnO. The electron density decreased rapidly at Ta ≥ 500 °C and was 2 × 1017 cm-3 at Ta = 600 °C. These results revealed that a complex consisting of a Eu3+ ion and an interstitial oxygen (Eu3+-Oi complex) is formed by high-temperature annealing and acts as a Eu3+ luminescent center in ZnO. © 2013 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.52.111101

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We report a study on Eu the luminescence properties of Eu-doped GaN (GaN:Eu) grown on a GaN substrate by organometallic vapor phase epitaxy (OMVPE). Thermal quenching of the Eu luminescence was suppressed using the GaN substrate, which is due to the preferential formation of a Eu luminescent site with a local structure with high symmetry. The preferential formation of this luminescent site was supported by the observation of strong near-band-edge emission. The strong near band-edge emission occurred as a result of suppressed formation of the dominant Eu luminescent site in GaN:Eu on a sapphire substrate, which is known to be coupled with a defect and to have a large capture cross section of photogenerated carriers. © 2013 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.52.08JM03

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The effects of Mg and Si codoping on Eu luminescence properties have been investigated in Eu-doped GaN (GaN:Eu). The Mg codoping into GaN:Eu produced novel luminescence centers consisting of Eu and Mg, and increased photoluminescence (PL) intensity in Eu,Mg-codoped GaN (GaN:Eu,Mg). However, this increased PL intensity was quenched by thermal annealing in N2 ambient, which is due to activation of Mg acceptors. In GaN:Eu,Mg codoped additionally with Si (GaN:Eu,Mg,Si), on the other hand, the Eu-Mg centers disappeared, while an additional luminescence center appeared. Furthermore, the additional luminescence center showed no quenching under N2 annealing because Si donors compensated for the Mg acceptors in GaN. Thermal quenching of the luminescence center was also approximately half of that in GaN:Eu. These results indicate that the codoping with additional impurities in GaN:Eu is a powerful technique to control Eu luminescence centers for realization of improved device performance in red light-emitting diodes using GaN:Eu. © 2013 The Japan Society of Applied Physics.

DOI： 10.7567/JJAP.52.08JM01

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The effects of thermal annealing on Eu,Mg-codoped GaN (GaN:Eu,Mg) grown by organometallic vapor phase epitaxy were investigated. After annealing in nitrogen ambient, Eu-Mg related photoluminescence emission was quenched to 13 without a change in the spectral shape. The quenched emission recovered to 65 of the original intensity after a subsequent annealing in ammonia ambient. Combined excitation emission spectroscopy and time-resolved photoluminescence results revealed that the quenching behavior is attributed to a nonradiative process induced by unpassivated Mg acceptors in the relaxation of excited 4f electrons of Eu ions. © 2013 American Institute of Physics.

DOI： 10.1063/1.4800447

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© Springer Japan 2013.Much attention has been paid to rare-earth (RE)-doped semiconductors as a promising new class of materials that can emit light from the RE 4f-shell by electrical injection. We have grown Er, O-codoped GaAs and Eu-doped GaN by atomically controlled organometallic vapor phase epitaxy (OMVPE), and demonstrated light-emitting diodes (LEDs) with the materials, operating at room temperature under current injection. The LEDs exhibit a characteristic emission due to the intra-4f shell transitions of trivalent RE ions that are effectively excited by the energy transfer from the hosts.

DOI： 10.1007/978-4-431-54064-9_21

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We have investigated the growth condition of Ge-doped β-FeSi2 on Si(1 1 1) substrates by molecular beam epitaxy (MBE). By the optimization of growth temperature (Ts) and Si/Fe flux ratio, the β-Fe(Si 1-xGex)2 with a flat surface was grown at Ts = 500 °C and Si/Fe=0.5, which were different from the optimized condition of the undoped β-FeSi2 (Ts = 670°C, Si/Fe = 2.0). In the dependence of lattice constants on Ge concentration, all the lattice constants expanded in the range ofx=0-11%. In the direct transition energies (Eg) measured by photoreflectance measurements, the Eg decreased with the increase of Ge concentration. These results revealed that ß-Fe(Si1-xGe x)2 was successfully grown on Si(1 1 1) substrate in the range of x=0-11%. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jcrysgro.2012.11.010

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The dependence of Eu 3 photoluminescence (PL) properties on Eu concentration was studied in Eu-doped ZnO (ZnO:Eu) thin films grown by sputtering-assisted metalorganic chemical vapor deposition (SA-MOCVD). The ZnO:Eu showed band-edge PL from ZnO and red emission lines due to the intra-4f transitions in Eu 3 ions at room temperature (RT). The intensities of band-edge and Eu 3 PL decreased with the increasing Eu concentration. In the temperature dependence of Eu 3 PL, the ZnO:Eu with high Eu concentration showed large thermal quenching of the PL intensity. In addition, the lifetimes of Eu 3 PL became short at high Eu concentration. The concentration quenching mechanism of Eu 3 PL using a model based on non-radiative recombination processes in ZnO and Eu 3 ions was presented. © 2011 Elsevier B.V.

DOI： 10.1016/j.jlumin.2011.12.042

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We investigated the changes in the electrical properties of a SiN/GaAs interface under high-temperature and high-humidity conditions, using photoreflectance (PR) spectroscopy and the electrical device characteristics. The PR spectra show the Franz-Keldysh oscillation (FKO); these spectra show that the period decreases after the sample is exposed to humidity. The electric field strength obtained from the FKO period indicates that the initial high electric field decreases with humidity exposure. Decomposed water molecules are supposed to diffuse into the SiN layer and react with the SiN/GaAs interface, causing a decrease in the interface states. © IEICE 2012.

DOI： 10.1587/elex.9.1592

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記述言語：英語   掲載種別：研究論文（学術雑誌）

[Pt(tpy)Cl]Cl (tpy: terpyridine) was successfully anchored to a series of mesoporous-silica materials that were modified with (3-aminopropyl) triethoxysilane with the aim of developing new inorganic-organic hybrid photocatalysts. Herein, the relationship between the luminescence characteristics and photocatalytic activities of these materials is examined as a function of Pt loading to define the spatial distribution of the Pt complex in the mesoporous channel. At low Pt loading, the Pt complex is located as an isolated species and exhibits strong photoluminescence emission at room temperature owing to metal-to-ligand charge-transfer (3MLCT) transitions (at about 530 nm). Energy- and/or electron-transfer from 3MLCT to O2 generate potentially active oxygen species, which are capable of promoting the selective photooxidation of styrene derivatives. On the other hand, short Pt⋯Pt interactions are prominent at high loading and the metal-metal-to-ligand charge-transfer (3MMLCT) transition is at about 620 nm. Such Pt complexes, which are situated close to each other, efficiently catalyze H2-evolution reactions in aqueous media in the presence of a sacrificial electron donor (EDTA) under visible-light irradiation. This study also investigates the effect of nanoconfinement on anchored guest complexes by considering the differences between the pore dimensions and structures of mesoporous-silica materials. Anchorman: [Pt(tpy)Cl]Cl (tpy: terpyridine) was anchored to a series of mesoporous-silica materials that were modified with (3-aminopropyl)trimethoxysilane to afford new inorganic-organic hybrid photocatalysts (see graphic). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/chem.201200959

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Sm-doped ZnO (ZnO:Sm) thin films with c-axis oriented wurzite structure were grown by sputtering-assisted metalorganic chemical vapor deposition (SA-MOCVD). In the photoluminescence (PL) measurements of annealed ZnO:Sm, sharp emission lines from intra-4f transitions in Sm 3+ ions were observed at room temperature under the excitation energy above the bandgap energy of ZnO (indirect excitation). In the dependence of PL intensity at 77 K on Sm concentration, the Sm 3+ PL intensity was the largest at Sm concentration of 0.4%. In time-resolved PL measurements, the lifetime of Sm 3+ PL became short at higher Sm concentration than 0.4%. These results revealed that a quenching of the Sm 3+ PL from ZnO:Sm was induced at higher Sm concentration than 0.4%. © 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnoncrysol.2011.12.099

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Unintentionally doped β-FeSi 2 epitaxial films were grown on silicon-on-insulator substrates by molecular beam epitaxy using a high-purity (5N) Fe source to investigate the effect of residual impurities on the transport properties of β-FeSi 2. From secondary ion mass spectroscopy analysis, impurities of As, Al, and Mn (∼10 17 cm -3); P and B (∼10 16 cm -3); and Cr and Pb (∼10 15 cm -3) were detected in the epitaxial layer. In Hall measurements at room temperature, the films exhibited n-type conduction with a carrier density of 4-6 × 10 16 cm -3 and a Hall mobility of 400-440 cm 2/Vs. In the temperature (T) dependence of the transport properties, a transition from band conduction to hopping conduction was observed at approximately T 230 K. At temperatures of 110-150 K, both negative and positive magnetoresistance (MR) were observed depending on the temperature and magnetic field. The MR exhibits mixed conduction of defect band conduction and band conduction in this temperature range. © 2012 American Institute of Physics.

DOI： 10.1063/1.4731246

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We investigated the photoluminescence properties of Eu,Mg-codoped GaN grown by organometallic vapor phase epitaxy. Some emission due to intra-4f shell transition of 5D 0- 7F 2 in Eu 3+ ions in a center with Eu and Mg was observed together with typical Eu emission. The peak intensity of the Eu-Mg emission was about five times higher than that of the typical Eu emission. The Eu-Mg emission exhibited a maximum at around 180 K, while the typical Eu emission intensity decreased monotonically with increasing temperature. It was found that only one type of Eu-Mg center contributed to the enhanced intensity up to 180 K. © 2012 American Institute of Physics.

DOI： 10.1063/1.4704920

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記述言語：日本語   掲載種別：研究論文（学術雑誌）

GaNをベースとした赤色発光ダイオード(LED)は,モノリシック型高精細LEDディスプレイやLED照明へ応用できるため,非常に期待されている.本研究では,有機金属気相エピタキシャル法によるEu添加GaNの作製を大気圧下によって行い,発光特性の向上を目指した.結果,発光に寄与するEu^<3+>イオン数の増大及びGaN母体材料からEu^<3+>イオンへのエネルギー輸送の促進ため,Eu添加GaNを活性層とするLED発光強度の顕著な向上が観測された.さらに,活性層厚の増大に伴い発光強度が増大し,活性層厚900nmにおいて光出力50μWを実現した.このとき,外部量子効率は0.12%あった.以上の結果より,Eu添加GaNによる赤色LEDの実用性を強く期待させる知見が得られた.

CiNii Article

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Direct bandgap energy (Eg) and lattice deformations were investigated in β-FeSi2 epitaxial films grown by molecular beam epitaxy (MBE) with different growth condition. As Si/Fe flux ratio during the MBE growth became smaller than Si/Fe = 2.0, the lattice constants deviated from those of β-FeSi2 single crystal, which indicated an enhanced lattice deformation at the lower Si/Fe ratio. In photoreflectance (PR) measurements, the PR spectra shifted to lower photon energy with the enhanced lattice deformation. These results revealed that the Eg of β-FeSi2 epitaxial film was modified by the lattice deformation depending on the growth condition.

DOI： 10.1016/j.phpro.2012.01.002

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We investigated the electroluminescence (EL) properties of Eu-doped GaN-based light-emitting diodes (LEDs) grown by organometallic vapor phase epitaxy (OMVPE). The thickness of the active layer was varied to increase the light output power. With increasing the active layer thickness, the light output power monotonically increased. The maximum light output power of 50 μW was obtained for an active layer thickness of 900 nm with an injected current of 20 mA, which is the highest value ever reported. The corresponding external quantum efficiency was 0.12%. The applied voltage for the LED operation also increased with the active layer thickness due to an increase in the resistance of the LED. Therefore, in terms of power efficiency, the optimized active layer thickness was around 600 nm. These results indicate that the optimization of the LED structure would effectively improve the luminescence properties. © 2011 Materials Research Society.

DOI： 10.1557/opl.2011.994

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

A new type of red light-emitting diode (LED) has been developed using Eu-doped GaN (GaN:Eu) as an active layer. The LED can emit characteristic emission due to the intra-4f shell transitions of Eu3+ ions doped in GaN at room temperature. By optimizing growth conditions during organometallic vapor phase epitaxy (OMVPE) of the GaN:Eu and device structures of the LED, the output light power became larger by more than one order in magnitude than before.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

High quality GaAs layer grown on silicon-on-sapphire (SOS) have been successfully achieved by thermal cyclic annealing (TCA) procedure using the two reactor MOCVD system after Si film deposition. The quality of silicon film measured by X-ray diffraction showed 50% narrowing of full width at half maximum intensity (FWHM) after TCA process. A spherical sapphire substrate was used to investigate substrate Offset angle dependence on crystalline quality of the GaAs layer. By applying TCA for SOS substrate before GaAs layer growth, extra smooth surface whose roughness of less than ± 30nm could obtained within a wide area of spherical SOS surface. At the smooth region, clear Franz-Keldysh oscillations (FKOs) were observed by photoreflectance (PR) spectroscopy. It also indicated that the cystalline quality of GaAs layer grown on TCA treated SOS was extremly high. © 2011 The Society of Materials Science, Japan.

DOI： 10.2472/jsms.60.998

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The modifications of direct transition energies by lattice deformations were investigated in β-FeSi2 epitaxial films, polycrystal films and single crystal, systematically. The lattice deformations depending on thermal annealing temperature (Ta) were observed in β-FeSi 2 epitaxial films. In photoreflectance (PR) measurements, the direct transition energies of the epitaxial films shifted to lower energies as the Ta increased. The polycrystal films did not show the lattice deformation and the shift of direct transition energies. These results show that the direct bandgap is modified by the lattice deformation originating from the lattice mismatch at the hetero-interface of β-FeSi2/Si. © 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2011.05.021

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担当区分：責任著者   記述言語：英語   掲載種別：記事・総説・解説・論説等（学術雑誌）

DOI： 10.1016/j.tsf.2011.05.018

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have investigated perfection of atomic rows on iron-based Heusler alloy films on Ge(111) planes by using ion channeling technique in order to find the dominant factors for the perfection. Fe3Si/Ge(111) and Fe 2CoSi/Ge(111) have a high quality of atomic rows at the heterointerface like that of perfect crystals. Fe3-xMn xSi/Ge(111) (x = 0.84, 0.72 and 0.36) interfaces have imperfection of atomic rows which may be controlled by both the lattice mismatch with the Ge substrate and the Mn-Si pairs due to the site disorder in the film with the Mn content x > 0.75. Analysis of axial channeling parameters employed in this study is very useful for quantitative evaluation of perfection of atomic rows at the heterointerface. © 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2011.05.024

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Temperature dependence of direct transition energies (Eg) was investigated in β-FeSi2 epitaxial films on Si(111) substrate. The lattice volume of the epitaxial films was reduced as the annealing temperature (Ta) increased. In photoreflectance measurements, the samples annealed at higher Ta showed a larger temperature dependence of Eg. These results revealed that the temperature dependence of Eg depended on the lattice deformation by the thermal annealing. The fact supports the band gap modifications by the lattice deformation. © 2010 Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2011.01.024

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Photoluminescence (PL) and photoreflectance (PR) properties were investigated in Si/β-FeSi2/Si(001) double heterostructure (DH) samples. The as-grown sample did not show clear PL, but the annealed one showed the 1.54 μm PL. In PR spectra, the direct transition energies (Eg) were observed at 0.910-0.935 eV in the samples. The Eg shifted to lower photon energy with the increase of annealing temperature, which indicates a modification of the band structure. These results revealed that the 1.54 μm PL was related to the transition at the indirect band gap. The effect of thermal annealing on the 1.54 μm PL was discussed. © 2010 Published by Elsevier B.V.

DOI： 10.1016/j.phpro.2011.01.025

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We obtained room-temperature red emission from GaN-based light-emitting diodes (LEDs) using a Eu-doped GaN (GaN:Eu) as an active layer. The bright emission was observed under normal lighting condition, which is associated with the intra-4f shell transition of Eu3+ ions. The LED properties depends on the growth condition of GaN:Eu layer. Since the high-quality GaN can be grown at higher growth pressure, the intense electroluminescence (EL) was observed in the LED with a GaN:Eu active layer grown at atmospheric pressure, which is due to the enhancement of the energy transfer efficiency from the GaN host material to the Eu ions. At a d.c. current of 20 mA, the light output power and external quantum efficiency were 17 μW and 0.04%, respectively. These results indicate the feasibility of GaN:Eu to realize a GaN-based red emitter for fabrication of nitride-based monolithic optical devices. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optmat.2010.10.010

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We investigated the luminescence properties of the Eu-doped GaN (GaN:Eu) grown at atmospheric (100 kPa) and low (10 kPa) pressures by organometallic vapor phase epitaxy (OMVPE). Although Eu concentration of atmospheric pressure GaN:Eu (AP-GaN:Eu) is lower than that of low pressure GaN:Eu (LP-GaN:Eu), the integrated photoluminescence (PL) intensity of the AP-GaN:Eu was 10 times higher than that of the LP-GaN:Eu (A. Nishikawa et al., Appl. Phys. Lett. 97, 051113 (2010)). Temperature dependent PL and time-resolved PL measurements revealed that the improved PL intensity was attributed to the higher crystal quality of the AP-GaN:Eu compared to that of the LP-GaN:Eu, which resulted in the enhancement of the energy transfer efficiency from the GaN host material to the Eu ions and in the increase in the number of optically active Eu ions. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssa.201000598

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Photoluminescence (PL) properties of Eu-doped ZnO (ZnO:Eu) grown by a sputtering-assisted metalorganic chemical vapor deposition technique were investigated. In PL measurements under the high-energy excitation above the band-gap energy of ZnO (indirect-excitation) at room temperature, the annealed sample showed clear red-emission lines due to the intra-4f shell transition of 5D0→7F2 in Eu3+. Under the low-energy excitation resonant to the energy levels of 7F0-5D3 transitions (direct-excitation), additional PL lines which showed fast thermal quenching were observed. These results revealed that the energy transfer from ZnO host to Eu3+ was accompanied, but there were inactive Eu3+ ions under the indirect-excitation. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssc.201000468

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have investigated the exciton spin dynamics in an ultrathin CdTe/ZnTe single quantum well (QW) and self-assembled quantum dots (QDs) by observing time-resolved Kerr rotation (TRKR). At temperatures low enough to suppress the thermal escape of holes from the quantum-confinement structures, excitons dominate the TRKR signal. It shows characteristic dependence on the magnetic field, which is distinctly different from that of isolated electrons. From the data, we have estimated the electron-hole exchange energy to be 137μeV in the QW, and larger than 190μeV in the QDs. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssb.201000805

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

RE-doped semiconductors have attracted much attention as a new class of materials with unique luminescent and magnetic properties. We have grown Er, O-codoped GaAs and Eu-doped GaN by OMVPE, and demonstrated LEDs with the materials as an active layer, operating at room temperature under current injection. The LEDs exhibit characteristic emission due to intra-4f shell transitions of the trivalent RE ions which are effectively excited by the energy transfer from the hosts.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Photoluminescence (PL) properties of Eu-doped ZnO (ZnO:Eu) grown by a sputtering-assisted metalorganic chemical vapor deposition technique were investigated. In PL measurements at 300 K, the samples annealed at 600 °C for 30 min showed clear red-emission lines due to the intra-4f shell transition of 5D0→7FJ (J=04) in Eu 3. In photoluminescence excitation (PLE) spectra, the PL was observed under the high-energy excitation above the band-gap energy of ZnO (indirect excitation) and the low-energy excitation resonant to the energy levels of 7F05D3 and 7F 05D2 transitions in Eu3 (direct excitation). The PL lifetime under the indirect excitation was shorter than that under the direct excitations. These PL properties revealed that the energy transfer from ZnO host to Eu3 was accompanied under indirect excitation. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physe.2010.03.012

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We investigated the growth temperature dependence of luminescence properties in Eu-doped GaN layers grown by organometallic vapor phase epitaxy (OMVPE). The dominant photoluminescence (PL) peak intensity at 621 nm, due to the intra-4f shell transitions of 5Do-7F2 in Eu3+ ions, became the highest when the sample was grown at 10001. Above 1000°C, the PL peak intensity decreased because of the lower Eu concentration associated with the surface desorption of Eu ions. On the other hand, although the Eu concentration of the layer grown at 900"C was only half of the layer grown at 1000°C, the pronounced decline in the PL peak intensity was observed with decreasing growth temperature from 10001 to 900°C, which results from the modification of the local structure around Eu ions. These results indicate that the growth temperature strongly influences the Eu concentration and the local structure around Eu ions. Therefore, an optimized growth temperature exists for strong Eu-related luminescence from Eu-doped GaN layer grown by OMVPE. © 2010 The Society of Materials Science, Japan.

DOI： 10.2472/jsms.59.671

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Photoluminescence (PL) properties of Er-doped β-FeSi2 (β-FeSi2:Er) and Er-doped Si (Si:Er) grown by ion implantation were investigated. In PL measurements at 4.2 K, the β-FeSi2:Er showed the 1.54 μm PL due to the intra-4f shell transition of 4I13/2→4I15/2 in Er3 ions without a defect-related PL observed in Si:Er. In the dependence of the PL intensity on excitation photon flux density, the obtained optical excitation cross-section σ in β-FeSi2:Er (σ=7×10 -17 cm2) is smaller than that in Si:Er (σ=1×10-15 cm2). In the time-resolved PL and the temperature dependence of the PL intensity, the 1.54 μm PL in β-FeSi2:Er showed a longer lifetime and larger activation energies for non-radiative recombination (NR) processes than Si:Er. These results revealed that NR centers induced by ion implantation damage were suppressed in β-FeSi2:Er, but the energy back transfer from Er3 to β-FeSi2 was larger than Si:Er. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physe.2009.10.052

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Photoluminescence (PL) properties of Eu-doped ZnO (ZnO : Eu) grown by a sputtering-assisted metalorganic chemical vapor deposition technique were investigated. In PL measurements at 30OK, the samples annealed at 600°C for 30min showed clear red-emission lines due to the intra-4/shell transition of 5Do → 7FJ (J = 2, 3) in Eu3+. In photoluminescence excitation (PLE) spectra, the PL were observed under the high-energy excitation above the band-gap energy of ZnO (indirect excitation) and the low-energy excitation resonant to the energy levels of 7F0-5D3 and 7F 0-5D2 transitions in Eu3+ (direct excitation). These results revealed that the energy transfer from ZnO host to Eu3+ was accompanied under indirect excitation in ZnO : Eu. © 2010 The Society of Materials Science, Japan.

DOI： 10.2472/jsms.59.690

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We investigated the effect of growth temperature on the luminescence properties of Eu-doped GaN layers grown by organometallic vapor phase epitaxy (OMVPE). The dominant photoluminescence (PL) peak intensity at 621 nm, due to the intra-4f shell transitions of 5D0-7F 2 in Eu3+ ions, became the highest when the sample was grown at 1000 °C. We consider three reasons for this temperature dependence. Firstly, Eu concentration became the highest when the sample was grown at 1000 °C. Secondly, Eu-doped GaN layer grown at 1000 °C had the local structure of Eu3+ ions, which emitted at 621 nm preferentially. Thirdly, the density of screw and mixed dislocations decreased with increasing growth temperature. These results indicated that an appropriate growth temperature exists for strong Eu-related luminescence from Eu-doped GaN layer grown by OMVPE. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200983470

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We investigated the luminescence properties of Eu-doped GaN (GaN:Eu) grown by atmospheric-pressure organometallic vapor phase epitaxy. The GaN:Eu exhibited radiant red emission due to the intra- 4f shell transition of Eu3+ ions at room temperature. The intensity of the dominant peak was about 4 times higher than that in the sample grown at 10 kPa, even though the Eu concentration was only half that of the 10 kPa sample. This was mainly caused by the enhancement of the energy transfer from the GaN host to Eu ions. The enhanced energy transfer resulted in improved luminescence properties of a GaN:Eu light-emitting diode. © 2010 American Institute of Physics.

DOI： 10.1063/1.3478011

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記述言語：英語   掲載種別：研究論文（学術雑誌）

CuPt-ordering and phase separation were directly investigated in In 1-xGaxAsyP1-y with a low arsenic content grown by organometallic vapor phase epitaxy on GaAs substrates. CuPt-ordering and phase separation in samples grown at the substrate temperatures of 630 and 690 °C were characterized by transmission electron diffraction and transmission electron microscopy. Although the immiscibility of InGaAsP was enhanced at the lower substrate temperature, the sample grown at 630 °C showed less phase separation than the 690 °C-grown sample. The degree of CuPt-ordering was significantly enhanced in the sample grown at 630 °C. The results demonstrated that the CuPt-ordering originating from surface reconstruction of P(2×4) suppressed the phase separation even in the miscibility gap. The detailed characterization of the phase separation clearly revealed a vertical composition modulation (VCM) in InGaAsP for the first time. The mechanism of the VCM formation is discussed based on the modulated-strain field on the surface. © 2010 Elsevier B.V.

DOI： 10.1016/j.jcrysgro.2010.03.038

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We investigated the electroluminescence (EL) properties of europium (Eu)-doped GaN-based red light-emitting diode (LED). Under current injection, the energy transfer from the GaN host material to Eu 3+ ions successfully occurred and the red emission from Eu 3+ ions was observed with naked eyes under normal lighting conditions at room temperature (RT). The operation voltage was as low as 2.4V. The dominant peak was observed at a wavelength of 621nm and its intensity increased with increasing applied voltage. The several peaks beside the main peak appeared with higher injected currents in the EL spectrum. The light output power, which was integrated over the main peak, as a function of injected current shows the saturated behaviour in the high injected current region. As a result, the external quantum efficiency was still lower than the conventional GaN-based blue and green LEDs at high injected current. However, this result suggests a novel way to realize GaN-based red LEDs, which leads to realize a monolithic device composed of red, green and blue GaN-based LEDs for full-colour display or lighting technology. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssa.200983467

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have grown Eu-doped GaN on a freestanding GaN substrate by organometallic vapor phase epitaxy and investigated its red luminescence that is due to intra-4f shell transitions of EU3+ ions. The optimum growth temperature for Eu luminescence was 50 °C higher than that of Eu-doped GaN on a sapphire substrate. The highest emission intensity was more intense than that on the sapphire substrate, while the Eu luminescence lifetime was identical for both substrates. These results indicate that energy transfer from the GaN host to the EU3+ ions occurs more efficiently in Eu-doped GaN on the GaN substrate because of a low dislocation density. © 2010 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.49.048001

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have studied the spin dynamics of confined electrons in an ultrathin CdTe/ZnTe quantum well and self-assembled quantum dots by time-resolved Kerr-rotation technique. The dependence of the spin-precession frequency on the magnetic field direction shows the anisotropy of the g -factor tensor, which is the opposite of the usual quantum wells with moderate widths. The geometrical anisotropy of the confinement also affects the initial orientation of the electron spins created optically, as revealed clearly with the use of oblique-incidence pump pulses. © 2010 The American Physical Society.

DOI： 10.1103/PhysRevB.81.125313

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記述言語：日本語   掲載種別：研究論文（学術雑誌）

CiNii Article

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We investigated the optical properties of Eu-implanted GaN and related-alloy semiconductors by photoluminescence (PL) and time resolved PL measurements at room temperature (RT). After thermal annealing, the red emission was observed in each sample due to the intra-4f transitions in Eu3+ ions. The PL intensity increases with Al incorporation into GaN while it decreases with In incorporation into GaN, indicating that the emission efficiency depends on the host materials while the emission wavelength is independent of the host materials. Since the decay times of Eu emission of the samples are found to be similar by time resolved PL measurements, the origin of the Eu emission of each sample is supposed to be same. Therefore, the difference in the PL intensity is attributed to the difference in the energy transfer efficiency because of the ion implantation damage and/or bandgap energy of the host materials. © 2009 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/191/1/012028

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We fabricated a laser diode (LD) exhibiting a lasing from strained GalnAs quantum wells (QWs) embedded in Er, O-codoped GaAs (GaAs:Er, O) by organometallic vapor phase epitaxy (OMVPE). The lasing wavelength was designed to tune to the energy separation between the second excited states 4I11/2 and the ground state 4I15/2 of Er3+ ions. The threshold current for the lasing at room temperature was six times larger than that of a GalnAs QW-LD without Er doping, reflecting ultrafast carrier capture by an Er-related trap in GaAs:Er, O. The Er intensity revealed initially steep increase with injected current density in the region for spontaneous emission from the GalnAs QWs. In the stimulated QW emission region, the intensity continued to increase with the current density. © 2009 Materials Research Society.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Structural and luminescent properties of Er-doped ZnO (ZnO:Er) grown by metalorganic chemical vapor deposition were investigated. In comparison to the undoped ZnO, the c -axis crystallographic orientation was deteriorated and the photoluminescence (PL) intensity of the band-edge became lower in the ZnO:Er. The weak band-edge PL in the ZnO:Er was due to the nonradiative recombination centers induced by the Er-doping processes. The band-edge PL intensity of ZnO:Er was drastically increased by the temperature annealing at 800 °C in O 2 ambient. The annealed ZnO:Er showed clear 1.54 μm PL originating from the 4I 13/2 → 4I 15/2 transitions of the Er3+ ions. These PL properties showed that the local arrangement of the Er ions was changed by the thermal annealing, resulting in a transformation from Er-related nonradiative centers in the as-grown sample to luminescent centers for 1.54 μm PL in the annealed one. © 2009 American Vacuum Society.

DOI： 10.1116/1.3204981

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Al-doped β-FeSi2 [β-Fe(Si1-xAlx)2] thin films with a thickness of 100 nm were epitaxially grown on Si(111) substrate by reactive deposition epitaxy (RDE). The reflective high-energy electron diffraction (RHEED) images showed epitaxial growth of β-Fe(Si1-xAlx) 2 (101)(110)//Si(111) in the composition range of 0 < x < 2.3 %. In high-resolution X-ray diffraction (HRXRD) measurements, the β(800) and β(406)(460) peaks shift to lower diffraction angles. The peak shifts linearly increase with Al composition. From an analysis of the peak shifts, Vegard's law of a, b, and c-axis in Al-doped β-FeSi2 was proven for the investigated Al-composition range. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssc.200881519

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We have fabricated two types of 1.5 μm light-emitting devices based on Er,O-codoped GaAs (GaAs:Er,O) using organometallic vapor phase epitaxy (OMVPE). In a device exhibiting a room-temperature lasing at the GaAs band-edge, the threshold current density increased with Er concentration. The Er intensity rose up steeply and then decreased gradually in the spontaneous emission region. In the stimulated emission region, it remained almost constant, reflecting ultrafast energy transfer to Er ions. In a device exhibiting a room-temperature lasing from strained GaInAs quantum wells (QWs) embedded in GaAs:Er,O, on the other hands, the lasing wavelength was designed to tune to the energy separation between the second excited states 4I11/2 and the ground state 4I15/2 of Er3+ ions. The Er intensity revealed initially steep increase with injected current density in the region for spontaneous emission from the GaInAs QWs. In the stimulated QW emission region, however, the intensity continued to increase with the current density. © 2009 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/165/1/012025

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Band structure of β-FeSi2 epitaxial and polycrystalline films was investigated by photoreflectance (PR) measurements. In the PR spectra, two critical points were obtained at Eg 0.918 eV and Ei 0.895 eV in the films. The Eg consistent with the direct transition energy at Y point in the Brillouin zone of β-FeSi2. The E i was assigned as a transition-energy between conduction band and the acceptor-level originating from Si vacancies in β-FeSi2. The energy from top of valence band to the acceptor-level was determined to be 23 meV. © 2009 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/165/1/012023

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Er-doped ZnO (ZnO:Er) thin films were grown by metalorganic chemical vapor deposition. Subsequent annealing improved the crystallinity of the ZnO:Er by suppressing nonradiative centers in the films. The annealed ZnO:Er showed clear 1.54 μm PL originating from the 4I13/2 → 4I15/2 transitions of Er3+ ions. This was in addition to luminescence from the ZnO host. Er-related PL intensity increased when prepared with annealing temperatures of 800-900°C, while annealing at 1000°C reduced the intensity. PL of 1.54 μm with high intensity was obtained in the ZnO:Er film that exhibited band-edge emission of free- or bound-excitons. © 2009 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/165/1/012027

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We investigated the relationship between optical properties and crystal quality of Eu-implanted GaN-based semiconductors. Emission peaks that are due to intra-4f shell transitions in Eu3+ ions were observed in Eu-implanted GaN, InGaN, and AlGaN. Emission wavelengths from the Eu ions were constant regardless of the matrix materials. The emission peak intensity in the Eu-implanted AlGaN was higher than that in the Eu-implanted InGaN or GaN because of less matrix damage by ion implantation. © 2009 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/165/1/012026

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Low-temperature Er-related electroluminescence (EL) properties have been investigated in Er,O-codoped GaAs (GaAs:Er,O) light-emitting diode (LED) grown by organometallic vapor phase epitaxy. Under forward bias at 77 K, the EL spectra from a cleaved edge of the LED were dominated by the luminescence due to an Er-2O center, indicating that injected carriers contribute effectively to the excitation of the Er-2O center. Excitation cross-sections of Er ions by current injection were obtained by the current density dependence of the EL intensity and its time response. The excitation cross-sections depended on temperature and the active layer thickness of the LED. © 2008.

DOI： 10.1016/j.optmat.2008.10.007

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have succeeded in the growth of europium (Eu)-doped GaN layer grown by organometallic vapor-phase epitaxy (OMVPE) and demonstrated the first low-voltage operation of current-injected red emission from a p-type/Eu-doped/n-type GaN light-emitting diode (LED) at room temperature. The bright red emission was obtained with an applied voltage as low as 3 V under normal lighting conditions. At a dc current of 20 mA, the output power, integrated over the 5D0-7F2transition in Eu3+ions (around 621 nm), was 1.3μ W. This result suggests a novel way to realize GaN-based red LEDs and monolithic devices comprising red, green and blue GaN-based LEDs. © 2009 The Japan Society of Applied Physics.

DOI： 10.1143/APEX.2.071004

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Modifications of direct transition energies by crystal lattice deformations were confirmed in Β -FeSi2 epitaxial films on Si(111) substrates. With an increasing of annealing temperature (Ta), lattice constants of a -axis expanded, and those of b - and c -axis shrank, resulting in the volume reduction in -0.2%. In photoreflectance measurements, the direct transition energy at Y point in the Brillouin zone of Β -FeSi2 (∼0.92 eV) was shifted to lower photon energy with the increase in Ta. These results revealed that the band-gap energy was modulated systematically by the lattice deformation, which suggests a possibility of band-gap engineering by the lattice deformation in Β -FeSi2 epitaxial films on Si(111) substrates. © 2009 American Institute of Physics.

DOI： 10.1063/1.3155204

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Carrier capturing in GaInP/Er,O-codoped GaAs (GaAs:Er,O)/GaInP laser diodes (LDs) was investigated by means of the threshold current density (Jth) of laser emission. The Er-doped LDs showed laser emission of the GaAs band edge at room temperature, and its Jth increases with the Er flow rate during the growth. In the dependence of Jth on reciprocal cavity length, the effective gain factor of the LDs decreased by the codoping of Er and O. These results reveal that ultrafast capturing of injected carriers at an Er-related trap level is accomplished even in the stimulated emission region of GaAs. The fast capturing process allowed us to observe both the spontaneous intra- 4f -shell emission due to Er3+ ions at 1.54 μm and the stimulated emission at the GaAs band edge (∼840 nm) in the Er-doped LDs. © 2008 American Institute of Physics.

DOI： 10.1063/1.3046784

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We have fabricated GaInP/Er,O-codoped GaAs (GaAs:Er,O) /GaInP double heterostructure (DH) laser diodes (LDs) by organometallic vapor phase epitaxy (OMVPE) and investigated their lasing characteristics at GaAs band-edge. Laser emission at the GaAs band-edge was observed from the DH LDs at room temperature. The threshold current density (Jth) increased by doping of Er. The slope of the Jth against the reciprocal cavity length (1/L) also increased by the Er doping, indicating reduced relaxation time of injected carriers in GaAs:Er,O. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200779280

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Spinel ferrite oxides doping non-magnetic ions show the photo-induced magnetization (PIM) effect at high temperature [1-3]. Such a magnetization enhancement by light irradiation is a unique property in this material. In order effectively to use the PIM effect and precisely to control the magnetism, direct light-emission from light-emitting element substrates would be a useful technique. In this study, spinel ferrite Al0.2Ru0.8Fe 204 (ARFO) thin films, with the high temperature PIM effect, were prepared on GaAs(001) substrates by a pulsed laser deposition technique to aim integration with light-emitting devices based on GaAs lattice-matched materials in the future. Results showed that (001)-oriented ARFO thin films were successfully grown by using MgO buffer layers. The magnetic properties were approximately the same as ARFO films using other substrates such as Al2O3(0001) or MgO(001). © 2008 Materials Research Society.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Wc have examined quality of axial oricntation along thc Ge<111> direction in order to find dominant factors for epitaxy control of Fe or Fe layers on Ge(111) by 2.0MeV- 4He+ ion channeling measurements. The axial channeling along thc Gc<111> orientation reveled that the axial orientation at thc interface betwccn the Heusler alloy layer and Ge dcgraded as thc Mn content increased. This dcgradation may be causcd by increasing of a lattice misfit bctween Fe3-xMnxSi and Ge. We discusscd on atomic displacements consisting of thermal vibration and static displaccment due to disorders in the lattice using results obtained from low tcmperature channeling measurements.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Er-related photoluminescence (PL) properties have been investigated in Er,O-codoped GaAs (GaAs:Er,O) grown by organometallic vapor phase epitaxy. The GaAs:Er,O which was slightly doped with Er exhibited both strong Er-related and band-edge luminescence. In the temperature dependence of the Er-related PL intensity, the intensity decreased with increasing temperature from 4.2 K to 30 K. The temperature region was quite coincident with the region where the Carbonrelated PL intensity decreased. This behaviour implies the existence of a Carbon-related nonradiative process in GaAs. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200779285

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Ultrafast dynamics of photoexcited carriers in Er,O-codoped GaAs (GaAs:Er,O) and Er-doped GaAs (GaAs:Er) have been investigated by means of pump and probe transmission spectroscopy, and discussed in relation to Er-related photoluminescence (PL) intensity. Time-resolved transmission signal in undoped GaAs showed a temporal increase due to saturation of optical absorption, and then decreased reflecting the recovery of the absorption. The decrease consisted of two components corresponding to intra-band relaxation (< 1 ps) and inter-band relaxation (> 50 ps). In GaAs:Er,O and GaAs:Er, on the other hand, an additional component was observed. The relaxation time was 4 ∼ 11 ps. This relaxation time, assigned to carrier trapping time by an Er-related trapping, became short with increasing Er-related PL intensity. These results suggest the fast carrier capturing plays an important role for the enhancement of the Er-related luminescence. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200779286

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Transition-metal (TM) doped zinc oxide (ZnO) films were grown by a developed plasma-enhanced chemical vapor deposition (PECVD) technique combined with RF sputtering. In the developed system, TMs such as Fe, Cr and Ni were doped into the ZnO films by RF sputtering with a stainless-steel electrode connected to a RF generator. X-ray diffraction (XRD) measurements revealed that the TM-doped ZnO films were successfully grown with c-axis orientation at 400 °C with RF power of 25 W. The doped TMs were segregated to the surface when the films were annealed at 700 °C in O2 ambient. After higher-temperature annealing at 800 °C, ZnO nanostructures with wire and tube shapes were formed by a catalytic influence of the segregated TMs. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200779282

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Effects of Al-doping on the iron silicide growth were investigated in reactive deposition epitaxy (RDE) on Si(111) substrates. ε-FeSi(111) layer was grown on the Si(111) substrate when the Fe of 50 Å was deposited at 750 °C. In Al-doped samples grown by co-deposition of Fe and Al, both the crystal orientation of ε-FeSi(111)//Si(111) and the surface flatness of the layer were improved with increasing Kundsen-cell temperature of Al (T Al). The highly-oriented ε-FeSi templates were annealed at 850 °C for a phase transition from ε-FeSi to β-FeSi2. X-ray diffraction (XRD) measurements of the annealed samples showed that the crystal orientation of β-FeSi2(202)(220)//Si(111) strongly depended on that of the ε-FeSi//Si. In undoped samples, XRD peaks originating from polycrystalline β-FeSi2 were observed in 2θ scan measurements. On the other hand, the peak intensities from the β-FeSi 2 polycrystal became much small in the Al-doped β-FeSi 2 grown at TAl = 925 °C. These results revealed that Al-doping during the RDE growth promotes the epitaxial growth of ε-FeSi(111)//Si(111) and the crystallographic orientation relationship between ε-FeSi and Si affects the epitaxial growth of β-FeSi 2(101)(110) on Si(111) by the post-annealing. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200779241

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Highly-insulating silicon oxide which contained hydrocarbon (CHn) groups (SiOCH) was deposited at room temperature by plasma-enhanced chemical vapor deposition using tetraethoxysilane. The carbon-rich SiOCH film deposited at 50W, 27 °C showed the high resistivity of 6 × 1015Ω cm at 0.5MV/cm. The insulating properties strongly depended on the deposition temperature and radio frequency (RF) power. The SiOCH films deposited at 300W, 53 °C showed the low carbon content and low resistivity due to the incorporation of hydroxyl (OH) groups generating electron traps. The room-temperature deposition at low RF power enabled the high-CHn addition, resulting in the suppression of OH incorporation into the films. The highly-insulating properties of the room-temperature deposited SiOCH originated from the suppression of OH incorporation. © 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2008.06.049

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Ultrafast carrier dynamics and terahertz radiation from Er,O-codoped GaAs (GaAs:Er,O) have been investigated by pump and probe reflectance and time-domain terahertz spectroscopy. In pump and probe reflectance measurements, GaAs:Er,O showed faster relaxation time (0.37-0.56 ps) of photoexcited carriers than undoped GaAs. In terahertz spectroscopy, the radiated terahertz amplitude decreased and the decay time of transient photocurrent became long with increasing Er concentration. The Er concentration dependence was understood by additional electron scattering due to the Er doping. The fast relaxation time and the terahertz radiation properties suggest new applications of GaAs:Er,O for the terahertz frequency region. © 2008 American Institute of Physics.

DOI： 10.1063/1.2901025

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Er,O-codoped GaAs (GaAs:Er,O) was grown by organometallic vapor phase epitaxy (OMVPE) using tris(dipivaloylmethanato)erbium [(C11H 19O2)3Er: Er(DPM)3] at different growth temperatures (Tg). In photoluminescence (PL) measurements, Er-related PL lines partly assigned as an Er-2O center were observed in the samples grown at Tg 500 - 550° C. The result revealed that the self formation of Er-2O center was accomplished by an incorporation of oxygen atoms in the Er(DPM)3 source. In the dependence of a H2 flow rate through the Er source on the PL properties, the intensity of the Er-related PL increased as that of the band-edge PL of GaAs host decreased. The correlation of PLs shows a highly efficient energy-transfer from GaAs host to the 4f-shell of Er ions in the GaAs:Er,O samples. © 2008 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/106/1/012007

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Energy-transfer processes in Er,O-codoped GaAs (GaAs : Er,O) have been investigated by means of a pump and probe reflection technique. Time-resolved reflectivity exhibited a characteristic dip; a negative signal due to bandgap renormalization in less than 1 ps and then a gradual recovery. In the recovery process, there were two components, fast and slow. The fast recovery time (several ps) was inversely proportional to Er concentration. The analysis based on a rate equation indicated that it is due to the capture of electrons by charged traps. The slow recovery (30-60 ps) was well coincident with the time (54 ps) predicted theoretically in the framework of a multiphonon-assisted model. Optical excitation cross section of Er ions in GaAs:Er,O has also been studied in various samples and shown to depend strongly on Er concentration. © 2008 WILEY VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssa.200776702

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Dynamics of photoexcited carriers in Er-doped GaAs (GaAs:Er) and Er,O-codoped GaAs (GaAs:Er,O) have been systematically investigated by means of a pump and probe technique. A characteristic ps-scale relaxation was clearly observed in transient reflectance (dR/R) and transmission (dT/T) curves. The relaxation was due to the trapping of photoexcited carriers by an Er-related trap, which was closely related to efficiency of Er3+ luminescence. © 2007.

DOI： 10.1016/j.physb.2007.08.155

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記述言語：日本語   掲載種別：研究論文（学術雑誌）

β-FeSi_2は屈折率が高く(n>5.2),これを用いた高コントラスト・フォトニック結晶は数々の性能向上が期待されている.しかし,高屈折率フォトニック結晶への光入射では,境界面で高い屈折率差が生じるため,反射損失が大きくなる.そこで作製が容易な構造をもつ共役反転格子フォトニック結晶を考案し,そのフォトニック結晶への光エネルギー透過率を時間領域差分法による導波解析によって検討した.その結果,共役反転格子フォトニック結晶を用いることで,境界面における光エネルギー透過率を89%に向上させることができた.

CiNii Article

その他リンク： http://ci.nii.ac.jp/naid/110006549257

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Dynamics of photoexcited carriers in Er,O-codoped GaAs (GaAs:Er,O) have been investigated by means of a pump-probe reflection technique. Time-resolved reflectivity exhibited an abrupt increase in amplitude, followed by a steep decrease to negative in less than 1 ps and then a gradual recovery. There were two components, fast and slow components, in the recovery process. The analysis indicated that the fast recovery corresponds to the capture of photoexcited carriers by a trap formed by Er and O codoping, and the slow recovery to energy-transfer from the GaAs host to 4f-shell of Er ions. © 2007 American Institute of Physics.

DOI： 10.1063/1.2729860

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Transient carrier dynamics in Er,O-codoped GaAs (GaAs:Er,O) have been investigated by terahertz (THz) emission from the sample surface. The THz radiation from GaAs:Er,O was observed under 800 nm optical excitation and depended on Er concentration. The radiated THz amplitude decreased and the decay time of transient photocurrent became long as the Er concentration was increased. GaAs:Er,O with the highest Er concentration of 8.7×10 18 cm-3 showed the decay time of 0.86 ps which was longer than that of 0.37 ps in an undoped GaAs epitaxial layer. These results were understood by electron scattering due to the codoping of Er and O.

DOI： 10.1109/icimw.2007.4516594

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記述言語：英語   掲載種別：研究論文（学術雑誌）

GaAs epitaxial layers were grown by organometallic vapor phase epitaxy (OMVPE) using TEGa and TBAs over a wide range of growth temperature (350°C-700°C) and V/III ratio (2-9). GaAs with excellent surface morphology was obtained when the growth temperature was higher than 600°C. The GaAs surface tended to be rough with decreasing growth temperature below 550°C. When the growth temperature was decreased to 400°C, p-type GaAs was obtained with specular surface. The hole concentration increased with decreasing V/III ratio. The hole concentration was as high as 5.5 × 10 17 cm 4 for the sample grown at 400°C with V/III ratio = 2. © 2007 The Society of Materials Science.

DOI： 10.2472/jsms.56.880

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（その他学術会議資料等）

DOI： 10.1016/j.tsf.2007.02.019

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We have investigated dry-etching properties of polycrystalline β-FeSi2 films formed by ion-beam sputter-deposition (IBSD) and the films epitaxially grown on Si by metal organic chemical vapor deposition (MOCVD) in order to realize fabrication of photonic crystals with several hundreds nanometers in dimension. Using reactive ion etching with magnetic neutral loop discharge (NLD) plasma, we succeeded in realizing a comparatively higher etching rate than that obtained by inductively coupled plasma (ICP). Both reactive ion etching and impact ion etching modes may contribute to etching of β-FeSi2. We have fabricated a two-dimensional photonic crystal of β-FeSi2 on Si substrates and confirmed its predicted photonic properties in a reflectance spectrum of polarized light. © 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2007.02.032

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We have investigated an optimal annealing process in order to enhance 1.55 μm light emission from semiconducting β-FeSi2 and found that two steps annealing at 600 °C and 800 °C is effective to its enhancement. Rutherford backscattering spectroscopy and SEM observations revealed that pronounced surface segregation of Fe atoms during annealing at 600 °C caused surface precipitate of β-FeSi2. The enhancement of light emission is attributed spatial isolation of the surface β-FeSi2 (light emitting layer) from damaged and defective layers with nonradiative recombination centers. © 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2007.02.024

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Ion-beam-synthesized β-FeSi2/Si interfaces were investigated by carrier-injection photoluminescence (CPL) measurements. The CPL intensity of Al-doped β-FeSi2/Si sample was larger than that of non-doped one. We obtained a carrier injection efficiency (γ) of γ = 0.41 in the Al-doped sample and γ = 0.19 in the non-doped one. These results revealed that Al-doping into β-FeSi2 is an effective technique for the improvement of β-FeSi2/Si interface which is defective due to ion implantation damages. © 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2007.02.058

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Carbon-doped silicon oxide (SiOCH) films were deposited by plasma-enhanced chemical vapor deposition (PECVD) using tetraethoxysilane (TEOS) at low temperatures (27-53 °C). The structural and insulating properties of the films deposited with Ar or N2 plasma were investigated. In the deposition with low plasma density and low substrate temperature, both plasmas produced films with high hydrocarbon (CHn) content. The films prepared using Ar plasma showed a low leakage current of 7 × 10 -10A/cm2 at 1 MV/cm due to the incorporation of CH n groups, while the films with high CHn content prepared using N2 plasma showed poor insulating properties. The deposition using N2 plasma formed films with a defective structure, resulting in a higher etch rate than that of the films deposited with Ar plasma. The deposition with the low-density plasma of inert Ar gas is suitable for the low-temperature deposition of SiOCH films with high resistivity. © 2007 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.46.1997

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

High-quality epitaxial Si films have been grown at low temperatures (500-600°C) by atmospheric pressure plasma chemical vapor deposition (AP-PCVD) with a high growth rate (0.31 μm/min at 600°C averaged over the 4-in. wafer). In contrast to the previous reports on other low-temperature CVD Si, the films in the present study are defect-free as observed by transmission electron microscopy and selective etching, and show no oxygen and carbon pileups at the film/substrate interface. To characterize defect-free epitaxial films with high sensitivity, we employed a photoluminescence (PL) method. When the epitaxial layer has better quality than the substrate, PL spectrum at 4.2 K mainly reveals the property of the substrate. On the other hand, room temperature PL measurements clearly show that the PL intensities of the surface-passivated epitaxial Si samples are much higher than that of Czochralski (CZ)-Si, which indicates a longer minority carrier recombination lifetime in the epitaxial Si layer than the bulk lifetime in CZ-Si. © 2007 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.46.2510

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Low-temperature plasma-enhanced chemical vapor deposition of amorphous carbon (a-C:H) films was investigated for surface passivation of carbon-doped silicon oxide (SiOCH) films. The a-C:H films were deposited using CH4 and Ar gases at 40-65°C. FT-IR results showed that the deposited films are a-C:H which incorporates hydrocarbon groups. In current-voltage measurements, the a-C:H showed a low leakage current of ∼10-10 A/cm2 in air, indicating that the a-C:H films have a potential as a surface passivation layer to prevent moisture absorption in air. The insulating properties of room-temperature deposited SiOCH covered by the a-C:H strongly depended on radio frequency (RF) power in the SiOCH deposition. In the SiOCH film deposited at high RF power of 200 W, the resistivity in air was improved by the a-C:H passivation.

DOI： 10.4028/0-87849-463-4.645

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Magnetic properties of Er-doped GaAs (GaAs:Er) and Er,O-codoped GaAs (GaAs:Er,O) have been investigated by using superconducting quantum interference devices (SQUID) magnetometer at low temperature. In M-H curves of GaAs:Er,O, a characteristic magnetization due to the codoping with Er and O was observed at 2 K, while GaAs:Er exhibited much smaller magnetization. The saturation magnetization of GaAs:Er,0 slightly increased with Er concentration. These results were discussed in relation to an atomic configuration formed selectively around Er3+ ions in GaAs:Er,O. © 2006 WILEY-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200672878

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記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/10022545752

記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/10022547724

記述言語：英語   掲載種別：研究論文（学術雑誌）

Dynamics of photo-excited carriers in Er,O-codoped GaAs have been systematically investigated by means of a pump and probe reflection technique. Time-resolved reflectivity exhibited an abrupt increase in amplitude, followed by a steep decrease to negative in less than 1 ps and then a gradual recovery. There were two components, fast and slow, in the recovery process. The fast recovery depended strongly on Er concentration and measurement temperature. The quantitative analysis indicated that the fast recovery corresponds to electron capture by a trap formed by Er and O codoping. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.12.140

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Photoluminescence (PL) properties of Al-doped β-FeSi2 grown by ion beam synthesis have been investigated. The Al-doped samples showed increase of the PL intensity. In the dependence of Al composition, the sample of low Al concentration showed the larger PL intensity and activation energy for non-radiative recombination path. The Al dependence indicates that there is competition of enhancement and retardation effects of the PL by the Al-implantation. © 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.12.200

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Carbon-doped silicon oxide (SiOCH) thin films were deposited by room-temperature plasma-enhanced chemical vapor deposition (PECVD) using tetraethoxysilane (TEOS). The deposition rate and composition of the films strongly depended on radio frequency (RF) power. The films deposited at low RF power contained more CHn groups. The SiOCH films showed high etch rate and low refractive index in proportion to the carbon composition. The deposition with low plasma density and low substrate temperature is effective for SiOCH growth by PECVD using TEOS. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.12.103

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Bulk β-FeSi2 crystals were grown by annealing of unidirectionally solidified structures with rods of the ε-FeSi in the α-FeSi2 matrix. The crystallographic orientation of annealed samples was investigated by means of electron-backscattered pattern analysis. It was found that there were fibrous single crystals of β-FeSi2 in the sample. The β-FeSi2 crystal was easily grown along the solidification direction. The formation of the fibrous β-FeSi2 single crystals resulted from limited nucleation at the initial stage. © 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physb.2005.12.199

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記述言語：日本語   掲載種別：研究論文（学術雑誌）

β-FeSi_2の1.55μmでの発光増強を目指してアニール条件を検討した.600℃でのプレアニールと800℃でのポストアニール(2ステップアニール法)で形成したβ-FeSi_2の発光は従来に比べて大幅に増強した.ラザフォード後方散乱分光法と断面SEM観察から, プレアニールではFe原子の顕著な表面偏析によってβ-FeSi_2層が表面に形成され, 消光の主な原因である注入損傷層と空間的に分離されることが発光増強の原因であることが分かった.

CiNii Article

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Carrier dynamics in Er,O-codoped GaAs (GaAs:Er,O) have been systematically investigated by means of a pump and probe reflection technique with a mode-locked Ti:sapphire laser. In GaAs:Er,O, it has been found that the codoping produces a single atom configuration (Er-2O configuration) as an Er atom located at the Ga sublattice with two adjacent O atoms together with two As atoms, resulting in extremely strong Er luminescence. Time-resolved reflectivity of GaAs:Er,O exhibited an abrupt increase in amplitude, followed by a steep decrease to negative in less than 1 ps and then a gradual increase in approximately 100 ps. The steep decrease is due to bandgap renormalization. The gradual increase in reflectivity depended strongly on Er concentration, indicating that a trap induced by Er and O codoping plays an important role in dynamics of nonequilibrium carriers in GaAs:Er,O. © 2005 Materials Research Society.

DOI： 10.1557/proc-866-v3.7

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記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/10022541840

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

We have measured photoluminescence (PL) spectra and time-resolved PL in CdTe quantum dots (QDs) under the longitudinal magnetic field up to 10T. Circular polarization of PL increases with increasing magnetic field, while its linear polarization is absent under linearly polarized excitation. Time-resolved PL measurements clarified that this behavior is caused by the suppression of spin relaxation induced by the longitudinal magnetic field. We believe that this behavior is related to the hyperfine interaction of electron spin with magnetic momenta of lattice nuclei. © 2005 American Institute of Physics.

DOI： 10.1063/1.1994613

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記述言語：日本語   掲載種別：研究論文（学術雑誌）

DOI： 10.2320/materia.44.471

CiNii Article

その他リンク： http://ci.nii.ac.jp/naid/10016439626

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We have succeeded in expitaxial growth of (101) and (110)-oriented β-FeSi2 films on (111)Si, (111)Si-buffered (111)YSZ and (111)YSZ substrates by metal organic chemical vapor deposition (MOCVD). All the films showed highly perfection in orientation irrespective of the substrate. After annealing at 900°C in Ar atmosphere, their photoluminescences (PL) around 1.54 μm were observed in the β-FeSi2 films grown on (111)Si and (111)Si-buffered (111)YSZ substrates, except for the film on (111)YSZ substrates. This suggests that the β-FeSi2/Si interface is a crucial structure for enhancement of PL and that the Si atom diffuses into β-FeSi2 is important factor to 1.54-μm PL. ©2005 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.44.L303

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記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/10015704647

記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/10015704607

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Ion-beam-synthesized (IBS) β-FeSi2/Si(100) heterojunctions were observed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Clear epitaxial growth of β-FeSi2 on Si(111) and large crystal domains laterally grown on the surface were demonstrated in Al-doped samples. The optical processes near the heterojunction were examined by photoluminescence spectra measured on the different optical configurations. The epitaxial growth due to Al doping was found to be effective in reducing the density of nonradiative recombination centers and enhancing an electron-hole injection. Solid phase epitaxy (SPE) of Si taking place at the Al-doped interface was found to be the dominant contribution to lateral growth on the surface and epitaxial growth of β-FeSi2. © 2005 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.44.2502

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We present the photoluminescence (PL) properties of surface oxidized β-FeSi2/Si(100) samples. X-ray photoelectron spectroscopy measurements showed the formation of a thick SiO2 layer at the surface when samples were annealed in air. In PL measurements, the samples annealed in air showed much larger PL intensity and activation energy for a nonradiative recombination than those annealed in vacuum. Surface oxidation is a new technique to enhance the PL at 1.54μ.m of β-FeSi2. © 2005 The Japan Society of Applied Physics.

DOI： 10.1143/JJAP.44.2492

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The growth processes and structures of Fe/Si(1 1 1) ultrathin films grown by solid-phase reactive epitaxy were investigated by coaxial impact-collision ion scattering spectroscopy (CAICISS). It has been revealed that the Fe(1 1 1) thin films with a bcc-type structure were epitaxially grown on a Si(1 1 1) crystal, even at room temperature, and formed a single-domain structure: Fe(1 1 1)〈1̄1̄2〉∥Si(1 1 1)〈112̄〉. After annealing at above 600 °C, the Fe(1 1 1) films were transformed into β-FeSi2 via the collapse of the bcc-type structure to an amorphous or polycrystalline structure. On the basis of the thickness dependences of the growth processes, this phenomenon was discussed in terms of the diffusion of Si into Fe thin films. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.susc.2005.01.051

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記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/10014505897

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Resistance measurements have been performed in a two-dimensional organic conductor λ-(BETS) 2Fe xGa 1-xCl 4 (x=0.45) to investigate the superconducting properties. In magnetic field parallel to the layers, the superconducting (S)phase is stabilized in a wide magnetic field range, which is qualitatively understood by Jaccarino-Peter compensation mechanism. Depending on the internal field created by the Fe 3d moments, three vortex phases in the S phase appear with increasing field; normal vortex, antivortex, and normal vortex phases. The superconducting transitions show characteristic field dependence, which is correlated to the vortex phases. In field perpendicular to the layers, the S phase appears only near the antiferromagnetic phase. The results for x=0.45 are also compared with those for the isostructural nonmagnetic salt x=0. ©2005 The American Physical Society.

DOI： 10.1103/PhysRevB.71.104525

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記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/210000105871

記述言語：英語   掲載種別：研究論文（学術雑誌）

We have succeeded in enhancing the photovoltaic properties of p-n heterojunctions using β-FeSi2/Si(1 0 0) by doping Al into β-FeSi2. Raman spectroscopy, Rutherford backscattering spectroscopy (RBS) and transmission electron microscope (TEM) observations revealed that Al doping contributes to the synthesis of a less defective interface and epitaxial growth of β-FeSi2 on Si(1 0 0). This feature of epitaxial growth may reduce the recombination rate of electron-hole pairs near the depletion region, such that the photoresponse can be enhanced. We observed a significant photoelectric response corresponding to the interband transition near the band-gap energy of β-FeSi2. This effect of the Al doping can be used in IR-photoelectric cells. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optmat.2004.08.036

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

This paper reports the measurements of Shubnikov-de Haas (SdH) and angular-dependent magneto-resistance oscillations (AMROs) for new layered organic conductors ET3Cl(DFBIB) and ET3Br( pBIB), where ET, DFBIB, and pBIB stand for bis(ethylenedithio)tetrathiafulvalene, 1,4-difluoro-2,5-bis(iodoethynyl) benzene, and p-bis(iodoethynl)benzene, respectively. Each of them has only a two-dimensional Fermi surface (FS), whose cross sectional area corresponds to about 50% of the first Brillouin zone. No significant difference between them is found in the size and shape of the cross-section of the FS. In spite of the similarity of the electronic state, the sharp peaks in the magnetoresistance are clearly observed for ET3Cl(DFBIB) under in-plane magnetic fields, while anomalous broad peaks for ET3Br( pBIB). The results suggest that the anion structure play an important role in the interlayer transport. ©2005 The Physical Society of Japan.

DOI： 10.1143/JPSJ.74.679

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Effects of impurity-doping on photoluminescence (PL) properties of ion-beam synthesized (IBS) β-FeSi2 have been investigated. The Al- and B-doped β-FeSi2 showed increase of both PL intensity and activation energy (Ea) for non-radiative recombination path. On the contrary, the Mn and Co doping reduced the PL intensity and Ea. We found that the doping of Al and B atoms which occupy the Si sites in β-FeSi2 is a technique to enhance the 1.54 μm photoluminescence. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.optmat.2004.08.037

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have measured photoluminescence (PL) spectra and time-resolved PL in CdTe quantum dots under the longitudinal magnetic field up to 10 T. Circular polarization of PL increases with increasing magnetic field, while its linear polarization remains zero under linearly polarized excitation. This behavior cannot be explained by the anisotropic exchange interaction of excitons. Time-resolved PL measurements clarified that this behavior is caused by the suppression of spin relaxation induced by the longitudinal magnetic field. We believe that this behavior is related to the hyperfine interaction of electron spin with magnetic momenta of lattice nuclei. ©2005 The American Physical Society.

DOI： 10.1103/PhysRevB.71.033314

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記述言語：日本語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： http://ci.nii.ac.jp/naid/10014297513

記述言語：日本語   掲載種別：研究論文（学術雑誌）

β-FeSi_2は1.55μm帯域の光エレクトロニクスヘの応用を目指した基礎研究が進んでいる.β-FeSi2のシリコン上での結晶成長(エピタキシャル成長,多結晶成長),格子ひずみを利用したバンドエンジニアリングの可能性,赤外発光・光電特性などの現状を紹介する.

CiNii Article

その他リンク： http://ci.nii.ac.jp/naid/110003311194

記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/10022540271

記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/10022540258

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Complete determination of all Raman active lines in the range between 180 and 480 cm-1 for an orthorhombic β-FeSi2 lattice has been performed by accurate polarized Raman measurements on β-FeSi 2 and a crystal rotation method along the 〈111〉 axis. The 20 Raman active lines including 7 new lines in the range between 180 and 480 cm-1 were observed. Further polarization relations for each observed Raman lines were analyzed from their intensity changes as a function of crystal rotation angle. The components of the Raman tensor of β-FeSi2 were discerned from the polarization curves. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2004.02.059

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Effects of structural changes near the interface, the implantation dose and the precipitate morphology on photoluminescence (PL) properties of ion-beam synthesized (IBS) β-FeSi2 have been investigated. The intrinsic PL spectrum attributed to the interband transition of β-FeSi2 was found by examining the dependence of the PL peak energy on temperature and the excitation power. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2004.02.057

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We present the temperature dependence of the lattice constants (a, b, c) of β-FeSi2 single crystals at low temperatures. a showed the largest temperature dependence of 0.14% and the relationship of a>c>b did not change at 8-300 K. The linear thermal expansion coefficients α showed remarkable anisotropy. α along the a-axis (α∥a) was much larger than α∥b and α∥c, and showed negative thermal expansion at temperatures below 60 K. From these results, we estimated the temperature dependence of the lattice mismatches at β-FeSi2/Si heterojunctions. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tsf.2004.02.080

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

MBE growth of self-organized dots of CdTe and (Cd,Mn)Te on the lattice-mismatched ZnTe surface and their optical properties are reported. The formation of nano-scale dots was confirmed when CdTe or Cd1-xMn xTe with the Mn composition x ≤ 0.1 was deposited on the ZnTe (0 0 1) surface beyond the critical thickness of 1.5-2 monolayers (MLs). In the PL measurement on CdTe dots, the zero-dimensional (0D) excitonic luminescence from the dots was observed. Though the emission from the wetting layer was not observed in the PL spectra, the existence of the wetting layer state was confirmed in the PLE measurement. The PL spectra from (Cd,Mn)Te dots were split into two lines in low temperatures less than 20K. The lower-energy line showed anomalous behaviors in the dependences on temperature and magnetic field. This is considered due to the magnetic polaron effect enhanced by the 0D confinement. © 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jallcom.2003.05.004

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The photoluminescence (PL) intensity in Al-doped β-FeSi2 was enhanced. The Al-doped sample showed the largest PL intensity even if it was annealed for a short time. The activation energy for nonradiative recombination increased in the Al-doped sample. Results show that Al doping is a technique to decrease nonradiative centers and enhance the PL intensity of β-FeSi2.

DOI： 10.1063/1.1646215

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Dynamics of spin-lattice relaxation of the magnetic Mn-ion system is investigated for nanostructures with (Cd,Mn)Te and (Cd,Mn)Se diluted-magnetic-semiconductor (DMS) quantum dots. A nonequilibrium phonon technique with optical detection of the induced heating of the magnetic ion system was exploited. A strongly nonexponential decay of the spin dynamics is found to be specific for the DMS quantum dots. It is explained in the frame of a model suggesting that the spin dynamics in quantum dots is strongly affected by a spin diffusion into/from a DMS wetting layer, where the spin-lattice relaxation rate differs from that in the quantum dots. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/pssb.200301916

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2015 IEEE.Orthorhombic FeSi2 (β-FeSi2) has been known as one of promising semiconductors for Si monolithic photonics circuits. β-FeSi2 shows clear light emission and photoresponse near 1.55 μm in wavelength and a high refractive index (>5.8) (Lange, 1997). These basic optical properties are appropriate to Si optoelectronic integrated circuits (Si-OEIC) consisting of Si waveguides being a crucial technology for monolithic fabrication. The monolithic fabrication of 1.55 μm-light emitting diodes and IR-photodetectors (Maeda, 2000) connected effectively with the Si waveguide can be made possibly by conventional fine ion beam synthesis (IBS) procedures of β-FeSi2. However, detailed mechanism of optical processes in β-FeSi2 has not been well understood. In order to obtain more intense 1.55 μm-emission and high sensitivity, an advanced technology for improvement of optoelectronics performance should be required. In this work, we have found pronounced effects of the Al-doping into β-FeSi2/Si heterostructures on the light emission and photovoltaic properties.

DOI： 10.1109/IMFEDK.2004.1566411

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We use the combination of nonequilibrium phonon and exciton luminescence techniques to study the spin dynamics in diluted magnetic semiconductor structures with (Cd,Mn)Te and (Cd,Mn)Se quantum dots (QDs). We show that the spin-lattice relaxation (SLR) of Mn ions in these structures differs strongly from the SLR in quantum wells. We explain the results by a model where SLR process in structures with QDs is modified by the spin diffusion on Mn ions from the QD to a wetting layer. © 2003 Plenum Publishing Corporation.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We have measured the temperature (T) dependence of the conductivity of cobalt films with various thickness (d). The conductivity shows In T dependence for d < 100 Å, which is mainly caused by electron-electron interaction effect. The coefficient of the In T dependence significantly decreases with decreasing thickness for d < 50 Å, where the conductivity approaches Mooij limit. The results suggest that the scattering for d <50 Å is dominated by the inhomogeneity of the films such as grain boundaries. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(02)02461-4

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We report resistance measurements in superconducting Al disks whose sizes are much smaller than the superconducting coherence length of Al bulk. In the magnetic field, the disks show nonperiodic resistance peaks depending on the sample size and topology. In circular and square disks with the size of 600 nm, there is no remarkable difference in the field intervals (ΔH) of the resistance peaks. However, significant difference in ΔH are observed between circular and square disks with the size of 500 nm. These results suggest that new vortex states depending on the sample topology appear when the size is sufficiently small. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(02)02348-7

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Resistance measurements have been performed to investigate the field induced superconductivity in λ-(BETS)2FexGa1-xCl4 (x = 0.47). In magnetic fields parallel to the conduction layers (c-axis), the superconducting (S) phase is induced between 5 and 24 T at 1.6 K. However, when the field is tilted from the c-axis to the b*-axis (normal to the conduction layers), the S phase disappears at around 6°. This strong anisotropic behavior shows that the orbital effect plays a significant role in the destructive mechanism of the superconductivity. The orbital critical field normal to the conduction layers is estimated to be 1.5 T at 1.6 K. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4534(02)02765-X

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The highest 19th-order longitudinal optical (LO) phonon-mediated relaxation was observed in photoluminescence excitation spectra of CdTe self-assembled quantum dots grown in ZnTe. Hot excitons photoexcited highly in the ZnTe barrier layer are relaxed into the wetting-layer state by emitting multiple LO phonons of the barrier layer successively. Below the wetting-layer state, the LO phonons involved in the relaxation are transformed to those of interfacial ZnxCd1-xTe surrounding CdTe quantum dots. The ZnTe-like and CdTe-like LO phonons of ZnxCd1-xTe and lastly acoustic phonons are emitted in the relaxation into the CdTe dots. The observed main relaxation is the fast relaxation directly into CdTe quantum dots and is not the relaxation through either the wetting-layer quantum well or the band bottom of the ZnTe barrier layer. This observation shows very efficient optical phonon-mediated relaxation of hot excitons excited highly in the ZnTe conduction band through not only the ZnTe extended state but also localized state in the CdTe quantum dots reflecting strong exciton-LO phonon interaction of telluride compounds. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-2313(02)00617-8

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Recently, a new organic conductor ET-TCNQ, which exhibits two resistance anomalies at T1= 80 K and T2 20 K, was synthesized. We present a systematic study of transport properties of ET-TCNQ under magnetic fields. Shubnikov-de Haas (SdH) oscillations are clearly observed and we find five distinct small Fermi surfaces (FS's). The cross-sectional areas of FS are estimated to be from 1 %(α) to 3.5 %(ε) of the first Brillouin zone. We detect Lebed resonance and Danner-Chaikin oscillation in measurements of angular-dependent magnetoresistance oscillation (AMRO), suggesting the existence of the quasi-one dimensional FS related to ET molecules. The origins of the two resistance anomalies are discussed in terms of nesting-driven density-wave transition. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00760-9

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We have performed resistance measurements in a wide field region for various λ-(BETS)2FexGa1-xCl4 and obtained the global magnetic phase diagram. For x>0.45, λ-(BETS)2FexGa1-xCl4 shows superconductivity only under high magnetic fields parallel to the conducting layer. As x decreases, the field induced superconducting phase shifts towards lower fields and a striking field-induced insulator to superconductor transition is observed below 4 T for x=0.45. The overall features of the global phase diagram are well understood in terms of Jaccarino-Peter compensation mechanism.

DOI： 10.1016/S0379-6779(02)01056-1

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We report the measurements of Shubnikov-de Haas (SdH) oscillation and angular dependent magnetoresistance oscillation (ADMRO) in a new layered organic conductor (BEDT-TTF)3Br(pBIB), where pBIB stands for p-bis(iodoethynyl)benzene. When magnetic fields are applied perpendicular to the layers, two distinct SdH oscillations are clearly observed, which arise from the two extremal cross-sectional areas of the slightly warped cylindrical Fermi surface (FS). The cross-sectional areas correspond to 50.9 and 51.6% of the first Brillouin zone. From the analysis of the ADMRO, the area of FS is estimated to be 52.5% of the first Brillouin zone. The ADMRO data also shows that the anisotropy of the FS is enhanced by change of Br(pBIB) for Cl(DFBIB), where DFBIB stands for 1,4-difluoro-2,5-bis(iodoethynyl)benzene. These results are consistent with the band calculation. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00248-5

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Electronic states have been investigated under high magnetic fields for quasi-two-dimensional organic conductors λ-(BETS)2FexGa1-xCl4 (x = 1.0, 0.47, 0.45, 0; BETS: bis(ethylenedithio)tetraselenafulvalene). Under magnetic field parallel to the c-axis, various electronic states appear, depending on x, field, and temperature. The global phase diagram for this alloy is presented and the evidence of the strong internal field due to the Fe moments is shown. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0379-6779(02)00392-2

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Organic alloys λ-(BETS)2FexGa 1-xCl4 show superconductivity only under very high magnetic fields parallel to the conducting layer for x ≥ 0.47. As x decreases, the field induced superconducting phase shifts towards lower fields and a striking field-induced insulator to superconductor transition is observed below 4 T for x = 0.45. We show that the overall features of the global phase diagram are well understood in terms of Jaccarino-Peter compensation mechanism. These results provide a new road map for the future design of high magnetic field superconductors. © 2003 The Physical Society of Japan.

DOI： 10.1143/JPSJ.72.369

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We report the photoluminescence and excitation spectra of CdTe self-assembled quantum dots grown by molecular beam epitaxy in ZnTe. In photoluminescence excitation spectra, multiple longitudinal-optical (LO) phonon structures up to the 19th order are observed even above ZnTe-matrix energy, and the wetting layer was clarified. Photoluminescence spectra of CdTe quantum dots having LO phonon structures under quasi-resonant excitation show that CdTe dots are surrounded by ZnxCd1-xTe (x ∼ 0.8, where x ranges from 0.5 to 1). Phonon-mediated carrier relaxation is discussed. Photoexcited carriers forming excitons are relaxed by emitting multiple LO phonons of the ZnTe matrix successively from the higher energy state of the matrix to the wetting layer. At the wetting layer, involved LO phonons are transformed to those of ZnxCd1-xTe surrounding the CdTe dots. ZnTe-like and CdTe-like LO phonons and, lastly, acoustic phonons, are emitted in relaxation to the CdTe-dot state.

DOI： 10.1143/JPSJ.71.3052

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Electronic states have been investigated under high magnetic fields for quasi-two-dimensional organic conductors λ-(BETS):FexGa1-xCl4, (x=1.0, 0.47, 0.45, 0). Under magnetic field parallel to the c-axis, various electronic states appear, depending on x, field, and temperature. The global phase diagram for this alloy is presented and the evidence of the strong internal field due to the Fe moments is shown.

DOI： 10.1142/s0217979202013626

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The electrical conductivities of Co thin films with the thickness in the range 2.5∼30 nm have been studied. In the low temperature region, the sheet conductivities for the films of 3.0∼5.0 nm show logarithmic temperature dependence. The dependence is interpreted by the electron-electron interaction effect rather than the weak localization effect. The coefficient of the logarithmic behavior is found to be suppressed as the thickness decreases, which may be interpreted in terms of the percolation effect.

DOI： 10.3131/jvsj.45.235

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記述言語：英語   掲載種別：研究論文（学術雑誌）

We report the re-entrant superconductivity of mesoscopic aluminum disk in contact with two narrow leads. As the magnetic field increases at 45 mK, superconductor/normal-metal/superconductor (S/N/S) junctions are induced since the critical field Hc of the leads is much larger than that of the disk. In the field region where S/N/S junctions are formed, the samples show the excess resistance larger than the normal-state value. After that, re-entrant superconductivity takes place near Hc of the leads. These results are explained in terms of the competition between the scattering of quasiparticles at the S/N boundaries and Josephson coupling over the thermal length. © 2002 Elsevier Science Ltd. All rights reserved.

DOI： 10.1016/S0022-3697(02)00078-1

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Shubnikov-de Haas (SdH) oscillations have been examined for organic conductors λ-(BETS)2FexGa1-xCl4 (x = 0, 0.45, 0.78, and 1.0). In spite of the variety of the magnetic phases, no significant difference is found in the Fermi surface among them. All the salts have similar cylindrical Fermi surfaces, whose cross-sectional areas correspond to ∼ 15% of the first Brillouin zone. For x ≠ 0, two different SdH frequencies are observed, which are ascribed to the internal magnetic field HJ due to the exchange interaction between the localized Fe moments and the conduction electron spins. The value of HJ for x = 1.0 is estimated to be 32 T and decreases with decreasing x. The large HJ suggests that the field-induced superconductivity for λ-(BETS)2FeCl4 is understood in terms of the Jaccarino-Peter effect.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

その他リンク： https://ci.nii.ac.jp/naid/110009773859

記述言語：英語   掲載種別：研究論文（学術雑誌）

Shubnikov-de Haas (SdH) oscillations have been examined for organic conductors (formula presented) (formula presented) 0.45, 0.78, and 1.0). In spite of the variety of the magnetic phases, no significant difference is found in the Fermi surface among them. All the salts have similar cylindrical Fermi surfaces, whose cross-sectional areas correspond to (formula presented) of the first Brillouin zone. For (formula presented) two different SdH frequencies are observed, which are ascribed to the internal magnetic field (formula presented) due to the exchange interaction between the localized Fe moments and the conduction electron spins. The value of (formula presented) for (formula presented) is estimated to be 32 T and decreases with decreasing x. The large (formula presented) suggests that the field-induced superconductivity for (formula presented) is understood in terms of the Jaccarino-Peter effect. © 2002 The American Physical Society.

DOI： 10.1103/PhysRevB.65.113101

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Measurements of the Shubnikov-de Haas (SdH) and angular-dependent magnetoresistance oscillations were performed to study the Fermi surface for a magnetic-field-induced superconductor λ-(BETS)2FeCl4. We found two SdH oscillations ascribed to the minimum and maximum cross-sectional areas of corrugated cylindrical Fermi surface, which are estimated to be 14% and 17% of the first Brillouin zone, respectively. The mass of the conduction electrons is 4.1 m0, suggesting the enhancement due to many-body effects. Assuming a parabolic energy band, we obtain a Fermi energy of ∼20 meV and an interlayer transfer integral of ∼1 meV.

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Self-organized dots of CdTe and Cd1-xMnxTe (x=0.06) were fabricated on the Zn1-yCdyTe (100) surface by MBE. The dot formation on ZnTe was not different between CdTe and Cd1-xMnxTe but different features appeared with the increase of y. In CdTe dots, the density was decreased continuously with y and the size was increased, in qualitative accordance with the decrease of the lattice mismatch ratio between CdTe and Zn1-yCdyTe. On the other hand, the dot formation of Cd1-xMnxTe dots was little dependent on y; the density was almost constant and the size was increased to only a little extent. In photoluminescence (PL) measurements on capped dots, the energies of the excitonic emission were red-shifted with y in both CdTe and Cd1-xMnxTe dots. The PL spectra from Cd1-xMnxTe quantum dots showed well-defined splitting into two lines at low temperatures less than 10 K and it was found that the Zeeman shift of the two lines was much different. © 2001 Elsevier Science B.V.

DOI： 10.1016/S1386-9477(01)00115-1

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The application of a sufficiently strong magnetic field to a superconductor will, in general, destroy the superconducting state. Two mechanisms are responsible for this. The first is the Zeeman effect, which breaks apart the paired electrons if they are in a spin-singlet (but not a spin-triplet) state. The second is the so-called 'orbital' effect, whereby the vortices penetrate into the supeconductors and the energy gain due to the formation of the paired electrons is lost. For the case of layered, two-dimensional supeconductors, such as the high-Tc copper oxides, the orbital effect is reduced when the applied magnetic field is parallel to the conducting layers. Here we report resistance and manetic torque experiments on single crystals of the quasi-two-dimensional organic conductor λ-(BETS)2FeCl4, where BETS is bis(ethylenedithio)tetraselenafulvalene. We find that for manetic fields applied exactly parallel to the conducting layers of the crystals, superconductivity is induced for fields above 17 T at a temperature of 0.1 K. The resulting phase diagram indicates that the transition temperature increases with magnetic field, that is, the superconducting state is further stabilized with magnetic field.

DOI： 10.1038/35073531

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Superconducting resistive transition in mesoscopic Al ring, disk, and wire samples is reported. In the ring sample, a periodic sharp peak structure, Little-Parks (LP) oscillation, is clearly observed as a function of magnetic field down to 40 mK. The oscillation period of about 56 G agrees with the value estimated from the sample size. The peak structure is also found in both of the disk and the wire samples. The peaks in the disk sample are qualitatively explained in the framework of the linearized Ginzburg-Landau theory, but those in the wire sample are not understood by the present theory. In all the samples, anomalous negative magnetoresistance is observed at low fields, which may be ascribed to normal superconducting junctions at the nodes. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0921-4526(01)00378-7

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

In the last five years, we have investigated quantum phenomena of low-dimensional materials and strongly correlated electron systems at high-magnetic fields under the Center of Excellence Development Program (COE project) at the National Research Institute for Metal. The second stage towards the realization of the solid-state quantum devices and measurement of the quantum properties began in April of this year. NMR spectra have been studied in CeP and various lithium fluoride crystals in anticipation of the crystal lattice quantum computer. The magneto-transport effect on tiny aluminum devices fabricated on semiconductors has been studied, and negative magnetoresistance has clearly been observed. An SPM which can be operated at various temperatures in the presence of high-magnetic fields has been developed to construct a magnetic resonance force microscope. The magnetic field effect on the magnetic recording pattern of an HDD was clearly measured up to 7 T. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0921-4526(01)00384-2

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Magnetoresistance measurements have been performed for the organic conductor κ-(BETS)2FeBr4 to investigate the Fermi surface. Three fundamental Shubnikov-de Haas oscillations (α, β and γ) were observed. The cross-sectional areas corresponding to the α and β oscillations are about 20% and 100% in the first Brillouin zone, respectively. The oscillations can be assigned to the closed orbit and the magnetic breakdown orbit. The effective masses of the conduction electrons are determined to be 5.2m0 for α and 7.9m0 for β. The heavy masses are probably due to the antiferromagnetic fluctuation effect of the Fe spins. The origin of the oscillation γ with very low frequency is not explained by the band calculation. © 2001 Elsevier Science B.V.

DOI： 10.1016/S0921-4526(01)00382-9

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Measurements of the Shubnikov–de Haas (SdH) and angular-dependent magnetoresistance oscillations were performed to study the Fermi surface for a magnetic-field-induced superconductor (formula presented) We found two SdH oscillations ascribed to the minimum and maximum cross-sectional areas of corrugated cylindrical Fermi surface, which are estimated to be (formula presented) and (formula presented) of the first Brillouin zone, respectively. The mass of the conduction electrons is (formula presented) suggesting the enhancement due to many-body effects. Assuming a parabolic energy band, we obtain a Fermi energy of (formula presented) and an interlayer transfer integral of (formula presented) © 2001 The American Physical Society.

DOI： 10.1103/PhysRevB.64.024531

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Magneto-optical studies on self-organized quantum dots (QDs) of Cd1-xMnxTe were reported. Cd1-xMnxTe QDs with Mn composition less than 10% were grown successfully on the ZnTe(1 0 0) surface by atomic layer epitaxy. A typical dot size of 20 nm in diameter and 2 nm in height and density of the order of 1011 cm-2 were confirmed by atomic force microscope (AFM) measurement. In photoluminescence (PL) measurements on capped QDs, the excitonic emission from Cd1-xMnxTe dots was observed but the spectra were composed of two lines with a separation of 20-26 meV at low temperatures. In the dependence on the temperature, the excitation intensity and the magnetic field, the PL line at the lower-energy side exhibited peculiar behaviors, compared to that in the higher-energy side - rapid quenching with an increase of temperature up to 20 K, much smaller Zeeman shift under magnetic fields, and the saturation of the circular polarization at low magnetic fields. These features of the lower-energy line were discussed in relation to the excitonic magnetic polaron in QDs. Preliminary results of time-resolved PL and spatial-resolved PL using the far-field microscope are also shown.

DOI： 10.1016/S0022-0248(00)00051-8

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Self-organized quantum dots (QDs) of Cd1-xMnxTe were successfully grown on the ZnTe(1 0 0) surface by atomic layer epitaxy. Atomic force microscope (AFM) measurement revealed the dot formation in a high density on the surface of 3.5-monolayer-thick Cd1-xMnxTe when the Mn composition x was less than 10%. The typical dot size was 20 nm in diameter and 2 nm in height. The density of dots ranged from 4 × 1010 to 1011 cm-2 for x = 0-10%, but it decreased abruptly when x was more than 10%. In photoluminescence (PL) measurements for capped QDs, excitonic luminescence from QDs was observed at 2.16-2.27 eV depending on the Mn composition. One of the features of PL spectra from QDs containing Mn is that the spectra are composed of two PL lines with a separation of 20-60 meV.

DOI： 10.1016/S0022-0248(00)00067-1

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Photoluminescence (PL) studies of self-organized quantum dots (QDs) of Cd1-xMnxTe under magnetic fields were reported. Cd1-xMnxTe QDs were grown successfully in the composition range of x = 0-10% on the ZnTe (100) surface by MBE. The PL spectra from capped Cd1-xMnxTe QDs were composed of two lines with a separation of about 20 meV at low temperatures. In the dependence on the temperature and magnetic field, the PL line in the lower-energy side exhibited peculiar behaviors, compared to that in the higher-energy side; with increasing temperature, the intensity of the lower-energy line was reduced rapidly and almost disappeared above 20 K, and Zeeman shift under magnetic fields was smaller and the degree of the circular polarization was larger and saturated at low magnetic fields. These features of the lower-energy line were discussed in relation to excitonic magnetic polaron in QDs.

DOI： 10.1016/S0022-2313(99)00415-9

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Self-organized quantum dots (QDs) of Cd1-xMnxTe were grown on the ZnTe(100) surface by atomic layer epitaxy. Atomic force microscope measurement on the surface of a 3.5-ML-thick Cd1-xMnxTe layer revealed dot formation in a high density of the order of 1010-1011 cm-2 when the Mn composition x was less than 10%. The typical dot size was given approximately by 20 nm in diameter and 2 nm in height. In photoluminescence (PL) measurements on the capped QDs, the excitonic emissions from the QDs were observed at 2.16-2.27 eV in the range of Mn composition x = 0%-10%. The PL spectra from Cd1-xMnxTe QDs with x = 0.6%-10.2% consisted of two lines separated by about 20 meV. The dependence of the PL energies on the Mn composition and the Zeeman shift were compared with the calculation. © 2000 American Institute of Physics.

DOI： 10.1063/1.126357

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Self-organized quantum dots (QDs) of CdTe were successfully grown on a ZnTe (100) surface by molecular beam epitaxy. Atomic force microscopy measurements of the uncapped samples revealed the formation of CdTe QDs with typical dot diameters of 20 ± 2 nm and heights of 2.7 ± 0.3 nm when a 3.5 monolayer-thick CdTe was deposited. In the photoluminescence (PL) measurements of the capped QDs, an intensive excitonic luminescence was observed at 4.2 K, the intensity of which was higher than the CdTe/ZnTe single quantum wells (SQWs) by 2-4 orders of magnitude. The temperature dependence of the intensity showed thermal quenching with an activation energy of 100 meV, which was about twice as large as those of SQWs. The PL decay time in QDs exhibited a different temperature dependence from SQWs - a temperature-independent decay time below 20 K. These results are interpreted as features of zero-dimensional confinement of excitons in QDs. © 1999 Publication Board, Japanese Journal of Applied Physics.

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

We report on micro photoluminescence (μ-PL) experiments in CdTe and CdMnTe quantum dots (QDs). PL spectra of the CdTe QDs indicate an ensemble of discrete narrow lines, each of which arises from a single dot emission. High emission efficiency of the present QDs allows the time resolving of the μ-PL signal. Dependence of the PL decay time on the QD size shows the evidence for the quantum size effect of the radiative recombination process. For CdMnTe QDs, it is found that the discrete spectral feature disappears in the μ-PL spectrum, reflecting the fast relaxation kinetics of excitons in the manganese doped QDs. © 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-2313(99)00120-9

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Self-organized quantum dots (QDs) of CdTe were successfully grown on a ZnTe (100) surface by molecular beam epitaxy. Atomic force microscopy measurements of the uncapped samples revealed the formation of CdTe QDs with typical dot diameters of 20 ± 2 nm and heights of 2.7 ± 0.3 nm when a 3.5 monolayer-thick CdTe was deposited. In the photoluminescence (PL) measurements of the capped QDs, an intensive excitonic luminescence was observed at 4.2 K, the intensity of which was higher than the CdTe/ZnTe single quantum wells (SQWs) by 2-4 orders of magnitude. The temperature dependence of the intensity showed thermal quenching with an activation energy of 110 meV, which was about twice as large as those of SQWs. The PL decay time in QDs exhibited a different temperature dependence from SQWs -- a temperature-independent decay time below 20 K. These results are interpreted as features of zero-dimensional confinement of excitons in QDs.

DOI： 10.1143/JJAP.38.2524

CiNii Article

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

The successful growth by molecular beam epitaxy (MBE) of self-organized quantum dots (QDs) of zinc-blende (ZB) MnTe onto CdTe(1 0 0) is reported. Mn and Te fluxes were supplied either simultaneously (conventional MBE) or alternately (atomic layer epitaxy - ALE) onto the surface to form MnTe. Atomic-force microscope measurements for uncapped samples revealed that cone-shaped dots were formed in both of the two growth methods, however with different sizes. The diameter and the height are, respectively, given typically by D = 140 ± 10 nm and h = 70 ± 10 nm in QDs grown by conventional MBE, and by D = 60 + 5 nm and h = 8 + 1 nm in QDs grown by ALE. In photoluminescence (PL) and time-resolved PL measurements, a broad emission band due to the Mn2+ d-d transition was observed at 2.02 eV. Its decay time was found to be of the order of several tens to hundreds of nanoseconds, which is shorter than those from ZB-MnTe films by two or three orders. © 1998 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/s0022-0248(98)80058-4

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記述言語：英語   掲載種別：研究論文（学術雑誌）

The successful growth of self-organized quantum dots (QDs) of CdTe on ZnTe (100) surface by molecular beam epitaxy is reported. Atomic force microscope measurements on the uncapped samples revealed the formation of CdTe QDs with typical dot diameters of 20±2nm and heights of 2.7±0.3nm at 3.5-ML-thick CdTe deposited. The intensity of photoluminescence (PL) from the capped QDs was higher than CdTe/ZnTe single quantum wells (SQWs) by a few orders of magnitude at 4.2 K, and exhibited a thermal quenching with an activation energy of 110 meV, which is about twice as large as those in SQWs. In time-resolved PL measurements, the decay time was almost independent of temperature below 20 K. This is interpreted as due to the zero-dimensional excitonic properties in QDs. © 1998 American Institute of Physics.

DOI： 10.1063/1.122885

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記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

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開催期間： 2018年07月24日 - 2018年07月27日   記述言語：英語   開催地：Vladivostok, Russia  

開催期間： 2018年07月21日 - 2018年07月22日   記述言語：日本語   開催地：静岡県立森林公園森の家  

開催期間： 2018年07月21日 - 2018年07月22日   記述言語：日本語  

開催期間： 2018年03月17日 - 2018年03月20日   記述言語：日本語  

開催期間： 2018年03月17日 - 2018年03月20日   記述言語：日本語  

開催期間： 2018年03月17日 - 2018年03月20日   記述言語：英語  

開催期間： 2018年03月17日 - 2018年03月20日   記述言語：日本語  

開催期間： 2017年12月01日 - 2017年12月03日   記述言語：日本語  

開催期間： 2017年12月01日 - 2017年12月03日   記述言語：日本語  

開催期間： 2017年09月05日 - 2017年09月08日   記述言語：日本語  

開催期間： 2017年09月05日 - 2017年09月08日   記述言語：日本語  

開催期間： 2017年09月05日 - 2017年09月08日   記述言語：日本語  

開催期間： 2017年09月05日 - 2017年09月08日   記述言語：日本語  

開催期間： 2017年09月05日 - 2017年09月08日   記述言語：日本語  

開催期間： 2017年07月29日 - 2017年08月04日   記述言語：英語  

開催期間： 2017年03月14日 - 2017年03月17日   記述言語：日本語  

開催期間： 2017年03月14日 - 2017年03月17日   記述言語：日本語  

開催期間： 2017年03月14日 - 2017年03月16日   記述言語：日本語  

開催期間： 2016年12月03日 - 2016年12月04日   記述言語：日本語  

開催期間： 2016年09月13日 - 2016年09月16日   記述言語：日本語  

開催期間： 2016年09月13日 - 2016年09月16日   記述言語：日本語  

開催期間： 2016年09月13日 - 2016年09月16日   記述言語：日本語  

開催期間： 2016年09月13日 - 2016年09月16日   記述言語：日本語  

開催期間： 2016年07月16日 - 2016年07月18日   記述言語：英語  

開催期間： 2016年07月16日 - 2016年07月18日   記述言語：英語  

開催期間： 2016年07月16日 - 2016年07月18日   記述言語：英語  

開催期間： 2016年07月16日 - 2016年07月18日   記述言語：英語  

開催期間： 2016年03月21日   記述言語：日本語  

開催期間： 2016年03月21日   記述言語：日本語  

開催期間： 2016年03月20日   記述言語：日本語  

開催期間： 2016年03月20日   記述言語：日本語  

開催期間： 2016年01月   記述言語：日本語  

イオンと同じ荷電粒子でありながら光電子で飛行時間型測定が実現しなかったのは、光電子がイオンに比べ質量が微量なため、外乱に妨げられるためとされていた。我々は磁気ボトル方式を採用することにより光電子を効率よく収集して検出器に導くことに成功し、パルスレーザーを励起源としてオシロスコープに飛行時間を表出することにより、仕事関数測定を可能にした。

CiNii Article

開催期間： 2016年01月   記述言語：日本語  

Si(111)上にエピタキシャル成長した等価ドメインをもつ&beta;-FeSi₂薄膜の多重イオン散乱解析を行った。このエピタキシャル成長では６つの等価なドメイン成長が可能で、Si(111)面上のそれらの積層欠陥が軸方向の原子列のランダムな変位を起こし、非チャネリング因子になっていることを、多重イオン散乱によるチャネリングデータの解析から突き止めた。

CiNii Article

開催期間： 2015年12月06日   記述言語：日本語  

開催期間： 2015年11月14日   記述言語：日本語  

開催期間： 2015年09月16日   記述言語：日本語  

開催期間： 2015年09月16日   記述言語：日本語  

開催期間： 2015年09月15日   記述言語：日本語  

開催期間： 2015年09月15日   記述言語：日本語  

開催期間： 2015年08月19日 - 2015年08月26日   記述言語：英語  

開催期間： 2015年08月19日 - 2015年08月26日   記述言語：英語  

開催期間： 2015年08月19日 - 2015年08月26日   記述言語：英語  

開催期間： 2015年08月19日 - 2015年08月26日   記述言語：英語