研究者詳細 - 林　靖彦

論文 - 林　靖彦

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The formation of a (111) texture of the diamond film on Pt/TiO2/SiOx/Si substrate by microwave plasma chemical vapor deposition 査読

Y Hayashi, Y Matsushita, T Soga, M Umeno, T Jimbo

DIAMOND AND RELATED MATERIALS 11 ( 3-6 ) 499 - 503 2002年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Heteroepitaxial diamond films were grown on Pt(111)/Si with a SiQ(x) intermediate layer between them to prevent silicidation by microwave plasma enhanced chemical vapor deposition. We found that adhesion of Pt films could be improved by depositing a TiO2 thin film between Pt and SiOx. During the diamond growth, the change of preferred orientation of the Pt film was observed by X-ray diffraction (XRD) measurements. The films grown on a Pt(111)/SiOx/Si substrate had a (111)-oriented diamond with full-width at half-maximum (FWHM) values of 3-5degrees in XRD rocking curve of diamond(l 11) diffraction. Raman spectroscopy revealed that the FWHM of the diamond peak at 1332.8 cm(-1) was approximately 7-10 cm(-1) over the growth temperature range 700-850 degreesC. All the films contained disordered graphitic carbon components or an amorphous carbon phase. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0925-9635(02)00021-3

その他リンク： http://orcid.org/0000-0002-4113-5548

Deposition of amorphous CNx by d.c. and rf plasma sputtering using a rf radical nitrogen beam source 査読

Y Hayashi, MM Rahman, K Kaneko, T Soga, M Umeno, T Jimbo

DIAMOND AND RELATED MATERIALS 11 ( 3-6 ) 1178 - 1182 2002年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Amorphous CNx thin films were deposited by d.c. and if Ar plasma sputtering combined with a nitrogen if radical beam source which supplies active nitrogen species to the growing film surface. The dependence modifications of the optical and the structural properties on nitrogen incorporation were investigated using ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy, a four-point-probe method and electron energy-loss spectroscopy. For the rf-sputtered films, the optical band gap was found to increase with the increase in the nitrogen content. For the d.c.-sputtered films, the optical gap first decreased to zero at low nitrogen content, and then increased with a further increase in the nitrogen content, C-K energy-loss near-edge structure (ELNES) showed a slight broadening on the lower energy side. The local environment of C and N atoms are almost similar as observed by comparing the C-K and N-K ELNESs. (C) 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0925-9635(02)00013-4

その他リンク： http://orcid.org/0000-0002-4113-5548

Optical properties of trimethylboron and nitrogen codoped amorphous carbon films 査読

Y Hayashi, S Ishikawa, T Soga, T Jimbo, M Adachi, M Umeno

INTERNATIONAL JOURNAL OF MODERN PHYSICS B 16 ( 6-7 ) 1096 - 1100 2002年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：WORLD SCIENTIFIC PUBL CO PTE LTD

We report on the efficient photoluminescence (PL) and optical properties of hydrogenated amorphous carbon thin films codoped with nitrogen and trimethylboron (TMB) grown by rf plasma-enhanced chemical vapor deposition at room temperature. The study clearly shows the observation of discrete PL emission peaks. The PL intensity of the film deposited with 20 seem TMB is more than 10(3) times than that of the film deposited without TMB, The change of optical bandgap and PL emission energy with TMB flow rate are discussed based on sp(3) and sp(2) C networks. Angular dependence of the PL spectra revealed that the origin of multiple sharp peaks is due to Fabry-Perot cavity interference effect.

DOI： 10.1142/S0217979202010920

その他リンク： http://orcid.org/0000-0002-4113-5548

Fabrication of a TiO2-based solid-state cell with an organic polymer as a sensitizer 査読

PM Sirimanne, T Soga, Y Hayashi, T Jimbo

JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 41 ( 2A ) L147 - L148 2002年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：INST PURE APPLIED PHYSICS

Poly [2-methoxy-5(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) was used as a sensitizer in a photovoltaic cell. The cell was fabricated by depositing MEH-PPV in between wide band gap n-TiO, and p-Cul films. A maximum open circuit voltage of 390 mV and short circuit current of 0.29 mA.cm(-2) were observed for the TiO2[MEH-PPV]CuI cell, under AM 1.5 conditions (100mW.cm(-2) of white light illumination).

DOI： 10.1143/JJAP.41.L147

その他リンク： http://orcid.org/0000-0002-4113-5548

Photovoltaic characteristics of boron doped amorphous carbon films deposited by pulsed laser deposition using graphite target 査読

XM Tian, M Rusop, Y Hayashi, T Soga, T Jimbo, M Umeno

MOLECULAR CRYSTALS AND LIQUID CRYSTALS 386 ( PART 1 ) 73 - 80 2002年

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：TAYLOR & FRANCIS LTD

This paper reports on the successful deposition of boron (B) doped carbon films (p-C(B)) and fabrication of p-C(B)/n-Si solar cells by pulsed laser deposition (PLD) technique at room temperature using graphite target. The B content in the film was determined by X-ray photoelectron spectroscopy (XPS) to be in the range of 0.2-1.7 atomic percentage. The photovoltaic values of the device, a maximum open circuit voltage, V-oc =250 mV and short circuit current density, J sc =2.113 mA/cm(2) were obtained, when exposed to AM 1.5 illumination (100 mW/cm(2) , 25degreesC). The maximum energy conversion efficiency was found tentatively to be about, eta=0.2%, together with the fill factor, FF=45%. In this paper, the dependence of the B content on electrical and optical properties of the p-C(B) films and the photovoltaic characteristic of the p-C(B)/n-Si structure photovoltaic solar cells are discussed.

DOI： 10.1080/10587250290113222

その他リンク： http://orcid.org/0000-0002-4113-5548

Preparation of carbon micro-coils involving the decomposition of hydrocarbons using PACT (plasma and catalyst technology) reactor 査読

Kuzuya C, Hayashi Y, Motojima S

Carbon 40 ( 7 ) 1071 - 1077 2002年

Origin of yellow luminescence in n-GaN induced by high-energy 7 MeV electron irradiation 査読

Y Hayashi, T Soga, M Umeno, T Jimbo

PHYSICA B-CONDENSED MATTER 304 ( 1-4 ) 12 - 17 2001年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The yellow luminescence band in high-energy 7 MeV electron-irradiated n-GaN is investigated as a function of electron irradiation dose. Both the yellow-band intensity and the near-bandedge photoluminescence (PL) intensity decrease continually with increasing electron irradiation dose. The decrease rate for the yellow-band intensity is less compared to the near-bandedge intensity; however, it is found that the ratio of the yellow-band intensity to the near-bandedge PL intensity increases with increasing electron irradiation dose. To interpret this phenomenon. a theoretical model is developed for the yellow-to-near-bandedge intensity ratio based on rate equations. The proposed model is in good agreement with the experimental observation. The electron spin resonance (ESR) and light-induced ESR (LESR) spectra are measured to investigate deep defects induced by electron irradiation. The ESR signal intensity at g = 1.9451 decreases with increasing electron irradiation dose and increases with the light-induced time. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(01)00499-9

その他リンク： http://orcid.org/0000-0002-4113-5548

Determination of optical properties of nitrogen-doped hydrogenated amorphous carbon films by spectroscopic ellipsometry 査読

Y Hayashi, G Yu, MM Rahman, KM Krishna, T Soga, T Jimbo, M Umeno

APPLIED PHYSICS LETTERS 78 ( 25 ) 3962 - 3964 2001年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Nitrogen-doped hydrogenated amorphous carbon films have been deposited on silicon substrates by radio-frequency plasma-enhanced chemical vapor deposition using different N-2/CH4 gas ratios from 0 to 3. The real and imaginary parts, n and k, of the complex index of refraction of these films-have been determined for wavelengths between 300 and 830 nm by spectroscopic ellipsometry. Excellent agreement has been found between measured and modeled spectra, in which an empirical dielectric function based on classical Lorentz oscillator and Tauc joint density of states, and a linear void distribution along the thickness of the films have been assumed. Decrease in the optical energy gap and increase in the extinction coefficient, k, with increase in nitrogen concentration:have been observed. Refractive index, n, increases rapidly with increase in nitrogen concentration up to 6.8 at. % (similar to7.0 at. %) and then increases slowly with further increase in nitrogen concentration. For all the samples, n is found to be highest: at the film-substrate interface which gradually decreases towards the film surface. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1374501

その他リンク： http://orcid.org/0000-0002-4113-5548

Spectroscopic properties of nitrogen doped hydrogenated amorphous carbon films grown by radio frequency plasma-enhanced chemical vapor deposition 査読

Y Hayashi, G Yu, MM Rahman, KM Krishna, T Soga, T Jimbo, M Umeno

JOURNAL OF APPLIED PHYSICS 89 ( 12 ) 7924 - 7931 2001年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

Nitrogen doped hydrogenated amorphous carbon thin films have been deposited by rf plasma-enhanced chemical vapor deposition using CH4 as the source of carbon and with different nitrogen flow rates (N-2/CH4 gas ratios between 0 and 3), at 300 K. The dependence modifications of the optical and the structural properties on nitrogen incorporation were investigated using different spectroscopic techniques, such as, Raman spectroscopy, Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible (UV-VIS) spectroscopy, electron spin resonance (ESR), photoluminescence (PL) and spectroscopic ellipsometry (SE). Raman spectroscopy and IR absorption reveal an increase in sp(2)-bonded carbon or a change in sp(2) domain size with increasing nitrogen flow rate. It is found that the configuration of nitrogen atoms incorporated into an amorphous carbon network gradually changes from nitrogen atoms surrounded by three (sigma bonded) to two (pi bonded) neighboring carbons with increasing nitrogen flow rate. Tauc optical gap is reduced from 2.6 to 2.0 eV, and the ESR spin density and the peak-to-peak linewidth increase sharply with increasing nitrogen flow rate. Excellent agreement has been found between the measured SE data and modeled spectra, in which an empirical dielectric function of amorphous materials and a linear void distribution along the thickness have been assumed. The influence of nitrogen on the electronic density of states is explained based on the optical properties measured by UV-VIS and PL including nitrogen lone pair band. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1371268

その他リンク： http://orcid.org/0000-0002-4113-5548

Growth and characterization of GaAs epitaxial layers on Si/porous Si/Si substrate by chemical beam epitaxy 査読

S Saravanan, Y Hayashi, T Soga, T Jimbo, M Umeno, N Sato, T Yonehara

JOURNAL OF APPLIED PHYSICS 89 ( 9 ) 5215 - 5218 2001年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The initial growth of GaAs films on a Si/porous Si/Si (SPS) substrate has been investigated using reflection high-energy electron diffraction. The morphology and the thickness have been examined by a Nomarski optical microscope and scanning electron microscope, respectively. The results of the low temperature photoluminescence studies have shown that a significant reduction in the residual thermal tensile stress can be achieved with reduced growth temperature. The 77 K photoluminescence spectra for GaAs/Si show a strain-induced splitting between the heavy and light hole valence bands which corresponds to a biaxial tensile stress of 2.45 kbar acting on the GaAs layer where the same for GaAs/SPS grown at 450 degreesC is 1.69 kbar. The results have shown that a SPS substrate with the combination of low temperature growth is a promising candidate for obtaining GaAs films with low stress. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1362339

その他リンク： http://orcid.org/0000-0002-4113-5548

Optical and structural properties of nitrogen doped amorphous carbon films grown by rf plasma-enhanced CVD 査読

Y Hayashi, KM Krishna, H Ebisu, T Soga, M Umeno, T Jimbo

DIAMOND AND RELATED MATERIALS 10 ( 3-7 ) 1002 - 1006 2001年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE SA

Nitrogen doped hydrogenated amorphous diamond-like carbon thin films have been synthesized by radio frequency (rf) plasma-enhanced chemical vapor deposition (PECVD) using CH4 as the source of carbon and with different N-2 flow rates (N-2/CH4 gas ratios between O and 3), at 300 K. The dependence of optical and structural properties/modifications on the nitrogen incorporation was investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV-visible spectroscopy and electron spin resonance (ESR) measurements. It was found that the configuration of nitrogen atoms incorporated into an amorphous carbon network gradually changed from nitrogen atoms surrounded by three (cr bonding) to two (pi bonding) neighbor carbons with increasing nitrogen flow rate. The Tauc optical gap was reduced from 2.6 to 2.0 eV with increasing nitrogen flow rate. The ESR spin density and the peak-to-peak linewidth increased drastically with increasing nitrogen flow rate. Significant structural modifications were observed above a gas ratio N-2/CH4 of 1. (C) 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0925-9635(00)00566-5

Low density of defect states in hydrogenated amorphous carbon thin films grown by plasma-enhanced chemical vapor deposition 査読

KM Krishna, H Ebisu, K Hagimoto, Y Hayashi, T Soga, T Jimbo, M Umeno

APPLIED PHYSICS LETTERS 78 ( 3 ) 294 - 296 2001年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER INST PHYSICS

The density of electronic defect states in most forms of amorphous carbon deposited at room temperature is found so far to be very high (10(18)-10(22) spins cm(-3)). In this letter, we demonstrate that the radio-frequency plasma-enhanced chemical vapor deposited hydrogenated amorphous carbon (a-C:H) thin film exhibits the lowest spin density of the order of 10(16) cm(-3), investigated by using electron spin resonance (ESR) spectroscopy, a very promising reproducible result comparable with high-quality a-Si:H. In addition, the optical gap of a-C:H has been tailored between a wide range, 1.8-3.1 eV. The ESR spectra of all the films reveal a single Lorentzian line whose linewidth DeltaH(pp) varies strongly with the optical gap. Also, there is a strong dependence of spin density on the optical gap, and we show that this dependency is a direct result of structural changes due to sp(3)/sp(2) carbon bonding network. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1335548

その他リンク： http://orcid.org/0000-0002-4113-5548

Low-temperature growth of GaAs polycrystalline films on glass substrates for space solar cell application 査読

M Imaizumi, M Adachi, Y Fujii, Y Hayashi, T Soga, T Jimbo, M Umeno

JOURNAL OF CRYSTAL GROWTH 221 ( 1-4 ) 688 - 692 2000年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

Preliminary results of growth of gallium arsenide poly-crystalline films on quartz glass substrate are reported. The films were grown using chemical beam epitaxy apparatus at substrate temperatures varied between 400 degreesC and 500 degreesC, The growth of polycrystalline GaAs has been realized at temperatures above 450 degreesC. X-ray diffraction (XRD) and Raman scattering show that the film grown at 500 degreesC has good crystallinity. Also, XRD and atomic force microscopy (AFM) have confirmed preferential columnar growth toward the (1 1 1) direction. Furthermore, AFM image reveals a naturally textured surface with a grain size of 0.5 - 1.0 mum. Optical energy gap, deduced from absorption coefficient of the film, is about 1.4eV. Hall measurement indicates electrical properties such as resistivity, carrier concentration, and carrier mobility of similar to 10(3) Omega cm, similar to 10(15) cm(-3), and less than a few cm(2)/Vs, respectively. The results reveal future prospects of the film for application in space solar cells. (C) 2000 Elsevier Science B.V, All rights reserved.

DOI： 10.1016/S0022-0248(00)00801-0

その他リンク： http://orcid.org/0000-0002-4113-5548

Effect of radio frequency power on the properties of hydrogenated amorphous carbon films grown by radio frequency plasma-enhanced chemical vapor deposition 査読

Y Hayashi, K Hagimoto, H Ebisu, MK Kalaga, T Soga, M Umeno, T Jimbo

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 39 ( 7A ) 4088 - 4093 2000年7月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN J APPLIED PHYSICS

We have studied the influence of radio frequency (RF) power on material properties of hydrogenated amorphous carbon (a-C:H) films prepared by RF plasma-enhanced chemical vapor deposition (CVD). The RF power has a significant impact on film properties such as electron spin resonance (ESR) spin density, the optical band gap, chemical bonding and photoluminescence (PL). Raman spectroscopy, infrared (IR) absorption and ESR measurements reveal that the residual defect density (ESR spin density) increases with increasing RF power due to the increase of sp(2) C-H-x components. We obtained an ESR spin density as small as 8 x 10(16) spins/cm(3) at a low RF power, which is comparable to that of high-quality amorphous silicon films. Plasma optical emission spectroscopy indicates that the intensity ratio (IC-H/I-H) between hydrogen peaks (I-H) and hydrocarbon peaks (IC-H) significantly decreases with increasing RF power. The optical band gap, obtained from UV-visible spectroscopy, varies from 3.0 to 1.9 eV with increasing RF power. The broad emission band centered around 2.4 eV was observed in the PL spectra of the samples deposited at lower RF powers. We found a 0.5-0.3 eV Stokes shift by comparing the PL emission and the absorption coefficient spectrum from the films deposited at less than or equal to 100W RF powers, whereas, we failed to observe a clear Stokes shift from the films deposited at >100W RF powers. A weak correlation between the PL peak and the optical band gap is demonstrated.

DOI： 10.1143/JJAP.39.4088

その他リンク： http://orcid.org/0000-0002-4113-5548

Analysis of hole transport in cubic phase of p-type GaN by relaxation time approximation 査読

Y Hayashi, T Soga, M Umeno, T Jimbo

PHYSICA B 272 ( 1-4 ) 256 - 259 1999年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ELSEVIER SCIENCE BV

The theoretical hole transport characteristics of the cubic phase of p-type GaN, that takes the Hall coefficient anisotropy factor of the energy surface for heavy- and light-hole bands into consideration, are investigated over a wide range of temperature using the "relaxation time approximation". The calculations show that the dominant lattice scattering mechanism for holes is the acoustic deformation potential. We show that Hall factors are very important when me attempt to compare the calculated drift mobility with measured Hall ones. (C) 1999 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0921-4526(99)00280-X

その他リンク： http://orcid.org/0000-0002-4113-5548

Theoretical studies on hole transport and the effective hall factor in cubic phase of p-type GaN 査読

Y Hayashi, K Watanabe, T Jimbo, M Umeno

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 ( 2A ) 622 - 630 1999年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN J APPLIED PHYSICS

The theoretical hole transport characteristics (Hall and drift mobilities, and effective Hall factor) are reported for the cubic phase of p-type GaN. These characteristics are calculated using the "relaxation time approximation" as a function of temperature. The calculations show that the dominant lattice scattering mechanism for heres is the acoustic deformation potential. In the calculation of the scattering rate for ionized impurity mechanism the activation energy of 120 or 250 meV is used at different compensation ratios of given acceptor concentrations. Comparing the scattering lime in these activation energies, it is found that the activation energy difference is negligible at high compensation ratios. We determined the anisotropy factors separately, due to the anisotropy of the energy surface for heavy- and light-hole bands, and these parameters are taken into account in the Hall factor calculations. The Hall factors are very important when we attempt to compare the calculated drift mobility with measured Hall ones. The theoretical Hall mobilities at total hole concentrations of 3.5 x 10(15) and 3.5 x 10(16) cm(-3) are about 312 and 225 cm(2)V(-1)s(-1), respectively, with the activation energy of 120 mt V and the compensation ratio of 0.5 at 300 K. It is found that Hall mobilities are strongly affected by the compensation ratios. The obtained effective Hall factor in the cubic phase of GaN is in the range of 1.4 (T = 120 K) to 1.8 (T = 400 K).

DOI： 10.1143/JJAP.38.622

その他リンク： http://orcid.org/0000-0002-4113-5548

Thermal stress relaxation in GaAs layer on new thin Si layer over porous Si substrate grown by metalorganic chemical vapor deposition 査読

Y Hayashi, Y Agata, T Soga, T Jimbo, M Umeno, N Sato, T Yonehara

JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 37 ( 11B ) L1354 - L1357 1998年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPAN J APPLIED PHYSICS

We have proposed and introduced a thin Si layer over porous Si (SPS) substrate instead of the conventionally used Si substrate to overcome the residual thermal stress in GaAs layer on Si substrate (GaAs/Si). From the results of X-ray diffraction, low-temperature photoluminescence and Raman scattering, it was found that a significant reduction of the residual thermal tensile stress has been achieved. Our data clearly show that the SPS substrate is a promising substrate for overcoming the problems in GaAs/Si.

DOI： 10.1143/jjap.37.L1354

その他リンク： http://orcid.org/0000-0002-4113-5548

Micro-Raman scattering study of internal strain relaxation in post-growth patterned GaN film grown on sapphire substrate 査読

Y Hayashi, H Ishikawa, T Egawa, T Soga, T Jimbo, M Umeno

BLUE LASER AND LIGHT EMITTING DIODES II 628 - 631 1998年

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）出版者・発行元：OHMSHA LTD

The internal strain in n-type GaN epilayer is investigated as a. function of post-patterned square area by spatially resolved Micro-Raman, scattering measurements. The relationship between the post-patterned area and the internal residual strain. distribution have been obtained. Results demonstrate a, drastic, strain relaxation in the patterned area. smaller than 40 mu m square. The spectral line shape of the LO-phonon-plasmon coupled (LPPC) mode shows little variation with the, internal strain.

Hydrogen absorbing and desorbing properties of Nd-Fe-B and Nd-Co-B amorphous alloys 査読

Tanaka K, Hayashi Y, Kimura M, Yamada M

Journal of Alloys and Compounds 253-254 101 - 105 1997年

ROOM-TEMPERATURE CW OPERATION OF SQW LASERS ON SI GROWN WITH ALGAAS/ALGAP INTERMEDIATE LAYERS BY MOCVD 査読

T EGAWA, Y HAYASHI, T GEORGE, T SOGA, T JIMBO, M UMENO

MATERIALS FOR OPTICAL INFORMATION PROCESSING 228 189 - 194 1992年

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