bluuebunny/crossref_metadata_2025 huggingface dataset:
Internal Friction near the Orthorhombic-to-Tetragonal Phase Transition in YBa2Cu3O7-x at 80–200 kHz
Authors: Ozawa Masakuni , Masahiko Inagaki Masahiko Inagaki , Suguru Suzuki Suguru Suzuki
Published: October 2002

The internal friction and compliance of YBa2Cu3O7-
x

are measured at temperatures from 300 to 1050K using a LiNbO3 composite oscillator technique. An anelastic relaxation due to oxygen movement at 80–200 kHz is observed to be associated with the orthorhombic-to-tetragonal (O-T) phase transition in YBa2Cu3O7-
x

at 850–900 K. By careful fitting for the measured internal friction against temperature, we provide data on the relaxation time and peak temperature in the highest frequency region for a linear Arrhenius plot that extends over 7 orders of magnitude.
Highly Oriented Crystalline Carbon Thin Films Obtained by DC Magnetron Sputtering with a Hot Filament
Authors: Onuma Yoshiharu , Kawai Yoshifumi , Masato Nakao Masato Nakao , Kiichi Kamimura Kiichi Kamimura
Published: October 2002

Highly orientated crystalline carbon thin films were prepared easily at relatively low substrate temperatures using a DC magnetron sputtering system with a hot filament. The crystal structure of the carbon films was investigated by X-ray diffraction and RHEED analysis, and FE-SEM. X-ray diffraction analysis of the films prepared at substrate temperatures from 600° C to 700° C and with the filament temperature up to 2000° C revealed very strong diffraction peaks at 2θ=40.22 degrees corresponding to chaoite (220) which are identical to that of carbyne, one of the carbon allotropes. FE-SEM images showed that a great number of microcrystallites of about 60 nm diameter exist on the surface of the film. RHEED patterns showed a <110> preferred orientation which coincided with the X-ray results.
Study of the Surface and Structural Changes of YBa2Cu3O7-δ Thin Films Induced by Low Energy O + Ions
Authors: Govind Pindoria Govind Pindoria , Kenichi Kawaguchi Kenichi Kawaguchi , Furen Wang Furen Wang , Madoka Nishiyama Madoka Nishiyama , Tadataka Morishita Tadataka Morishita
Published: October 2002

The interaction of a low energy O+ ion beam on cuprate oxide, superconducting thin film surfaces was investigated in Ultra High Vacuum. Following the process by Reflection High Energy Electron Diffraction and Rutherford Backscattering and Ion Channeling we found that the O+ ion beam can change the surface structure, forming a different compound, and disordering the films, down to a depth of 300 Å. Using an Atomic Force Microscope we found that this process smoothes the surface of the films, with a rate that was found to be an exponential function of the ion energy, with a threshold energy of 50 eV.
Substrate Orientation Dependence of Optical Properties of GaP/AlP Short-Period Superlattices
Authors: Doi Kenji , Asahi Hajime , Kim Joon Hong , Kumiko Asami Kumiko Asami , Shun-ichi Gonda Shun-ichi Gonda
Published: October 2002

GaP/AlP short-period superlattices (SLs) are grown on GaP substrates by gas-source molecular beam epitaxy. Strong photoluminescence (PL) emission is observed at 4.2 K from SLs grown on (100) substrates, while those for SLs grown on (411)A, B and (311)A, B, and (111)A substrates are about two orders of magnitude and four orders of magnitude weaker, respectively. PL intensities observed for the GaP layers grown on GaP substrates show weak substrate orientation dependence. The results indicate that a pseudo-direct band gap is formed due to the zone folding and band mixing effect for SLs grown on (100) substrates, while the SLs grown on (111)A substrates remain indirect because the X-point is not folded to the Γ- point for [111] direction.
Study of a Length Coefficient for an Extended Drift-Diffusion Model for Metal-Oxide-Semiconductor (MOS) Device Simulation
Authors: Ken-ichiro Sonoda Ken-ichiro Sonoda , Koji Kanno Koji Kanno , Kenji Taniguchi Kenji Taniguchi , Chihiro Hamaguchi Chihiro Hamaguchi
Published: October 2002

A length coefficient for an extended/augmented drift-diffusion model for device simulation was extracted under an exponentially increasing electric field using a multi-valley-band Monte Carlo simulator. The length coefficient increases with electric field and tends to saturate at 0.026 µm, which is half of the previously reported value [Appl. Phys. Lett. 52 (1988) 141]. It was also shown that the coefficient is independent of the low-field mobility.
Fabrication of REBa2Cu3Ox (RE=Y, Nd) Films on Yttria-Stabilized Zirconia by Liquid Phase Epitaxial Method with Ba–Cu–O–F Flux
Authors: Niiori Yusuke , Yamada Yasuji , Yutaka Yoshida Yutaka Yoshida , Izumi Hirabayashi Izumi Hirabayashi
Published: October 2002

We have fabricated thick REBa2Cu3O

x

(RE=Y, Nd) films on yttria-stabilized zirconia (YSZ) substrates by a liquid phase epitaxial (LPE) method. In order to promote LPE growth, we coated the substrates with an about 150-nm-thick RE123 seed layer of the same composition as RE123 for LPE growth by pulsed laser deposition. Lowering of the LPE growth temperature using a novel Ba–Cu–O–F flux results in suppression of the reaction between the RE123 seed layer and YSZ substrate and makes LPE growth of RE123 on YSZ substrates possible. The LPE-grown films were highly c-axis oriented and showed excellent in-plane epitaxial alignment. The crystallinity of LPE-grown RE123 is better than that of predeposited thin seed layers of RE123, based on the results of X-ray diffraction analysis.
Accurate Pulse Shaping of Femtosecond Lasers Using Programmable Phase-Only Modulator
Authors: Takasago Kazuya , Sakai Makoto Takekawa
Published: October 2002

Accurate pulse shaping of femtosecond optical pulses is obtained using a 128-pixel liquid crystal spatial light modulator, which manipulates the spectral phase of the optical frequency components in a Fourier-transformed plane. The spectral phase shifts produced by the modulator can be programmed using a simulated annealing optimization code so as to obtain the desired pulse shapes. Significant improvement in the pulse shaping accuracy is achieved by increasing the number of gray levels in the spectral phase mask to 128. Several examples of pulse shaping operation, including high-repetition-rate pulse trains and asymmetric pulse trains, are described.
Super-Twisted-Nematic Liquid Crystal Displays with Multi-Domain Structures
Authors: Li Jianlin , Lee Eung Sang , Hema Vithana Hema Vithana , Philip J. Bos Philip J. Bos
Published: October 2002

We have investigated the improvement of viewing characteristics super-twisted-nematic (STN) displays with multi-domain structures. An unconventional two-domain structure was found to present the best horizontal viewing angle for a STN liquid crystal display. The viewing characteristics of this STN-LCD are compared to those of STN-LCDs using other possible two-domain structures. The advantages and disadvantages of using four-domain structures for STN-LCDs are also presented and discussed.
Indentation Creep of Nitrogen-Containing Carbon Films
Authors: Tanaka Daisuke , Ohshio Shigeo , Jun-ichi Nishino Jun-ichi Nishino , Hidetoshi Saitoh Hidetoshi Saitoh
Published: October 2002

An Indentation creep test has been used to investigate the micro-mechanical properties of nitrogen-containing carbon films. The time-dependent indentation depth of the nitrogen containing carbon films indicates a monotonic increase at the initial stage of creep procedure and remains constant. Using results of the slope of the time-displacement relation at the initial stage of creep procedure, the strain rate sensitivity exponent m and the k value which is equivalent to viscosity are obtained. The m and k values rapidly decrease with increasing deposition temperature, although the nano-indenter hardness test cannot be used to clarify differences in the mechanical properties of the deposited films. We present results that indicate that the nano-indentation creep technique enables clarification of the micro-mechanical properties of nitrogen-containing carbon films.
Voltage- and Polarity-Tunable Multicolor Organic Electroluminescent Devices
Authors: Hamaguchi Maki , Fujii Akihiko , Yutaka Ohmori Yutaka Ohmori , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Electroluminescent (EL) properties of organic EL devices with a three-layer structure of tris(8-hydroxyquinoline aluminum) (Alq)-doped poly(2,5-dinonyloxy- p-phenylenevinylene) (NOPPV)/an aromatic diamine derivative/ poly(9,9-dihexylfluorene) (PDHF) have been studied. Their electroluminescence was blue for negative voltage on the PDHF side electrode, and varied from orange dominated by the emission from NO-PPV to green dominated by the emission from Alq as the positive voltage on the PDHF side electrode was increased. The mechanism of the multicolor emission is discussed in terms of an energy band diagram of the devices.
A Drying Method Using Naphthalene for Flexible Microgripper Fabrication
Authors: Takeshi Irita Takeshi Irita , Yoshihiko Suzuki Yoshihiko Suzuki
Published: October 2002

A new technique for the microfabrication of a flexible microgripper is presented. In order to avoid sticking between the microgripper fingers due to capillary force, a drying method using naphthalene as a drying solvent (the naphthalene drying method) is proposed and demonstrated. Using this method, a new type of flexible microgripper was successfully fabricated without any sticking between the fingers. The advantages of the naphthalene drying method include simplicity, compatibility with atmospheric pressure, and suitability to batch fabrication.
Determination of the Kerr Coefficient Using the Reflection Technique for Measuring the Pockels Coefficient of a Poled Polymer Film
Authors: Lee Myung-Hyun , Lee Hyung-Jong , Han Seon Gyu , Hye-Young Kim Hye-Young Kim , Yong Hyub Won Yong Hyub Won
Published: October 2002

A simple reflection method proposed by Teng and Man for the measurement of the Pockels coefficient of a poled polymer film has been expanded to measure the Kerr coefficient. Basic equations for estimating the Pockels and Kerr coefficients have been presented. The method has been demonstrated by measuring values not only of the Pockels coefficient (r
333) but also the Kerr coefficient (p
3333) of a 4-dimethylamino-4'-nitro-stilbene (DANS)-side chain poled polymer.
Photoluminescence and Raman Scattering of Electrochemically Deposited CdS Films
Authors: Shirai Katsunori , Ichimura Fumitaka Goto
Published: October 2002

CdS films were electrochemically deposited from acidic solutions containing CdSO4 and Na2S2O3. Photoluminescence spectra of these films were measured using the 325 nm line of a He–Cd laser as the light source at 77 K. For the films annealed at 300° C, we observed overlapping peaks at 488 and 502 nm. The peak at 488 nm was assigned to the band-edge emission of CdS. The peak at 502 nm was thought to be due to point defects generated by annealing. As the annealing temperature was raised, the band-edge emission became weaker and the luminescence due to the point defects shifted to longer wavelengths. These results were compared with the results of Raman scattering.
ZnSe–Zn0.78Cd0.22Se Multi-Superlattice Structure for Effective Optical Pumping and Multicolor Emission
Authors: Guan Z. P. , Ullrich B. , Q.-B. Zheng Q.-B. Zheng , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

A ZnSe–Zn0.78Cd0.22Se multi-superlattice consisting of superlattices with differing well widths (2, 3.8, and 8.2 nm) was investigated. It was found that this structure is highly suitable for effective optical pumping which might provide new opportunities in multicolor emission and band structure engineering. The features of the multi-superlattice were compared with that of a ZnSe–ZnCdSe single superlattice.
ac Field-Induced Localization of an Electron in a Double-Well Quantum Structure
Authors: Tsukada Noriaki , Gotoda Mitsunobu , Isu Toshiro , Nunoshita Masahiro , Nishino Taneo
Published: October 2002

We investigate the time-dependent Schrödinger equation for a coupling between two levels in a double-well quantum structure perturbed by a dc bias and an ac field. Almost complete localization of an electron is achieved for appropriate values of dc and ac field parameters. It is also shown that semi-infinite ac pulses can be used to localize an electron in one of the wells. General conditions required to localize the electron in one of the wells are also given based on an analytical treatment.
Fabrication and Characterization of NdBaCuO-Josephson Junctions on MgO-Substrates Damaged by a Focused Ion Beam
Authors: Ishimaru Yoshihiro , Mizuno Yuuji , Katsumi Suzuki Katsumi Suzuki , Youichi Enomoto Youichi Enomoto
Published: October 2002

We have fabricated a NdBa2Cu3O7 Josephson junction using a narrow-focused Ga-ion beam to damage MgO(100) substrates prior to film deposition. NdBa2Cu3O7 films with smooth surface morphology and without particulates have been deposited by RF magnetron sputtering under rather low oxygen partial pressures. I
c values at 4.2 K of several junctions with the same fabricating conditions vary from several µA to several mA. The junctions with higher I
c exhibit flux-flow type I-V curves and Fraunhofer-like diffraction patterns of I
c under magnetic field. The junctions with lower I
c show RSJ type I-V curves and SQUID-like diffraction patterns of I
c under magnetic field.
Fabrication of InGaAs Vertical-Cavity Surface-Emitting Laser by Molecular Beam Epitaxy and Its Room-Temperature Operation on (411)A GaAs Substrates
Authors: Hanamaki Yoshihiko , Watanuki Yoshiyuki , Akiyama Hidefumi , Takeuchi Tetsuya , Ogasawara Nagaatsu , Yasuhiro Shiraki Yasuhiro Shiraki
Published: October 2002

We investigated the optimum molecular beam epitaxy (MBE) growth conditions for fabrication of a high-reflectivity distributed Bragg reflector (DBR) on (411)A GaAs substrates with extremely flat heterointerfaces. A high-reflectivity DBR mirror consisting of AlAs/GaAs was successfully fabricated under the investigated optimum conditions of growth temperature of 580°C with V/III ( As4/Ga) ratio of ∼8. Using this high-reflectivity DBR mirror, we succeeded for the first time in the optically pumped pulse operation of InGaAs vertical-cavity surface-emitting lasers (VCSELs) at room temperature on (411)A GaAs substrates with a threshold excitation power density of 11 MW/cm2.
Smoothing of Spiking Output in Cr,Tm:YAG Lasers using a Germanium Plate
Authors: Yoichi Kemmochi Yoichi Kemmochi , Takanobu Yamamoto Takanobu Yamamoto , Fumio Matsuzaka Fumio Matsuzaka
Published: October 2002

Spiking laser oscillation, which is often observed in solid-state lasers, in a flashlamp-pumped Cr,Tm:YAG laser was smoothed by insertion of a Ge crystalline plate in the laser cavity as a nonlinear optical limiting element. Although the laser efficiency was reduced more with the use of this Ge plate than with SHG crystals, Ge is expected to be used for low-cost and field-use systems because of its robustness.
Surface Modification of Niobium (Nb) by Atomic Force Microscope (AFM) Nano-Oxidation Process
Authors: Shirakashi Jun-ichi , Ishii Masami , Matsumoto Kazuhiko , Miura Naruhisa , Konagai Makoto
Published: October 2002

Nanometer-scale surface modification of niobium (Nb) thin films deposited on SiO2/Si substrates was investigated by means of the atomic force microscope (AFM) nano-oxidation process for the first time. The modified structures were fabricated by applying negative bias voltages to the metal-coated conductive cantilever in air. The size of the modified structures was well controlled by changing the scanning speed of the cantilever and the applied negative bias voltage. By changing the negative bias voltage from 7 V to 20 V, the size of the modified structures was controlled, ranging from 18 nm to 93 nm in width and 0.5 nm to 5 nm in height. Through Auger electron spectroscopy (AES) analysis, it is revealed that the modified structure consists of Nb and a large amount of oxygen (O), suggesting the formation of Nb oxide.
Pressure Dependence of Negative Hydrogen Ion Production in a Cesium Seeded Tandem Volume Source
Authors: Osamu Fukumasa Osamu Fukumasa , Eiji Niitani Eiji Niitani
Published: October 2002

Effects of cesium vapor injection on H- production in a tandem volume source are studied numerically as a function of plasma parameters. Model calculation is performed by solving a set of particle balance equations for steady-state hydrogen discharge plasmas. Here, the results with a focus on gas pressure and electron temperature dependences of H- volume production are presented and discussed. Considering H- surface production caused by both H atoms and positive hydrogen ions, enhancement of H- production and pressure dependence of H- production observed experimentally are qualitatively well reproduced in the model. For enhancement of H- production, however, so-called electron cooling is not very effective if plasma parameters are initially optimized with the use of a magnetic filter.
Solid Surface Density Determination Using the Glancing-Takeoff X-Ray Fluorescence Method
Authors: Kouichi Tsuji Kouichi Tsuji , Kazuaki Wagatsuma Kazuaki Wagatsuma
Published: October 2002

This paper proposes a method to determine both the density of a sample's surface and the zero angle. We accomplish this by analyzing the relative peak angles in the takeoff-angle dependent curves of fluorescent X-rays from the ultrathin film. The merit of this method is that the density of a solid surface can be determined without knowing the absolute takeoff angle. We applied this method to a Ni film, and obtained a density of 7.37 g/cm3.
Analysis of Misoriented Crystal Structure by Ion Channeling Observed Using Ion-Induced Secondary Electrons
Authors: Kudo Hiroshi , Sakamoto Akihiko , Yamamoto Shunya , Aoki Yasushi , Naramoto Hiroshi , Inoue Tomoyasu , Satoh Masataka , Yamamoto Yasuhiro , Umezawa Kenji , Seki Seiji
Published: October 2002

Channeling measurements using secondary electrons induced by MeV ions such as 2 MeV H+ and 3.5 MeV/u O8+ were carried out to investigate the lattice disorder in Ni and epitaxially grown CeO2 crystals, which was hardly detected by backscattering spectroscopy with MeV ions. The keV electron yield under channeling incidence conditions sensitively reflects the degree of misorientation of atomic rows with a mean deviation angle on the order of 0.1°. The measurements for a small critical angle for channeling is extremely useful for analysis of a ten-nanometer-thick surface layer containing a strained lattice.
Influence of Sub-Gap Illumination on Light-Induced ESR in Undoped a-Si:H
Authors: Rudolf Durny Rudolf Durny , Mitsuo Takeda Mitsuo Takeda , Minoru Kumeda Minoru Kumeda , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

Light-induced ESR (LESR) in undoped hydrogenated amorphous silicon (a-Si:H) excited simultaneously with band-gap light (1.75 eV) and infrared (IR) light of either photon energy E < 0.99 eV (IR1) or E < 0.7 eV (IR2) was studied. Both the IR1 and IR2 lights decrease all three components (the narrow, broad and neutral dangling bond components) of the 1.75 eV LESR signal, but the IR1 light has a stronger effect than the IR2 light. While the IR2 light decreases the spin density of both the broad component (N
b) and the narrow component (N
n), which means the N
b/N
n ratio remains approximately constant and independent of the IR2-light intensity, the IR1 light decreases the broad component more markedly so that the N
b/N
n ratio decreases with increasing IR1-light intensity. The illumination of a-Si:H films with IR light alone gives an LESR signal only in the case of IR1.
Mercury-Sensitized Hydrogen Radical Photoetching of Hydrogenated Amorphous Silicon
Authors: Masato Hiramatsu Masato Hiramatsu , Yoshito Kawakyu Yoshito Kawakyu
Published: October 2002

A study of the etching of hydrogenated amorphous silicon films has been carried out by using hydrogen radical produced by mercury-photosensitization of hydrogen gas. There was found it be an incubation period before etching began, and the incubation period depended on surface pretreatment conditions. It can be explained that the variation in incubation period strongly depend on unevenness of the a-Si:H surface. It has also been found that the actual etching rate of undoped a-Si:H increases with decreasing the substrate temperature. The authors consider that surface reaction, that is, adsorption of hydrogen radical, is dominant in this etching process.
Oxygen Plasma Reactive Ion Etching of Tetrahedral Amorphous Carbon
Authors: Milne J. S. Park
Published: October 2002

The reactive ion etching (RIE) of tetrahedral amorphous carbon (ta-C) has been studied using an O2 rf plasma. The ta-C films were deposited using a filtered cathodic vacuum arc (FCVA) system. A series of films was deposited by varying the substrate bias and hence the energy of the depositing carbon ions. The dependence of etch rate on rf power, oxygen flow rate and reactor pressure has been investigated. Under the same etching conditions lower etch rates were observed for films deposited at higher negative substrate bias. This can be explained from the fact that the diamond-like nature of such films increases with increasing ion energy up to a maximum around 120 eV. The addition of hydrogen to the growing film was found to cause a decrease in the s
p
3 bond fraction of the film and hence led to an increase in the etch rate.
Crystal Orientation Effect on Valence-Subband Structures in Wurtzite-GaN Strained Quantum Wells
Authors: Ohtoshi Tsukuru , Atsuko Niwa Atsuko Niwa , Takao Kuroda Takao Kuroda
Published: October 2002

We analyze theoretically for the first time valence-subband structures in wurtzite-GaN strained quantum wells (QWs) for various crystal orientations. The calculation is based on the Bir-Pikus effective-mass theory, where deformation potentials are determined by a semi-empirical tight-binding method. The obtained results show that the hole effective masses of strained QWs with non-(0001) orientation, in particular, around the (10*BAR*1*BAR*2) orientation, are markedly lighter than those of (0001) cases. We also found that the optical matrix elements of non-(0001) strained QWs are twice as large as those for (0001) strained QWs.
Effects of Tungsten Polycidation on the Hot-Carrier Degradation in Buried-Channel LDD p-MOSFET's
Authors: D. S. Ang D. S. Ang , C. H. Ling C. H. Ling
Published: October 2002

Hot-carrier immunity of LDD buried-channel p-MOSFET's is severely degraded following tungsten polycidation of device gate and incorporation of F in the oxide, in contrast to the reliability enhancement commonly observed for n-MOSFET's. Possible mechanisms involving enhanced trapping at F-related oxide bulk traps and reduced field-induced detrapping rate are discussed. The reduction in hot-carrier reliability of WSi
x
gate p-MOSFET's may raise concern over the use of WF6-based tungsten polycide technology in deep submicrometer CMOS circuits.
Estimation of Inductance for High-Tc dc-SQUID's in Coplanar Waveguide
Authors: Fuke Hiroyuki , Saitoh Kazuo , Tadashi Utagawa Tadashi Utagawa , Youichi Enomoto Youichi Enomoto
Published: October 2002

We have investigated the electrical properties of high-T
c dc-SQUID's formed in a coplanar waveguide, and discussed their applicability to single flux quantum (SFQ) circuits. The planar type Josephson junctions were fabricated in NdBa2Cu3O
y
(NBCO) superconducting thin films by a narrow-focused ion beam (FIB) irradiation technique. The critical current and normal resistance values of the Josephson junction at 4.2 K were 115 µA and 8 Ω, respectively. The inductance was estimated by applying a direct injection of the control current into the dc-SQUID loop and measuring the periodic voltage response. A loop inductance of 47 pH was obtained for a 25 µm-wide and 20 µm-long dc-SQUID at 4.2 K. It has been clarified that for a stable operation of SFQ logic circuits, a 10 µm-square dc-SQUID's are required.
Fabrication of LiNbO3 Phase Gratings by Excimer Laser Ablation through a Silica Phase Mask
Authors: Luo G. P. , Lu Y. Q. , Zhu Y. Y. , Lu Y. L. , Guo X. L. , Ge C. Z. , Liu Z. G. , Ming N. B. , Wu J. W. , Lu Z. H.
Published: October 2002

Lithium niobate ( LiNbO3) wafer phase gratings were fabricated by excimer pulsed ablation through a transmission silica phase mask grating. Surface morphology of the LiNbO3 phase gratings was studied using an atomic force microscope as well as an optical microscope. Crystal structures and the diffraction patterns of the gratings were characterized by X-ray diffraction and using a He–Ne laser beam, respectively.
Single Local Mode Propagation through Ion-Exchanged Waveguide Elements with Quasi-Abrupt Transitions
Authors: Jesús Liñares Jesús Liñares , Marí a C. Nistal Marí a C. Nistal
Published: October 2002

An effective adiabatic condition is derived in order to obtain a single local mode operation regime in integrated devices formed by waveguide elements with quasi-abrupt boundaries. An ion-exchange process, producing this type of graded index transition, is presented in a such a way that many difficulties of both fabrication and design of waveguide elements can be overcome.
Improvement of Low Voltage Cathodoluminescent Properties of Zinc Sulfide Phosphors by Sol–Gel Method
Authors: Hiroko Kominami Hiroko Kominami , Takato Nakamura Takato Nakamura , Yoichiro Nakanishi Yoichiro Nakanishi , Yoshinori Hatanaka Yoshinori Hatanaka
Published: October 2002

The phosphors used in conventional cathode ray tubes (CRTs) are difficult to use at voltages lower than 500 V, because of charge buildup on their surface. To overcome this drawback a ZnS:Ag,Cl phosphor was coated with a very thin In2O3 conductive layer by the sol-gel method using tri-iso-propoxyindium. Properties of the cathodoluminescence at voltages ranging from 50–500 V were studied and compared with those of the as-received ZnS:Ag,Cl phosphor. It was found that the luminance of the In2O3-coated phosphor was far better than that of the as-received phosphor when they were excited using an electron beam with an energy of less than 500 eV. Furthermore, the aging characteristics of the cathodoluminescence showed marked improvement.
Model for Dopant-Induced Enhancement in Solid-Phase Epitaxial Recrystallization of Amorphous Si
Authors: Byungwoo Park Byungwoo Park
Published: October 2002

A model is proposed for the effect of solute atoms on the solid-phase epitaxial regrowth kinetics in amorphous Si. The enhanced growth rate with p-type or n-type solutes is explained in terms of reduction of the bond strength, caused by excess holes or electrons residing at the crystal-amorphous interface supplied from the crystalline side due to the Fermi-level shift. This makes the bond-breaking (formation) process easier at ledges along the interface during recrystallization, creating more thermally generated dangling bonds compared to the intrinsic case.
Evaluation of Ultratrace Metallic Impurities in Thin Copper Layers, Barrier Metals and Silicon Wafers for Copper Metallization Technology
Authors: Takenaka Miyuki , Tachibe Tetsuya , Kozuka Shoji , Masaru Hayashi Masaru Hayashi , Hideki Matsunaga Hideki Matsunaga
Published: October 2002

An analytical method for the determination of ultratrace concentrations of metals in several semiconductor-related materials for copper metallization technology such as thin Cu layers, barrier metals and silicon wafers has been developed. Using this method, the concentration of Cu impurities in Si wafers resulting from diffusion of Cu from Cu metallization layers through barrier layers of TiN, TiSiN, or WSiN was found to be less than 1012 atoms/cm3.
Direct Wafer Bonding of a (001) InP-Based Strained Multiple Quantum Well on a (110) Si Substrate with a GaAs Buffer Layer, Aligning Cleavage Planes of InP and Si
Authors: Tamura Yae Okuno
Published: October 2002

We demonstrate direct wafer bonding of a (001) InP-based structure and a (110) Si substrate with a GaAs buffer layer. Cleavage planes of the InP and Si are aligned to obtain a smooth cleaved facet of the InP. Cross-sectional transmission electron microscope observation shows that the InP region is dislocation-free, and that an unexpected In region is formed at the bonded interface. Strong intensity is achieved in the photoluminescence spectrum from the strained multiple quantum well in the InP region, although a peculiar feature is observed in the spectrum measured at room-temperature. The results confirm that our method of direct bonding makes it possible to achieve smooth cleaved facets and high crystalline quality in a III–V layer fabricated on a Si substrate.
Low-Temperature Epitaxial Growth of CeO 2(110)/Si(100) Structure by Evaporation under Substrate Bias
Authors: Tomoyasu Inoue Tomoyasu Inoue , Yasuhiro Yamamoto Yasuhiro Yamamoto , Masataka Satoh Masataka Satoh
Published: October 2002

Epitaxial growth of CeO2 layers on silicon (100) substrates is studied using electron-beam evaporation under substrate bias application in an ultrahigh vacuum. Both negative and positive biases are proved to be effective for lowering the epitaxial temperature. Sample current characteristics are measured as a function of the bias voltage. Under negative bias condition, as the bias voltage increases, the sample current varies from negative to positive with a transition point at -42 V and then reaches a saturation value of ∼ +4 µA above -60 V. Use of a negative bias of -60 V leads to epitaxial growth temperature lowering of at least 40°C. Under positive bias application, the sample current is negative and increases with the bias voltage, where the sample current components are anions and electrons (46%) as determined by mass separation with magnetic field application. It is experimentally clarified that the degree of enhancement of epitaxial growth is greater than that in the negative bias experiment (epitaxial growth temperature lowering of more than 55°C) and the enhancement is attributed to the electron component. It is found that a negative current of ∼ -0.15 mA flows at zero bias, indicating that even in conventional evaporation, electrons somewhat promote epitaxial growth.
Surfactant Effects of Atomic Hydrogen on Low-Temperature Growth of InAs on InP
Authors: Chun Yong Jin , Yoshitaka Okada Yoshitaka Okada , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

We have investigated the initial stage of InAs grown on InP at low temperature with atomic hydrogen (H). At 350°C, the critical layer thickness (CLT), above which lattice relaxation begins to start, increases from 30 to 46 Å by atomic H supply during growth. When the growth temperature is lowered to 250°C, the CLT increases to above 100 Å with atomic H (with-H), while only small change in the CLT appears without atomic H condition (without-H). The lattice relaxation process with-H is delayed significantly and the oscillation of the specular beam intensity of reflection high-energy electron diffraction persists for longer time than without-H. These results indicate that atomic H has beneficial effects on the considerable increase in the CLT and the formation of flat surface.
Bias Dependence of Scanning Tunneling Microscopy Images of Sr Atoms Adsorbed on SrTiO 3(100) √ 5×√ 5 Surfaces
Authors: Kubo Akihiro , Tanaka Hiroyuki , Tabata Hitoshi , Takuya Matsumoto Takuya Matsumoto , Tomoji Kawai Tomoji Kawai
Published: October 2002

We have observed significant bias dependence of Scanning Tunneling Microscopy (STM) images of Sr atoms adsorbed on SrTiO3(100) √5×√5 surfaces. A large protrusion of Sr atoms is observed only for the filled states. This bias dependence is interpreted using first principles DV-Xα calculations, which give the distribution of each atomic orbital near the Fermi level.
Alkyl Chain Length Effect on Growth Kinetics of n-Alkanethiol Self-Assembled Monolayers on Gold Studied by X-Ray Photoelectron Spectroscopy
Authors: Ishida Takao , Nishida Naoki , Tsuneda Satoshi , Hara Masahiko , Hiroyuki Sasabe Hiroyuki Sasabe , Wolfgang Knoll Wolfgang Knoll
Published: October 2002

Growth kinetics of self-assembled monolayers (SAMs) of n-alkanethiols on gold substrates was studied by X-ray photoelectron spectroscopy (XPS). We compared adsorption kinetics for three alkanethiol homologues: butanethiol (C4SH), dodecanethiol (C12SH), and octadecanethiol (C18SH). Results of quantitative analysis by XPS suggested that the adsorption rate of short alkyl chain thiols is higher than that of long ones on gold substrates at the initial growth stage, in contrast to previous reports. For C4SH SAM formation, we have also confirmed the occurrence of a replacement effect from contamination to SAM on gold, based on our observation of a decrease in the amount of carbon and an increase in the amount of gold where as determined from XPS spectra.
Control of Levitation in Electromagnetic Levitators under Microgravity
Authors: Minagawa Hideki , Suzuki Yoshikazu , Kawabata Junichi , Shimokawa Katsuyoshi , Ueda Yoshinobu , Iwasaki Shigehiro , Shinohara Jouji , Ueno Hiroyuki , Nishizawa Eitaroh , Sakurai Hideyo , Kaburagi Michiya , Iida Mitsuhiro , Nogi Kiyoshi , Kudo Isao , Kitagawa Sadao , Suzuki Norio
Published: October 2002

A containerless electromagnetic levitator has been now constructed for precise measurement of the thermophysical properties of molten silicon in the 10 s Japan Microgravity Center (JAMIC) drop shaft. Precise control of the levitated sample position from normal gravity to microgravity was aimed and a compact electromagnetic levitator for demonstrating the control technology at the gravity transition point was tested at the 1.3 s HNIRI (Hokkaido National Industrial Research Institute) drop tower. The oscillation generated at the transition was completely eliminated with current control of electromagnetic coil.
Si Quantum Dot Formation with Low-Pressure Chemical Vapor Deposition
Authors: Nakajima Anri , Sugita Yoshihiro , Kawamura Kazuo , Hirofumi Tomita Hirofumi Tomita , Naoki Yokoyama Naoki Yokoyama
Published: October 2002

We report a simple technique for fabricating a layer of isolated Si quantum dots. The procedure uses conventional low-pressure chemical vapor deposition (LPCVD) for an extremely short deposition time in the early stage of poly-Si film growth. The layer resulting from a deposition time of 60 s has isolated Si nanocrystals 5–20 nm in diameter and 2–10 nm in height. Optical absorption measurement shows that the Si-nanocrystal spectrum changes drastically and the onset of absorption shifts to higher energies compared to that of bulk Si. This shift can be explained by the energy gap widening caused by quantum size effects. Special attention is paid to the Brownian migration of Si nanocrystals for fabricating Si quantum dots.
The Dynamics of Thermal Annealing in Arsenic-Ion-Implanted GaAs
Authors: Chen Wen-Chung , Gong-Ru Lin Gong-Ru Lin , C.-S. Chang C.-S. Chang
Published: October 2002

The effect of thermal annealing on the surfaces of arsenic-ion-implanted GaAs has been investigated by transmission electron microscopy, deep level transient spectroscopy and temperature-dependent resistance measurements. For the annealed films of arsenic-ion-implanted GaAs arsenic precipitates and a band of deep-level defects with the activation energy of around 0.6 eV near the surface are observed. The mean size and concentration of As precipitates in samples implanted at a dosage of 1016 cm-2 are about 2–3 nm and 7×1016 cm-3, respectively. The cross section of the deep level defects near the surface is calculated to be 7×10-14 cm2. The carrier-transport mechanisms of both as-implanted GaAs and post-annealed GaAs are shown dominantly to be hopping type conduction and active type conduction, respectively.
Heavily Carbon-Doped P-Type GaAs Grown on GaAs Substrates with Various Orientations by Metalorganic Molecular Beam Epitaxy
Authors: Li-Qi Guo Li-Qi Guo , Makoto Konagai Makoto Konagai
Published: October 2002

Heavily carbon-doped p-type GaAs epitaxial layers have been grown on (100), (711)A, (411)A, (411)B, (111)A and (111)B semi-insulating (SI) GaAs substrates simultaneously, by metalorganic molecular beam epitaxy (MOMBE) using elemental As ( As4) and trimethylgallium (TMG) for the first time. It was found that the hole concentration depends strongly on the substrate orientation. The highest hole concentration, which was measured by Hall measurement, was obtained in the layer grown on (411)A substrate at a growth temperature of 385°C. By X-ray rocking curve analysis, it was also revealed that the largest lattice mismatch of Δd/d=-0.48% due to heavy doping of carbon occurred on the sample grown on (411)A substrate. The hole concentration determined by Hall measurement was in good agreement with the carbon concentration determined by X-ray rocking curve analysis.
InGaN Multi-Quantum-Well-Structure Laser Diodes with Cleaved Mirror Cavity Facets
Authors: Nakamura Shuji , Senoh Masayuki , Nagahama Shin-ichi , Iwasa Naruhito , Yamada Takao , Matsushita Toshio , Hiroyuki Kiyoku Hiroyuki Kiyoku , Yasunobu Sugimoto Yasunobu Sugimoto
Published: October 2002

InGaN multi-quantum-well (MQW)-structure laser diodes (LDs) fabricated from III–V nitride materials were grown by metalorganic chemical vapor deposition on sapphire substrate with (11*BAR*2*BAR*0) orientation (A face). The mirror facet for a laser cavity was formed by cleaving the substrate along the (1*BAR*1*BAR*02) orientation (R-face). As an active layer, the InGaN MQW structure was used. The InGaN MQW LDs showed a sharp peak of light output at 415.6 nm that had a full width at half-maximum of 0.05 nm under pulsed current injection of 1.17 A at room temperature. The laser threshold current density was 9.6 kA/cm2.
Correlation between Ge E′ Centers and Optical Absorption Bands in SiO2:GeO2 Glasses
Authors: Hosono Hideo , Mizuguchi Masafumi , Kawazoe Hiroshi , Nishii Junji
Published: October 2002

Correlations between optical absorptions in ultraviolet and vacuum ultraviolet regions and Ge E′ centers were examined using 9SiO2·1GeO2 glasses irradiated with ArF excimer laser light in order to determine the optical absorption bands due to Ge E′ centers and the oscillator strength. A good correlation between the band peaking at 6.3 eV and Ge E′ centers was found in the isochronal annealing experiment. The oscillator strength of the 6.3 eV band was determined to be 0.5±0.1 on the assumption of the above correlation. The large oscillator strength of the 6.3 eV band due to Ge E′ centers is compatible with the Kramers-Kronig mechanism for photoinduced Bragg grating formation.
Ultra-Large-Scale Step-Free Terraces Formed at the Bottom of Craters on Vicinal Si(111) Surfaces
Authors: Homma Yoshikazu , Aizawa Noriyuki , Ogino Toshio
Published: October 2002

We report the self-controlled planarization of Si(111) surfaces at the bottom of craters. A (111) plane with a step spacing as large as 10 micrometers can be obtained at the bottom of a crater by heating a misoriented Si(111) substrate with craters at around 1200°C in ultrahigh vacuum. The (111) plane grows preferentially by filling adatoms in the crater until the plane surface reaches one of the top edges of the crater. The resulting surface has an extremely small miscut angle (<0.002°), making it useful for fundamental research into crystal growth as well as for device fabrication.
Blue-Green Electroluminescence in Copolymer Based on Poly(1,4-phenylene ethynylene)
Authors: Kazuya Tada Kazuya Tada , Mitsuyoshi Onoda Mitsuyoshi Onoda , Masaharu Hirohata Masaharu Hirohata , Tsuyoshi Kawai Tsuyoshi Kawai , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Optical characteristics of poly(2,5-dialkoxy-1,4-phenylene diethynylene- co-2,5-pyridinylene) (ROPPE-Py) were investigated. Intense blue-green electroluminescence (EL) emission was observed in light emitting diode (LED) with Al/ROPPE-Py/indium-tin-oxide (ITO) structure. This result suggests that triple bonds in the main chain are resopnsible for the blue shift and enhancement of EL, due to the shortening the effective conjugation length and effective confinement of excitons or exciton-polarons. However, the effects of triple bonds were suppressed by the introduction of electron-rich moieties in the main chain such as poly(2,5-dialkoxy-1,4-phenylene diethynylene- co-9,10-anthracenylene) (ROPPE-An). Electronic energy structures obtained from optical absorption spectra and cyclicvoltammetry measurements confirmed the effect of the electron-rich moieties, which is due to the delocalization of π-electrons and the enhancement of interchain interactions.
Detection of Physiological Parameters without Any Physical Constraints in Bed Using Sequential Image Processing*
Authors: Nakajima Kazuki , Osa Atsushi , Kasaoka Shunji , Nakashima Ken , Maekawa Tsuyoshi , Tamura Toshiyo , Hidetoshi Miike Hidetoshi Miike
Published: October 2002

Physiological parameters, specifically, body movement and respiratory waveform, were observed utilizing an original image sequence processing system. In this study, sequential image processing methods were used to observe both patients with acute myocardial infarction and normal subjects in bed. The results of standard differential image processing and a gradient-based method were strongly correlated with body movement of the subject. Furthermore, the respiratory waveform was detected using the gradient-based method. This image sequence processing system appears very promising for the evaluation of physical activity without any physical constraints in bed.
Comment on “Second-Order Piezoresistance Coefficients of n-Type Silicon”
Authors: Yamichi Ohmura Yamichi Ohmura , Wataru Morinaga Wataru Morinaga
Published: October 2002

It has been shown that nine components of the second-order piezoresistance coefficients of n-type silicon recently reported by K. Matsuda, Y. Kanda and K. Suzuki [Jpn. J. Appl. Phys. 28 (1989) L1676] are inconsistent with symmetry relationships and the conductivity model from which they were derived.
Effect of the Trimethylgallium Flow during Nucleation Layer Growth on the Properties of GaN Grown on Sapphire
Authors: Keller Stacia , Kapolnek David , Keller Bernd P. , Wu Yifeng , Heying Benjamin , Speck James S. , Umesh K. Mishra Umesh K. Mishra , Steven P. Denbaars Steven P. Denbaars
Published: October 2002

We report on the effect of the trimethylgallium flow during nucleation layer growth on the electrical, optical and structural properties of epitaxial GaN films grown on basal plane sapphire by atmospheric pressure metalorganic chemical vapor deposition. The 1.2 µm thick GaN films grown on nucleation layers with the optimum trimethylgallium flow of 45 µmol/min had a room temperature mobility of 644 cm2/s and minimum width of the (002) and the (102) X-ray diffraction peaks. The roughness of the as-grown nucleation layers decreased with increased trimethylgallium flow. However, smooth, as-grown, nucleation layers showed a strong tendency for island coarsening and an increased surface roughness after heating to the bulk GaN growth temperature.
High Quality GaN Growth on (0001) Sapphire by Ion-Removed Electron Cyclotron Resonance Molecular Beam Epitaxy and First Observation of (2×2) and (4×4) Reflection High Energy Electron Diffraction Patterns
Authors: Iwata Kakuya , Asahi Hajime , Yu Soon Jae , Asami Kumiko , Fujita Hideki , Masahiro Fushida Masahiro Fushida , Shun-ichi Gonda Shun-ichi Gonda
Published: October 2002

GaN layers are grown on (0001) sapphire substrate by electron cyclotron resonance molecular beam epitaxy (ECR-MBE) using an ECR plasma cell with ion removal magnets on the cell top for the nitrogen source. The efficiency of the ion removal magnets in this ECR plasma cell is 99%. High-quality GaN layers are obtained. In particular, (2×2) and (4×4) RHEED (reflection high-energy electron diffraction) patterns are observed during GaN growth and during cooling after growth, respectively, indicating a flat and smooth surface of GaN. These results show the superiority of the ion-removed ECR plasma cell.
Abnormal Threshold Voltage Dependence on Gate Length in Ultrathin-Film n-Channel Metal-Oxide-Semiconductor Field-Effect Transistors (nMOSFET's) Using Separation by Implanted Oxygen (SIMOX) Technology
Authors: Yasuhisa Omura Yasuhisa Omura , Masao Nagase Masao Nagase
Published: October 2002

We describe abnormal dependences of threshold voltage (V
TH) on gate length in 8-nm-thick silicon-on-insulator (SOI) n-channel metal-oxide-semiconductor field-effect transistor (nMOSFET) devices on separation by implanted oxygen (SIMOX) substrates. It is shown experimentally that as the gate length decreases, V
TH increases at 30 K. It is assumed that the parasitic resistances of the source and drain regions induce an effective negative substrate bias, and this model is used to formulate the V
TH equation. It is strongly indicated that the freeze-out effect of the parasitic resistance contributes to the clear appearance of the V
TH roll-up behavior by means of the effective negative substrate bias at temperatures less than 100 K.
Domain Inversion by an Electron-Beam-Induced Electric Field in MgO:LiNbO3, LiNbO3 and LiTaO3
Authors: Kurimura Sunao , Ichiro Shimoya Ichiro Shimoya , Yoshiaki Uesu Yoshiaki Uesu
Published: October 2002

This report is, as far as we know, the first to demonstrate ferroelectric domain inversion in a photorefractive-damage-resistant MgO:LiNbO3 (MgO:LN) crystal upon electron beam irradiation. The domain inversion was found to be achieved by applying an electron-beam-induced electric field (EBIEF). By comparing the requirements of electron beam irradiation for domain inversion in MgO:LN, LiNbO3 and LiTaO3, a domain in MgO:LN was found to exhibit the highest critical values of current i
c and time t
c among these crystals. The relationship between i
c and t
c was explained in terms of a simple charge leakage model.
Real-Index Guided Blue-Green Laser Diode with Small Beam Astigmatism Fabricated Using ZnO Buried Structure
Authors: Yokogawa Toshiya , Kamiyama Satoshi , Yoshii Shigeo , Ohkawa Kazuhiro , Ayumu Tsujimura Ayumu Tsujimura , Yoichi Sasai Yoichi Sasai
Published: October 2002

Real index-guided blue-green lasers with a small beam astigmatism have been demonstrated. A ZnO buried layer with low refractive index and high resistivity was used to obtain the real index-guided structure. The ridge stripe was fabricated by electron cyclotron resonance plasma etching with Cl2/H2 discharge which realizes anisotropic etching. The beam astigmatism value for the ZnO buried ridge waveguide laser was measured to be less than 0.5 µm as a result of the real index-guiding effect, in contrast to 25 µm for the conventional gain-guided laser. A stable single lateral mode operation was also obtained at up to 18 mW for the real index-guided laser.
The Effect of a Metal Electrode on the Electroluminescence of Poly(p-phenylenevinylene)
Authors: Peng Junbiao , Yu Byung-Yong , Pyun Chong-Hong , Kim Chang-Hong , Kim Keun-Youl , Jin Jung-Il
Published: October 2002

The effect of metal on the emission characteristics of a ITO-poly(p-phenylenevinylene)-M (M: Al, In, Mg, or Ca) electroluminescence device was studied. The emission peak at 550 nm is substantially smaller than that at 515 nm for devices with metals which have a larger work function. In the case of photoluminescence, the thinner the poly(p-phenylenevinylene) (PPV) film the smaller is the 550-nm peak observed using an Al electrode. These results are discussed in terms of the interaction of metal with PPV at the PPV-metal interface.
Optical Emission and Microwave Field Intensity Measurements in Surface Wave-Excited Planar Plasma
Authors: Nagatsu Masaaki , Xu Ge , Yamage Masashi , Kanoh Masaaki , Hideo Sugai Hideo Sugai
Published: October 2002

A large-planar (22 cm diam.) high-density ( ∼2×1012 cm-3) plasma is produced in argon gas at 140 Pa by 2.45 GHz–1 kW discharges, using a microwave launcher of small slot antennas. The two-dimensional distributions of optical emission intensities as well as microwave field intensities are measured near the plasma surface irradiated with microwaves. Both the optical emission and the microwave field clearly show stationary patterns of azimuthal mode m=3 and radial mode n=3 at higher pressures (140 Pa), while a mode change to m=6 and n=2 is observed at lower pressures (44 Pa). These patterns are attributed to the excitation and absorption of standing surface waves near the cutoff layer.