bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Acid Diffusibility in a Chemical Amplification Resist Using Acidic Water-Soluble Film
Authors: Watanabe Hiroshi , Sumitani Hiroaki , Kumada Teruhiko , Inoue Masami , Marumoto Kenji , Yasuji Matsui Yasuji Matsui
Published: October 2002

A new method is proposed to evaluate the acid diffusibility in a chemical amplification resist using acidic overcoat film. This method is easy and effective for both positive- and negative-tone resists and is not influenced by the uncertainty in optical images. The acid diffusion coefficient was estimated for various process conditions. The acid loss reaction was introduced in Fick's law, and the calculation showed a good agreement with experimental results. In order to obtain good profile patterns with sufficient controllability, the distribution of acids in the resist must be controlled as well as diffusion length. The resist patterns replicated using X-ray lithography corresponded to those expected from experimental results.
Crystal Growth of Nd:YAG Laser Films on Various Substrates by Pulsed Laser Deposition
Authors: Ezaki Mizunori , Kumagai Hiroshi , Kobayashi Katsutaro , Toyoda Koichi , Minoru Obara Minoru Obara
Published: October 2002

Fabrication of textured Nd doped yttrium aluminum garnet ( Y3Al5O12, YAG) crystalline thin films on Si and MgO single-crystal substrates by the pulsed laser deposition technique has been demonstrated for the first time. The films were characterized by means of Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). The results indicate that the composition of these films is the same as that of YAG doped with Nd (8.3 at.%), and the AFM image shows that the submicron Nd:YAG crystallites were oriented on the silicon surface at the substrate temperature of 700° C. The formation of these submicron crystallites was observed on the surface of Nd:YAG films grown on substrates having a large lattice mismatch with Nd:YAG.
Fabrication of Silicon Field Emitter Arrays with 0.1-µm-Diameter Gate by Focused Ion Beam Lithography
Authors: Yamaoka Yoshikazu , Goto Takashi , Nakao Masao , Kanemaru Seigo , Itoh Junji
Published: October 2002

Cone-shaped silicon (Si) field-emitter arrays (FEAs) with 0.1-µ m-diameter gates were fabricated by focused ion beam (FIB) lithography. In the fabrication process, a 200 keV Be2+ FIB with a beam diameter of 0.06 µ m was irradiated to a positive-tone electron-beam resist to form an array of silicon oxide ( SiO

x

) disks used as masks for cone-shape etching of a Si substrate. We have succeeded in the operation of the present FEA and obtained the emission current of 1 nA/tip at the gate voltage of 25 V.
Submicron Gate-Fitted Superconducting Junction Using a Two-Dimensional Electron Gas
Authors: Takayanagi Hideaki , Tatsushi Akazaki Tatsushi Akazaki
Published: October 2002

We fabricated submicron-gate superconducting junctions which are coupled with an InAs channel inserted in an InAlAs/InGaAs heterostructure. Electron beam lithography, and chemical and rf sputter etching techniques are used to fabricate a junction in the submicron range. The fabrication process of the junction is described in detail. The fabricated gate configuration shows high controllability of both the superconducting critical current and normal resistance of the junction using gate voltage. This provides a voltage gain of over 1 and enables the first demonstration as a Josephson field effect transistor. Moreover, new quantum phenomena,e.g., Fabry-Pérot interference and quantization of critical current as well as focusing of Andreev-reflected holes in a quantum point contact, were observed. Junction characteristics from the viewpoints of both three-terminal operation and the new quantum phenomena are reported.
Deposition of SiO2 Films on Strained SiGe Layer by Direct Photo Chemical Vapor Deposition
Authors: Lin Chung-Te , Chang Shoou-Jinn , Nayak Deepok K. , Shiraki Yasuhiro
Published: October 2002

High quality SiO2 layers were deposited on strained SiGe by direct photochemical vapor deposition with a deuterium lamp as the excitation source. It was found that the deposition rate increases linearly with the chamber pressure. The Auger electron spectroscopy profile shows that neither was Ge rejected nor was a Ge-rich layer formed after devices were fabricated. At room temperature, the leakage current is about 3×10-9 A/cm2 under a 2×106 V/cm electric field. The breakdown field can reach over 16 MV/cm for these SiGe metal-oxide-semiconductor (MOS) diodes.
H2O2 Decomposition and Its Impact on Silicon Surface Roughening and Gate Oxide Integrity
Authors: Schmidt Harald F. , Meuris Marc , Mertens Paul W. , Rotondaro Antonio L. P. , Heyns Marc M. , Hurd Trace Q. , Hatcher Zach
Published: October 2002

In this study the impact of temperature and metal contamination on the stability of hydrogen peroxide in the two most common wet chemical cleaning mixtures for wafer process operations has been investigated. The stability of the caustic mixture ( NH4OH/H2O2/H2O) was found to be very sensitive to certain metallic contaminations in the sub-ppb range, while the stability of the acid mixture ( HCl/H2O2/H2O) is mainly influenced by non metallic, anionic components of the solution itself. We observed also a strong oscillating behaviour of the rate of the oxygen gas evolution caused by the decomposition of H2O2. Furthermore it was found, that the oxygen gas bubbles, formed by the decomposition of hydrogen peroxide cause a certain kind of micro-roughness on the silicon surface through a micro masking mechanism. In a series of experiments we could prove that this kind of surface roughness has a significant impact on the integrity of thin gate oxides.
Effect of Fowler-Nordheim Stress on Charge Trapping Properties of Ultrathin N2O-Oxynitrided SiO2 Films
Authors: Fukuda Hisashi , Shigeru Nomura Shigeru Nomura
Published: October 2002

Charge trapping properties of ultrathin rapid thermal N2O-oxynitrided (RTON) SiO2 film have been investigated by Fowler-Nordheim (F-N) electron injection. By applying F-N stress, gate voltage decreases at the initial stage and then increases with increasing injected charge. A model of trap filling and trap generation in the oxide films indicates that the RTON film has a one order of magnitude smaller trap generation rate compared with pure SiO2 film.
A 0.4 µm Gate-All-Around TFT (GAT) Using a Dummy Nitride Pattern for High-Density Memories
Authors: Maegawa Shigeto , Ipposhi Takashi , Maeda Shigenobu , Nishimura Hisayuki , Tanina Osamu , Kuriyama Hirotada , Inoue Yasuo , Nishimura Tadashi , Natsuro Tsubouchi Natsuro Tsubouchi
Published: October 2002

We propose a novel thin-film-transistor (TFT) structure named gate-all-around TFT (GAT). Its fabrication process is very simple, in that we realize the gate-all-around structure using only a dummy nitride pattern. The GAT shows high channel conductance and features of shield structure peculiar to the double-gate structure. It can also eliminate an anomalous leakage current which appears in the sub-half-micron regime. Combining this process with sacrifice oxidation of the channel poly-Si, we obtained a GAT whose performance is nearly equal to that of single-crystalline metal-oxide-semiconductor field-effect transistors (MOSFETs). Since the GAT requires only one additional mask layer and no increase in TFT area as compared with the conventional single-gate TFT, it is suitable for a high-density and low-cost static-random-access-memory (SRAM). SRAM cells with this GAT have the potential to exhibit performance equivalent to that of the full-complimentary-MOS (CMOS) cell.
Separated Drift Field Magnetotransistor with a p+ Ring around an Emitter
Authors: Kang Uk-Song , Lee Seung-Ki , Min-Koo Han Min-Koo Han
Published: October 2002

A novel magnetotransistor using a separated drift field with a p+ ring around an emitter has been designed and fabricated. The operating principle of the proposed magnetic field sensor is based on the emitter injection modulation. The p+ ring around the n-type emitter confines drifted electrons in the emitter and hence, the induced Hall voltage in the emitter is increased. The measured relative sensitivity of the separated drift field magnetotransistor with the p+ ring is about 140 times larger than that of the device without the ring.
High Performance Bottom Gate TFTs by Excimer Laser Crystallization and Post Hydrogenation
Authors: Gosain Dharam Pal , Westwater Jonathan , Setsuo Usui Setsuo Usui
Published: October 2002

Small grain poly-Si has defects of the order of 1018 to 1019 spins/cm3. Hydrogen is generally used to terminate these defects, which is introduced from a hydrogen plasma. Damage caused by UV emitted from the plasma glow discharge was identified as one of the causes limiting the quality of the bottom gate thin film transistor (TFT) devices. The effect of UV on the TFT transfer characteristics was studied. ESR was used to measure the change in the poly-Si dangling bond density as a result of UV irradiation. It was confirmed that plasma UV creates damage in the poly-Si. A combination of plasma hydrogenation and SiN

x

: H passivation and thermal annealing was found to be particularly effective in reducing the defect density by reconstruction of dangling bonds and redistribution of hydrogen without hydrogen loss. The excellent characteristics obtained using this hydrogenation method are presented.
Photoluminescence from a Silicon Quantum Well Formed on Separation by Implanted Oxygen Substrate
Authors: Takahashi Yasuo , Furuta Tomofumi , Ono Yukinori , Ishiyama Toshihiko , Michiharu Tabe Michiharu Tabe
Published: October 2002

We have observed strong photoluminescence (PL) from a well-defined two-dimensional (2D) Si structure formed on a SIMOX (separation by implanted oxygen) wafer, where the thin ( <5 nm) single crystalline silicon film is sandwiched between SiO2 layers. The PL intensity has a sharp maximum at a Si thickness of about 2 nm, whereas the peak photon energy of the PL spectra (1.65 eV) is almost independent of the Si thickness. These results can be interpreted with a three-region model in which electron-hole pairs are excited in the Si well and luminescence occurs at the upper and lower Si/SiO2 interfaces. Furthermore, temperature dependence of PL intensity in the present 2D system is found to be different from previously reported dependence in 0D or 1D Si structures.
Highly Reliable Silicon Nitride Thin Films Made by Jet Vapor Deposition
Authors: Wang Xie-wen , Ma Tso-Ping , Cui Guang-Ji , Tamagawa Takashi , Golz John W. , Karechi Simon , Halpern Bret H. , Schmitt Jerome J.
Published: October 2002

This paper reports our results on the properties of gate-quality silicon nitride thin films produced by the jet vapor deposition (JVD) technique at room temperature. It will be shown that the electrical properties and reliability of the metal-nitride-silicon (MNS) capacitors, in terms of their densities of interface traps, leakage current, and resistance against hot-carrier or radiation damage, are significantly better than similar devices made by any other deposited nitrides previously reported.
Auger Depth Profiles of a GaAs/AlAs Superlattice Structure Obtained with O2
+ and Ar+ Ion Sputtering
Authors: Lee Hyung-Ik , Mitsuhashi Riichiro , Inoue Masahiko , Shimizu Ryuichi , Hofmann Siegfried
Published: October 2002

Employment of a LaB6 cathode with Re filament for an electron-bombardment ion gun has enabled O2
+ ions as well as Ar+ ions to be provided for surface analysis in ultrahigh vacuum. This technique was applied to depth profiling of a GaAs/AlAs superlattice by monitoring the Auger peak-to-background ratio of the following high-energy peaks; Ga-LMM (1066 eV), As-LMM (1222 eV), Al-KLL (1390 eV) and O-KVV (508 eV). The energy shift of O-KVV Auger peak was also monitored. Results show the deficiency of As atoms and the formation of Al oxides at the surface of O+
2-sputtered AlAs layers.
Influence of Atmosphere on Molten Silicon Density
Authors: Ikari Atsushi , Sasaki Hitoshi , Tokizaki Eiji , Terashima Kazutaka , Shigeyuki Kimura Shigeyuki Kimura
Published: October 2002

The influence of atmosphere on the density of molten silicon has been studied. The density was measured by an improved Archimedean method with the accuracy of 1.1%. The density under argon gas mixed with hydrogen 7.15% is found to be equivalent to that under pure argon gas at the melting point, but showed higher values at higher temperatures (1430-1500° C) with the thermal volume expansion coefficient of about 8.8×10-5 K-1. The density under the hydrogen-containing argon also shows a time-dependent variation over 5 h after melting. The solubility of hydrogen in molten silicon is estimated to be below 3×1018 atoms cm-3. This result suggests that the increase of the density in the presence of hydrogen is caused by the change of the arrangement of the silicon atoms.
Reducing the Thermal Budget of Solid Phase Crystallization of Amorphous Si Film Using Si0.47Ge0.53 Seed Layer
Authors: Ryu Myung-Kwan , Kim Jin-Won , Kim Tae-Hoon , Kim Ki-Bum , Hwang Chang-Won
Published: October 2002

We have proposed a Si/Si0.47Ge0.53 bilayer (BL) structure as the active layer of thin-film transistor (TFT) to reduce the overall thermal budget of the solid-phase crystallization (SPC) of the conventional amorphous Si film. From X-ray diffractometry (XRD), we found that amorphous Si/Si0.47Ge0.53 bilayer film deposited onto thermal oxide by molecular beam epitaxy (MBE) was fully crystallized after an hour of annealing at 600° C. Furthermore, transmission electron microscopy (TEM) observation suggested that the evolution of grain microstructure was noticeably changed from dendrite to equiaxial growth mode by using Si0.47Ge0.53 seed layer compared to that observed for amorphous Si single layer (SL) with the same thickness.
Film Formation by a New Chemical Vapor Deposition Process Using Ionization of Tetraethylorthosilicate
Authors: Adachi Motoaki , Okuyama Kikuo , Fujimoto Toshiyuki
Published: October 2002

A new chemical vapor deposition (CVD) method called ionization CVD, where source molecules were ionized and deposited on a substrate by Coulombic forces in an electric field, was proposed. Film formation from tetraethylorthosilicate (TEOS)/ozone CVD was used to demonstrate this method. Film-growth rates increased linearly with increasing electric fields from 0 to 1.67 kV· cm-1. The FT-IR spectra of the resulting films showed they were composed of SiO2. It was found that 60% of the intermediates had a negative charge and that the electric field required to deposit them was lower than 1.67 kV· cm-1.
Effect of the Molecular Structure of Weakly Rubbed Organic Solvent Soluble Polyimides with Trifluoromethyl Moieties on Anchoring Strength of Liquid Crystals
Authors: Seo Dae-Shik , Nishikawa Michinori , Yabe Yoshikazu , Shunsuke Kobayashi Shunsuke Kobayashi
Published: October 2002

We have investigated the effect of molecular structure of weakly rubbed organic solvent soluble polyimides (PI) with trifluoromethyl moieties on polar (out of plane-tilt) anchoring strength and the surface ordering of nematic liquid crystal (NLC), 5CB.
We have found that the polar anchoring strength of 5CB is dependent on the molecular structure of these unidirectionally rubbed PI surfaces. Also, we have clearly observed that the polar anchoring strength of 5CB strongly depends on the surface ordering of weakly rubbed PI surfaces.
Unique Electroluminescent Characteristics of Light-Emitting Diode Utilizing Poly(3-alkylthiophene) Containing Fluorescent Dye
Authors: Yoshida Masayoshi , Kawahara Hideaki , Fujii Akihiko , Ohmori Yutaka , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Electroluminescent (EL) diodes utilizing poly(3-alkylthiophene) containing fluorescent dyes have been fabricated and their unique characteristics have been studied. The EL efficiency has been enhanced by a factor of 100 in poly(3-alkylthiophene) diodes doped with cyclopentadiene derivative compared with that in undoped poly(3-alkylthiophene) diodes. Color-variable light emission with increasing applied voltage, as well as improvement of the EL efficiency, has been observed in diodes with poly(3-alkylthiophene) containing oxadiazole derivative.
Crystal Growth of Tl2Ba2Ca2Cu3O10 (Tl-2223) Superconductors
Authors: Matsushita Yoshitaka , Hasegawa Masashi , Sakai Fumiko , Takei Humihiko
Published: October 2002

Growth of Tl2Ba2Ca2Cu3O10 superconductor crystals has been investigated using a mixed state of solid with melt. Single crystals are grown by soaking and slow cooling in a very narrow temperature range between 900 and 870° C in a sealed Au capsule. The obtained crystals are in a form of thick plates, and their maximum size is 0.8×0.8×0.4 mm3, with a plane of (001). The chemical composition is determined by an electron-probe microanalyzer to be Tl1.91-2.00Ba2.03-2.08Ca1.70-1.79Cu3.03-3.13O10, where oxygen stoichiometry is assumed. The as-grown crystals show a sharp superconductive transition at 115 K.
Fabrication of Josephson Junction on (001) YBa2Cu3Ox Single Crystal Substrate
Authors: Konishi Masaya , Youichi Enomoto Youichi Enomoto
Published: October 2002

We have fabricated a junction consisting of an a-axis oriented film and a (001) substrate of YBa2Cu3O

x

. First, a multi-layer structure has been prepared by film deposition at rather low substrate temperature, and the junction with an area of 40×40 µ m2 has been fabricated by conventional photolithography and etching technique. This junction exhibits supercurrent below 65 K and Shapiro-steps under microwave irradiation at 5 GHz. This Josephson junction is the first one formed on the high-T
c single crystal substrate, which has high possibility of improvement in reproducibility due to the high quality electrodes.
Performance of All-Optical Switch Utilizing the Spin-Dependent Transient Rotation in a Multiple-Quantum-Well Etalon
Authors: Nishikawa Yuji , Tackeuchi Atsushi , Yamaguchi Masaomi , Muto Shunichi , Osamu Wada Osamu Wada
Published: October 2002

The performance of the spin-dependent transient rotation (STR) for a multiple-quantum-well (MQW) etalon is studied. An on/off contrast of 4:1 obtained for a pump pulse energy of 50 fJ/µ m2 at room temperature is larger than that obtained by other picosecond switching methods using etalons. The experimentally observed polarization-rotation angle of the probe beam has been found to be proportional to the total well thickness, which is consistent with the theoretical prediction. It is predicted that the contrast can be improved to over 20:1 for a pump pulse energy of 50 fJ/µ m2 by using a MQW etalon with a total well thickness of 1 µ m.
Silicon Wafer Direct Bonding through the Amorphous Layer
Authors: Fujino Seiji , Matsui Masaki , Hattori Tadashi , Hamakawa Yoshihiro
Published: October 2002

We found that excess water molecules and hydrocarbons, existing in the bonding interface and thought to cause voids, were absorbed in the damaged area of the amorphous layer formed on the surface of the wafer upon direct bonding of silicon wafers, thus making it possible to suppress void formation with relatively low heat-treatment temperature of 600° C for 3 h.
Spectral Sideband Caused by Amplitude Modulation of Dye Laser Amplifier Excited by Intensity-Fluctuated Pumping Laser
Authors: Nemoto Koshichi , Fujii Takashi , Minowa Yoshibumi
Published: October 2002

The spectral sideband caused by the amplitude modulation of a copper-vapor-laser-pumped dye laser MOPA, was distributed in a frequency region of more than 3 GHz and its intensity was about 0.01 compared with the average DC component at the modulation frequency of 1 GHz, according to the results of Fourier analysis for a pulse waveform measured with a streak camera and the rate equation analysis.
Cracking Efficiency of Hydrogen with Tungsten Filament in Molecular Beam Epitaxy
Authors: Sutoh Atsushi , Okada Yoshitaka , Ohta Shigeru , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

Atomic hydrogen is known to exert various important effects on the growth of semiconductors in molecular beam epitaxy (MBE). In this work, the cracking efficiencies of hydrogen molecules into atomic hydrogen with a hot tungsten (W) filament have been experimentally determined. Hydrogen atoms recombine at the surface of a heated platinum detector to form molecules releasing the heat of reaction, which results in a temperature increase of the platinum detector, and the cracking efficiencies of atomic hydrogen can be determined by considering the enthalpy of atomization. The cracking efficiency increased exponentially with W filament temperature. At a filament temperature of 1600° C and a H2 gas flow rate of 1.5 ccm for example, the cracking efficiency was determined to be about 1.5% or equivalently, the number of hydrogen atoms resulting from cracking was 2×1016 cm-2·s-1 at a H2 pressure of 1.87×10-2 Pa.
A New Technology for Negative Ion Detection and the Rapid Electron Cooling in a Pulsed High-Density Etching Plasma
Authors: Tae Hyuk Ahn Tae Hyuk Ahn , Keiji Nakamura Keiji Nakamura , Hideo Sugai Hideo Sugai
Published: October 2002

Time-resolved measurements of key parameters in an inductively-coupled pulsed discharge in chlorine are carried out to elucidate a feature of pulsed plasma etching. Langmuir probe diagnostics in the afterglow phase show a very fast decrease in the electron temperature from 3.5 eV to 0.8 eV within 10 µs, along with a plasma potential drop from 22 V to 5 V. A new technique for measuring the time-varying absolute negative ion density is developed, which is based on laser-induced photodetachment and electron-beam excited instabilities at plasma frequency. This novel method reveals that the dissociative electron attachment yields a large increase in the chlorine negative ion density of up to 2×1010 cm-3 (∼50 % of the positive ion density) at an afterglow time of 20 µs.
Controlling Spatiotemporal Chaos by Pinning Method in Two-Dimensional Coupled Map Lattices
Authors: Ohishi Yuji , Ohashi Hirotada , Mamoru Akiyama Mamoru Akiyama
Published: October 2002

Spatiotemporal chaos in two-dimensional logistic coupled map lattices is controlled by a pinning method, which is a partial-site local control scheme. The effectiveness of the control depends not only on the pinning density, but also on the pinning distribution pattern. The control is more successful with increase of the pinning density, and more effective with use of an optimal pinning pattern which sets more pinning sites around a no-pinning site.
A Novel Multi-Domain Wide-Viewing Angle Liquid Crystal Display
Authors: Nick A. J. M. van Aerle Nick A. J. M. van Aerle
Published: October 2002

A novel and simple method is described to obtain wide-viewing angle twisted-nematic liquid-crystal displays (TN-LCDs) by generating multi-domain splayed (MDS) TN structures within each pixel. These structures are obtained by covering one substrate with a mixture of a low pretilt θ1 and a high pretilt θ2 polymer, which phase separates into small domains during coating and drying; and providing the opposing substrate with a polymer that induces an intermediate pretilt angle θ3 (θ1<θ3<θ2). Both substrates are rubbed, assembled to a twisted cell, and finally filled with a properly doped LC mixture. In this way a MDS-TN display is obtained that contains two types of randomly distributed splayed-TN configurations, with complementary optimum viewing angle, resulting in a wider viewing angle and suppressed gray-scale inversion.
Flattening Transition on GaAs (411)A Surfaces Observed by Scanning Tunneling Microscopy
Authors: Hiroshi Yamaguchi Hiroshi Yamaguchi , Takumi Yamada Takumi Yamada , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

We have studied the atomic structures of GaAs (411)A surfaces by using scanning tunneling microscopy, and have found that the surface flatness largely depends on the As coverage. In contrast to the As-rich surface, which has no flat (411)A terraces but has (311)A and (511)A microfacets, the As-deficient surface shows flat (411)A terraces with 0.07-nm-high monomolecular steps. The detailed analysis based on the observed atomic arrangements indicates that the flattening transition can occur because the electron counting rule is broken at all monomolecular steps on the As-deficient surface.
(112)-Oriented Growth of CuInSe2 on (001) Mo Single-Crystal Substrates
Authors: Osamu Igarashi Osamu Igarashi
Published: October 2002

CuInSe2 depositions on (001) Mo single-crystal substrates were achieved by the Se(CH3)2-halogen transport method and the crystallinity of the layers were characterized by reflection high-energy electron diffraction. On the (001) Mo substrates, {001} CuInSe2 was not obtained; CuInSe2 deposited on (001) Mo was composed of four sets of (112)-oriented crystallites which were rotated every 90° about the substrate surface normal. To explain the appearance of the (112) plane, a minimum lattice-mismatch criterion taking into consideration the fact that Mo has a bcc structure was proposed. To obtain Debye-Scherrer-ring-free CuInSe2 films, introducing Br2 to transport In and Cu before introducing Se(CH3)2 was essential.
Low-Concentration GaSb Avalanche Photodiodes Grown by Liquid-Phase Epitaxy Using the Compensation Method
Authors: Sun Yuh-Maoh , Jyh-Ming Wang Jyh-Ming Wang , Meng-Chyi Wu Meng-Chyi Wu
Published: October 2002

The fabricated GaSb mesa avalanche photodiodes exhibit good characteristics of low dark currents, low junction capacitances, and high breakdown voltages. The GaSb layers in these diodes, which have a low electron concentration of 4.3×1015 cm-3, were grown by liquid-phase epitaxy from Sb-rich solutions and by compensation using polycrystalline Te-doped GaSb in the growth solutions.
High-Mobility Doped Polymers
Authors: Borsenberger Paul M. , Gruenbaum William T. , Zumbulyadis Louis J. Sorriero
Published: October 2002

Hole mobilities have been measured in 1,1-bis(di-4-tolylaminophenyl)cyclohexane (TAPC) doped in a series of segmented thermoplastic polymers. For TAPC concentrations of 25 wt%, the mobilities are as high as 3×10-3 cm2/V·s. To our knowledge, these values are a factor of 100 higher than any hole mobilities described in the literature for this dopant concentration.
Crystal Growth and Polarized Photoluminescence Spectra in Ce-Doped Single Crystal of SrGa2S4
Authors: Tanaka Katsu , Ohgoh Tsuyoshi , Kimura Kazuya , Yamamoto Hajime , Shinagawa Kiminari , Sato Katsuaki
Published: October 2002

Polarized photoluminescence (PL) spectra were measured in single crystal of SrGa2S4:Ce prepared by chemical vapor transport technique. A PL band with double peaks at 450 and 493 nm showed strong polarization dependence in shapes and intensities between E∥c and E⊥c polarizations. The PL spectra have been discussed in the framework of the crystal-field theory by which the two peaks have been assigned to transitions between crystal-field and L-S coupling multiplets of 5d- and 4f-states of Ce3+ in D4h
symmetry. Polarized PL spectra calculated on the basis of the crystal-field theory show good agreement with the experimental ones. From these results we suggest a possibility of controlling the chromaticity in blue electroluminescent (EL) phosphors using epitaxial films with well-defined growth orientation.
Negative Differential Resistance on Electron Transport through Ultrasmall Particles
Authors: Hiroshi Nakashima Hiroshi Nakashima , Kiyohiko Uozumi Kiyohiko Uozumi
Published: October 2002

We present a theoretical study on a new one-dimensional array of normal tunnel junctions which produces a negative differential resistance. The junctions are composed of ultrasmall particles, and one of them goes in the direction opposite that of the external electric field. We show dc current-voltage characteristics for this system in terms of a basic single-electron tunneling model. In this system, negative resistance arises due to single-electron tunneling behavior.
Laser-Induced Dry Lift-off Process
Authors: Yong-Feng Lu Yong-Feng Lu , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: October 2002

A dry lift-off process has been achieved using pulsed KrF excimer laser irradiation in air to remove AZ resist and to form SiO2 patterns on GaAs substrate. SiO2 patterns with a resolution of quarter-micron order can be obtained by this process. The process is attributed to the laser photodecomposition of the resist material.
Formation of Epitaxial Twins by Perfluoro-N-Alkane Evaporated on Alkali Halide Crystal
Authors: Ishida Kenji , Horiuchi Toshihisa , Kai Shouichi , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

Structural evaluation of perfluoro-n-alkane, CF3(CF2)18CF3, thin films evaporated on KCl(001) single crystal was performed using a recently developed total reflection X-ray diffractometer. The molecular chain axes of the perfluoro-n-alkane crystals in the evaporated films were revealed to be normal to the substrate, where the molecules assembled in hexagonal symmetry and grew epitaxially on the KCl(001) surface with fourfold symmetry, arranging their <100>hexdirections along the <110> directions of the KCl crystal. Furthermore, detailed analysis suggested that the epitaxially grown crystals form a slightly distorted twin with facing their (14̄30) planes, referred to here as an “epitaxial twin”.
A Novel Amorphous Silicon Double Barrier Homojunction Device with Negative Resistance
Authors: Fang Yean-Kuen , Chen Kuin-Hui , Ching-Ru Liu Ching-Ru Liu
Published: October 2002

A novel amorphous silicon homojunction device with double-barrier doping-profile was fabricated and analyzed. The device possesses a structure of ITO/n/i/p/i/n/i/p/i/n/Al. The double i/p/i-layers form the double barriers. An N-type negative resistance occurs due to the resonant tunneling in the i/n/i quantum well. On the basis of the experimental results, the characteristic of negative resistance is very sensitive to the thickness of i-layer. The optimum thickness of the amorphous silicon i-layers is 30 Å, and a peak to valley current ratio of 3.48 can be obtained at room temperature.
Quantum Chemical Analysis of Metal Adsorption Mechanism onto Silicon Surface in Cleaning Solution
Authors: Miyashita Moriya , Kubota Hiroyasu , Matsushita Yoshiaki , Yoshimura Reiko , Tada Tsukasa
Published: October 2002

Fe3+ and Al3+ complex ion structures in aqueous solution were estimated by ab initio molecular orbital theory. The reactivity between the metal complex ions and Si surface depends on the pH of the solution, which was well explained by the frontier orbital theory. Based on the result of theoretical estimation, the addition of a chelating agent to basic solution to prevent the OH- ion from coordinating with metal ions is demonstrated to be effective in suppressing metal adsorption to the silicon surface.
Nonlinear Optical Properties of Cesium Lithium Borate
Authors: Mori Yusuke , Kuroda Ikuo , Nakajima Satoshi , Sasaki Takatomo , Nakai Sadao
Published: October 2002

Nonlinear optical (NLO) properties of CsLiB6O10 (CLBO) have been investigated. Frequency quadrupling of the 1.064 µ m Nd:YAG laser output for type-I phase matching was observed by using CLBO.
The walk-off angle and the effective NLO coefficient deff were estimated to be 1.83° and 1.01 pm/V for fourth harmonics generation of Nd:YAG laser output, respectively. Phase matching for sum frequency generation of 4ω (fourth harmonics of Nd:YAG laser)+ω (fundamental of Nd:YAG laser), resulting in fifth harmonics of Nd:YAG laser output, has been observed.
Photorefractive Effect in Proton-Exchanged Waveguiding Layers Formed on Lithium Niobate and Lithium Tantalate Crystals
Authors: Kondo Yukiko , Yoichi Fujii Yoichi Fujii
Published: October 2002

The photorefractive effect in the proton-exchanged waveguiding layers formed on lithium niobate and lithium tantalate crystals is investigated. Although the resistance to the photorefractive effect is decreased in the proton-exchanged lithium niobate waveguides by the annealing process, it increases in the case of the proton-exchanged lithium tantalate waveguides. The annealed proton-exchanged waveguides formed on the lithium tantalate crystals are proven to be the most resistant to the photorefractive effect, and are attractive materials for short-wavelength applications.
Internal Resonating of Second-Harmonic Wave by Scanning Fundamental Cavity Length
Authors: Zhou Wang-Long , Mori Yusuke , Sasaki Takamoto , Sadao Nakai Sadao Nakai
Published: October 2002

Simultaneous resonating of the second-harmonic wave with oscillation of its fundamental wave in the same cavity, by scanning the cavity length, was reported. Dual resonance has been achieved by using an Nd:YVO4 microchip laser with the etalon effect of the cavity elements, rather than dispersive phase shift. An enhancement of ∼89 times the harmonic intensity internal to the cavity was obtained. It is possible to realize intracavity fourth-harmonic generation with this method.
Blue-Emitting ac-Electroluminescent Cells Based on ZnS:Tm, Li Powder Phosphors
Authors: Qian Yifan , Hara Kazuhiko , Munekata Hiro , Hiroshi Kukimoto Hiroshi Kukimoto
Published: October 2002

The preparation and characterization of a blue-emitting alternating-current electroluminescent (ac-EL) cell based upon ZnS:Tm, Li powders are described. EL spectra clearly show dominant blue emission peaking at 2.6 eV originating from 1G4→3H6 transition. Advantages and problems of the powder-based ac-EL cell have been discussed in comparison with thin-film-based ac-EL cells.
Near- 1.3-µm High-Intensity Photoluminescence at Room Temperature by InAs/GaAs Multi-Coupled Quantum Dots
Authors: Tackeuchi Atsushi , Nakata Yoshiaki , Muto Shunichi , Sugiyama Yoshihiro , Inata Tsuguo , Naoki Yokoyama Naoki Yokoyama
Published: October 2002

We propose a new quantum dot system called multi-coupled quantum dots. In this system, since quantum dots couple with adjacent dots, the photoexcited carriers tunnel into the larger quantum dots which have lower energy states. This energy relaxation results in narrower and stronger photoluminescence than with conventional quantum dots. InAs/GaAs self-organized multi-coupled quantum dots show strong photoluminescence near 1.3 µ m at room temperature, whose intensity is as large as in the well-known highly efficient InGaAs/GaAs quantum wells.
In Situ Monitoring of Al Growth in Chemical Vapor Deposition by Detecting Reflected Laser Light Intensity
Authors: Sugai Kazumi , Okabayashi Hidekazu , Kobayashi Akiko , Yako Tadaaki , Kishida Shunji
Published: October 2002

A nondestructive, noncontact monitoring method has been developed for Al chemical vapor deposition (CVD). This monitoring method involves irradiating He-Ne laser light on the substrate surface and detecting the reflected light intensity. The intensity changes with deposition time corresponded to the following stage of Al island formation, island coalescence, continuous smooth film formation, and surface roughening. The effectiveness of this method was demonstrated by applying it to Al growth on both in situ sputtered Ti and SiO2 pretreated with tetrakisdimethylamino-titanium for nucleation enhancement.
Atomic-Resolution Imaging of ZnSSe(110) Surface with Ultrahigh-Vacuum Atomic Force Microscope (UHV-AFM)
Authors: Sugawara Yasuhiro , Ohta Masahiro , Ueyama Hitoshi , Seizo Morita Seizo Morita
Published: October 2002

Atomic-resolution imaging of a ZnSSe(110) surface grown by molecular beam epitaxy on a GaAs substrate was demonstrated for the first time with an ultrahigh-vacuum atomic force microscope (UHV-AFM). A rectangular lattice with spacing of 5.6±0.6 Å and 4.0±0.4 Å is resolved. This result suggests that the UHV-AFM has potential to image the group II-VI compound semiconductor surfaces having dangling bonds, on an atomic scale.
Inductive Acceleration with High Demagnetization Rate ∂B/∂t
Authors: Shigeo Kawata Shigeo Kawata
Published: October 2002

A high demagnetization rate ∂B/∂t can be obtained through fast decoupling of a magnetic field from an electric circuit which generates the magnetic field. Nowadays fast decoupling is possible by present switching technologies. Consequently, a high particle-acceleration gradient can be obtained in an inductive acceleration system compared with that in a conventional induction accelerator. Based on this new proposal, inductive electron acceleration is investigated numerically in this work.
Plasma Enhanced Chemical Vapour Deposition of Hydrogenated Amorphous Silicon from Dichlorosilane and Silane Gas Mixtures
Authors: Osborne Ian S. , Hata Nobuhiro , Akihisa Matsuda Akihisa Matsuda
Published: October 2002

Hydrogenated amorphous silicon films have been deposited from mixtures of dichlorosilane ( SiH2Cl2) and silane by plasma enhanced chemical vapour deposition. The deposition rate is found to increase with the addition of SiH2Cl2. At a given rf power, the deposition rate decreases with increasing total flow rate, opposite to that found for deposition with only silane. These results are compared to optical emission data measured under identical deposition conditions, and are discussed in terms of electron attachment to the chlorinated species which modifies the electron energy distribution within the plasma.
New Fabrication Method for Poly(vinyl alcohol)/Liquid Crystal Composite Films with Controlled Droplet Size
Authors: Ono Hiroshi , Kawatsuki Nobuhiro
Published: October 2002

A new fabrication method for poly(vinyl alcohol) (PVA)/liquid crystal (LC) composite film with controlled LC droplet size was presented by changing the dispersion state of hydroxyl groups in the PVA (block character). The LC droplet size could be controlled by the block character without changing the refractive index of the PVA matrix. The threshold voltage was strongly dependent on the LC droplet size though the anchoring strength was dependent on the block character.
New Bistable Electrooptic Effect in Side-Chain Ferroelectric Liquid Crystalline Polymer
Authors: Hwang Jenn Chiu , Fuwa Yoshiaki , Moritake Hiroshi , Gu Hongshen , Ozaki Masanori , Yoshino Katsumi
Published: October 2002

Transient light scattering upon polarity reversal of applied voltage in the chiral smectic C ( Sm C*) phase of ferroelectric liquid crystalline polymer (FLCP) has been studied. The response time of the transient light scattering becomes shorter with increasing applied voltage. The continuous opaque state has been obtained by repeated voltage polarity reversal. At low temperature in the Sm C* phase, a new bistable electrooptic effect, in which both the transparent and opaque states can be maintained after removing the applied voltage, has been demonstrated.
Blue Electroluminescence from Poly(2,5-diheptyloxy-1,4-phenylene)
Authors: Hamaguchi Maki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Poly(2,5-diheptyloxy-1,4-phenylene) has been prepared by oxidative coupling ofp-diheptyloxybenzene using iron (III) chloride as catalyst in chloroform at room temperature. The polymer obtained was completely soluble in chloroform. An electroluminescence diode based on this polymer emitting blue light was fabricated, and its properties are discussed in terms of the band structure of the diode.
Density Measurement of Negative Hydrogen Ions by DC Laser Photodetachment Method
Authors: Mitsuru Yokoyama Mitsuru Yokoyama , Motoi Wada Motoi Wada
Published: October 2002

The change of the electron saturation current of a Langmuir probe in a hydrogen discharge due to irradiation of Ar+ laser has been measured as a function of the distance between the probe and the laser beam. The increase of the probe current caused by the photodetachment of negative ions of hydrogen ( H-) induced by the laser is inversely proportional to the distance. The H- density can be determined from this dependence of the increase of the probe current upon the laser-probe distance. However, a simplified treatment of the measured characteristics results in an overestimation of the H- density, and a correction to account for the effect of sheath formation around the probe is made. The H- density determined after the correction ranges from 15% to 50% of the electron density.
Determination of Valence Band Alignment at Ultrathin SiO2/Si Interfaces by High-Resolution X-Ray Photoelectron Spectroscopy
Authors: Alay Josep L. , Fukuda Masatoshi , Bjorkman Claes H. , Nakagawa Kazuyuki , Yokoyama Shin , Sasaki Sumio , Hirose Masataka
Published: October 2002

The valence band spectra of ultrathin SiO2/Si interfaces have been measured by high-resolution X-ray photoelectron spectroscopy. The energy shifts found in the Si2p and O1s core-level peaks arising from the charging effect are carefully corrected and the valence band density of states for ultrathin SiO2 is obtained by subtracting the bulk Si contribution from the measured spectrum. Thus the band alignment at ultrathin SiO2/Si interfaces has been determined to be 4.36±0.10 eV independent of oxide thickness between 1.8 and 3.7 nm.
Construction of a Dispersion-Allocated Soliton Transmission Line Using Conventional Dispersion-Shifted Nonsoliton Fibers
Authors: Nakazawa Masataka , Hirokazu Kubota Hirokazu Kubota
Published: October 2002

It is shown for the first time that a nonsoliton transmission line consisting of dispersion shifted fibers can be converted into a soliton transmission line by using a dispersion-allocated soliton technique. This technique is similar to linear pulse propagation but its inherent nature is that of soliton propagation.
Titanium Nitride Deposition Using Chemical Beams of Metalorganic Precursors and ECR Plasma-Activated Nitrogen
Authors: Tsuda Hiroshi , Youichirou Numasawa Youichirou Numasawa
Published: October 2002

This letter presents TiN deposition by using chemical beams. In this deposition, nitrogen activated by electron cyclotron resonance, and metalorganic precursors of titanium are supplied onto a substrate as molecular beams in a high vacuum. Dependencies of deposition rate, film composition and resistivity on d.c. bias applied to the substrate show that positive ions are important in deposition and in improving film properties. Moreover, controlling a particular reaction area and the angle of incidence of the molecular beam results in bottom coverage of more than 80% in the contact holes with an aspect ratio of about 3.
Reduction of Ohmic Contact Resistance on n-Type 6H-SiC by Heavy Doping
Authors: Tsutomu Uemoto Tsutomu Uemoto
Published: October 2002

Ohmic contacts with low contact resistances were fabricated on n+ 6H-SiC layers grown by liquid phase epitaxy. Ni was deposited on the layers for the contact metal Ohmic characteristics were obtained on as-deposited n+ samples with carrier concentrations higher than about 5×1019 cm-3. The contact resistance was lowered by thermal annealing at 1000° C for 5 minutes. A specific contact resistance as low as 1×10-6 Ω· cm2 was fabricated on an n+ layer with a carrier concentration of 4.5×1020 cm-3. It was found that Ti/Al, which is widely used as a p-type ohmic contact metal, also made a good ohmic contact on the n+ layer.
Iron-Related Donor Level in N-Type Silicon
Authors: Shuji Tanaka Shuji Tanaka , Hajime Kitagawa Hajime Kitagawa
Published: October 2002

Iron introduces a donor level at about E
c-0.4 eV in n-type silicon. In this work, the electrical properties of this donor state have been studied by deep-level transient spectroscopy (DLTS). It is found, by resolving the overlapping DLTS peaks obtained after room temperature annealing, that the donor decomposes into several other states. Isothermal annealing of samples containing different amounts of phosphorus show that phosphorus has no significant effect on the annealing decay constant of the donor, indicating that phosphorus atoms do not take part in the annealing decay of the donor. A Poole-Frenkel field emission effect is observed in the donor level as expected for donors in n-type silicon.
A Critique on the Use of Window Structure in Travelling Wave Semiconductor Optical Amplifiers
Authors: Lui Wayne W. , Magari Katsuaki , Hasumi Yuji , Yokoyama Kiyoyuki , Mitsuru Naganuma Mitsuru Naganuma
Published: October 2002

The inclusion of window structure to the conventional design of travelling wave semiconductor optical amplifier was thought to help significantly reduce facet reflectivity. A theoretical study, in which wave propagation in the window region is also taken into consideration, shows that the significant reduction can be realized only if the window thickness can be as precisely controlled as the anti-reflection coating thickness. Since this is not viable in practice, conventional design principle and strategy are found necessary to be revised.
Elementary Processes in Atomic Hydrogen-Assisted GaAs Molecular Beam Epitaxy
Authors: Okada Yoshitaka , Fujita Tomoya , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

It has been shown that a continual irradiation of atomic H generated by a hydrogen cracker during the growth of GaAs in molecular beam epitaxy (MBE) serves to promote a step-flow growth mode on GaAs(001) substrates. Fundamentally important observations related to the elementary processes of the growth have been presented based on reflection high-energy electron diffraction (RHEED) measurements. A growth model for the atomic hydrogen-assisted GaAs MBE is therein proposed.
Optical Gain Calculation of Wurtzite GaN/AlGaN Quantum Well Laser
Authors: Kamiyama Satoshi , Ohnaka Kiyoshi , Suzuki Masakatsu , Uenoyama Takeshi
Published: October 2002

Optical gain properties of wurtzite GaN/Al0.2Ga0.8N quantum well lasers are theoretically analyzed using physical parameters from ab initio calculations for the first time. The valence band of wurtzite GaN exhibits strong non-paraboticity, and the hole density of states is significantly large in comparison with the conventional zincblende crystals. This valence band feature causes high transparency cartier density of 7.5×1018 cm-3 in the 50 Å thick GaN quantum well. This result predicts that the threshold current of wurtzite GaN/AlGaN quantum well laser is higher than the conventional lasers with zincblende crystals.
The Importance of the Electric Interaction for Stabilizing the Antiferroelectric Smectic Liquid-Crystalline Phase
Authors: Kusumoto Tetsuo , Isozaki Tadaaki , Suzuki Yoshiichi , Takanishi Yoichi , Takezoe Hideo , Fukuda Atsuo , Hiyama Tamejiro
Published: October 2002

The importance of the interlayer molecular interaction to stabilize the antiferroelectric smectic C A
* (S*
C A
) phase is shown using dimer molecules in which chiral mesogenic units are connected by a polymethylene chain. According to the conformational effect of the polymethylene chain, two mesogenic units tend to align parallel or anticlinically for even or odd carbon number, respectively. In a dimer molecule with a longer chain length, however, another interaction overcomes the conformational effect and stabilizes the S*
C A
phase. This observation suggests the importance of the electric, possibly the dipole-dipole, interaction between mesogens in S*
C A
.
Effects of Plasma Modification on Hole Transport Layer in Organic Electroluminescent Diode
Authors: Mori Tatsuo , Miyake Seiya , Mizutani Teruyoshi
Published: October 2002

Crystallization of a diamine derivative (TPD), used as hole transport layer, could be successfully suppressed by plasma modification. Crystallization could not be observed in the plasma-modified TPD thin film after 30 days. The EL efficiency of the organic LED with a plasma-modified TPD layer was lower than that of conventional organic LEDs. This is explained by the quenching of Alq3 excitons due to the interfacial oxidation layer between emission layer and the plasma-modified TPD.
The EL efficiency of the organic LED with a plasma-modified TPD layer was restored by the redeposition of TPD on the plasma-modified surface. However, although the crystallization of TPD was suppressed, the lifetime of the organic LED under the application of current could not be improved by plasma modification.