bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Post Annealing and Oxidation Processes on the Removal of Damage Generated during the Shallow Trench Etch Process
Authors: Young-Jun Lee Young-Jun Lee , Soon-Won Hwang Soon-Won Hwang , Kyung-Hee Oho Kyung-Hee Oho , Jung-Yong Lee Jung-Yong Lee , Geun-Young Yeom Geun-Young Yeom
Published: October 2002

In this study, 0.3–0.5 µm deep silicon trenches were etched using Cl2/10%N2 and Cl2/50%HBr inductively coupled
plasmas, and the defects remaining on the etched silicon trench surfaces and the effects of various
annealing and oxidation on the removal of the defects were studied. High resolution transmission
electron microscopy was used to investigate the degree of remaining defects and X-ray photoelectron
spectroscopy was also used to investigate surface contamination of the etched silicon wafers.
Defects were found on the silicon trench surfaces etched using both Cl2/10%N2 and Cl2/50%HBr.
A thermal oxidation of 200 Å at the temperature up to 1,100°C did not remove the remaining defects
completely and more defects were remained on the silicon trench etched using Cl2/10%N2. More defects
remaining on the oxidized silicon trench for Cl2/10%N2 appear to be related to the formation of silicon
oxynitride on the silicon trench etched in Cl2/10%N2, therefore, forming less thermal oxide during the
oxidation process. The annealing of the etched silicon trenches from 900°C to 1,000°C for 30 min in N2 also
decreased the number of defects, however, to remove the defects formed in our experiments, the annealings
at the temperature higher than 1,000°C in N2 for 30 min appears to be required. A combination process of
annealing at 1,000°C and oxidation at 900°C was also effective in removing the defects completely.
Effect of Post Plasma Treatment on Reliability of Electron Cyclotron Resonance Chemical Vapor Deposited SiOF Films
Authors: Seoghyeong Lee Seoghyeong Lee , Jong-Wan Park Jong-Wan Park
Published: October 2002

Fluorine doped silicon dioxide (SiOF) films have a low dielectric constant. Unfortunately, the drawback of regarding SiOF is its low resistance to moisture which causes the increment of dielectric constant with time. Also, fluorine desorption of SiOF film during the postmetallization process causes degradation of metal interconnections. In this study, oxygen postplasma treatments are applied to as-deposited SiOF films for improving their dielectric properties and thermal stabilities. It has been observed that the postplasma treatment of SiOF films is quite an efficient method for blocking moisture and for the stabilization of the dielectric constant. Furthermore, the O2 postplasma treatment of Cu/W–N/SiOF/Si stacks by suppressing interdiffusion improved the thermal stability between SiOF and metal interconnections.
Novel Fabrication Process of Freestanding Metallic Microstructures Using Double Electroplating
Authors: Baek Chang-Wook , Kim Yong-Kweon
Published: October 2002

A simple electroplating surface micromachining process for fabricating freestanding
microstructures using UV lithography of thick photoresist and double electroplating is presented.
Compared with the conventional surface micromachining process, this process can be used to fabricate
various shapes of freestanding “out-of-plane” microstructure. Two different materials electroplated
continuously in a single mold are used as a sacrificial and a structural layer, respectively. Shape of the
sacrificial layer is determined by changing width and space of the patterned plating base electrodes.
The released structure is obtained after selective etching of the sacrificial layer. The shape of released
structure is automatically determined by shape of sacrificial layer. The gap and thickness of the
structure are easily controlled by electroplating times. Using this process, a simple microactuator with
inclined side-support beams is successfully fabricated. This technique can be applied to fabricate a
novel type of surface micromachined actuating component.
Fabrication of Field Emitter Arrays Using Si Delamination by Hydrogen Ion Implantation
Authors: Tanemasa Asano Tanemasa Asano , Daisuke Sasaguri Daisuke Sasaguri
Published: October 2002

Field electron emitter arrays (FEAs) have been fabricated
using the void cut and delamination of hydrogen ion implanted Si. The
process utilizes the mold made of single-crystal Si. The delaminated
Si thin film forms the gate electrode which is self-aligned to the
emitter. Investigation of process conditions shows that hydrogen-ion
dose, bonding between the mold Si wafer and a supporting substrate,
and wafer size are critical. An FEA with 700 WSi2 emitter tips
operates by the application of voltages less than 50 V.
Effective Pair Potentials of NaCl- and CsCl-type KBr Determined by X-Ray Absorption Fine Structure under Pressure
Authors: Yoshiasa Akira , Nagai Takaya , Murai Kei-ichiro , Yamanaka Takamitsu , Kamishima Osamu , Shimomura Osamu
Published: October 2002

A difference in effective pair potentials between the NaCl- and CsCl-type KBr has been investigated using the X-ray absorption fine structure (EXAFS) technique under pressure. In the potential parameter fitting, we have directly carried out the numerical integration of the EXAFS function and evaluated the precise effective pair potential. The effective pair potential is influenced not only by pressure but also by coordination numbers. The high pressure CsCl-type phase has broader effective pair potentials than the NaCl-type phase.
Excimer-Laser-Induced Lateral-Growth of Silicon Thin-Films
Authors: Kensuke Ishikawa Kensuke Ishikawa , Motohiro Ozawa Motohiro Ozawa , Chang-Ho Oh Chang-Ho Oh , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

A new excimer-laser crystallization method called the “gradient method", has been developed for large-grain growth of Si thin-films on glass. The method is based on a spatial modulation of an incident light intensity, which triggers the lateral grain growth. Grains of size as large as 5 µm were grown by a single shot irradiation at a substrate temperature of 500°C. By combining a step motion of the sample and the proposed method, the grain could be enlarged drastically.
Epitaxial Growth of ZnO Films on (0001) Sapphire at Low Temperatures by Electron Cyclotron Resonance-assisted Molecular Beam Epitaxy and Their Microstructural Characterizations
Authors: Hee-Bog Kang Hee-Bog Kang , Kiyoshi Nakamura Kiyoshi Nakamura , Sung-Hwan Lim Sung-Hwan Lim , Daisuke Shindo Daisuke Shindo
Published: October 2002

The details of epitaxial growth and microstructural characteristics of ZnO films grown on (0001) sapphire were investigated using X-ray diffraction (XRD), reflection high energy electron diffraction (RHEED), and plan-view and cross-sectional transmission electron microscopy (TEM). The films were grown by electron cyclotron resonance-assisted molecular beam epitaxy (ECR-assisted MBE). The ECR-assisted MBE was found to be capable of growing high quality epitaxial ZnO films at low temperatures in comparison with chemical vapor deposition (CVD) and RF sputtering. The films exhibited a high degree of epitaxy, a sharp interface between film and substrate, and a smooth surface morphology. The TEM observations revealed that the films were epitaxial with an orientational relationship of (0001)ZnO ∥(0001)Al_2O_3 and [1̄21̄0]ZnO ∥[1̄100] Al_2O_3. This is equivalent to a 30° rotation of ZnO relative to sapphire in (0001) plane.
Contact Structure for a Superconducting Field Effect Transistor Using SrTiO3/YBa2Cu3O7- x Films
Authors: Inada Hiroshi , Nakamura Takao , Iiyama Michitomo
Published: October 2002

A contact structure for a superconducting field effect transistor (SuFET) was developed using a sequentially-deposited SrTiO3 (STO)/YBa2Cu3O7-x
(YBCO) bilayer. A buried contact structure was proposed to contact the edge of the ultrathin YBCO layer of the STO/YBCO bilayer, which was used as a channel layer of a SuFET. To reduce the contact resistance, focused ion beam (FIB) etching of the bilayer and in situ noble metal deposition were adopted. Specific contact resistance was reduced to 5×10-8 Ω cm2 for a 30-nm-thick YBCO film without annealing. Furthermore, annealing in ozone caused a reduction of specific contact resistance to 3×10-8 Ω cm2 for a 20-nm-thick YBCO film. This structure is useful to shrink the device dimensions and to improve the modulation characteristics of a SuFET.
Magnetization Reversal Mechanism and Magnetic Properties of Co/Pd Multilayers
Authors: Jeong Soon Young , Shan Zheng Sheng , Sellmyer David J.
Published: October 2002

To study the magnetization reversal mechanism and the magnetic properties of Co/Pd multilayers fabricated at various Ar sputtering pressures, we first demagnetized the samples using the field-demagnetization method, then measured initial and magnetization curves and minor loops. The coercivity and the perpendicular magnetic anisotropy were obtained from the parallel and perpendicular magnetization curves measured at different temperatures. We interpret our experimental results by applying several qualitative methods. From this study, we found that the domain wall pinning with a small pinning site is the dominant magnetization reversal mechanism.
AlGaAs Semiconductor Quasiphase-Matched Wavelength Converters
Authors: Xu Chang-qing , Takemasa Keizo , Nakamura Koji , Okayama Hideaki , Kamihoh Takeshi
Published: October 2002

Wavelength conversion based on sum frequency generation (SFG) using a semiconductor quasiphase-matched (QPM) waveguide with a periodically crystal domain inverted structure has been studied both theoretically and experimentally. Mathematical expressions with clear physical insight into QPM SFG are derived, taking into account waveguide propagation loss. SFG from AlGaAs QPM waveguides fabricated by a direct wafer bonding technique have been characterized. Nearly polarization insensitive wavelength conversion is demonstrated, and a normalized conversion efficiency of 810%/(W cm2) is obtained for a 0.5-mm-long waveguide with a propagation loss of over -100 dB/cm. The dependence of conversion efficiency and polarization sensitivity on device length is also discussed, and it is shown that the experimental results agree well with the theoretical simulations.
All-Optical Logic Functions in a Bent Nonlinear Y-Junction Waveguide
Authors: Kim Chan Ki , Jeong Je-Myung , Chang Hosung
Published: October 2002

We propose and study all-optical logic gates, performing two input AND, OR and exclusive-OR (XOR) functions in a bent nonlinear Y-junction waveguide. The operation of the proposed device is based on the evolution of a nonlinear guided wave along a bent nonlinear waveguide. Since the characteristics of beam propagation depend on the nonlinearity, input power and bending angle of the waveguide, we could implement several all-optical logic functions (AND, OR and XOR) in the waveguide end and nonlinear medium, varying the above parameters.
Electron-Beam Writing Fabrication of Periodic Structure for Quasi-Phase-Matching Second-Harmonic Generation in Dimethyl Nitrophenyl Pyrazole Crystal Waveguide
Authors: Nakao Akira , Fujita Kazunari , Suhara Toshiaki , Nishihara Hiroshi
Published: October 2002

We demonstrate fabrication of a periodic structure for quasi-phase-matching (QPM) second-harmonic generation (SHG) in 3,5-dimethyl-1-(4-nitrophenyl) pyrazole (DMNP) by electron-beam (EB) writing. It is found that DMNP loses optical anisotropy and is changed to an amorphous phase by EB irradiation. This indicates that the SHG coefficient is zero at the irradiated part. Periodic structures with 0.5 µm period and 0.5 duty ratio were obtained in channel waveguides at a dose of approximately 5000 µC/cm2.
Interfacial Reaction of SrRuO3 Prepared Directly on TiN
Authors: Hiratani Masahiko , Okazaki Choichiro , Takagi Kazumasa
Published: October 2002

The interfacial reaction of a SrRuO3 (SRO)/TiN layered film was evaluated using resistivity measurements and X-ray diffraction. When the SRO film was deposited on TiN at temperatures below 500°C, the TiN film was not entirely oxidized and the resistivity of both TiN and SRO remained low irrespective of the oxygen pressure during SRO growth. The resistance between SRO and TiN increased when SRO was deposited on TiN in a vacuum, but it did not increase significantly when SRO was deposited in a vacuum during the initial stage of growth and subsequently in 100 mTorr of O2. This is attributed to insufficient SRO oxidation at the interface as a result of oxygen diffusion into the TiN film when SRO is deposited in vacuum.
Photoinduced Formation of CdSSe Nanocrystals in Glass
Authors: Tadaki Miyoshi Tadaki Miyoshi , Hirofumi Fukuda Hirofumi Fukuda , Naoto Matsuo Naoto Matsuo
Published: October 2002

The optical transmission and luminescence spectra of CdSSe-doped glass before heat treatment were measured. This glass does not contain CdSSe nanocrystals. The optical transmittance decreases and luminescence intensity increases upon laser irradiation. These results indicate that the CdSSe nanocrystals are formed by laser irradiation. When the wavelength of laser light is changed, a notable change in the absorption edge of induced absorption is not observed. Transient characteristics of luminescence from the CdSSe-doped glass are compared with those from the CdSSe-doped glass after heat treatment.
Computational Studies on the Erosion Process in a Magnetron Sputtering System with a Ferromagnetic Target
Authors: Ido Shunji , Suzuki Takeshi , Kashiwagi Mieko
Published: October 2002

The erosion process is studied using computational simulations for a magnetron sputtering system with a ferromagnetic target. The magnetic field analysis is carried out with a finite element method (FEM) code. Plasma generation and erosion are examined via the particle orbit simulations. A new model is developed to examine the erosion process in a ferromagnetic target. It is shown that the erosion profile obtained in computational studies is in good agreement with experimental results.
Density Distributions in a Rectangular Positive Column at Intermediate Pressures
Authors: Sato Masumi
Published: October 2002

Spatial profiles of the plasma density and ion drift velocity in an infinite rectangular dc discharge positive column at intermediate pressures are obtained based on the quasi-neutral transition theory for two-dimensional geometry. Assuming that the ionization by electron impacts occurs at a constant ratio in the two directions, relevant differential equations for plasma parameters are solved by means of variable separation and the plasma profiles are determined as explicit functions of actual distances in the column. The results derived are an extension of the high-pressure Schottky theory to the low-pressure region.
Structural Analysis of Porous Silicon Multilayer using X-Ray Diffraction
Authors: Takehiro Maehama Takehiro Maehama , Chushin Afuso Chushin Afuso , Nobuo Itoh Nobuo Itoh
Published: October 2002

A porous silicon monolayer (PSL) and four types of porous silicon multilayers (PSMLs) with 2-, 3-, 7-, and 50-layers were studied using the X-ray double crystal method. PSMLs were formed by controlling the anodization current density. Only three distinct peaks were observed in each rocking curve for these PSMLs, which showed two kinds of porous silicon layers with good crystallinity. It was also shown that the PSL and PSMLs were slightly different in the state of lattice strain. To observe the structure and depth-distribution of lattice strain of PSMLs, a new X-ray cross-sectional topographic technique (XCST) has been proposed. Applying XCST to a three-layer porous silicon consisting of 5 µm, 10 µm, and 5 µm layer thicknesses resulted in a clear X-ray cross-sectional topograph. From the topograph and the corresponding rocking curves, the precise distribution of the lattice strain was revealed. The XCST is useful for evaluating not only the PSML, but also general crystal multilayer structures such as superlattice hetero structures.
Control of Step Arrays on Normal and Vicinal SrTiO3(100) Substrates
Authors: Nie Jiacai , Shoji Akira , Koyanagi Masao , Takashima Hiroshi , Terada Norio , Endo Kazuhiro
Published: October 2002

The surface morphologies of SrTiO3 substrates have been investigated by atomic force microscopy. Periodic step arrays could be developed on both normal and vicinal SrTiO3 (100) substrates by a new method employed both buffered NH4F-HF (BHF) solution and O2 annealing. An explanation is given for the surface morphologies observed which involves the surface stoichiometrical change upon BHF solution and surface diffusion upon oxygen annealing.
Optical Waveguide of MeV Hydrogen Ion Implanted KTiOPO4
Authors: Wang Ke-Ming , Lu Fei , Meng Ming-Qi , Shi Bo-Rong , Li Wei , Wang Feng-Xiang , Shen Ding-Yu , Cue Nelson
Published: October 2002

The first MeV hydrogen ion implanted waveguide in KTiOPO4 is
reported. The planar optical waveguide in KTiOPO4 was fabricated by
1.0 MeV hydrogen ions to a dose of 2×1016 ions/cm2 at room
temperature. The dark modes were observed by prism coupling. Both
refractive index profiles before and after annealing show a typical
barrier waveguide in KTiOPO4 formed by 1.0 MeV hydrogen ion
implantation. After annealing at 200°C for 30 min, a 0.4%
decrease in the refractive index was observed. Loss is estimated
to be less than 2.2 dB/cm.
Spatially Selective Metal Deposition into a Hole-Array Structure of Anodic Porous Alumina Using a Microelectrode
Authors: Masuda Hideki , Yotsuya Masato , Ishida Masaya
Published: October 2002

Spatially selective electrochemical deposition of a metal (Ni) into the
ordered nanohole-array structure of anodic porous alumina was performed
using a microelectrode. A patterned deposit consisting of fine Ni cylinders
of 70 nm diameter was obtained in the hole-array structure with spatial
resolution on the order of tens of micrometers, and its size was in good
agreement with that of the microelectrode used as a tip.
Optical Properties of GaN Thin Films on Sapphire Substrates Characterized by Variable-Angle Spectroscopic Ellipsometry
Authors: Yang Tao , Goto Shigeo , Kawata Masahiko , Uchida Kenji , Niwa Atsuko , Gotoh Jun
Published: October 2002

The optical properties of GaN thin films grown on sapphire substrates by low-pressure metal
organic chemical vapor deposition were investigated by variable-angle spectroscopic ellipsometry.
Accurate refractive indices (n, k) below, through, and above the fundamental bandgap of GaN in the
spectra range of 1.5 to 3.8 eV (330 to 830 nm) were determined by using a parametric semiconductor
model that took the surface roughness effect into account. The fundamental bandgap energy (3.41 eV)
of GaN determined by the model was exactly the same as that obtained from an optical
transmission experiment using the same sample. The high-frequency dielectric constant ε
∞ (=5.2) of
GaN for (E⊥c) obtained from the ellipsometric measurement was also in excellent agreement with
the experimental value of 5.2±0.1 (E⊥c) from the IR reflectivity measurements.
Excimer Laser Crystallization of Amorphous Indium-Tin-Oxide and Its Application to Fine Patterning
Authors: Hosono Hideo , Kurita Masaaki , Kawazoe Hiroshi
Published: October 2002

Polycrystalline indium-tin-oxide (ITO) thin films were prepared at an ambient
temperature by irradiation of amorphous (a-) ITO with KrF excimer laser pulses of
≥40 mJ/cm2/pulse. Electrical resistivity of the specimen at ∼300 K decreased from
5.9×10-4 Ω·cm to 2.7×10-4 Ω·cm upon laser crystallization. Irradiation of a-ITO thin films
through a phase mask led to the formation of a periodic structure composed of a-ITO
and crystalline (c-) ITO. The micropattern of c-ITO was successfully formed by the
chemical etching of the irradiated specimens, utilizing the large differences in the
chemical etching rate between crystallized and amorphous ITOs.
Improved Electron Mobility of AlInSb/InAsSb/AlInSb Heterostructures Grown Lattice-Mismatched on GaAs Substrates
Authors: Kudo Makoto , Mishima Tomoyoshi
Published: October 2002

We have improved the electron mobility of AlxIn1-xSb/InAsySb1-y/AlxIn1-xSb heterostructures grown by molecular beam epitaxy. By using Al0.15In0.85Sb as high-resistivity barrier layers and by using InAsySb1-y(whose composition was chosen to be lattice-matched with the Al0.15In0.85Sb) as a channel layer, high electron mobility exceeding 24,000 cm2·V-1·s-1was obtained at room temperature. This value is an order of magnitude larger than that of an Al0.15In0.85Sb/InSb/Al0.15In0.85Sb lattice-mismatched heterostructure grown as a reference. Mobility is improved by using an InAsySb1-ychannel because the lattice-mismatch between the barrier and channel layers is minimized.
Formation of an S2
- Molecular Ion and Its Luminescence Characteristics in KCl:MnS Crystals
Authors: Ye Rongbin , Tazawa Hideaki , Baba Mamoru , Nishidate Kazume , Schwan Lother O. , Schmid Dankward
Published: October 2002

It was found that when a KCl crystal doubly doped with a trace of MnS was irradiated with UV light, the S2
- molecular ions were effectively produced
through a photochemical reaction. These S2
- molecular ions exhibited characteristic vibronic luminescence composed of zero-phonon lines and phonon-side bands below 160 K. Such a vibronic structure related to zero-phonon lines could also be observed for the first time in the
luminescence excitation band. From the analysis of the spectral positions of zero-phonon lines in the emission and excitation spectra, the average vibrational frequencies of the S2
- molecular ion in the ground state and excited state were determined to be 1.78×1013 s-1 and 1.13×1013 s-1 respectively.
A Physics-Based, SPICE (Simulation Program with Integrated Circuit Emphasis)-Compatible Non-Quasi-Static MOS (Metal-Oxide-Semiconductor) Transient Model Based on the Collocation Method
Authors: Woo Hwang Sung , Han Kwon Tae-Woong Yoon , Seop Yu Yun , Hyuk Kim Ki
Published: October 2002

The collocation method has been applied to derive a new SPICE (Simulation Program with Integrated Circuit Emphasis)-compatible non-quasi-static MOS (metal-oxide-semiconductor) transient model. Contrasting to the conventional approximation methods, the collocation method is simple for the model derivation and efficient in optimizing the variables of the continuity equation. The derived model is fully physics-based in that all the transient currents are directly expressed by only physically meaningful, optimized quantities. The model adequately predicts transient currents in the bias region such as the weak inversion region where conventional models show numerical difficulties.
Direct Oxidation of Si1- xGe x Layers Using Vacuum-Ultra-Violet Light Radiation in Oxygen
Authors: Chen Liang-Po , Chan Yuen-Chang , Chang Shoou-Jinn , Huang Guo-Wei , Chang Chun-Yen
Published: October 2002

Oxidation of Si1-x
Ge
x
films has been carried out by direct photo chemical vapor deposition (direct photo-CVD) directly with activated O2 induced by Vacuum-Ultra-Violet (VUV) light radiation. The Auger electron spectroscopy profiles show that no Ge-pileup layer at the oxide/Si1-x
Ge
x
interface is observed after VUV-induced Si1-x
Ge
x
oxidation process. The X-ray photoelectron spectroscopy analysis of the samples reveals that Si and Ge are oxidized simultaneously in oxidation process and a mixed oxide layer consisting both SiO2 and GeO2 is formed. This might be the reason that Ge pileup effect is eliminated in this study.
Effects of Arsenic Concentration in Gate Oxide on Electrical Properties of Metal-Oxide-Si Capacitors
Authors: Chang-Liao Kuei-Shu , Chen Chung-Hsien
Published: October 2002

The effects of drive-in temperature/time for As+ implantation on the electrical
properties of metal-oxide-Si (MOS) capacitors are investigated. It is found that As
in the gate oxide degrades significantly the stability and reliability of MOS devices.
When the drive-in temperature/time is increased, the sheet resistance of the gate
electrode is decreased while the changes in the electrical properties of MOS devices
become significant. From the results of neutron activation analysis (NAA) of
arsenic concentration in various gate oxides, changes in the electrical properties of
MOS devices could be attributed to the diffusion of arsenic into the gate oxide
and/or the SiO2/Si interface.
Room-Temperature Pulsed Operation of GaN-Based Laser Diodes on a-Face Sapphire Substrate Grown by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Kimura Yoshinori , Miyachi Mamoru , Takahashi Hirokazu , Tanaka Toshiyuki , Nishitsuka Mitsuru , Watanabe Atsushi , Ota Hiroyuki , Chikuma Kiyofumi
Published: October 2002

We report on the room-temperature pulsed current operation of GaN-based laser diodes on a (1120)
(a-face) sapphire substrate grown by low-pressure metalorganic chemical vapor deposition (LP MOCVD).
Ethyl biscyclopentadienyl magnesium (Et-Cp2Mg) and methyl silane (Me-SiH3) were
used as precursors for dopants. The cavity mirror facets were formed by cleaving an a-face
sapphire substrate along (1102) (r-face). The threshold current density was 41 kA/cm2 and the
operating voltage at the threshold was 35 V. Above the threshold, laser emission was observed at
411 nm.
Effects of High-Resistivity, Low-Temperature Layer in Transient Capacitance Measurements of GaAs n-i-p Structures
Authors: Chen Jenn Fang , Wang Pai Yong , Chen Nie Chuan
Published: October 2002

Deep-level transient spectroscopy and transient capacitance
measurements are performed on a molecular-beam-epitaxially grown GaAs
n-i-p diode with a 2000-Å-thick low-temperature (LT)-grown layer immersed in
its intrinsic region. The transient capacitance measurements reveal that the
time constant and activation energy are the same for both the emission and
capture processes. An equivalent circuit based on capacitance-frequency
spectra is derived and used to obtain the resistivity values of the LT layer that
are in agreement with experimental results. It is concluded that the transient
capacitance observed corresponds to the resistance-capacitance time
constant due to the LT-layer. In addition, the value of the activation energy is
explained based on the equivalent circuit.
Capacitance-Voltage Characteristics of SiO 2 Films Prepared by Electron Cyclotron Resonance Plasma Chemical Vapor Deposition as a Function of O 2 Content and Microwave Power
Authors: Moonsang Kang Moonsang Kang , Yongseo Koo Yongseo Koo , Chul An Chul An
Published: October 2002

The capacitance-voltage characteristics of SiO2 films were investigated as a function of O2
content and microwave power using the electron cyclotron resonance plasma chemical vapor deposition
method. The interface trap density was
1010∼5×1011 eV-1·cm-2. From the capacitance-voltage characteristics,
we may assume
that positive ions (O2
+ or O+) exist in the SiO2 films and these positive ions
increase with increasing O2 content or microwave power. Low ion energy is important for
avoiding positive ions in oxide films so that high-quality oxide can be obtained.
Cross-Substitutional Alloys of InSb for Write-once Read-many Optical Media
Authors: Williams Edward W. , Kubo Takahiro
Published: October 2002

Cross-substitutional alloys of InSb are attractive for novel write-once read-many optical media such as CD-R because of the low melting point and the phase diagram of the alloys. The low melting point means that laser ablation is possible with low power solid state lasers and the two phase material in the alloy phase diagram can be converted irreversably into a single phase material. In both cases the reflectivity difference between the hole and the land and the two-phase and the single phase material should be sufficient to make digital recording possible. This is the first time that these materials have been reported for write-once optical recording.
Effects of H Plasma Passivation on the Optical and Electrical Properties of GaAs-on-Si
Authors: Wang Gang , Zhao Guang Yuan , Soga Tetsuo , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

The effects of hydrogen plasma passivation on optical and electrical properties of metalorganic
chemical vapor deposition (MOCVD) grown GaAs-on-Si epilayers have been studied. The intensity of photoluminescence (PL) was enhanced as much
as four times by H plasma passivation followed by annealing in AsH3 ambient at 400°C. The minority carrier lifetime was also
increased effectively by the passivation process. Compared to the results of deep-level transient spectra (DLTS) measurements, the improvement
in optical properties appears to be a result of the passivation of the dislocation-associated deep defects in the GaAs-on-Si epilayers by H
plasma passivation. The passivation effects persist even after the annealing process at 400°C, which suggests that the H plasma
passivation may be a useful method for improving the properties of the GaAs-on-Si-based devices.
A Large Output Voltage Swing of a Resonant Tunneling Flip-Flop Circuit Employing a Monostable-Bistable Transition Logic Element (MOBILE)
Authors: Koichi Maezawa Koichi Maezawa , Hideaki Matsuzaki Hideaki Matsuzaki , Jiro Osaka Jiro Osaka , Masafumi Yamamoto Masafumi Yamamoto , Taiichi Otsuji Taiichi Otsuji
Published: October 2002

A resonant tunneling flip-flop circuit was fabricated based on a
monostable-bistable transition logic element (MOBILE). In this work, an
Source Coupled FET Logic (SCFL) type output buffer and depletion-mode High
Electron Mobility Transistors (HEMTs) were employed instead of a Direct
Coupled FET Logic (DCFL) type buffer and enhancement-mode HEMTs used in
previous studies. A practical output voltage level close to the SCFL
interface was demonstrated for the first time with a MOBILE circuit
operating at a high bit rate of up to 20 Gb/s. This indicates that the
MOBILE has sufficient current drivability.
Electrical Characterization of InGaP/GaAs Heterointerfaces Grown by Metalorganic Chemical Vapor Deposition
Authors: Nittono Takumi , Fukai Yoshino K. , Hyuga Fumiaki , Maeda Narihiko
Published: October 2002

The electrical properties of InGaP/GaAs heterointerfaces grown
by metalorganic chemical vapor deposition have been studied using
capacitance-voltage and Hall-effect measurements. It is found that
n-type carriers at concentrations near 1×1012 cm-2 accumulate
unintentionally at the heterointerface. It is also found that the
accumulated-carrier concentration does not vary in the temperature
range of 4 to 296 K. These results indicate that a donor-type defect
exists in the InGaP side of the heterointerface and that its energy
level is higher than that of the lowest conduction band of GaAs.
Effect of n=1 Buffer Layers on n=2 and n=3 Thin Films of Bi 2Sr 2Can-1CunOy
Authors: Takahiro Oku Takahiro Oku , Osamu Ajisaka Osamu Ajisaka , Hiroyuki Inuzuka Hiroyuki Inuzuka , Yuuji Horie Yuuji Horie , Teruaki Nomiyama Teruaki Nomiyama , Tomoyuki Miyazaki Tomoyuki Miyazaki
Published: October 2002

The effect of n=1(2201) buffer layers on n=2(2212) and n=3(2223) thin films of Bi2Sr2Ca
n-1CunOy was investigated to reduce the strain caused by the lattice mismatch between the films and the substrates. The bilayer thin films of 2223/2201 and 2212/2201 were grown epitaxially on SrTiO3 (100) substrates by dc sputtering.
When the thickness of the buffer layer was 10–25 nm, the superconducting transition temperature increased by ∼20 K for 2223/2201 and by ∼6 K for 2212/2201.
The increase was attributed to the reduction of the strain from the experimental results of the full width at half-maximum of X-ray diffraction peaks, the length along the c-axis and the roughness of the film surface.
Low Noise Directly-Coupled High Tcdc Superconducting Quantum Interference Device Magnetometers for Magnetocardiogram
Authors: Kwon Hyukchan , Kim In-Seon , Lee Yong-Ho , Kim Jin-Mok , Park Yong Ki , Park Jong-Chul
Published: October 2002

Directly-coupled dc superconducting quantum interference device (SQUID) magnetometers have been fabricated on SrTiO3bicrystal substrates with 30° misorientation angle. YBa2Cu3O7-δsingle layers were deposited by laser ablation and patterned by standard photolithography and Ar ion milling. The magnetometer consists of a 9 mm×9 mm pickup loop coupled to a long slit. The magnetometers have been characterized at 77 K using conventional flux-locked loop electronics with a bias current reversal. The magnetometers exhibited high junction resistance of up to 10 Ω and large voltage modulation depth as high as 65 µV with a flux-to-voltage transfer function of 253 µV/Φoat the working point. A magnetic field noise level of 74fT/√ Hz at 1 kHz and below 100fT/√ Hz down to 4 Hz, including electronics noise, was achieved inside a magnetically shielded room. The performance of the magnetometer was demonstrated by magnetocardiograms with high quality.
Design of Modified Wiggler for Higher Harmonic Lasing of Free Electron Laser
Authors: Nakao Naoya , Imasaki Kazuo , Fujita Masayuki , Moon Ahsa , Kokubo Masayuki , Ohigashi Nobuhisa , Tsunawaki Yoshiaki , Mima Kunioki , Nakai Sadao , Yamanaka Chiyoe
Published: October 2002

To improve the harmonic gain of Free Electron Laser (FEL), we have developed a
wiggler having a harmonic wiggler field. We call such a wiggler the “modified wiggler”.
The modified wiggler consists of a conventional planar wiggler and high-permeability shims.
Owing to the simplicity of design, we can develop wigglers having various types of modified
fields, easily and economically. We show the design basis for the modified wiggler. Then,
we develop a modified wiggler for 5th-harmonic generation.
Thermal Stress Relaxation in GaAs Layer on New Thin Si Layer over Porous Si Substrate Grown by Metalorganic Chemical Vapor Deposition
Authors: Agata Yasuhiko Hayashi , Tetsuo Soga Tetsuo Soga , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno , Nobuhiko Sato Nobuhiko Sato , Takao Yonehara Takao Yonehara
Published: October 2002

We have proposed and introduced a thin Si layer over porous Si
(SPS) substrate instead of the conventionally used Si substrate to
overcome the residual thermal stress in GaAs layer on Si substrate
(GaAs/Si). From the results of X-ray diffraction, low-temperature
photoluminescence and Raman scattering, it was found that a
significant reduction of the residual thermal tensile stress has been
achieved. Our data clearly show that the SPS substrate is a promising
substrate for overcoming the problems in GaAs/Si.
Ferroelectricity in the Lyotropic Cholesteric Phase of Poly L-Glutamate
Authors: Byoungchoo Park Byoungchoo Park , Yoshitaka Kinoshita Yoshitaka Kinoshita , Hideo Takezoe Hideo Takezoe , Junji Watanabe Junji Watanabe
Published: October 2002

Relatively strong second-harmonic generation (SHG) was observed in the lyotropic cholesteric phase of the poly(γ-benzyl-L-glutamate-co-γ-methyl L-glutamate) (PBMLG) in benzyl alcohol (BA) with application of an electric field. Using an SHG interferometry technique, we confirmed that the phase of SHG was reversed by reversing the electric field, clearly indicating the switching of nonlinear polarization. By applying a triangular wave voltage, a switching current peak was observed, indicating the existence of spontaneous polarization. Based on these experimental results, we safely concluded that the cholesteric phase of the PBMLG-BA lyotropic system is in fact a ferroelectric cholesteric phase, where a polar plane rotates along the helical axis. This is the first proper ferroelectricity in liqiud crystals.
Optical Properties of InGaN/GaN Quantum Wells with Si Doped Barriers
Authors: Minsky Milan S. , Chichibu Shigefusa , Fleischer Siegfried B. , Abare Amber C. , Bowers John E. , Hu Evelyn L. , Keller Stacia , Mishra Umesh K. , DenBaars Steven P.
Published: October 2002

Optical properties of InGaN/GaN multi-quantum wells with Si doped barriers are
studied using cw and time resolved photoluminescence (TRPL) and photoluminescence
excitation (PLE) spectroscopy. The room temperature carrier lifetime depends
strongly on the Si doping level in the quantum well barriers, decreasing
from 10 ns to 1 ns as the doping level is increased from unintentionally doped to
5×1018 cm-3 (Si:GaN). The shift between the absorption edge and emission peak
decreases from 220 meV to 110 meV as the doping is increased. Temperature dependent
photoluminescence measurements indicate a higher density of non-radiative centers in the undoped structures.
Formation of Stacking Fault Tetrahedra in Silicon Rapidly Solidified from Melt
Authors: Oshima Ryuichiro , Hori Fuminobu , Komatsu Masao , Mori Hirotaro
Published: October 2002

In situ observations of melting silicon have been carried out using an ultrahigh-voltage
electron microscope, and lattice defects induced by rapid cooling from a partly molten state
are examined in detail by conventional transmission electron microscopy. Stacking fault
tetrahedra are found to form, indicating that the clustering and the collapse of thermal
vacancies take place on the {111} planes at high temperatures. Their formation mechanism is discussed.
Formation of Thin Oxide Films on Room-Temperature Silicon (100) by Exposure to a Neutral Beam of Hyperthermal Atomic and Molecular Oxygen
Authors: Tagawa Masahito , Ema Tatsuhiko , Kinoshita Hiroshi , Ohmae Nobuo , Umeno Masataka , Minton Timothy K.
Published: October 2002

Silicon (100) surfaces at room temperature were oxidized in a hyperthermal beam containing
nearly equal fractions of atomic and molecular oxygen. An oxide layer with a terminal
thickness of 4.5 nm was formed on the Si surfaces, and this layer was composed mostly of
silicon dioxide (SiO2). However, a significant fraction of suboxide (SiO
x
, x<2) was formed
at the Si/SiO2 interface, where the intrinsic stress was high. Post annealing in vacuum at
1000°C for 30 min decreased the amount of suboxide and stress at the interface.
Effects of Na Incorporation in p-Type CuInS2
Authors: Yamamoto Tetsuya
Published: October 2002

We have investigated the electronic structures of Na-incorporated In-rich CuInS2based onab initioelectronic band structure calculations. We find that the formation of ionic NaCu–S bonds decreases the Madelung energy, resulting in a shift in the energy levels of S 3porbitals in the vicinity of the Na atoms towards lower energy regions. Forp-type CuInS2:VCu, we find that interstitial Na species, except for NaCu, are very unstable and move easily within the crystal. This indicates that the mobile Na will act as a passivator of donor states such as InCuand interstitial In.
Analysis of High-Order Harmonics of Temperature Wave for Fourier Transform Thermal Analysis
Authors: Morikawa Junko , Hashimoto Toshimasa
Published: October 2002

The high-order harmonics of temperature wave were detected in a thin film by
inputting a square pulse train with a variable duty factor to generate temperature
modulation. In Fourier analysis, the harmonics were observed up to the 42th order
and the mathematical rule was experimentally confirmed. This principle was
applied to a technique called “Fourier transform thermal analysis,” which made it
possible to determine simultaneously thermal diffusivity and heat capacity per unit
volume as a function of frequency and temperature.
Femtosecond Optical Kerr Effect in the Gold Nanoparticle System
Authors: Hideyuki Inouye Hideyuki Inouye , Koichiro Tanaka Koichiro Tanaka , Ichiro Tanahashi Ichiro Tanahashi , Kazuyuki Hirao Kazuyuki Hirao
Published: October 2002

We observed an ultrashort response of the gold nanoparticle system
that was as fast as 240 fs in a femtosecond optical-Kerr-shutter
experiment. The ultrafast response is attributed to the self-diffraction
of the pump pulse due to the transient grating. We estimated χ(3) of the gold nanoparticle system to be 2.0 ×10-8 esu in
the femtosecond region.
Behaviors of Auger Intensities Emitted from a Si(111)√ 3×√ 3–Al Surface During Incident Beam Rocking of Reflection High-Energy Electron Diffraction
Authors: Yoshimi Horio Yoshimi Horio
Published: October 2002

Auger electrons emitted from a Si(111)√3×√3–Al surface were measured by a cylindrical mirror analyzer (CMA) during reflection high-energy electron diffraction (RHEED) experiment. Enhancements of Al(LMM) Auger intensity were detected upon changing the glancing angle and this behavior was analyzed considering an electron wave field. It was found that the enhancements of Al(LMM) Auger intensity are explained relatively well by the localizations of the electron wave field on the Al atomic sites. The surface structure was treated as a T4 site model with a relaxed substrate, which was deduced from the RHEED rocking curve analysis with many beam dynamical calculations.
Characteristics of a Large-Diameter Surface-Wave Mode Microwave-Induced Plasma
Authors: Kaneko Eiji , Okamoto Tetsu , Watanabe Seiichi , Okamoto Yukio
Published: October 2002

A large-diameter unmagnetized argon plasma is generated by an Okamoto cavity operated in a surface-wave mode. A quartz discharge tube (16 cm inner diameter, 12 cm long) is placed inside the cavity. An argon plasma is produced in the discharge tube and effuses in a process chamber. The electron density, electron temperature, ion current density and floating potential in the chamber are measured as a function of spatial position using a Langmuir probe. An electron density over 1011 cm-3, with an electron temperature in the range of 2–3 eV and a floating potential with respect to the chamber wall of less than 5 V is obtained at pressure in the mTorr range with 2.45 GHz, 700 W input microwave power. A high ion current density (over 10 mA/cm2) of uniformity (standard deviation/average) within 4.4% over 16 cm is achieved.
Effective Reduction of Debris Emitted from a Laser-Produced Plasma
Authors: Kandaka Noriaki , Kondo Hiroyuki
Published: October 2002

In the practical application of laser-produced plasma as a soft X-ray source, the most serious problem is the emission of debris from the plasma. We have quantitatively evaluated the amount of debris, and have described its effective reduction by means of a buffer gas. With a tantalum target material, we substantially reduced the amount of debris by employing a buffer gas combined with protective covering.
Effective Bonding Parameters for the Prediction of Electronic Transition of CdS Clusters
Authors: Kiyohisa Okano Kiyohisa Okano , Toyoharu Hayashi Toyoharu Hayashi
Published: October 2002

The excited electronic states of CdS clusters as models of CdS ultrafine particles were studied by a semiempirical molecular orbital method. The bonding parameters used in the resonance integral evaluation were adjusted so that the values of the electron polpulation calculated ab initio and by the semiempirical molecular orbital method agree with each other. Improved bonding parameters are proposed using which, the electronic transition energies of CdS clusters were almost successfully predicted.
Study of Carrier Emission and Capture Processes at Electron Traps in 3C-SiC
Authors: Ichimura Masaya , Koga Yoshihiro , Yamada Noboru , Abe Tetsushi , Arai Eisuke , Tokuda Yutaka
Published: October 2002

The n-type 3C-SiC grown on Si(001) substrates by chemical vapor deposition was characterized by deep-level-transient spectroscopy (DLTS). DLTS peaks appeared near 160 K and 260 K with the emission rate being 26 s-1. For the shallower level, the activation energy E
a is 0.34 eV and the capture cross section at infinite temperature σ∞ is 6.0×10-17 cm2. For the deeper level, E
a=0.52 eV and σ∞=9.5×10-18 cm2. The capture cross section at the peak temperature was obtained by changing the injection pulse width, and it was found that the energy barrier of electron capture is negligibly small for these two traps.
Carbon Nanotubes on SiC Powder Surface Grown by a Vacuum Heating Process
Authors: Hirofumi Takikawa Hirofumi Takikawa , Ryuichi Miyano Ryuichi Miyano , Miki Yatsuki Miki Yatsuki , Tateki Sakakibara Tateki Sakakibara
Published: October 2002

Silicon carbide (SiC) powders were baked on a resistively heated tungsten (W) boat at 1,600–1,700°C for 10–15 min in vacuum. The surface morphology of the treated SiC powders was observed using a high resolution scanning electron microscope (HR-SEM). Carbon nanotubes were observed on the surface of 40% of SiC powder. The nanotubes were dense, but slightly dispersed and their growth direction was almost perpendicular to the original surface. The nanotubes on SiC were considerably shorter than that prepared by carbon arc method, but significantly longer than that prepared by laser sublimation of SiC. Energy dispersive X-ray spectrometory (EDX) analysis suggested that W and O were doped on or in the vicinity of the powder surface.
Ordering Reduction in In0.5Ga0.5P Grown by Solid Source Molecular Beam Epitaxy
Authors: Cheng Yi-Cheng , Tai Kuochou , Chou Shu-Tsun , Huang Kai-Feng , Tu Shun-Lih
Published: October 2002

In0.5Ga0.5P grown on GaAs substrates with different tilting angles by solid source molecular beam epitaxy (SSMBE) is studied. The results showed that a weak ordering effect still exists in SSMBE grown epilayers with tilted substrates. However, the ordering effect can be drastically reduced by growing In0.5Ga0.5P on a 15° tilted substrate with an InAlP/InGaP superlattices (SL) buffer layer. The In0.5Ga0.5P epilayer grown by this method showed a peak photoluminescence (PL) energy of ∼1.91 eV at room temperature, which is similar to the reported value for a fully disordered sample. The intensity of the ordering effect is characterized by polarized PL spectroscopy, and the reduction in the ordering intensity is attributed to the elimination of initial surface strain by the SL buffer layer.
A Novel Delayed Flip-Flop Circuit Using Resonant Tunneling Logic Gates
Authors: Koichi Maezawa Koichi Maezawa , Hideaki Matsuzaki Hideaki Matsuzaki , Tomoyuki Akeyoshi Tomoyuki Akeyoshi , Jiro Osaka Jiro Osaka , Masafumi Yamamoto Masafumi Yamamoto , Taiichi Otsuji Taiichi Otsuji
Published: October 2002

A novel delayed flip-flop circuit using monostable-bistable transition logic elements (MOBILEs) was proposed, and was fabricated using resonant-tunneling-diode/high-electron-mobility-transistor integration technology on an InP substrate. Error free operations at up to 12.5 Gb/s were demonstrated at room temperature.
Comparison of Fe- and p/n/p-Doped InP as a Current Blocking Layer for Monolithically Integrated InGaAsP/InP Laser Diodes with Passive Waveguides
Authors: Lee Sangmin , Kim Kangho , Oh Kwang Ryong , Kim Jeong Soo , Oh Dae Kon , Kim Hong Man , Pyun Kwang Eui
Published: October 2002

We have fabricated InGaAsP/InP waveguide integrated laser diodes for the 1550 nm wavelength region. The passive waveguide was butt-coupled using the CH4/H2 reactive ion etching and metal-organic chemical vapor deposition regrowth techniques. We compared the performances of waveguide integrated laser diodes with different current blocking layers, i.e., Fe-doped InP and p/n/p-doped InP layers. On the whole, Fe-doped InP was better than p/n/p-doped InP as a current blocking layer. In particular, the reverse leakage current through the butt-coupling region with Fe-InP current blocking layer was approximately 99.9 µA, while that with p/n/p-InP was 193.7 µA. We also discussed the leakage current characteristics of waveguide integrated laser diodes with analyses of IdV/dI vs I curves.
Interfacial Layers between Si and Ru Films Deposited by Sputtering in Ar/O2 Mixture Ambient
Authors: Aoyama Tomonori , Murakoshi Atsushi , Koike Mitsuo , Takeno Shiro , Imai Keitaro
Published: October 2002

Ru films are fabricated by dc magnetron sputtering in Ar/O2 ambient for the bottom electrode of Ba0.5Sr0.5TiO3 thin film capacitors. The Ru films deposited on Si in ambient of 10% O2 do not form Ru2Si3 following thermal process even at 700°C. It becomes clear that there exist very thin amorphous and crystalline layers composed of Ru, Si and O between the Ru films and Si. A contact resistance of 1.6×10-7 Ω cm2 between Ru and n+-Si is obtained after annealing at 700°C. The effective SiO2 film thickness of 0.42 nm is obtained for 42 nm actual Ba0.5Sr0.5TiO3 film thickness and the leakage current is less than 1×10-8 A/cm2 in the range between -1.5 V and +1.8 V for Ru/Ba0.5Sr0.5TiO3/Ru/n+-Si capacitor.