bluuebunny/crossref_metadata_2025 huggingface dataset:
Hall Effect in Anisotropic SixGe1-x Polycrystals
Authors: Yonenaga Teimouraz R. Mchedlidze
Published: October 2002

We studied carrier transport in Si

x

Ge1-
x

polycrystalline bulk alloys grown by the Czochralski method. The grains in the alloys are elongated in the growth direction due to the supercooling effect. At a high concentration of grains, the anisotropy of their shape leads to an observable anisotropy in the electrical properties of the alloys. The “two-phase geometrical model” was applied to estimate the transport properties of the grains and grain boundary materials from the Hall effect measurements in different directions of the alloys. The results show that in the SiGe polycrystalline alloy, conductive grains are surrounded by high-resistivity barriers. The height of the barriers was calculated to be 0.38 eV and “electrical” thickness 3×10-5 cm.
Comprehensive Study of Plasma Pretreatment Process for Thin Gate Oxide ( <10 nm) Fabricated by Electron Cyclotron Resonance Plasma Oxidation
Authors: Chang Kow-Ming , Li Chii-Horng , Fahn Fu-Jier , Wang Ta-Hsun Yeh
Published: October 2002

In this work, we comprehensively study the effect of ECR plasma pretreatment on ECR plasma grown SiO2 film. The ECR plasma grown gate oxide growth rate in the case of no plasma pretreatment is lower than that in the case of use of the plasma pretreatment step. Because the growth processes for these two methods (with and without pretreatment) differ only in terms of the initial surface conditions, the growth mechanisms are concluded to be determined by the initial Si surface conditions before plasma oxidation. The mid-gap interface states (D
it-m) of the ECR plasma grown SiO2 films in the case of plasma pretreatment are lower than those in the case of no plasma pretreatment. Through use of the plasma pretreatment process, the Si surface can be improved and cleaned before plasma oxidation. For SiO2 films pretreated with N2 or Ar gas, the breakdown fields (E
bd) are higher than those for SiO2 films not pretreated with N2 or Ar gas. However, for NH3 gas pretreated films, the E
bd is lower than those for SiO2 films pretreated with N2 or Ar gas. This is because the NH3 gas contains H atoms which cause deterioration of F-N tunneling characteristics. Moreover, with the plasma pretreatment step, the stress-induced leakage currents (SILC) are lower than those without this step.
Electrical Properties of Microwave-Sintered (Sr0.4Pb0.6)TiO3 Ceramics
Authors: Chang Horng-Yi , Liu Kuo-Shung , Lin Chen-Ti Hu
Published: October 2002

The resistivity-temperature (ρ-T) characteristics of the (Sr0.4Pb0.6)TiO3 materials prepared by a microwave sintering process were examined. The resistivities were significantly lowered by increasing the rate of cooling and were substantially increased by a heat-treatment process. The Curie temperature was not altered by a fast cooling process but was shifted from T
c=302° C to 210° C when the as-sintered samples were post-heat-treated at 1200° C for 1 h. The high Curie temperature of the as-sintered samples was proposed to be due to the core-shell structure of the grains. The “shell”, which contained Pb-rich perovskite of the composition (Sr0.29Pb0.71)TiO3, was homogenized with core material during heat treatment. The variation in resistivity was ascribed to the modification of the concentration of cationic vacancies. The donor level (E
d) and the deep trap level (E
t) of the materials were, respectively, evaluated from the Arrhenius plot of ρ-T characteristics at T<T
c and T>T
max regimes to be E
d≈0.078–0.193 eV and E
t\cong1.66 eV+E
f, where E
f is the Fermi level.
Electrical Properties of Heavily Carbon-Doped GaAs Epilayers Grown by Atmospheric Pressure Metalorganic Chemical Vapor Deposition Using CBr 4
Authors: Son Chang-Sik , Kim Seong-Il , Min Byung-Don , Kim Yong , Kim Eun Kyu , Min Suk-Ki , Choi In-Hoon
Published: October 2002

Heavily carbon (C)-doped GaAs epilayers with hole concentrations as high as 3.1×1020 cm-3 were grown by atmospheric pressure metalorganic chemical vapor deposition using CBr4 as the dopant source. The electrical properties of C-doped GaAs epilayers simultaneously grown on exact and 2° off (100) GaAs substrates were investigated. The hole concentration in the epilayer grown on the exact (100) substrate was higher than that in the epilayer on the 2° off (100) substrate grown under equivalent conditions. The hole concentration for the exact (100) substrates exhibited saturation as the growth temperature increased. The hole concentration for the 2° off (100) substrates exhibited thermal activation behavior. The activation energy of the hole concentration as a function of the growth temperature did not change significantly regardless of the V/III ratio (E
a ∼63 and 71 kcal/mol). The higher desorption rate of C-containing species due to the higher adsorption rate of AsHx species on the 2° off (100) substrate, which has a higher step density than the exact (100) substrate, is responsible for this thermal activation behavior.
Computer Simulation of Deeply Doped Layers in Si Using Double-Pulse Excimer Lasers
Authors: Masayuki Jyumonji Masayuki Jyumonji
Published: October 2002

A deeply doped layer in Si with high crystalline quality and a smooth surface can be obtained by sequential irradiation of two KrF excimer lasers (λ=248 nm). This novel technique, referred to as double-pulse irradiation, involves high-speed diffusion of dopant and recrystallization of the molten layer induced by laser irradiation. At the typical 1st laser fluence of 2.4 J/cm2 and the 2nd laser fluence of 0.5 J/cm2, the numerical simulations of thermal diffusion in the Si substrate during the laser irradiation reveal that the suppression of the surface roughness by the double-pulse irradiation is mainly caused by the re-heating induced by the 2nd pulse. In addition, the simulations also indicated that the average resolidification velocity of the double-pulse irradiation was estimated to be ∼3.7 m/s, which was smaller than that of single KrF excimer laser irradiation of 4.8 m/s. This result corresponds to the improvement of the crystalline quality of the sample irradiated by double-pulse lasers.
Electron-Beam-Induced Deposition of Pt for Field Emitter Arrays
Authors: Hiroji Morimoto Hiroji Morimoto , Takehisa Kishimoto Takehisa Kishimoto , Mikio Takai Mikio Takai , Shinsuke Yura Shinsuke Yura , Akihiko Hosono Akihiko Hosono , Soichiro Okuda Soichiro Okuda , Stephan Lipp Stephan Lipp , Lothar Frey Lothar Frey , Heiner Ryssel Heiner Ryssel
Published: October 2002

Pt emitters were deposited using electron-beam-induced reaction on overetched Si emitters fabricated by a conventional dry etching process. An emission current of 10 µA was obtained from a 100-tip field emitter array (FEA) at an extraction voltage of 100 V. A prototype of a nanometer-sized field emitter was fabricated using focused ion beam (FIB) etching and electron-beam-induced deposition (EBID).
A New Self-Aligned Process for Fabrication of Microemitter Arrays Using Selective Etching of Silicon
Authors: Tanemasa Asano Tanemasa Asano , Junji Yasuda Junji Yasuda
Published: October 2002

Field electron emitter arrays (FEAs) have been fabricated by a novel self-aligned process. In this process the crystal-orientation dependent (anisotropic) and doping density dependent etching characteristics of single crystal Si are fully utilized. The emitter is formed by depositing a material in a mold prepared by anisotropic etching and thermal oxidation of Si. The gate is made of highly boron doped single-crystal Si, which acts as the etching mask for the mold formation. Gate/emitter spacing is determined by well-controlled ion implantation and thermal diffusion processes. FEAs with WSi2 emitters have been fabricated. The results demonstrate a small dispersion in gate/emitter spacing 3σ=0.19 µm where σ is the standard deviation. FEA operation at about 10 V is demonstrated.
Fabrication of a Split-Gate Quantum Wire Having a Ferromagnetic Dot
Authors: Kikutani Tomoyuki , Aoki Nobuyuki , Oki Akio , Hong Chulun , Hidenobu Hori Hidenobu Hori , Syoji Yamada Syoji Yamada
Published: October 2002

We have fabricated split-gate quantum wires having a buried ferromagnetic dot, by successively utilizing electron-beam (EB) and two-step scanning tunneling microscope (STM) fabrication. For STM fabrication, we used an STM/scanning electron microscope (SEM) combined with a system operated in high vacuum. The fabrication method is a kind of electrical evaporation with a tungsten (W) tip (top curvature is less than 50 nm). In the first step, a W tip was brought between the split-gate, and then a hole was fabricated by applying a pulse voltage between the W tip and the sample surface. In the second step, a W tip coated with nickel (Ni) was brought near the fabricated hole. Then by applying a pulse voltage between the Ni-coated W tip and sample surface, electrically evaporated Ni from the tip is buried into the hole. In a preliminary measurement at 0.3 K, we obtained the following unique transport properties. In a 4-terminal conductance (G
4t) as a function of gate voltage (V
g), we observed a clear “kink” (an abrupt change of dG
4t/ dV
g and step structures) before full pinch-off of the wire. In both regions of G
4t, that is, when V
gk<V
g (before the kink appears) and when V
g<V
gk (after the kink appears) (V
gk is the gate voltage at which the “kink” appears), some step structures are seen. The step difference (ΔG
4t) is, however, different between the two regions. That is, ΔG
4t=2-4×(2e
2/h) before the kink appears, while ΔG
4t=(1/8)-(1/4)×(2e
2/h) after the kink appears.
SiO2/c-Si Bilayer Electron-Beam Resist Process for Nano-Fabrication
Authors: Gorwadkar Sucheta M. , Wada Toshimi , Haraichi Satoshi , Hiroshima Hiroshi , Kenichi Ishii Kenichi Ishii , Masanori Komuro Masanori Komuro
Published: October 2002

We have developed an SiO2/c-Si bilayer electron beam resist process in order to overcome the problems encountered in our previously developed SiO2/poly-Si resist system. The process parameters which include the electron beam exposure conditions, thicknesses of resist layers, etching of SiO2 and c-Si by using buffered HF solution and NMD-3 solution, respectively, are optimized. The developed SiO2/c-Si EB resist system is used to produce a suspended mask structure with an opening of 12 nm width for the double angle deposition of Ti for our proposed ultrasmall metal-insulator-metal tunnel junction fabrication process. We have also demonstrated the successful lift-off of inorganic resist by removing underlying c-Si layer of 40 ×40 µ m2 area using NMD-3 solution at 70° C, leaving an array of isolated Ti–TiO

x

–Ti dots, each having few hundred nm2 area, on the substrate.
Novel Fabrication Method of Si Nanostructures Using Atomic Force Microscope (AFM) Field-Enhanced Oxidation and Anisotropic Wet Chemical Etching
Authors: Araki Kiyoshi , Morimoto Kiyoshi , Morita Kiyoyuki , Hirai Masaaki Niwa
Published: October 2002

We have demonstrated a novel method of fabricating Si nanostructures. Based on a combination of atomic force microscope (AFM) field-enhanced oxidation and anisotropic wet chemical etching, Si nanostructures with a minimum width of 50 nm are successfully obtained within the intended area with precise alignment. Overlay patterning followed by AFM field-enhanced oxidation is carried out with high accuracy. It is confirmed that the field-enhanced oxide line with a thickness of at least about 3 nm can act as an mask against anisotropic wet chemical etching. This method enables the realization of sub-10 nm Si nanostructures.
Elastic and Dielectric Properties of Ba2-xSrxTi9O20 Ceramics
Authors: Rodrigues Nelson , Philip Jacob , Sreemoolanathan Hariharan , Sebastian Mailadil Thomas
Published: October 2002

The Ba2-
x

Sr

x

Ti9O20 ceramics with different values of x ranging from 0–2 have been prepared by the solid state reaction route. The longitudinal and transverse elastic constants of these samples have been measured by the ultrasonic Pulse Echo Overlap method. The composition and temperature dependence of the elastic constants have been investigated. The low frequency dielectric constant of the samples have been measured. The frequency and temperature dependence of dielectric constant have been studied and the results are interpreted in terms of the composition dependent microstructural phase transformation taking place in the system.
Piezoelectricity in Aromatic Polyamide Thin Films Prepared by Vapor Deposition Polymerization
Authors: Linford Matthew R. , Iijima Masayuki , Hattori Takeshi , Yoshikazu Takahashi Yoshikazu Takahashi , Eiichi Fukada Eiichi Fukada
Published: October 2002

Thin films of aromatic polyamide were prepared from 4,4′-diamino diphenyl ether (ODA) and 4,4′-biphenyl dichloride (BPDC) by the vapor deposition polymerization method. The evaporation temperature of the ODA was fixed at 120° C and that of BPDC was varied from 118° C to 128° C. The film was poled by a corona discharge at 250° C for 30 min. The maximum piezoelectric constant e
31 of 0.8 mC/m2 was obtained at the BPDC evaporation temperature of 124° C. The piezoelectric activity persisted up to 210° C.
Effects of Al3Ta/TaN Bilayered Diffusion Barriers in the Al/Si Contact Systems
Authors: Takeyama Mayumi , Sasaki Atsushi Noya
Published: October 2002

A thermally stable contact system of Al/Al3Ta/TaN/Si, which tolerates post-metallization annealing even at 600° C for 1 h, was successfully prepared by achieving a state of chemical pseudo-equilibrium at the interface of Al/Al3Ta and that of Al3Ta/TaN. No solid-phase reactions took place at these interfaces due to the realization of minimum free energy states. The thermal stability of the interfaces in the contact system was discussed from the point of view of the solid-phase reaction of thin films. It was also revealed by X-ray diffraction analysis that the absence of structural change due to grain growth in both the TaN and Al3Ta layers by annealing is effective for the total stability of the contact system. We have been successfully able to demonstrate the validity of realizing the chemical pseudo-equilibrium interfaces for preparing thermally stable contact systems.
Raman Spectroscopic Study of YBa2Cu4O8 Thin Film Grown from Amorphous Precursor
Authors: Yoshida Yukihisa , Haruhisa Ohtsuka Haruhisa Ohtsuka , Tadataka Morishita Tadataka Morishita
Published: October 2002

Raman spectroscopic study was performed on YBa2Cu4O8 (Y124) thin films prepared by in situ annealing of sputtered precursor. The amorphous precursors were deposited at 450° C in 50 mTorr. The films are a-axis oriented. The ratio of the vibrational intensity of oxygen in double Cu–O chain to that of apical oxygen (I
O d
/I
O a
) corresponded well to the volume fraction of the Y124 phase in the films. With decrease in the composition Cu/Y, depending on oxygen pressure during deposition, the double Cu–O chain is suffered by the oxygen defects, which was confirmed by observing decreases in I
O d
/I
O a
and the appearance of the 537 cm-1 mode. The Y124 growth around the boundary of the stability region (1≤P
O2
≤200 Torr, 625≤T≤820° C) between Y124 and Y123 indicates that higher temperature and higher oxygen pressure during in situ annealing is preferable for the growth of Y124 films. The Y124 films annealed at 820° C under 200 Torr O2 showed I
O d
/I
O a
of 1.00, which is the same as the result for Y124 bulk prepared by a high-pressure technique.
A Novel High-Density EEPROM Cell Using a Polysilicon-Gate Hole (POLE) Structure Suitable for Low-Power Applications
Authors: Takebuchi Masataka , Noda Jun-ichiro , Tohyama Daisuke , Ueno Shu , Kanji Osari Kanji Osari , Kuniyoshi Yoshikawa Kuniyoshi Yoshikawa
Published: October 2002

A novel-high density electrically erasable and programmable read only memory (EEPROM) cell technology is proposed. The new cell utilizing a polysilicon-gate hole (POLE) structure can be used to reduce the channel length and the substrate current I
sub by 2 orders of magnitude in comparison with a conventional stacked-gate flash cell by isolating the charge transfer region and thus strongly reducing band-to-band tunneling current. A 36 µm2 cell, which is 20% smaller than that of a floating gate tunnel oxide (FLOTOX) type EEPROM, with a 0.6 µm design rule can be realized. Furthermore, stable write and erase (W/E) operations are confirmed, and the characteristics of 1 million W/E cycles and 10-year data retention have been achieved.
Impact Ionization Model Using Average Energy and Average Square Energy of Distribution Function
Authors: Ken-ichiro Sonoda Ken-ichiro Sonoda , Scott T. Dunham Scott T. Dunham , Mitsuru Yamaji Mitsuru Yamaji , Kenji Taniguchi Kenji Taniguchi , Chihiro Hamaguchi Chihiro Hamaguchi
Published: October 2002

A new impact ionization model is developed using both the average energy and the average square energy of electrons. The accuracy of the model in an inhomogeneous electric field is verified through comparison with results calculated with Monte Carlo simulation. Our model predicts the generation rate even in an inhomogeneous field more accurately than local field, non-local field, and local energy models.
Ettingshausen and Nernst Effects of QMG-YBa2Cu3O7-δ in Magnetic Fields up to 14 T
Authors: Sasaki Takako , Sawamura Mitsuru , Awaji Satoshi , Watanabe Kazuo , Kobayashi Norio , Kimura Keiichi , Miyamoto Katuyoshi , Hashimoto Misao
Published: October 2002

The dissipation behavior in the mixed state of a high-T
c oxide superconductor YBa2Cu3O7-δ has been investigated by measuring thermomagnetic effects, namely the Ettingshausen and Nernst effects. These two effects were measured for the same sample prepared by the quench and melt growth (QMG) method without Pt addition. The Ettingshausen effect was also measured for a sample with 0.5% Pt. The temperature and magnetic field dependences of the temperature gradient produced by the Ettingshausen effect and the electric field induced by the Nernst effect are presented. Combining these data with the electrical resistivity and the thermal conductivity, the transport energy of a vortex line is obtained. The effect of the Pt addition on the Ettingshausen effect is also discussed.
Experimental Study of Impact Ionization Phenomena in Sub- 0.1 µm Si Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs)
Authors: Hori Atsushi , Hiroki Akira , Kaori Moriyama Akamatsu Kaori Moriyama Akamatsu , Shinji Odanaka Shinji Odanaka
Published: October 2002

Impact ionization phenomenon in sub-0.1 µm Si metal-oxide-semiconductor field effect transistors (MOSFETs) has been examined in detail. N-MOSFETs with gate oxide of 4, 6 and 8 nm thickness were fabricated using pocket implantation technology. The test devices have n+ polysilicon gate electrodes and shallow extension formed by arsenic implantation at the acceleration voltage of 15 keV. Sub-band-gap impact ionization can be observed for the 0.08 µm N-MOSFET. It is clearly observed that thin gate oxide suppresses impact ionization. Simulation results reveal that the lateral electric field near the drain is decreased by thinner gate oxide of 4 nm thickness. In addition, the dependence of the impact ionization rate on the gate oxide thickness decreases with decreasing gate length.
Characteristics of YBCO Josephson Junction Prepared by a Focused Ion Beam Technique
Authors: Fujimoto Manabu , Hayashi Kunihiko , Katsumi Suzuki Katsumi Suzuki , Youichi Enomoto Youichi Enomoto
Published: October 2002

In order to clarify the formation and working mechanism of the YBCO Josephson junction, the dependence of the junction characteristics on the oxygen pressure during YBCO deposition was observed. An MgO substrate was damaged by a focused ion beam (FIB) and then a YBCO film was deposited on the substrate. When the oxygen pressure during depositions was 200 mTorr, the junction did not show the Josephson effect. At 100 mTorr, the junction showed the Josephson effect. The transition temperature (T
c) and the c-axis lattice constant of the film did not change from 200 to 100 mTorr. Therefore, we considered that the oxygen was lacking more at the junction than in the film and a Josephson junction was formed without film degradation.
The Role of Stress in Amorphous Magnetic Materials*
Authors: Kalyan Mandal Kalyan Mandal
Published: October 2002

The internal stresses in amorphous Fe40Ni40B20 alloy have been relieved by passing short duration current pulses through the samples. Temperature dependence (100 K≤T≤250 K) of magnetisation of the sample which shows maximum relaxation of internal stresses after heat treatment, has been measured under the influence of external tensile stresses. Analysing the experimental data on the basis of spin-wave theory, it has been observed that the saturation moment, spin-wave stiffness constant and range of interaction change with the application of external stresses.
Contactless Characterization of Thermally Oxidized, Air-Exposed and Hydrogen-Terminated Silicon Surfaces by Capacitance-Voltage and Photoluminescence Methods
Authors: Koyanagi Satoshi , Tamotsu Hashizme Tamotsu Hashizme , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Contactless and nondestructive characterization of the electrical properties of the free surfaces of single-crystalline silicon wafers is accomplished for the first time by combined use of the contactless metal-insulator-semiconductor (MIS) capacitance-voltage (C-V) technique and the photoluminescence surface state spectroscopy (PLS3) technique. The thermally oxidized, air-exposed and hydrogen-terminated silicon (111) surfaces were investigated. Thick thermally oxidized surfaces showed well-behaved characteristics with a minimum of a broad U-shaped interface state density (N
ss) distributions in a range of 1010 cm-2eV-1. On the other hand, the air-exposed Si surface exhibited a GaAs MIS-like behavior with strong Fermi level pinning near the charge neutrality level E
HO caused by a narrow U-shaped state distribution. Surprisingly, hydrogen-terminated surfaces showed even stronger Fermi level pinning at E
0 = E
c - 0.43 eV due to high density of amphoteric discrete state which may be due to silicon dangling bonds.
Formation of SiGe Source/Drain Using Ge Implantation for Floating-Body Effect Resistant SOI MOSFETs
Authors: Akira Nishiyama Akira Nishiyama , Osamu Arisumi Osamu Arisumi , Mamoru Terauchi Mamoru Terauchi , Shiroh Takeno Shiroh Takeno , Ken Suzuki Ken Suzuki , Chie Takakuwa Chie Takakuwa , Makoto Yoshimi Makoto Yoshimi
Published: October 2002

SiGe was formed by Ge implantation into silicon on insulator (SOI) substrates with the dosage range from 0.5 to 3×1016 cm-2 and subsequent annealing in N2. The implantation dosage dependence of the crystalline quality, bandgap and sheet resistance of the SiGe layers are investigated. The implantation damage for Ge dosage up to 1×1016 cm-2 can be removed at a temperature as low as 700°C. A SiGe crystalline network is formed by the annealing at the same time. With a Ge dosage of 1×1016 cm-2 or more, bandgap narrowing of the SiGe layer was detected. Sheet resistances of SiGe N+ and P+ layers gradually increase for higher Ge dosage. SOI MOSFET characteristics in terms of the floating-body effect with the SiGe source/drain layers are presented. The bandgap narrowing suppresses the floating-body effect of fully depleted SOI MOSFETs, while maintaining the reverse leakage current of the p-n junction between the source/drain and channel at a low level.
Thin-SOI Process Using Bonding and Etch-back Method without Epitaxial Growth
Authors: Hideyuki Unno Hideyuki Unno , Kazuo Imai Kazuo Imai
Published: October 2002

A new thin-SOI process is proposed. This process is classified as a single etch-stop method. It uses an etch-stopped layer as an active layer by decreasing boron concentration in the etch-stopped layer so that an epitaxial layer is not needed. The boron concentration in the 500-nm-thick p+ layer after etch-stopping is decreased from 7×1019 cm-3 to less than 2×1017 cm-3 by hydrogen annealing at 1100°C for 3 h. Additionally, surface roughness is decreased from 2.3 nm to about 0.2 nm. This value is almost equivalent to a polished wafer roughness. This process is simple and does not require complicated equipment, thus allowing for the manufacture of a low-cost SOIs.
Transition from Antiferromagnetic Coupling to Biquadratic Coupling in Fe/FeSi Multilayers
Authors: Saito Yoshiaki , Yusu Koichiro Inomata
Published: October 2002

The detailed temperature dependence of interlayer exchange coupling in Fe/FeSi multilayers prepared by ion beam sputtering was investigated and compared with the data for Fe/Si multilayers. Significant differences between interlayer exchange coupling in Fe/FeSi and Fe/Si multilayers were observed. The coupling between Fe layers in Fe/FeSi multilayers showed a transition from antiferromagnetic to 90° coupling with decreasing temperature. This was due to the strong temperature dependence of J
2 (biquadratic coupling), which outweighs that of J
1 (collinear coupling) at low temperatures.
A Theoretical Investigation of Migration Potentials of Ga Adatoms near Step Edges on GaAs(001)-c(4×4) Surface
Authors: Shiraishi Tomonori Ito
Published: October 2002

Migration potentials of Ga adatoms near step edges on c(4×4) surface are investigated using the empirical interatomic potential and an energy term due to the charge redistribution on the surface. The energy term, as a function of the number of electrons remaining in the Ga dangling bonds, is extracted from ab initio calculations. The calculated results imply that the lattice sites along A-type step edges are stable for Ga adatoms, whereas no preferential adsorption site is found near B-type step edges. This is simply because the number of electrons remaining in the Ga dangling bond is suppressed by Ga adatoms occupying lattice sites along A-type step edges as opposed to being unchanged by those occupying lattice sites near B-type step edges.
Spectral Response of Photocurrent in Glassy and Crystalline Ag-Rich Ag–As(Ge)–S Compounds
Authors: Takeshi Kawaguchi Takeshi Kawaguchi , Shigeo Maruno Shigeo Maruno
Published: October 2002

Photocurrent in Ag–As(Ge)–S glasses of 16–45 at% Ag and the related crystals sandwiched between Au films has been measured to reveal the electronic band structure of Ag-rich glasses. The intensity was found to increase exponentially with increasing Ag content. The peak energy of the spectral response was greater by 0.5 eV than the optical gap for all the glasses. The results suggest that the Ag–S bonding states in Ag-rich glasses form the valence band, and the peak of photocurrent spectra lies at around the mobility edge of the valence band.
Low-Temperature Growth of Oriented Silicon Carbide on Silicon by Reactive Hydrogen Plasma Sputtering Technique
Authors: Nobuo Sonoda Nobuo Sonoda , Yong Sun Yong Sun , Tatsuro Miyasato Tatsuro Miyasato
Published: October 2002

Highly oriented β-SiC film is prepared on (100) Si substrate at 800°C by reactive hydrogen plasma sputtering of a ceramic SiC target. The highly oriented β-SiC film can be grown on (100) Si substrate without void formation at the SiC film/Si interface. Hydrogen plasma etching of the growing film plays an important role in the growth of the oriented β-SiC films. Voids at the SiC film/Si interface are formed at a temperature of about 800°C due to the reaction of SiC film with Si substrate. Also, a thin amorphous buffer layer of 5 nm thickness is formed at the SiC film/Si interface. The results of this study indicate that the buffer layer can be eliminated by a suitable surface treatment of Si substrate before film growth.
Reduced Process Method for Thin-Film-Transistor Liquid-Crystal Display (TFT-LCD) with Dry-Etching Tapered ITO Data Bus Lines
Authors: Ugai Yasuhiro , Yukawa Teizo , Yoshihisa Hatta Yoshihisa Hatta , Shigeo Aoki Shigeo Aoki
Published: October 2002

For years, many studies have been conducted for the purpose of reducing the number of TFT processes. We have developed a top-gate TFT-LCD fabricated using only indium-tin-oxide (ITO: In2O3–SnO2) data bus lines by eliminating the metal data bus line process. Substituting ITO dry-etching for wet-etching allows tapering of the side walls of thick ITO data bus lines. Controlling the tapered angle of ITO data bus lines to be less than 40° results in successful fabrication of a transistor with no offset voltage. As a result, we have developed a 6-inch-diagonal TFT-LCD fabricated with data bus lines as well as drain-source electrodes of single-layered ITO.
Investigation of Transient Substrate Currents in Lateral Power Devices on Silicon-on-Insulator
Authors: Sumida Hitoshi , Tagami Atsuo Hirabayashi
Published: October 2002

In this work, transient substrate currents during switching under an inductive load of the lateral insulated gate bipolar transistor (IGBT) and metal-oxide-semiconductor field effect transistor (MOSFET) on silicon-on-insulator (SOI) film were investigated numerically and experimentally. Substrate currents at the turn-on and turn-off transients of the two devices were estimated, and their behavior was compared. Both devices have high substrate currents at the turn-on transient. Differences between the two devices appear at the turn-off transient. In the IGBT a low substrate current flows, whereas the MOSFET has a high substrate current like that at the turn-on transient. This is attributed to the difference in the mode of operation at the turn-off transient in the two devices.
Grazing Incidence X-Ray Diffraction Study of Dimyristoylphosphatidic Acid Monolayers on Aqueous Subphases in the Presence of Calcium or Magnesium Ions
Authors: Takahashi Hiroshi , Murase Yasuyuki , Kurihara Kazue , Hatta Ichiro , Arakawa Etsuo , Takeshita Kunikazu , Matsushita Tadashi
Published: October 2002

Focusing on the difference in the isotherms of dimyristoylphosphatidic acid (DMPA) monolayers on aqueous subphases in the presence of calcium and magnesium ions, the structures of the DMPA monolayer on the aqueous subphases were investigated by grazing incidence X-ray diffraction. We observed the reflections from the lattice of hydrocarbon chain packing of DMPA monolayers. It was found that the lattice spacings observed by X-ray diffraction in the presence of calcium ions are shorter than those in the presence of magnesium ions at every surface pressure measured. We discussed this result in terms of the hydration of these ions.
Molecular Design of Optical and Structural Properties of Organic Semiconductor Films: Thiophene-Based Oligomers
Authors: Kanemitsu Yoshihiko , Suzuki Katsunori , Shimizu Naoya , Shiraishi Yotaro , Kuroda Masami
Published: October 2002

Vacuum-deposited thin films of thiophene-based oligomers were prepared on fused silica glasses in order to elucidate the correlation between molecular structures and optical properties of solid films. Thiophene-based oligomers have well-barrier-well structures in quasi-one-dimensional backbone chains. It is demonstrated that both optical and structural properties of thiophene-based oligomer crystalline films can be controlled by the modification of the conjugation length and the barrier structure. These results represent a significant step toward good quality organic thin film devices.
Effect of the Thickness of Alignment Layer on the Low-Frequency Dielectric Dispersion of a Nematic Liquid Crystal
Authors: Jun Nakanowatari Jun Nakanowatari , Katsumichi Ono Katsumichi Ono
Published: October 2002

The low-frequency dispersion of the complex dielectric constant of a nematic liquid crystal was measured as a function of the thickness of the polyimide alignment layer at 25 and 50° C. The dielectric relaxation strength of the low-frequency dispersion was strongly dependent on the thickness of the alignment layer and decreased with increasing thickness. A simple model assuming series combination of the alignment layer and liquid crystal phase was proposed to explain the frequency dependence of equivalent parallel capacitance of the liquid crystal cell. The experimental dispersion curves were excellently fitted by the equation based on the proposed model. This made possible the accurate determination of both the capacitive and conductive components of the alignment layer and the liquid crystal phase. The capacitive component of the alignment layer was proportional to the reciprocal of the thickness. The result indicated that the low-frequency dielectric dispersion of the cell is due to the Maxwell-Wagner effect of the alignment layer and the liquid crystal phase having different values of conductance. This made it possible to explain completely the quantitative aspect of the ionic effect in the nematic liquid crystal cell.
Thermal Diffusion of Antimony into Nanostructured Porous Silicon
Authors: Nishimura Kohsuke , Yasuyuki Nagao Yasuyuki Nagao , Noriaki Ikeda Noriaki Ikeda
Published: October 2002

The thermal diffusion of Sb was carried out from Sb-doped silicate glass into porous silicon (PS) layers. The depth profiles of diffused Sb in PS layers were fitted to complementary error function curves in order to estimate diffusion coefficients. It was found that diffusion coefficients of Sb in PS were larger and had lower activation energy than those of Sb in hydrogenated amorphous silicon (a-Si:H) for the temperature range investigated. The experimental results are discussed in relation to the diffusion mechanisms in a-Si:H.
Fabrication of One-Dimensional Silicon Nanowire Structures with a Self-Aligned Point Contact
Authors: Namatsu Hideo , Nagase Masao , Kurihara Kenji , Seiji Horiguchi Seiji Horiguchi , Takahiro Makino Takahiro Makino
Published: October 2002

We propose a novel one-dimensional Si nanowire structure with a point contact. Wire structures are fabricated in a {110} Si layer by using KOH solution. Both the {111} planes projecting obliquely along the wire and the vertical {111} sidewalls of the wire are spontaneously exposed. By oxidation of this {111} plane structure, the wire structure is converted into the one-dimensional nanowire structure. In addition, since the nanowire structure is based on a form of the {111} plane structure, the planes projecting obliquely produces a point-contact structure which gradually increases in diameter toward the source and drain regions. The Si nanowires fabricated by this technique shows clear quantized conductance with little fluctuation on the plateaus.
Enhanced Sub-Picosecond Electromagnetic Radiation from YBa2Cu3O7-δ Thin-Film Bow-Tie Antennas Excited with Femtoseconds Laser Pulses
Authors: Tani Masahiko , Tonouchi Masayoshi , Wang Zhen , Sakai Kiyomi , Hangyo Masanori , Tomozawa Seiji , Murakami Yoshishige
Published: October 2002

We demonstrate the emission of sub-picosecond electromagnetic waves from YBa2Cu3O7-δ thin-film bow-tie antennas. Femtosecond laser-pulse irradiation creates a radiative supercurrent transient in the films, and freely propagated radiation is detected and characterized. The low-frequency component of the radiation was greatly enhanced by using bow-tie antennas instead of dipole antennas. We discuss the antenna effects on both the radiation spectra and the radiation power.
Intense-Electron-Beam Transport Through a Short Insulator Beam Guide
Authors: Shigeo Kawata Shigeo Kawata , Shinichi Nishiyama Shinichi Nishiyama , Masataka Mori Masataka Mori , Kenta Naito Kenta Naito , Shigeru Kato Shigeru Kato , Musuhi Hakoda Musuhi Hakoda
Published: October 2002

We previously proposed [Jpn. J. Appl. Phys. 34 (1995) L520] a new system for intense-electron-beam transport using an insulator guide which covers the whole beam-transport region. In this paper we present a numerical study of intense-electron-beam transport through an insulator guide whose length is short compared to beam-transport length. Positive ions are extracted in a self-regulated manner from the plasma, generated at the insulator surface, by the electron beam space charge. The ions expand over the transport region, and are extracted from the guide region by the electron beam space charge into the outer region which is not covered by the insulator. Consequently, the beam space charge is neutralized even in the outer region, and the beam propagates effectively in this system.
A New 2×2 Matrix Representation for Twisted Nematic Liquid Crystal Displays at Oblique Incidence
Authors: Chen A. Lien
Published: October 2002

A new 2×2 matrix representation for the twisted nematic liquid crystal display (TN-LCD) at oblique incidence was obtained. Compared with the previous representation developed by Lien [Appl. Phys. Lett. 57 (1990) 2767 and SID 91 Dig. (1991) 586], the optical transmissions calculated by this new 2×2 matrix method are much closer to those calculated by the 4×4 matrix method with spectrum averaging to account for the nonzero band-width of the incident light. The discrepancy between the last two is generally less than 1%. The simplicity and accuracy makes this new 2×2 matrix method very useful.
4×4 Matrix Method for Biaxial Media and Its Application to Liquid Crystal Displays
Authors: Chen C.-J. , Lien A. , Nathan M. I.
Published: October 2002

The 4×4 matrix method for uniaxial media developed by Berreman [J. Opt. Soc. Am. 62 (1972) 502] and by Wöhler et al.. [J. Opt. Soc. Am. A 5 (1988) 1554] is extended to biaxial media by making simple modifications to solutions of surface normal wave vector. For uniaxial media, the well known analytical expressions can be directly deduced from the modified solutions. This 4×4 matrix method for biaxial media is applied to demonstrate that, for viewing directions away from the principal planes of an optically compensated bend mode liquid crystal display, the compensation effects of a single biaxial film are generally different from those of the combination of two uniaxial films.
Pulsed Laser Deposition of Bioceramic Hydroxyapatite Thin Films on Polymer Materials
Authors: Shigeki Hontsu Shigeki Hontsu , Masaya Nakamori Masaya Nakamori , Hitoshi Tabata Hitoshi Tabata , Junya Ishii Junya Ishii , Tomoji Kawai Tomoji Kawai
Published: October 2002

The ArF excimer laser deposition technique has been used to fabricate bioceramic hydroxyapatite (HAp) thin films on polymer materials such as polyimides (PI), polytetrafluoroethylene (PTFE), silicone rubber (SR), and polyethyleneterephthalate (PET). The crystallinity, structure, composition and surface morphology of HAp films are evaluated by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and atomic force microscopy (AFM). Crystallized HAp films are obtained on PI and PTFE, and mechanical properties of HAp films on the polymer materials are examined using an Instron testing machine. This result is very important to enable the application of organic/inorganic-ceramic composite materials in medical fields.
Feasibility Study on a Novel Type of Computerized Tomography Based on Scanning Probe Microscope
Authors: Ohta Takayuki , Sugawara Yasuhiro , Seizo Morita Seizo Morita
Published: October 2002

A novel type of computerized tomography (CT) using a scanning probe microscope (SPM) was proposed. For an electrostatic force microscope (EFM) which is a kind of SPM, electrostatic force data was processed using CT to reconstruct the electric charge distribution in the sample. The conjugate gradient method (CGM) was used for the charge reconstruction. The result of computer simulation shows that it is possible to reconstruct the electric charge distribution in the sample from the electrostatic force distribution measured by EFM. In the same way, it will be feasible to reconstruct the inner structure of samples from other SPM data.
Gate-Controlled Lateral Diodes Formed in Undoped Heterostructure
Authors: Yoshiro Hirayama Yoshiro Hirayama
Published: October 2002

We developed a gate-controlled diode that has a Schottky gate on an undoped heterostructure with n- and p-type ohmic regions at opposite ends of the gate. Either two-dimensional electron or hole gas (2DEG or 2DHG) can be formed at the same heterointerface by an electric field from the surface gate. When this diode is biased in the forward direction, current flow is observed in the two gate voltage ranges corresponding to the formation of 2DEG and 2DHG in the undoped heterostructure. When the drain voltage between the p- and n-type contacts exceeds a certain value, a double injection forms a novel current channel that differs from the conventional 2DEG or 2DHG.
Thin Film Fabrication of Bi2(Sr, Ca)2CuOx Phase at Temperatures between 450 and 650°C by Plasma-Assisted Ion Beam Sputtering
Authors: Endo Tamio , Yan Haodong , Wakuta Masahito , Hiroaki Nishiku Hiroaki Nishiku , Masahiro Goto Masahiro Goto
Published: October 2002

Thin films of Bi2(Sr, Ca)2CuO

x

(2201) were prepared by ion beam sputtering with supply of oxygen molecules or plasma to the substrate at various substrate temperatures T
s. The high-quality 2201 single phase can be grown with T
s in the range of 550–600° C using oxygen molecules, while it can be grown in the range of 450–650° C using oxygen plasma. Use of this plasma allows reduction of the processing temperature by 100° C and suppresses 2201 dissociation at higher T
s. X-ray linewidths of the films prepared using plasma are extremely narrow, like those of MBE-grown films fabricated at higher T
s using ozone or atomic oxygen, indicating that the films have thick crystalline domains and less strain.
Low Temperature Flow of High-Water Containing Glasses Prepared by Chemical Vapor Deposition
Authors: Takeshi Haraguchi Takeshi Haraguchi , Osamu Sugiura Osamu Sugiura
Published: October 2002

Silicon dioxide films with a high water content were deposited by chemical vapor deposition using tetra-isocyanate-silane and water at substrate temperatures between 70° C and 100° C. The films flowed upon annealing in steam at 120° C and provided smooth topographies when the water content was higher than 8 weight percent. However, the films did not flow at all upon annealing in nitrogen.
Emission Characteristics of the Molybdenum-Coated Silicon Field Emitter Array
Authors: Park Heung-Woo , Ju Byeong-Kwon , Lee Yun-Hi , Park Jung-Ho , Myung-Hwan Oh Myung-Hwan Oh
Published: October 2002

Uniform and reproducible silicon tip arrays were fabricated using the reactive ion etching followed by the re-oxidation sharpening. Molybdenum was coated on the some of the silicon tip array. Current-voltage characteristics and current fluctuations were tested in the high vacuum level. Turn-on voltage of the uncoated tip was 35 V and maximum current was 1 mA, while turn-on voltage of the coated tip was 15 V and maximum current was 6 mA. While uncoated silicon tip was destroyed after 13 minutes after operation and showed rapid lowering of emission current, coated tip showed stable emission characteristics. Obtained currents were proved to be field emission currents using the Fowler-Nordheim plot studies.
Self-Injection-Locked, Narrow-Linewidth, Flashlamp-Pumped Ti:Al2O3 Laser
Authors: Suzuki Hiroyuki , Hideki Takeda Hideki Takeda , Fumihiko Kannari Fumihiko Kannari
Published: October 2002

A narrow-linewidth, Q-switched, tunable Ti:Al2O3 laser, which is pumped by short-pulse flashlamps is developed using self-injection locking. By electro-optically switching the light from a second resonator consisting of a grazing incidence grating and a tuning mirror, which generates a narrow-linewidth seed pulse, to a conventional main resonator with a large volume, output energies of up to ∼57 mJ/pulse were obtained with a linewidth of ∼10 pm and a pulsewidth of ∼20 ns. The laser was tunable within a range of 760 nm to 830 nm with high spectral purity.
Down-Conversion of Microwave Optoelectronic Signals in a GaAs Microstrip Ring Resonator
Authors: Lee Jong-Chul , Yeh C. L. , Ho C. H. , Taylor H. F. , Weichold M. H. , Chang K.
Published: October 2002

We report the mixing performance of a GaAs microstrip ring resonator in which a Schottky photodetector is monolithically integrated in a coupling gap. A spectrum of down-conversion between an optically modulated RF signal and an independently applied LO (Local Oscillator) signal is demonstrated and the system conversion loss of RF to IF (Intermediate Frequency) is measured as a function of LO frequency and compared with other data.
Molecular Alignments in Liquid Crystal Mixtures of 8CB with 10CB Determined by Scanning Tunneling Microscopy
Authors: Tsutomu Kadotani Tsutomu Kadotani , Seiji Taki Seiji Taki , Hirotaka Okabe Hirotaka Okabe , Shoichi Kai Shoichi Kai
Published: October 2002

We observed the specific structures of molecular alignments in the liquid crystal mixtures of n-alkylcyanobiphenyl (mCB: m=8 and 10) on highly oriented pyrolytic graphite (HOPG) substrates by scanning tunneling microscopy (STM). The alignment structures, which were quite different from previously reported alignments for each monophase 8CB and 10CB, showed two different alignments and packings of both molecules depending on the mixing rate of 8CB and 10CB. One was observed in a mixture with a rather low mixing rate of 8CB in 10CB, in which the unit structure was composed of two 8CB molecules and four 10CBs with bilayer conformations. The other was a unit structure that consisted of four 8CBs and of six 10CBs in the mixture with a rather high mixing rate of 8CB. No other combination was observed.
Property Change of Si(111) Surface by Scanning Tunneling Microscope Manipulation
Authors: Seiji Heike Seiji Heike , Tomihiro Hashizume Tomihiro Hashizume , Satoshi Watanabe Satoshi Watanabe , Mark I. Lutwyche Mark I. Lutwyche , Yasuo Wada Yasuo Wada
Published: October 2002

Scanning tunneling microscopy (STM) has been used to form trench lines 0.2–0.6-nm deep and 10-nm wide by applying a high voltage and/or a large tunneling current between the tip and the Si(111)-7×7 surface. We have found that the apparent height of the surface area surrounded by a complete square trench is 0.1–0.3 nm lower than the outside, while no apparent height difference is measured in the case of a square trench with one open corner. We have also observed that the trench formation is hindered or made difficult inside the complete surface square trench, while the effect is negligible in the case of the open trench.
Mirrorless Lasing in Conducting Polymer poly(2,5-dioctyloxy-p-phenylenevinylene) Films
Authors: V. Frolov Sergey , V. Vardeny Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

We report mirrorless lasing in thin films of poly(2,5-dioctyloxy- p-phenylenevinylene) (DOO-PPV), that we identify as superradiance. We have measured the characteristic properties associated with this phenomenon including spectral narrowing, polarization memory, thickness and intensity dependencies. From the measurements of picosecond transient gain and loss in DOO-PPV we conclude that DOO-PPV films are excellent candidates for solid state lasers.
Profile Evolution during Pulsed Plasma Etching
Authors: Mutumi Tuda Mutumi Tuda , Kouichi Ono Kouichi Ono
Published: October 2002

Evolution of etched profiles has been studied numerically during pulsed low-pressure, high-density plasma etching of Si in Cl2. The time-dependent behavior of chlorinated surface coverage and etch rate was calculated assuming Langmuir adsorption kinetics. Etched profiles were then simulated using the time-averaged etch rates obtained, to examine etch anisotropy and microscopic uniformity. The model predicted that under pulsed plasma conditions, the surface coverage is increased at the bottom of microstructures, resulting in highly anisotropic, aspect-ratio independent etching.
Comparison of Dopant and Oxygen Striations at the Same Point in Czochralski Silicon Crystals
Authors: Kanda Tadashi , Kusano Ken-ichiro , Tomokage Hajime
Published: October 2002

Dopant and oxygen striations, and grown-in defect striations in Czochralski silicon crystals grown under long-period temperature fluctuations in the melt were measured at the exact same position in the crystal by spreading resistance measurement and an electron-beam-induced current method with Au diffusion, X-ray topography and micro-Fourier transform infrared spectroscopy, and an optical-precipitate-profiler (OPP) method, respectively. We observed that the rapid variations in dopant striations caused by remelting during crystal growth do not appear for oxygen striations. OPP defects were found to be distributed along the regions of the high oxygen concentration.