bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of Spatial Extent of a Defect Cluster in Si Induced by Single Ion Irradiation
Authors: Koyama Masato , Cheong Chon-wa , Yokoyama Koji , Ohdomari Iwao
Published: October 2002

In order to estimate the spatial extent of a defect cluster in Si induced by single Ar ion irradiation, we analyzed the dependence of the series resistance of ion-irradiated Schottky diodes on the total ion dose. Ar ions were implanted into Si at 75 keV at doses ranging from 1010 ions/cm2 to 1015 ions/cm2 at room temperature. The series resistance increased abruptly between 1012 ions/cm2 and 1013 ions/cm2 by two orders of magnitude. The diameter of high-resistivity regions in Si induced by a single ion impact was 21 nm under our experimental conditions. We conclude that heavily damaged regions around amorphous cores are responsible for the high-resistivity regions.
Ferro-magnetic Material Loaded Untuned RF Cavity for Synchrotron
Authors: Yoshihisa Iwashita Yoshihisa Iwashita
Published: October 2002

A new scheme for a ferromagnetic-material-loaded untuned RF cavity is proposed. The multi-feed coupling scheme can increase the shunt impedance while maintaining low VSWR. This scheme should widen the applicability of untuned cavities.
Investigation of Grown-in Defect Formation in Czochralski Silicon Crystals by Optical Precipitate Profiler
Authors: Kanda Tadashi , Hourai Masataka , Tomokage Hajime
Published: October 2002

The grown-in defects in Czochlalski silicon with various growth-striation intervals are investigated using the optical precipitate profiler and compared with the distribution of interstitial oxygen concentrations [Oi]. The striation intervals do not influence the density or size of the grown-in defects. However, the defect size in the peak [Oi] region is the same as the size in the valley [Oi] region and the total defect volume in the peak is larger than the volume in the valley. It is suggested that the grown-in defects grow by gathering vacancies into some nuclei in the peak region.
Preparation of Phosphorus-Doped Microcrystalline Silicon by Mercury-Sensitized Photochemical Vapor Deposition Process
Authors: Masato Hiramatsu Masato Hiramatsu , Yoshito Kawakyu Yoshito Kawakyu
Published: October 2002

Phosphorus-doped microcrystalline silicon (µc-Si) films were prepared on intrinsic hydrogenated amorphous silicon (a-Si:H) by mercury photosensitized decomposition of silane-phosphine-hydrogen gas mixture. We have obtained a high deposition rate of 15 nm/min and a high dark conductivity of 1.2 (Ω·cm)-1 at the substrate temperature of 240° C. The photothermal deflection spectroscopy (PDS) measurement of n-type µc-Si film on a-Si:H showed that the µc-Si/a-Si:H interface state density made by photo-CVD was small compared with that of the same structure made by the conventional plasma enhanced CVD (PECVD) method.
Growth of Bi 2Sr 2CaCu 2Oy Single Crystals Using a Vertical Bridgman Method
Authors: Akito Tanaka Akito Tanaka , Satoru Kishida Satoru Kishida , Atsuhiko Shibasaki Atsuhiko Shibasaki , Heizo Tokutaka Heizo Tokutaka , Kikuo Fujimura Kikuo Fujimura
Published: October 2002

We prepared Bi2Sr2Ca
n-1CunOy (BSCCO) single crystals using a vertical Bridgman method. From the results we found that the single crystals were plate-like and in (2212) single phase, and that the typical size was 4×10 mm2. The resistance-temperature characteristics indicated that the critical temperature of a single crystal was about 80 K. Therefore, the vertical Bridgman method is thought to be effective for growing a (2212) phase BSCCO single crystal.
Observation of Vicinal Si(111)7×7 Surface by Energy-Filtered Reflection High-Energy Electron Diffraction
Authors: Yoshimi Horio Yoshimi Horio , Yasuyuki Hashimoto Yasuyuki Hashimoto
Published: October 2002

Extra spots near the specular spot have clearly been observed for a vicinal Si(111)7×7 surface by zero-loss energy-filtered reflection high-energy electron diffraction (EF-RHEED) at [112] incidence with 10 kV electron beam. The extra spots are distributed in a line across the specular spot. From the geometrical consideration of these extra spots, the mean terrace length parallel to the [112] direction was reasonably estimated based on a regularly arranged step surface with single step height. Glancing angle dependences of the extra spots were also simulated, and good agreement with the experimental results was obtained.
Timing Jitter Reduction in a Passively Mode-Locked Fiber Laser
Authors: Endo Michiyuki , Ghosh Gorachand , Tanaka Yuichi
Published: October 2002

We generated laser pulses of 270 fs in the 1.55 µ m band with a repetition rate of 45.4 MHz in a passively mode-locked, erbium-doped fiber ring laser, pumped by a laser diode. We reduced the timing jitter by minimizing the intensity fluctuation of the pump source using a feedback loop and by controlling the air fluctuation of the laser resonator in a sealed box. The rms timing jitter is below 0.9 ps in the range of 30–3000 Hz.
A New Theoretical Model of a Dye-Sensitized Nanocrystalline Photoelectrochemical Cell
Authors: Akira Usami Akira Usami
Published: October 2002

A new theoretical model of a dye-sensitized nanocrystalline photoelectrochemical cell based on battery theories is developed under a short-circuit condition. Carrier and recombination distributions in the cell change extensively in response to changes in the diffusion coefficient of the redox species in the electrolyte. Quantum efficiency has little influence on the change when the cell does not operate under the trap-filled condition. The solution of a simple diffusion equation for electrons is a good approximation for a calculation of quantum efficiency and short-circuit current under the trap-unfilled condition.
Electroluminescence from an InGaAs-Based High Electron Mobility Transistor Designed for High-Speed Operation
Authors: Naoteru Shigekawa Naoteru Shigekawa , Takatomo Enoki Takatomo Enoki , Tomofumi Furuta Tomofumi Furuta
Published: October 2002

The electroluminescence (EL) of an InGaAs-based high electron mobility transistor (HEMT) designed for high-speed operation was first investigated by cleaving the device and measuring the EL coming from the exposed side of the channel. The gate length and the gate-source separation of the HEMT were 0.1 and 0.55 µm, respectively. We observed the EL attributed to the recombination of the majority electrons and the ionization-induced holes in the InGaAs channel for a drain-source voltage larger than 1.3 V. This means that the EL is useful for evaluating the impact ionization in such devices. Furthermore we proposed an expression relating the EL intensity to the concentration of the holes at the source edge, and investigated the gate-source voltage (V
GS) dependence of the concentration. We found that their concentration reveals a peak at V
GS=-0.4 V.
Oxygen Controlled Melt Growth of Filamentary Nd123 Oxide Superconductor by Solution Spinning Method
Authors: Tomoko Goto Tomoko Goto , Tadanori Miura Tadanori Miura , Tatsuhiro Hayashi Tatsuhiro Hayashi
Published: October 2002

The oxygen controlled melt growth process for the filamentary Nd123 superconductor produced by solution spinning to obtain a high J
c was examined. The filaments have been prepared by dry spinning through a homogeneous aqueous solution containing mixed acetates of Nd, Ba and Cu, poly(vinyl alcohol) and organic acids. By controlling the starting compositions and the melt growth process, a high T
c of 94.5 K and a high J
c of more than 1.3x104 A/cm2 at 77 K and 0 T were achieved for the filamentary Nd1.18Ba2.12Cu3.09O
x
superconductor with a diameter of 60 µm. The grains in the sample are not always aligned along the fiber length.
Mechanism Activating the 21Ag State in all-trans-β-Carotene Crystal to Resonance Raman Scattering
Authors: Hashimoto Hideki , Koyama Yasushi , Yuzo Mori Yuzo Mori
Published: October 2002

The mechanism governing the additional excitation peak of the C=C stretching Raman line was studied by comparing randomly oriented crystals of all- trans-β-carotene at 11 K with microcrystals dispersed in a KBr disk at 11 K, a spin-coated film at 11 K and an isopentane solution at 160 K. Only the randomly oriented crystals gave rise to the additional peak. The peak at 14500 cm-1 is assigned to the electronic forbidden transition to the 21A
g
state, and its oscillator strength is estimated as f
a∼1×10-2. An asymmetric distortion in the crystal is proposed to activate the forbidden transition at low temperature.
Control of Aperture Size of Optical Probes for Scanning Near-Field Optical Microscopy Using Focused Ion Beam Technology
Authors: Muranishi Masaru , Sato Kazutaka , Hosaka Sumio , Kikukawa Atsushi , Shintani Toshimichi , Ito Kenchi
Published: October 2002

We propose a fabrication technique for apertures of optical probes for scanning near-field optical microscopy (SNOM) using a focused ion beam (FIB) process. We tried two FIB processes, FIB drilling and FIB slicing. The FIB slicing technique is very useful for fabrication of nm-sized SNOM apertures of less than 50 nm. The problem with the FIB drilling process is that it is difficult to identify the apex of the tip and to control the beam onto the apex. The FIB slicing technique can easily fabricate an aperture at an apex and control aperture size by cut-off-depth. It is easy for a sharp tip to obtain accurate size of aperture. It can be considered to obtain accurate size of aperture with fabricated error of 35 nm in a sharp tip with cone angle of 30 deg.
Application of Solid Immersion Lens to High-Resolution Photoluminescence Imaging of Patterned GaAs Quantum Wells
Authors: Takeaki Sasaki Takeaki Sasaki , Motoyoshi Baba Motoyoshi Baba , Masahiro Yoshita Masahiro Yoshita , Hidefumi Akiyama Hidefumi Akiyama
Published: October 2002

The solid immersion lens has been applied to high-resolution microscopic photoluminescence (PL) imaging of a strip-line-patterned GaAs quantum well structure. An improved resolution corresponding to the numerical aperture of 1.25 was realized. The enhanced emission of PL from edges, and the significantly increased collection efficiency of PL were demonstrated.
Analysis of Deposits Evaporated from Boron-Doped Silicon Melt
Authors: Maeda Susumu , Kato Masaki , Abe Keisei , Nakanishi Hideo , Keigo Hoshikawa Keigo Hoshikawa , Kazutaka Terashima Kazutaka Terashima
Published: October 2002

The influence of the addition of boron on weight variation of silicon melt due to evaporation was investigated. It was found that the evaporation loss of the 1021 atoms/cm3 boron-doped silicon melt was larger than that of non-doped silicon melt. In particular, it appeared that boron enhanced the weight variation of the silicon melt at high temperature (1550° C) by assisting the evaporation from the melt. Deposits collected by a well designed collector were analyzed by electron probe microanalysis (EPMA) in order to identify the chemical species evaporated from the boron-doped silicon melt. It was found that the predominantly evaporated species from the boron-doped silicon melt was silicon oxide. It could be concluded that the addition of boron into the silicon melt enhances the evaporation of silicon-oxide.
Step-Coverage Characteristics of Silicon-Dioxide Films Formed by a New Low-Temperature Chemical-Vapor-Deposition Method
Authors: Yasutaka Uchida Yasutaka Uchida , Shu Takei Shu Takei , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Step-coverage characteristics have been investigated for hydrogen-free SiO2 films deposited by a newly-developed low-temperature chemical-vapor-deposition (CVD) method using a gas mixture of tetra-iso-cyanate-silane and tertiary-methyl-amine. The effective diffusion length of CVD source molecules estimated from open-cavity experiments was around 300 µm. Scanning electron microscopy (SEM) observation showed that the film filled a 1-µm-wide and 2.7-µm-deep trench with excellent conformity.
Highly Sensitive MOSFET Gas Sensors with Porous Platinum Gate Electrode
Authors: Fukuda Hisashi , Seo Hiroaki , Kasama Kouichirou , Endoh Toshiaki , Nomura Shigeru
Published: October 2002

Novel gas-sensing devices based on a porous platinum (Pt) gate metal-oxide-semiconductor field-effect transistor (MOSFET) have been fabricated. The catalytic properties of the porous Pt surface for hydrogen (H2) enhance the gas detection sensitivity of the MOSFET gas sensor. The threshold voltage decreased rapidly with time when the device was exposed to H2 gas. It was possible to detect 22 ppm of H2 gas with a response time of less than 2 min at a device temperature of 27°C. The gas sensitivity could be enhanced to about 10 times higher than that of an unmodified Pt surface. The device detection mechanism presented corresponds well with the experimental data.
Electron Beam Induced Damage of MOS Gate Oxide
Authors: Konishi Morikazu , Kubota Michitaka , Koike Kaoru
Published: October 2002

Threshold voltage (V
th) shift of a metal oxide semiconductor (MOS) system due to electron beam (EB) exposure can be expressed quantitatively as a function of the EB dosage which was derived easily as a solution of a differential equation based on the hole capturing model in the gate oxide. The theoretical model assumes two steps for hole capturing. First is the hole capturing by intrinsic hole traps leading to steep V
th shift with EB dosage at early exposure stages. The second is the hole capturing by newborn hole traps due to the EB injection, leading to a rather slow V
th variation at a higher EB dosage. The model shows good agreement with the experimental result over a wide range of electron beam dosages. Moreover, hole injection efficiency in the gate oxide is found to be higher for the third Aluminum interconnection layer exposure than for the first Al layer, corresponding to higher deposition energy around the gate oxide obtained by the Monte Carlo simulation result.
Novel Ultra-Clean Self Aligned Silicide (Salicide) Technology Using Double Titanium Deposited Silicide (DTD) Process for 0.1 µm Gate Electrode
Authors: Hiroshi Kotaki Hiroshi Kotaki , Masayuki Nakano Masayuki Nakano , Kotaro Kataoka Kotaro Kataoka , Seizo Kakimoto Seizo Kakimoto
Published: October 2002

We clarified that the fluorine contamination caused by the gate sidewall etching inhibits the silicidation reaction and accelerates agglomeration. To overcome these problems, a novel “double titanium deposited silicide (DTD)” process has been developed. The key point of this process is the deposition and subsequent removal of dummy titanium before silicidation. Contaminated silicon and gate poly-silicon surface layer caused by reactive ion etching was removed perfectly and an ultra-clean surface was obtained. As a result, low sheet resistance (3 Ω/\Box) was obtained in both n+ and p+ very fine 0.1 µm gates.
Shallow Trench Isolation Characteristics with High-Density-Plasma Chemical Vapor Deposition Gap-Fill Oxide for Deep-Submicron CMOS Technologies
Authors: Lee Seung-Ho , Son Jeong-Hwan , Lee Hi-Deok , Yang Wouns , Lee Young-Jong
Published: October 2002

Shallow trench isolation (STI) characteristics were systematically studied based on various deposition conditions of high-density-plasma (HDP) chemical vapor deposition (CVD) gap-fill material with different trench lining oxide thicknesses. The effects of post-chemical-mechanical-polishing (CMP) processes on STI characteristics were also considered, together with a comparison of high-temperature-low-pressure dielectric (HLD) gap filler. The diode leakage data showed negligible Si reactive ion Si etching (RIE) damage and negligible sputter effect of HDP even with low deposition/sputter (D/S) ratio on the trench sidewall surface. The leakage current was, however, mainly affected by the fact that the weak trench top corners were exposed during successive HF cleanings and RIE etchings after the CMP process. It was also found that there were negligible interface hole-trapping effects of generated electron-hole pairs in HDP oxide, which was induced by the plasma source of the HDP system. The results also showed excellent isolation characteristics and a narrow width effect.
Gate Oxide Defects in MOSLSIs and Octahedral Void Defects in Czochralski Silicon
Authors: Itsumi Manabu , Ueki Takemi , Watanabe Masaki , Yabumoto Norikuni
Published: October 2002

The origin of insulator defects in gate oxides and poly-oxides was thoroughly investigated. We clarified that octahedral void defects originating in a Czochralski silicon substrate are responsible for gate-oxide defects and that polyhedral void defects produced during annealing or oxidation are responsible for defects in insulators on poly-silicon. These are expected to be the principal defects affecting the yield and reliability of next-generation metal-oxide-silicon large-scale integrated-circuits or flash memories. In addition, defects in the buried oxides of a silicon-on-insulator substrate were also examined. Octahedral defects or polyhedral defects were observed just under the buried-oxide defects. Octahedral defects and polyhedral defects may be common in standard metal-oxide-silicon large-scale integrated-circuits, flash memories, and silicon-on-insulator substrates.
Long-Term Reliability of the Blocking Capability and Failure Voltage of Electrostatic Discharge of the SOI High-Voltage Device and IC
Authors: Sumida Hitoshi , Hirabayashi Atsuo , Shimabukuro Hiroshi
Published: October 2002

The reliability of silicon-on-insulator (SOI) high-voltage devices and ICs has been confirmed experimentally by two accelerated tests for the long-term reliability of their blocking capability and electrostatic discharge (ESD) test. A lateral insulated gate bipolar transistor (IGBT) and p-channel metal-oxide-semiconductor field-effect- transistor (PMOS) for the accelerated tests, and a 200 V-class power IC for the ESD testing, were fabricated on SOI. The failure voltage of the ESD of the IC on SOI (SOI-IC) was compared with that of the IC on a junction isolated wafer (JI-IC), which had the same specification as the SOI-IC. The IGBT and PMOS could pass the two accelerated tests, but the test results of the PMOS depended strongly on its cell pattern. The failure voltage of ESD of the SOI-IC was lower than that of the JI-IC.
Improved Recessed-Gate Structure for Sub-0.1-µm-Gate InP-Based High Electron Mobility Transistors
Authors: Tetsuya Suemitsu Tetsuya Suemitsu , Takatomo Enoki Takatomo Enoki , Haruki Yokoyama Haruki Yokoyama , Yasunobu Ishii Yasunobu Ishii
Published: October 2002

An improved recessed-gate structure for high-performance short-gate InP-based InAlAs/InGaAs high electron mobility transistors (HEMTs) is presented. The effective gate length of the HEMTs is found to be related to the electron density in the side-etched region between the gate and the ohmic capped region. The higher electron density in the side-etched region is efficiently suppresses the effective gate length. A new gate recess process, which consists of a sequence of wet-chemical etching and Ar-plasma etching, enables us to reduce the effective gate length. The new recessed-gate structure successfully provides improved performance with high uniformity. A cutoff frequency of 300 GHz is achieved even with 0.07-µm-gate HEMTs.
High-Performance HEMT with an Offset-Gate Structure for Millimeter-Wave Monolithic Microwave ICs
Authors: Ohta Hiroshi , Tanimoto Takuma , Ohbu Isao , Higuchi Katsuhiko , Takatani Shinichiro , Kurita Naoyuki , Kamozaki Keigo , Kondoh Hiroshi
Published: October 2002

A process technology for a pseudomorphic high electron mobility transistor (P-HEMT) with an offset-gate structure has been developed for millimeter-wave monolithic microwave ICs (MMICs). A HEMT with the offset-gate structure showed both reduced gate-to-drain capacitance and drain conductance compared with a device with a non-offset-gate structure. The device showed a maximum available gain (MAG) of 9 dB at 77 GHz. The device was applied to a 77 GHz three-stage power amplifier, which showed a small-signal gain of 16.5 dB. Under preliminary life testing, this amplifier showed a stable small-signal gain for over 160 hours of testing at 175°C.
InGaAsP Lasers on GaAs Fabricated by the Surface Activated Wafer Direct Bonding Method at Room Temperature
Authors: Chung TaekRyong , Hosoda Naoe , Suga Tadatomo , Takagi Hideki
Published: October 2002

1.3 µm InGaAsP/InP strained-layer quantum wells ridge waveguide lasers have been successfully fabricated on a GaAs substrate by the surface activated wafer direct bonding method at room temperature. In this method, the surfaces of two wafers are activated by Ar fast atom beam irradiation and mated in a high vacuum. A high bonding strength was attained. No microcracks and voids were found under transmission electron microscopy(TEM). A threshold current density of 500 A/cm2 was achieved. This technique is very promising to realize a monolithic of optoelectronic integrated circuits for optical communications and interconnections.
Metalorganic Vapor Phase Epitaxy Growth of High Quality Cubic GaN on GaAs (100) Substrates
Authors: Wu Jun , Yaguchi Hiroyuki , Onabe Kentaro , Shiraki Yasuhiro , Ito Ryoichi
Published: October 2002

We report on the growth of high quality cubic GaN films on GaAs (100) substrates by low pressure metalorganic vapor phase epitaxy. The GaN films exhibit a smooth surface which is free from cracks. X-ray diffraction shows the cubic nature of the GaN films. X-ray rocking curve with ω scan shows that the crystal quality of GaN films improves markedly with increasing growth temperatures. Photoluminescence measurements confirm the high quality of the cubic GaN films. The full width at half maximum of excitonic emission from the cubic GaN films is as narrow as 70 meV at 300 K.
Electrical Properties of Regrowth ZnSe Homointerfaces Formed by Molecular Beam Epitaxy
Authors: Yamagata Yuji , Sawada Takayuki , Imai Kazuaki , Suzuki Kazuhiko , Tsubono Isao
Published: October 2002

Electrical properties of ZnSe/ZnSe homointerfaces formed by molecular beam epitaxy (MBE) regrowth processes were investigated by I-V, C-V and deep level transient spectroscopy (DLTS) measurements of Au/n-ZnSe/n+-GaAs Schottky diodes, for the first time. It was found that a potential barrier of about 0.73 eV was formed at the air-exposed and chemically etched regrowth homointerface owing to the generation of high-density interface states. This potential barrier lowered the current level by four orders of magnitude from that of the reference sample without regrowth homointerface. Almost the same potential barrier was formed even when the growth was interrupted in vacuum. The observed capacitance dispersion and the capacitance decrease within a forward bias region were well fitted using the interface state distribution deduced from I-V characteristics.
Controlled Formation of Narrow and Uniform InP-Based In0.53Ga0.47As Ridge Quantum Wire Arrays by Selective Molecular Beam Epitaxy
Authors: Fujikura Hajime , Hanada Yuuki , Kihara Michio , Hasegawa Hideki
Published: October 2002

Attempts have been made to form precisely size-controlled, narrow and highly uniform In0.53Ga0.47As/In0.52Al0.48As ridge quantum wire arrays by selective molecular beam epitaxy (MBE) on patterned InP substrates. Precise size control of the wire has become possible by combining (1) control of the wire width through the growth time of the underlying InAlAs barrier layer and (2) the semi-self-limiting growth phenomenon in InGaAs wire layer growth. As a result, a minimum wire width of 35 nm was achieved in a controlled fashion. This wire showed large blue shift in the transition energy of 400 meV, which is the largest value ever reported for selectively grown InP-based InGaAs quantum wires. Using a high-temperature-grown InGaAs buffer layer, the wire uniformity was drastically improved, resulting in a minimum photoluminescence (PL) peak width of 28 meV, which indicates that the uniformity of the present wire is also the best of all the selectively grown InP-based InGaAs quantum wires reported so far.
Perfect Spatial Ordering of Self-Organized InGaAs/AlGaAs Quantum Disks on GaAs (311)B Substrate with Silicon-Nitride Dot Array
Authors: Kuramochi Eiichi , Temmyo Jiro , Kamada Hidehiko , Tamamura Toshiaki
Published: October 2002

To control the position of self-organized InGaAs/AlGaAs quantum disks on a GaAs (311)B substrate, the use of fine silicon nitride dot array was examined. The pentagonally shaped hollow arrays were formed on the metal-organic vapor phase epitaxy grown AlGaAs layer by buried SiN dots due to the competition between the facet and the lateral growth. The following InGaAs layer grew preferentially in these hollows and self-organized quantum disks were formed during growth interruption. Successive growth of AlGaAs/InGaAs epi-layers induced the stacking of quantum disks right on top of the bottom disks. The upper quantum disks were perfectly spatially ordered when the pitch of the array was matched with the self-organized growth mode, with a simultaneous achievement of lateral positioning.
Characteristics of Nanoscale Lithography Using AFM with a Current-Controlled Exposure System
Authors: Ishibashi Masayoshi , Heike Seiji , Kajiyama Hiroshi , Wada Yasuo , Hashizume Tomihiro
Published: October 2002

We have developed an atomic force microscopy (AFM) lithography system using a current-controlled exposure system. The constant current feedback system significantly reduces variation in the width of the line patterns compared with the common constant bias feedback system. We fabricate line-and-space patterns on a commercial negative-type resist, RD2100N (Hitachi Chemical Co.), and evaluate the lithography's characteristics, including the current-voltage (I-V) characteristics, sensitivity curve, cross-sectional shape, dose-margin, resolution, and proximity effect. We find that the cross-sectional shape of the developed resist pattern depends on the exposure dose. The sensitivity, dose-margin, and resolution depend on the resist thickness and a minimum line width of 27 nm is obtained for a 15-nm-thick resist. The proximity effect is much smaller than that of electron beam (EB) lithography. We also evaluate the electric-field mapping inside the resist and explain the characteristics of the AFM exposure system based on the proposed exposure mechanism.
Fabrication and Characterization of a Ring-Tunnel Junction Quantum Electron Interferometer
Authors: Zhilyaev Ivan N. , Boronin Sergey G.
Published: October 2002

A quantum electron interferometer on the basis of ring connected with the tunnel junction in series have been fabricated and investigated. In the superconducting transition region, the ring order parameter oscillates with the changes in the magnetic field applied perpendicular. This oscillations control the resistance of the tunnel junction owing to the nonlocality effect.
Si Pillar Formation and Height Countrol by Furnace Oxidation of the Si (111) Surface with Ultra-Small SiN Nuclei
Authors: Yamamoto MichiharuTabe , Nagasawa Tadashi , Murakami Kenji
Published: October 2002

Lithography-free Si pillar formation has been demonstrated by SiN nucleation and subsequent selective oxidation steps, where nm-scale SiN nuclei thermally formed on the clean Si (111) surface were planned to be used as oxidation masks. In this experiment, dry oxidation at 800°C in a furnace was employed as the oxidation step. As a result, Si pillars were successfully formed and the arrangement of the pillars was mostly random but partially characteristic, reflecting that of the original SiN nuclei. It was found, however, that average pillar height decreases with decreasing nitridation temperature, indicating the imperfect mask ability of low-temperature SiN. This result is ascribed to the formation of SiON during oxidation, which has an inappreciable blocking effect for oxygen diffusion.
Fabrication of Twin Nano Silicon Wires Based on Arsenic Dopant Effect
Authors: Tang Xiaohui , Baie Xavier , Colinge Jean-Pierre
Published: October 2002

This paper reports a simple fabrication process of Si “twin nano wires” based on As dopant effect which gives rise to a significant increase of the oxidation rate at the peak concentration of As. The processing procedures consist of As doping, deposition of silicon nitride layer, electron beam lithography, reactive ion etching, wet oxide and deposition of polysilicon. The resulting Si “twin nano wires” have a small top wire with a dimension of 10 nm and a triangular channel wire with a height of 250 nm. A possible application of the “twin nano wires” to a future single-electron memory device on silicon on insulator (SOI) wafer is also discussed.
A New Approach to Grow Polycrystalline CuGaSe2 Thin Films: Chemical Vapor Deposition with I2 as Transport Agent
Authors: Jäger-Waldau Arnulf , Meyer Nikolaus , Weiss Tilmann , Fiechter Sebastian , Lux-Steiner Martha Ch. , Tempelhoff Klaus , Richter Wolfgang
Published: October 2002

Polycrystalline CuGaSe2 thin films have been prepared onto glass by a chemical vapor deposition (CVD) method which uses iodine as the transport agent. The source material was a polycrystalline CuGaSe2 powder which was pressed into pellets. Single phase CuGaSe2 films were prepared in a temperature range from 460°C to 560°C and had grain sizes between 0.5 and 5 µm. Thermochemical calculations were performed for the system under equilibrium conditions to model the deposition process. The necessary values for the heat of formation H
298 and the standard entropy S
298 for CuGaSe2 were estimated to be H
298=-251 kJ/mol and S
298=155 J/K mol. The calculations are in good agreement with the experimental observations.
Organic-on-Inorganic Heterostructure Diodes for Microwave Applications
Authors: Peter Urbach Peter Urbach , Frank Felbier Frank Felbier , Arno Sörensen Arno Sörensen , Wolfgang Kowalsky Wolfgang Kowalsky
Published: October 2002

Organic-on-inorganic heterostructure diodes based on crystalline thin films of the organic materials PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) and CuPc (copper phtalocyanine) deposited on n-type InP, are investigated with regard to their microwave applications. Among conventional methods, a characterization technique operating directly in the microwave regime was developed, which enables the prediction of the complete equivalent circuit in the whole operation voltage range. The optimization of the device structure for reduced forward voltages and high cutoff frequencies up to 11.2 GHz is discussed, and the detector and mixer performance of the devices is investigated. Finally, a single balanced mixer based on microstrip technology with improved frequency conversion at low power levels is presented.
Neutral Electron Trap Generation and Hole Trapping in Thin Oxides under Electrostatic Discharge Stress
Authors: Chim Wai Kin , Teh Gim Leong
Published: October 2002

Neutral electron trap generation and hole trapping under electrostatic discharge (ESD) stressing of thin oxides are investigated. The results show that the number of neutral electron traps generated by the ESD stress has an empirical power-law relation to the charge injected during ESD stress. Hole trapping is also shown to be linearly related to neutral electron trap generation, the slope of the straight line in a plot of the two quantities against each other being close to unity. This suggests that the hole traps and neutral electron traps originate from the same mechanism under ESD stress.
Luminescence Study of Thermally-Oxidized Porous Si under Subgap or Overgap Excitation
Authors: Shiba Kazutoshi , Miyazaki Seiichi , Hirose Masataka
Published: October 2002

The temperature dependence and the temporal decay of photoluminescence from thermally-oxidized porous silicon have been studied under 1.80 or 2.54 eV excitation which is below or above the optical bandgap value of 2.2 eV determined from the luminescence excitation spectrum. No significant difference between luminescence spectra under the subgap and the overgap excitation is observed at emission energies below 1.65 eV. The luminescence under the subgap excitation exhibits a weak temperature dependence compared to the overgap excitation case. This can be interpreted in terms of the suppressed thermal emission-rate for carriers photogenerated near the radiative recombination centers to the extended states. It is also revealed that, in the pulsed subgap excitation, the luminescence shows a fast decay in the time region below 1 µs and a slow decay component follows, as observed in the case of the pulsed overgap excitation. The carriers photogenerated directly at radiative recombination centers or neighboring sites under the subgap excitation are likely to be responsible for the observed fast decay.
Iron Gettering Controlled by Size and Density of Oxygen Precipitates in Czochralski-Grown Silicon
Authors: Takahashi Hideki , Yamada-Kaneta Hiroshi , Suezawa Masashi
Published: October 2002

The gettering efficiency of iron (Fe) was investigated as a function of the size and density of oxygen precipitates in Czochralski-grown silicon (CZ-Si). During the precipitation treatments, in order to control the size and density of oxygen precipitates, we monitored the oxygen concentration ([Oi]) so that the final [Oi] of the samples were equal to each other. By comparing Fe concentration ([Fe]) determined by electron spin resonance (ESR) in the samples, we discovered that the sample containing precipitates of large size and low density has a stronger gettering efficiency during cooling from a temperature of 1050°C. In contrast, the sample containing precipitates of small size and high density has a stronger gettering efficiency during isothermal annealing at 190°C.
Simulation of Antimony Diffusion in Heavily Arsenic-Doped Silicon
Authors: Uematsu Masashi
Published: October 2002

Sb diffusion profiles in heavily As-doped Si have been simulated using just two essential parameters for Sb diffusion. These parameters correspond to the diffusion of dopant species that contribute to Sb diffusion, and they are the effective diffusivities of the vacancy mechanism via single and double negatively charged vacancies. We discuss which diffusing species affect diffusion profiles based on the integrated diffusion model.
Photoresist Chemical Mechanical Polishing for Shallow Trench Isolation
Authors: Itoh Akio , Imai Masahiko , Arimoto Yoshihiro
Published: October 2002

We investigated the chemical mechanical polishing (CMP) characteristics of photoresist for the first time. It was found that photoresist polishing rates are strongly dependent on photoresist baking temperature. The photoresist polishing rate exceeded 7000 nm/min, which is 87 times higher than the value for SiO2, after baking at 170°C, but matched that of SiO2 after baking at 220°C at a polishing pressure of 230 g/cm2. The photoresist polishing rate after baking at 240°C was lower than that of SiO2. Using these photoresist CMP characteristics, a simple shallow trench isolation (STI) process was achieved.
A New Poly-Si Thin Film Transistors with Partial Amorphous Si Channel
Authors: Choi Kwon-Young , Park Kee-Chan , Choi Hyoung-Bae , Han Min-Koo
Published: October 2002

We have proposed and fabricated a new bottom-gate poly-Si thin-film transistor (TFT) with local amorphous-Si region in the channel by employing the selective laser annealing. The ON/OFF current ratio of the new poly-Si TFT is larger by the magnitude of three orders than that of conventional poly-Si TFT. In the proposed device, the significant reduction of leakage current may be obtained due to the highly resistive a-Si region. However, under the ON state, the resistance of local a-Si is decreased significantly by the inducement of channel electrons in the a-Si channel. The total mask number and the fabrication process of the proposed device are almost identical to those of a commercial a-Si:H TFT.
Correlation between Structure and Optoelectronic Properties of Undoped Microcrystalline Silicon
Authors: Frank Siebke Frank Siebke , Shigeo Yata Shigeo Yata , Yoshihiro Hishikawa Yoshihiro Hishikawa , Makoto Tanaka Makoto Tanaka
Published: October 2002

Undoped microcrystalline silicon with various crystallinities was deposited by rf-glow discharge. We investigate the correlation between crystallinity and optoelectronic properties. The use of a constant photocurrent method for characterization of undoped microcrystalline silicon is discussed. In the case of high crystallinity this method measures the true absorption coefficient but with decreasing crystallinity, the constant photocurrent method underestimates the absorption coefficient at low photon energies. At these energies, carriers are mainly photo generated in the crystalline phase. Carriers generated in isolated grains give a smaller contribution to the photocurrent than carriers generated in grains forming percolation paths. This results in a strongly decreased absorption coefficient measured by the constant photocurrent method at photon energies of about 1.7 eV and below. Therefore, stable microcrystalline silicon with a high crystallinity can be easily distinguished from an unstable material with poor crystallinity.
Simulation on a Novel Body-Driven Silicon-on-Insulator Metal-Oxide-Silicon Field-Effect-Transistor for Sub-0.1 µm Small Logic Swing Operation
Authors: Risho Koh Risho Koh
Published: October 2002

A body-driven silicon-on-insulator metal-oxide-silicon field-effect-transistor (body-driven SOI-MOSFET, BD-MOS) is proposed, and the device characteristics are estimated using a device simulator. This device can remove excess holes within several picoseconds. Additional body contact, which requires additional device area, is not required for removing holes. A small S factor (76 mV/dec.) and a small V
th roll-off (ΔV
th=15 mV for ΔV
d = 0.4 V) were obtained for the channel length of 0.08 µm, without using very thin gate oxide. An enhancement operation and the large drain current required for complementary-MOS(CMOS)-compatible circuits are achieved.
Fabrication Procedures and Characteristics of 6H-SiC Au-gate Metal-Semiconductor Field-Effect Transistor for Use at High Temperatures
Authors: Toda Tadao , Ueda Yasuhiro , Ibaraki Akira
Published: October 2002

A 6H-SiC Au-gate metal-semiconductor field-effect transistor (MESFET) was fabricated by reactive ion etching (RIE) for device isolation and ion implantation for the n+ contact regions of the source and drain. The device exhibited a pinch-off voltage of -9 V, transconductance (g
m) of 5.3 mS/mm, and gate breakdown voltage of -200 V. The characteristics of the MESFET were investigated at high temperatures. This MESFET can be operated at 400°C.
An Attenuation of Magnetostatic Wave Envelope Solitons
Authors: Lihong Li Lihong Li , Ken'ichiro Yashiro Ken'ichiro Yashiro , Sumio Ohkawa Sumio Ohkawa
Published: October 2002

Numerical analysis of the attenuation of magnetostatic wave envelope (MSWE) solitons has been performed to obtain a good insight into the decay properties of MSWE solitons. The numerical calculations indicate that the amplitude of MSWE wave-packets decays at the rate of exp
(- αηt) in yttrium iron garnet films, where α is an attenuation factor and η is a damping coefficient. The value of α is found to be dependent on the ratios of dispersion to dissipation and nonlinearity to dissipation and to vary in the range of 1 ≤α≤2 . The full-width at half maximum of MSWE solitons broadens due to loss and the broadening rate is as sensitive to loss as the amplitude decay rate. The decay characteristics of MSWE solitons presented here provide us with useful information on how to choose experimental parameters for the formation of MSWE solitons.
A Laser Succesive Pulse Heating of a Moving Slab: Akinetic Theory Approach
Authors: Yilbas Bekir S. , Sami M. , Danisman K.
Published: October 2002

Laser successive pulse heating of engineering surfaces becomes fruitful for thermal treatment of the engineering parts. In this case, thermal integration of the surface temperature becomes essential. In the present study, a 3-dimensional mathematical model allowing a laser successive pulse heating is introduced using an electron kinetic theory approach. A laser beam is considered to scan the workpiece surface with a constant velocity. However, the energy equation so derived is in the form of an integro-differential equation which does not yield an analytical solution. Therefore, a numerical method using an explicit scheme is introduced to obtain the temperature profiles. It is found that energy gain of the lattice site atoms through successive electron-phonon collisions is considerable in the surface vicinity. Moreover, some oscillations in surface temperature occur in response to repetitive pulse frequency. It is less likely that the temperature profile follows the pulse profile which is due to the conduction losses and the motion of the slab.
Resonance Raman Spectrum of β-Carotene in Liquid-core Optical Fiber*1
Authors: Li Li , Zuowei Zuowei , Li Li , Jinan Jinan , Gao Gao , Suqin Suqin
Published: October 2002

The resonance Raman effect is produced in liquid-core optical fiber, enhancing the Raman spectral intensity 109 times. The absorption band and concentration of the sample effect the intensity of resonance Raman spectra. The optimum length of the optical fiber depends on the sample concentration. Good resonance Raman spectra of β-carotene in CS2 have been obtained and the intensity of the resonance Raman spectra has been enhanced 102–103 times. The Raman spectra of samples with low concentration (1×10-13 mol/L) have also been obtained. In the experiment, we have noted that the frequency deviation of the Raman line shifts when the concentration of β-carotene in CS2 is low.
Fractoluminescence Spectra in Crystalline Quartz
Authors: Yoshizo Kawaguchi Yoshizo Kawaguchi
Published: October 2002

Fractoluminescence and charge emission upon three-point-bending fracture of synthetic and natural quartz crystals have been studied. Broad luminescence bands centered at about 2.0, 2.9, and 5.0 eV have been observed in both cases. Time-resolved luminescence measurement could be performed on the 2.0 and 2.9 eV bands. The 2.9 eV band has a maximum intensity at about 5 ms after the fracture, and this band decayed within about 13 ms. On the other hand, the decay profile of the 2.0 eV band differed between synthetic and natural crystals. The 2.9 eV band might be due to the relaxation of the oxygen vacancy on the fracture surface, as in the case of silica glass. The 2.0 eV band seems to be due to an impurity center.
Investigation of Grain-Size Influence on the Ferroelectric-to-Paraelectric Phase Transition in BaTiO3 Ceramics by Means of AC Calorimetry
Authors: Tura Vasile , Mitoseriu Liliana , Papusoi Constantin , Osaka Toshio , Okuyama Masanori
Published: October 2002

Barium titanate ceramic samples of four different average grain sizes from 0.5 µm to 20 µm were studied by means of the ac calorimetric method. The ferroelectric-to-paraelectric transition temperature decreased with decreasing grain size. The temperature dependence of heat capacity showed hysteresis during a heating/cooling cycle. The thermal hysteresis was found to be grain-size dependent, with a possible maximum for grain sizes between 0.5 µm and 2.5 µm. The small shift of the Curie temperature detected in these ac calorimetry experiments suggests that internal stresses are the main cause of the observed grain-size effects.
Stabilized Platinum Electrodes for Ferroelectric Film Deposition using Ti, Ta and Zr Adhesion Layers
Authors: Maeder T. , Sagalowicz L. , Muralt P.
Published: October 2002

Pt-based metallizations using different adhesion layers (Ti, Zr and Ta) were studied for use as electrodes for ferroelectric thin films on oxidized silicon substrates. Different ways of oxidizing the adhesion layers prior to ferroelectric film growth are compared, with regard to obtaining stable, adherent Pt films of well-defined (111) orientation, while avoiding lead diffusion through the electrode. Upon in-situ deposition of PbTiO3 at high excess lead flux, lead diffusion through the Pt film was found to depend strongly on the adhesion layer and the stabilization treatment. Pre-oxidation reduces lead diffusion during the later processing. Ti diffuses through the electrode upon oxidation, whereas Ta and Zr stay in place, in analogy to the diffusivities in the corresponding oxides. A novel oxidation treatment was developed to produce stable, adherent metallizations with controlled orientation and good barrier properties against lead diffusion.
A Comparison of Poly Silicon and Titanium Polycide for Field Emission Tip
Authors: Park Cheol-Min , Lim Moo-Sup , Han Min-Koo , Choi Yearn-Ik
Published: October 2002

We propose a novel lateral field emission triode, which does not require any additional vacuum sealing process and exhibits superb field emitter triode performance. The purpose of this paper is to compare titanium polycide tip with polycrystalline silicon tip. A new experimental results of the device, such as variation of tip material, device stability experiment, measurement of the novel device in vacuum chamber in order to verify the proposed vacuum sealing process, and transconductance characteristics at each current level. The minimum turn-on anode to cathode voltage of titanium polycide tip is considerably decreased compared with polysilicon tip. The anode current measured in 10-8 Torr vacuum chamber is similar to the anode current measured in atmospheric pressure, which shows that the proposed vacuum sealing process is reliable. The stable current of 300 µA is maintained during 60 h.
Low-energy Ion Scattering Measurement of Near-surface Damage Induced by the SiO2 Dry-Etching Process
Authors: Matsui Miyako , Uchida Fumihiko , Katsuyama Kiyomi , Tokunaga Takafumi , Kojima Masayuki
Published: October 2002

Si(100) surface crystallinity after dry etching was measured using low-energy ion scattering spectroscopy (LEIS). We used 4-keV He+ ions as the incident beam, and neutral particles back-scattered at 180° were detected. A heavily damaged layer was observed immediately after reactive ion etching. After the heavily damaged layer was removed using a post-etch treatment, channeling and focusing effects were observed. The presence of a modified layer was confirmed even after the suboxide-rich layers were removed, because the channeling and focusing effects were slightly weaker than those of the surface without dry etching.
Development of an Ion and Electron Dual Focused Beam Apparatus for Three-Dimensional Microanalysis
Authors: Tetsuo Sakamoto Tetsuo Sakamoto , Zhaohui Cheng Zhaohui Cheng , Masanori Takahashi Masanori Takahashi , Masanori Owari Masanori Owari , Yoshimasa Nihei Yoshimasa Nihei
Published: October 2002

We are developing a novel three-dimensional (3D) microanalysis method by means of successive cross-sectional Auger mapping. In this method, a 3D elemental map will be obtained by repetition of the cross-sectioning of a sample using a gallium focused ion beam (Ga FIB) and Auger mapping of the cross section using an electron beam (EB). On the basis of this concept, an ion and electron dual focused beam apparatus was developed by combining a Ga FIB and a mass spectrometer with a scanning Auger microprobe. In this paper, we describe the concept and instrumentation of the dual focused beam apparatus. Two types of preliminary experiments; i) successive cross-sectioning of a microparticle (6.8 µmφ) and ii) successive cross-sectional sample current imaging of a bonding wire of an IC, demonstrated the capability to create flat analytical surfaces favorable for the 3D analysis with arbitrary shape and heterogeneity.