bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of a 600 Mbyte 90 mm Phase-Change Optical Disk against Disk Tilt
Authors: Sugaya Toshihiro , Taguchi Toyoki , Shimura Kei , Taira Kouzoh , Honguh Yoshinori , Satoh Hiroharu , Kobayashi Tadashi , Nakamura Naomasa
Published: February 2005

The performance of a 0.6-mm-thick substrate disk was studied for tilted disk conditions. It was shown by numerical calculation that the reduction in the peak intensity of the optical spot was 0.5 dB under a disk tilt of 7 mrad when the numerical aperture (NA) of an objective lens was 0.6. The tilt angle dependence of the reading/writing performance was measured for a double-sided disk with a wavelength of 690 nm. Excellent signal quality was obtained, such as carrier-to-noise ratio of over 50 dB, erasability of more than 27 dB, crosstalk of under -27 dB, and jitter of under 30% of the window width for a tilt angle of 7 mrad.
Recording Experiment with Rotating Optical Head for Magnetooptical Tape Recording System
Authors: Tokumaru Haruki , Arai Kiyotaka , Shin-ichi Yoshimura Shin-ichi Yoshimura , Hideo Oshima Hideo Oshima
Published: February 2005

For the rotating optical head of an optical tape recorder, whose optics are divided into a fixed part and a rotating part, and whose beam is controlled with a lens in the fixed part, the focusing operation causes a change of both the diameter of the incident beam to an objective lens and the optical magnification. Therefore, we developed an optical system which does not cause these changes and confirmed stable focused-spot characteristics for a ±60 µm displacement of the recording medium by carrying out recording experiments.
Controlled, Periodic Domain Formation in Strontium Barium Niobate Induced by Volume Holograms
Authors: Kewitsch Anthony , Segev Mordechai , Neurgaonkar Amnon Yariv
Published: February 2005

We demonstrate an all-optical technique of controlled, periodic ferroelectric domain reversal induced by electronic space charge fields associated with photorefractive volume holograms. This technique may be used to selectively fix and update individual holograms in photorefractive crystals.
Digital Video Disc Recorder Using Second Harmonic Generation Green Laser
Authors: Seo Joong Eon , Park In Sik , Oh Young Nam , Lee Seung Hoon , Seong Pyong Yong , Jang Yoon Ki , Dong Ho Shin Dong Ho Shin
Published: February 2005

A prototype of a digital video disc recorder (D-VDR) with laser-disc-quality video and compact-disc-quality audio is developed and demonstrated using a second harmonic generation (SHG) green laser, narrow-track magneto-optical disk (MOD), mark edge recording and data compression.
Effect of Interstitial Oxygen on Formation of Amorphous SiOx Layerin Directly Bonded Czochralski Silicon Wafers
Authors: Ishigami Shun-ichiro , Kawai Yukio , Furuya Hisashi , Saitoh Takayuki Shingyouji
Published: February 2005

We have investigated the effect of interstitial oxygen in CZ silicon wafers on the formation of the amorphous SiO
x
layer (x=0.2-0.3 after annealing at 1100°C for 2 h) at the interface in directly bonded silicon wafers using high-resolution transmission electron microscopy (HR-TEM) and energy dispersive X-ray (EDX). As the annealing time became longer, the thickness and the oxygen concentration in this layer increased, depending on the concentration of interstitial oxygen in wafers. These changes are caused by the diffusion of oxygen atoms from the bulk toward the bonded interface. However, they must not play such an important role in the initial stage of the formation of this layer because the layer existed discontinuously and was not affected by rotational misorientation or the microroughness.
Interfacial Layers of High-Barrier Schottky Diode of Al/n-Type (100)Si Exposed to H2 Plasma
Authors: Iwakuro Hiroaki , Tokonami Masayasu , Kuroda Tsukasa , Tamaki Shozo , Kitatsuji Yasuji
Published: February 2005

Al/Si Schottky diodes were fabricated from n-type silicon wafers which were exposed to several kinds of plasma in a magnetron using gases of hydrogen, deuterium, helium, nitrogen, oxygen and argon. The influence of plasma exposure on the Schottky barrier height is examined. The Schottky barrier height increases for only H2-containing plasma exposure. Hydrogen plays an important role in the increase of the Schottky barrier height. The plasma-exposed silicon surfaces are characterized by transmission electron microscopy, X-ray photoelectron spectroscopy and secondary ion mass spectrometry. H2 plasma exposure produces both a surface hydrogen-absorbing zone about 10 nm thick and a zone including planar defects under the hydrogen-absorbing zone. In Ar plasma exposure, the only zone including planar defects is formed from the surface to 30 nm in Si. The increase in the Schottky barrier height can be attributed to the formation of the hydrogen-absorbing zone in Si.
Properties of Disk Resonators and End-Coupled Disk Filters with Superconducting Films
Authors: Nagai Yasuhiro , Hebert David F. , Duzer Theodore VAN , Michikami Naobumi Suzuki
Published: February 2005

We report the properties of disk resonators and end-coupled disk filters. High quality factors of 60,000 at 3 GHz and 27,000 at 7 GHz, respectively corresponding to TM11 and TM31 modes, were confirmed in a Nb disk resonator with a diameter of 18 mm on a sapphire substrate. End-coupled three-pole disk filters were also fabricated using the 7-mm-diameter Nb disks (TM11 mode). The disk filter with frequency of 7.5 GHz, fractional bandwidth of less than 1%, and insertion loss of less than 0.7 dB exhibited higher power handling capability of up to 22.5 dBm (180 mW). This high capability is thought to be achieved by reducing the current concentration at the edges of each resonators.
Cu Multiply Twinned Particle Precipitationin Low-Temperature Fired Ni-Zn-Cu Ferrite
Authors: Fujimoto Masayuki , Hoshi Ken-ichi , Mutsuo Nakazawa Mutsuo Nakazawa , Shoichi Sekiguchi Shoichi Sekiguchi
Published: February 2005

Cu metal precipitates and truncated Cu metal multiply twinned particles (MTPs) were observed in low-temperature fired ferrite with a small excess of Ni-Zn-Cu chemical composition. The Cu metal precipitates suggest the existence of Cu solid solution and accelerated grain growth during the sintering accompanied with the formation of defect structures, such as oxygen vacancies in the ferrite spinel structure. The defect structure compensation during the cooling process after sintering results in Cu metal precipitation at the multiple grain junction.
Effect of Molecular Field Periodicity on Energy of Free Electrons in Ferro-Paramagnetic Multilayers
Authors: Antonio Hernando Antonio Hernando , Julián Velazquez Julián Velazquez
Published: February 2005

The diffraction of free electrons through the localised magnetic moments contributes to the magnetic coupling between ferromagnetics layers separated by metallic paramagnetic spacers. It is shown that the energy of free electrons is lower for the case of antiferromagnetic coupling. Calculations have been performed in second-order perturbation approximation. The perturbative potential is the Zeeman coupling between the electron spins, and the molecular field is described by different Fourier expansions according to the ferro- or antiferromagnetic configurations. It is concluded that, for perfectly planar interfaces, the coupling carried through free electrons is always antiferromagnetic. Presumably, more complicated mechanisms are responsible for the observed oscillations. The molecular field penetration into the paramagnetic spacer can account for the ferromagnetic coupling observed for very thin paramagnetic layers.
Determination of Spin-Hamiltonian Parameters D and E of Cr3+ in SnO2 Crystals
Authors: Takeda Kosei , Hikita Harumi , Kimura Yutaka
Published: February 2005

We have experimentally determined the absolute signs and the magnitudes of the spin-Hamiltonian parameters D and E for substitutional Cr3+ ions in SnO2 crystals by use of a method combining the angular and the temperature dependence. Electron paramagnetic resonance (EPR) measurements have been carried out at the X-band in the temperature range of 123-300 K. Firstly, we obtained E/D=-0.20±0.01 from the angular dependence of the EPR spectra. Secondly, we measured the temperature dependence of the EPR intensity ratio of allowed and forbidden transitions to obtain each sign of D and E. The signs and the magnitudes of D and E obtained were -0.703±0.002 cm-1 and +0.146±0.001 cm-1, respectively. These results are consistent with the theoretical estimates which were obtained using the developed superposition model for rutile-type crystals.
Contribution of Population or Thermal Grating to Phase Conjugation in Saturable Xanthene-Dye-Doped Polymer Films
Authors: Kawano Katsunori , Kazuo Nakagawa Kazuo Nakagawa , Hirofumi Fujiwara Hirofumi Fujiwara
Published: February 2005

The time constant of a decaying phase-conjugate (PC) signal was measured as a function of a grating period in polyvinyl alcohol films doped with xanthene dyes such as erythrosin B, eosin Y, and uranin. The time constant was independent of the grating period and was of the same order as the time required for the population grating of each dye to decay. These experimental results indicated that there was a population grating contribution but not a thermal grating contribution in the generation of PC signals by these saturable xanthene-dye films.
Fast Lateral Transport of Excitons in a GaAs/AlGaAs Quantum Well
Authors: Muraki Yutaka Takahashi , Fukatsu Susumu , Kano Satoru S. , Shiraki Yasuhiro , Ito Ryoichi
Published: February 2005

We have studied the lateral transport of excitons in a GaAs/AlGaAs single quantum well by the exciton time-of-flight technique. The lateral motion of excitons has been measured as a function of temperature (4 K to 40 K) and excitation density (≥108 cm-2). Our analysis shows that the exciton diffusivity at temperatures below 10 K becomes considerably enhanced, implying extremely long (several micrometers) exciton mean free paths. This behavior is discussed in terms of several scattering mechanisms including interaction with non-equilibrium phonons emitted during energy relaxation of carriers.
Current Density-Voltage Characteristics of AC Thin-Film Electroluminescent Devices with Different Dielectric-Phosphor Interfaces
Authors: Li Jiin Wen , Yan Kuin Su Yan Kuin Su , Meiso Yokoyama Meiso Yokoyama
Published: February 2005

Four kinds of AC thin-film electroluminescent devices constructed with different insulating layers were prepared to study the I-V characteristics. In this study, we evaluated the I-V characteristics from the charge density-voltage (Q-V) characteristics which are measured using a Sawyer-Tower circuit and a simple series capacitor model. The results of these two methods are very similar to each other. From the I-V characteristics of these samples, a simple conclusion can be drawn: the sample with higher brightness and efficiency has higher current density. The relationships between brightness and transferred charge (B-Q), brightness per unit transferred charge and transferred charge (B/Q-Q), and the differential value of ΔB/ΔQ and transferred charge (ΔB/ΔQ-Q) of these samples have been discussed. From these results, we can conclude that the interface between the low-resistivity insulating layer and the active layer can provide the more efficient electrons for exciting the luminous centers.
Growth of Y2O2S:Eu Thin Films by Reactive Magnetron Sputtering and Electroluminescent Characteristics
Authors: Sowa Kunihiro , Tanabe Masami , Furukawa Seigo , Nakanishi Yoichiro , Hatanaka Yoshinori
Published: February 2005

Y2O2S:Eu phosphor films were prepared by reactive magnetron sputtering with a Y2O3:Eu target in a H2S and argon mixed atmosphere, and hot carrier injection (HCI)-type EL devices with Y2O2S:Eu/ZnS/Y2O2S:Eu structure were fabricated. It is found that the crystal structure of Y2O2S:Eu films depends on the sulfur concentration in the film. With increasing atomic ratios of S/Y, the crystal phase is changed from cubic to hexagonal. Luminescent spectra from the films are dependent on the crystal structures.
Variation of the Density Observed during the Pressure-Induced Phase Transition of a Single Crystal of RbCl
Authors: Nomura Yoichiro Itoh
Published: February 2005

Pressure dependence of the density of a large-size single crystal of RbCl was observed cyclicly up to 860 MPa at 294 K and 383 K. The hysteresis loop observed in the second cycle was overlapped with that in the first cycle. While clicking sound accompanying the discontinuous increase in density was produced in the forward transition both in the first and second cycles, no sound was detected in the reverse one. The time variations of density at constant pressure were observed, where the density was nearly constant in the forward transition at 294 K, whereas steady decrease was observed in the reverse transition. Separate mechanisms are proposed, that is the Martensite transition in the forward transition, and the nucleation and its growth in the reverse one. At higher temperatures the nucleation and its growth in the forward transition are also proposed.
An Approach to Convergency of Kinetic Theory to Fourier Theory in Relation to Laser Heating Process
Authors: Bekir S. Yilbaş Bekir S. Yilbaş , Ahmet Z. Şah\uin Ahmet Z. Şah\uin
Published: February 2005

Fourier theory may be derived from analytical considerations of the heat transfer process in a substance and neglecting of higher order terms in Fourier analysis becomes important at high input power fluxes. It is apparent from the previous work that the kinetic theory equations governing the heat conduction process are more general than the Fourier equation. The special case may exist where the kinetic theory solutions converge to solutions extracted from the Fourier analysis. Consequently, research into the convergence of kinetic theory approach to Fourier analysis becomes necessary. To achieve this, the special case in which local thermal equilibrium is assumed to exist between the electrons and atoms at any section on the surface region of the solid substance is studied in the present work, providing that the study does not allow the existence of phase changes. For this purpose, an analytical approach is introduced and a computer solution of the reduced integral equations is obtained. It is found that the solutions of electron kinetic theory equations based on the assumption of existence of thermal equilibrium between electrons and atoms are identical with those obtained from Fourier theory.
Improved Screening Constants for Plasma
Authors: Kawata Shigeo , Kiyokawa Shigeru Kato
Published: February 2005

We present the new screening constants, with which the atomic energy levels for the finite temperature materials are obtained by the screened-Hydrogen model. The new screening constants are obtained for each of 33 materials. Each set of screening constants has a temperature dependence in order to realize a better reproducibility of the Hartree-Fock-Slater (HFS) energy levels. The deviations from the HFS calculation are 5.15% for n=1 and 54.1% for n=2, based on the average of 33 materials. Here n is the principal quantum number.
Estimation of Impurity Burning due to MeV-Region Neutral Beam Injection
Authors: Nobuhiro Nishino Nobuhiro Nishino
Published: February 2005

Decrement of the α heating power and radiation loss due to light impurities are compared with the fusion power of the high-energy deuterium and light impurity reaction. The high-energy deuterium ions in a plasma are produced by MeV-region neutral beam injection. Lithium and beryllium are selected as the light impurities. The calculated results show that the Li fusion power exceeds the decrement of α-particle heating power under the low density condition of international thermonuclear experimental reactor (ITER) class plasma; however, under the high-density condition the Li fusion power is less than the bremsstrahlung power. Therefore, the burning of Li impurities due to the MeV neutral beam will affect the energy balance under only the low-density condition.
Diffusion Coefficient Obtained from Arrival-Time Spectrum
Authors: Yamada Tadahiko , Ushiroda Sumio , Kajita Shougo , Yoshitaka Kondo Yoshitaka Kondo
Published: February 2005

We propose a numerical method to obtain the drift velocity and the diffusion coefficient for ions moving in neutral gases using random walk theory. This method can be applied to the experimental study of ion swarms very efficiently. We verified the validity of our method with computer simulation and the analysis of the experimental result obtained by Takebeet al. [J. Chem. Phys. 73 (1980) 4071]
Characterization of Gadolinium Plasma in Gadolinium Vapor at High-Rate Evaporation by Electron Beam Heating
Authors: Ohba Hironori , Akihiko Nishimura Akihiko Nishimura , Takemasa Shibata Takemasa Shibata
Published: February 2005

The characteristics of gadolinium plasma in gadolinium vapor at high-rate evaporation using electron beam heating have been measured with Langmuir probes. Electron temperature was lower than 0.1 eV and close to the atomic excitation temperature, which was much lower than the evaporation surface temperature. Ion flux ratio to vapor flux was 0.4%. This value agreed well with the estimated value on the assumption that the atoms are ionized by collision with high-energy electron beams.
Preparation of a-Si1-xNx:H Film Using N2 Microwave Afterglow Chemical Vapor Deposition Method
Authors: Nagayoshi Hiroshi , Hoe Wong Chee , Noguchi Haruya , Ueno Tomo , Kamisako Koichi , Kuroiwa Koichi , Shimada Toshikazu , Yasuo Tarui Yasuo Tarui
Published: February 2005

Composition, deposition rate, hydrogen bond density and residual stress of hydrogenated amorphous silicon nitride film deposited by N2 microwave afterglow method were investigated. A slight addition of less than 1% of H2 to N2 at the discharge tube showed a marked increase in deposition rate at low-pressure deposition. The H2 introduced into the discharge tube has no particular effects on the atomic bonding structure of the film. This slight addition of H2 served to excite the N2 reactant producing active nitrogen species efficiently. The [N]/[Si] ratio of the film deposited within the given experimental conditions was retained at more than 1.2. The film exhibited good electrical characteristics.
Improvement of Dose Uniformity in Large Exposure Field for Synchrotron Radiation Lithography
Authors: Yukihiko Maejima Yukihiko Maejima , Naoki Awaji Naoki Awaji
Published: February 2005

We have developed a new exposure method which provides both high X-ray intensity and dose uniformity in a large exposure field for synchrotron radiation (SR) lithography. This method uses a scanning mirror method and electron beam wobbling in combination in SR beamlines. The advantage of this method was confirmed experimentally in a 25-mm-square exposure field. In addition, simulation results show that dose uniformity of ≤±2% can be achieved in a 50-mm-square exposure field.
Lithographic Performance Enhancement Using Dummy Diffraction Mask
Authors: Yoo Hyung Joun , Oh Yong-Ho , Park Byung-Sun , Choi Sang Soo , Jeon Young Jin , Lee Choochon , Sin-Chong Park Sin-Chong Park
Published: February 2005

The basic lithographic characteristics of the dummy diffraction mask which has two (dummy and main) mask layers, are investigated by simulation and experiment. The basic principle and theoretical details of the dummy diffraction mask are explained. Influences on the aerial image by the gap size and misorientation between two mask layers and by the nonideal phase grating, are simulated. Also, results of the lithographic performances for the simple patterns (line/space, isolated line, isolated space) and the complex patterns (V-shape active pattern in dynamic random access memory core cell) are presented.
Fine Pattern Etching of W-Ti Absorber for X-Ray Mask with Electron Cyclotron Resonance Discharge Plasmas
Authors: Marumoto Kenji , Yabe Hideki , Aya Sunao , Matsuba Motoko , Sasaki Kei , Watakabe Yaichiro , Yasuji Matsui Yasuji Matsui
Published: February 2005

The process of etching an amorphous W-Ti absorber using a Cr mask and electron cycrotron resonance discharge plasmas was investigated to fabricate an X-ray mask with a resolution below 0.1 µm. Highly selective and anisotropic etching has been achieved using a mixture of SF6, CHF3 and He gases, by cooling the stage to about -50°C and with the control of the plasma conditions to increase ion assist reactions. It was also found that high selectivity (50-150) of W-Ti to Cr or ITO and a small microloading effect were advantageous to uniformly etch patterns of various sizes. Moreover, the microfabrication of a smooth W-Ti absorber has been demonstrated for lines and spaces patterns below 0.1 µm and 1-Gbit-class dynamic random access memory patterns.
Mechanical Response of X-Ray Masks
Authors: Laudon Matthew F. , Laird Daniel L. , Roxann L. Engelstad Roxann L. Engelstad , Franco Cerrina Franco Cerrina
Published: February 2005

Overlay accuracy remains one of the major challenges in 1× lithography. In the case of X-ray masks, it is necessary to have a precise pattern on the mask itself and ensure that the pattern is not distorted due to mounting. A detailed study has been performed of the distortions induced in the membrane when the mask is held kinematically in various configurations, e.g., horizontal, vertical and inverted orientations (for e-beam writing, X-ray exposure and point source exposure, respectively). The new proposed X-ray mask standard has been used for all results presented. Finite element models were used to simulate alignment techniques and magnification correction procedures and subsequently determine maximum resultant distortions. Results show it necessary to optimize the mounting strategy to meet the stringent error budget required for 0.25 µm technology (and below).
X-Ray Mask Pattern Accuracy Improvement by Superimposing Multiple Exposures Using Different Field Sizes
Authors: Ohki Shigehisa , Yoshihara Tadahito Matsuda
Published: February 2005

A method to improve the accuracy of patterns written by an electron-beam writing machine (e-beam) is evaluated. The method is based on a multiple-exposure method that involves superimposing e-beam exposure patterns with different main-field and sub-field sizes. The main-field and sub-field sizes are varied to eliminate main-field and sub-field stitching on the chip. The stitched areas are overwritten with other exposures and blurred out. When applied to the preparation of X-ray masks for device fabrication, this method improves the e-beam writing pattern placement accuracy of the X-ray masks to 0.04 µm (3σ). Both the field stitching accuracy and the uniformity of the exposed pattern width are also improved to 0.02 µm (3σ).
Electron Beam Column Developments for Submicron- and Nanolithography
Authors: Gesley Mark , Abboud Frank , Colby Dave , Frederick Raymond Frederick Raymond , Sterling Watson Sterling Watson
Published: February 2005

Recent advances in thermal field emission (TFE) electron beam optics column design for lithography are described. Innovations include source vibration mode mapping, accelerating electron gun lens, gun arc-suppression, automated cathode pyrometer, and experimental deflection control system. Several of these column optics and system enhancements, which improve the accuracy and reliability of MEBES°
R
IV-TFE systems, have enabled patterning of 64 Mbit dynamic random access memory (DRAM) 5×-reduction reticles. A 13000-hour cathode lifetime has been achieved in a production environment. Automated column setups over the entire operating range with 99% success and 5 min average times are possible. Blanking at 160 MHz with 30 nm (3σ) critical dimension control is achieved. Data obtained with a new experimental deflection control method can quickly compensate stripe butting drift to high accuracy. Challenges in mask patterning for advanced applications are then considered. Several accuracy and throughput issues for advanced 5× reticles for DRAM, 1× masks, and nanolithography are discussed. Examples are given of scaling recent system data as a means of estimating future error budget components.
Verification of the Model of Inductive Coupling between a Josephson Oscillator and a Stripline
Authors: Kudo Keisuke , Yoshida Keiji , Keiji Enpuku Keiji Enpuku , Kaoru Yamafuji Kaoru Yamafuji
Published: February 2005

In order to realize an efficient coupling between a flux-flow-type Josephson oscillator (FFO) and a stripline, we have carried out experiments to verify the mathematical model of the inductive coupling scheme between FFO and a stripline resonator in the frequency range between 50 GHz and 350 GHz. It is shown that the simulation using the proposed equivalent circuit for the inductive coupling scheme well explains the experimental results. The experimentally obtained center frequency and the bandwidth of the matching circuit were as large as 120 GHz and 40 GHz, respectively, which are also in reasonable agreement with those obtained in the simulation.
Improved Registration Accuracy in E-Beam Direct Writing Lithography
Authors: Kojima Yoshikatsu , Mukai Hiroshi , Ken Nakajima Ken Nakajima , Naoaki Aizaki Naoaki Aizaki
Published: February 2005

This paper reports on techniques for improving registration accuracy in electron beam (EB) direct writing lithography for a 0.25 µm process. An analysis of registration accuracy for the EB writing system was performed with the goal of minimizing registration errors, since mark detection and stage positioning accuracies are not sufficient for a 0.25 µm process. To improve mark detection accuracy, a new technique based on the correlation parameter optimization method was developed, and the stage guide mechanism was reinforced to improve stage positioning accuracy. Using these two techniques, the calculated registration accuracy was improved to 0.070 µm(||
x̄||
+3σ). EB direct writing incorporating the above was applied to the development of a 256 Mbit DRAM, having a minimum feature size of 0.25 µm. A sufficient registration accuracy of 0.075 µm(||
x̄||
+3σ) was obtained for the EB writing layer.
Correlation of Nano Edge Roughness in Resist Patterns with Base Polymers
Authors: Yoshimura Toshiyuki , Shiraishi Hiroshi , Jiro Yamamoto Jiro Yamamoto , Shinji Okazaki Shinji Okazaki
Published: February 2005

The origin of ultra small edge roughness in delineated resist patterns (nano edge roughness) is investigated from the viewpoint of molecular structures of the base polymers of the resists. In this article, conventional two-component negative-type electron beam resists are studied to clarify the correlation of the nano edge roughness with base polymers. The base polymers are cresol novolak and polyvinylphenol mixed with the same concentrations of photoactive azide compound. The weight-average molecular weight (M
w) and polydispersity (M
w/M
n) of the base resins are controlled. Nanometer feature microscopic surface characteristics obtained with an atomic force microscope (AFM) show that the cresol novolak-based resist exhibits a rougher surface than the polyvinylphenol-based one. Nano edge roughness can be suppressed by using base resins with lower M
w and M
w/M
n, suggesting that nano edge roughness reflects the molecular characteristics of the base polymers. There is nanometer level swelling in resist patterns (nano swelling) in polyvinylphenol-based resist. These results suggest that the structures of the base polymers and the interaction with developers affect the nano edge roughness.
Model for Al Etch-Rate Enhancement at Low Temperatures
Authors: Uchida Takashi , Aoki Hidemitsu , Hane Masami , Ikawa Shinya Hasegawa
Published: February 2005

A surface reaction model for aluminum etching by chlorine is proposed, which takes into account the temperature dependence of the thermal processes and the ion-assisted processes simultaneously. In the model, chlorine physisorption and chemisorption are treated separately, based on the previous work on chlorine adsorption on aluminum. In particular, cluster formation was introduced into the chlorine physisorption process to allow physisorbed species to exist on the Al surface. The model reproduced the measured Al etch rate, including the Al etch-rate enhancement in the low-temperature regime. This etch-rate enhancement was found to be brought about by the increase in physisorbed chlorine on the Al surface, followed by ion-assisted reaction and desorption.
Nanometer-Scale Direct Carbon Mask Fabrication Using Electron-Beam-Assisted Deposition
Authors: Ochiai Yukinori , Watanabe Heiji , Fujita Jun-ichi , Baba Masakazu , Shoko Manako Shoko Manako , Shinji Matsui Shinji Matsui
Published: February 2005

We demonstrate direct mask fabrication using a finely-focused electron beam and subsequent electron-beam-assisted etching for pattern transfer onto a GaAs substrate. An electron beam at 50 kV is irradiated in a styrene gas ambient to deposit a mask on a GaAs substrate, and a flood electron beam is irradiated on a GaAs surface in a chlorine gas ambient. The deposition rate of the EB irradiated mask is about 0.05 nm/(µC/cm). At a 7 µC/cm line dose, the selective ratio between the deposited mask and the GaAs is enough to fabricate a nanometer-scale GaAs line pattern.
Photon-Stimulated Ion Desorption from Semiconductor Surfaces
Authors: Mochiji Kozo , Ochiai Isao , Ogawa Tarou , Yamamoto Seiji , Itabashi Naoshi , Lee Kaidee , Hanson David M.
Published: February 2005

Photon-stimulated ion desorption (PSD) from chemically and physically modified Si and GaAs surfaces are investigated by using synchrotron radiation. It is found that the ion species of desorption, their yields, and their kinetic energies are greatly changed depending on the bonding state of the surface atoms or adsorbates. These phenomena are caused by PSD mechanism in which ion desorption is based on electronic transitions of surface atoms by photon absorption. In addition to reporting our experimental results, we discuss the possibilities of using PSD for controlling surface structure on the atomic scale.
Sub-Half-Micron Periodic Structures on Polymer Surfaces with Polarized Laser Irradiation
Authors: Mariana Sendova Mariana Sendova , Hiroyuki Hiraoka Hiroyuki Hiraoka
Published: February 2005

A quarter-micron space-and-width linear periodic structures and an array of dot images are obtained with the Nd:YAG 4th harmonic laser irradiation on Kapton polyimide films, poly(ethylene terephthalate) films, spin-coated polyimide films and others. Our solid state Nd:YAG laser source is different from the excimer laser irradiation, in that it provides polarized beams without the need for a polarizer. Atomic force microscope (AFM) and scanning electron microscope (SEM) studies have been carried out. X-ray photoelectron spectroscopy (XPS) studies of laser-exposed areas indicate that no significant chemical reactions took place on exposed areas.
Micropatterning of Quartz Substrates by Multi-WavelengthVacuum-Ultraviolet Laser Ablation
Authors: Sugioka Koji , Wada Satoshi , Tsunemi Akira , Sakai Toshiaki , Takai Hiroshi , Moriwaki Hiroki , Nakamura Akira , Hideo Tashiro Hideo Tashiro , Koichi Toyoda Koichi Toyoda
Published: February 2005

Photoablation of synthetic fused quartz by simultaneous irradiation of multi-wavelength beams of a vacuum-ultraviolet (VUV) laser using high-order anti-Stokes Raman scattering is described. The VUV laser, which emits widely spread Raman-shifted lines from 133 nm to 594 nm, is ideal for effective laser ablation of the fused quartz. The well-defined patterns with a cross-sectional profile of a rectangular shape are formed by using a contact mask at an ablation rate as high as 13 nm/s. An effective absorption coefficient of 3.4×10-5 cm-1, which indicates that the multi-wavelength irradiation effect has an important role in the process, is obtained.
GaAs/AlAs Trench-Buried Quantum Wires (<20 nm×20 nm) Fabricated by Metalorganic Chemical Vapor Deposition on Nonplanar Substrates
Authors: Sogawa Tetsuomi , Ando Seigo , Kanbe Hiroshi
Published: February 2005

We report the fabrication of quantum wires buried in U-grooved trenches grown by metalorganic chemical vapor deposition on V-grooved (001) substrates. These trench structures with vertical (110) sidewalls were formed as a result of the faceting of (110) planes, and lateral growth of these planes reduced the trench width to less than 20 nm. A cross-sectional scanning electron micrograph shows that these trench-buried structures have GaAs wires of about 20 nm lateral width. Photoluminescence (PL) blue shifts and strong PL anisotropy confirm two-dimensional quantum confinement.
Quantum Dots and Quantum Wires with High Optical Quality by Implantation-Induced Intermixing
Authors: Prins Freek E. , Lehr Georg , Burkard Manfred , Nikitin Sergej Yu. , Smith Heinz Schweizer
Published: February 2005

The use of a near-surface quantum well as a starting material in conjunction with a low implantation energy is demonstrated to be a key parameter for the realization of homogeneous nanostructures for optical applications by implantation-induced intermixing. Using this technique we have realized GaAs/AlGaAs quantum wires with wire widths down to 45 nm and quantum dots with diameters ranging from 400 to 70 nm. The optical properties of the structures have been studied by low-temperature photoluminescence and photoluminescence excitation spectroscopy. In photoluminescence the structures show a high intensity, and from the observed increasing blue shift with decreasing size, steep confining potentials are concluded. The excitation spectra clearly demonstrate the advantage of the near-surface quantum wells by the reduction of level broadening compared to previous results on quantum wires.
Fabrication of InAs Single-Crystal Free-Standing Wires for the Study of Electron and Thermal Transport
Authors: Yoh Kanji , Nishida Akira , Kunitomo Hisaaki , Takashi Ogura Takashi Ogura , Masataka Inoue Masataka Inoue
Published: February 2005

We report the fabrication of single-crystal InAs free-standing wires by utilizing electron beam lithography and wet-chemical etching on an InAs/AlGaSb heterostructure grown by molecular beam epitaxy (MBE). Nanostructure free-standing wires as thin as 150 Å have been successfully fabricated and confirmed by the scanning electron microscope (SEM) observation. Atomic force microscope (AFM) measurements also revieled that once the cladding layer is removed, a compressively stressed free-standing wire relaxes to regain the original length resulting in a shape of a suspention bridge. The novel method of thin film strain measurement has been applied to free-standing-wires of various structures.
Estimation of Damage Induced by Focused Ga Ion Beam Irradiation
Authors: Yamamoto Takahiro , Yanagisawa Junichi , Gamo Kenji , Takaoka Sadao , Murase Kazuo
Published: February 2005

We have measured the ballistic length l
bFIB of a GaAs/AlGaAs sample using the electron focusing effect and the mean free path l
eFIB of the narrow channel, both formed by focused ion beam (FIB) irradiation, to estimate the damage induced by FIB irradiation. It is observed that scattering centers are induced by FIB irradiation, which exhibit dependence on the electron density, unlike scattering centers due to grown-in defects. The FIB-induced scattering centers distribute far beyond the distance of the FIB spot size. This may be due to the exponential tail distribution of FIB.
Silicon Field Emitter Capable of Low Voltage Emission
Authors: Urayama Masao , Ise Tomokazu , Maruo Yuji , Kishi Akira , Reiko Imamoto Reiko Imamoto , Takeo Takase Takeo Takase
Published: February 2005

A silicon field emitter of a very low voltage emission type has been obtained. In this emitter, a thermal SiO2 film was used as an insulator which separates the gate electrode from the cathode substrate. It is easy to decrease the distance between the gate electrode and the emitter by thermal oxidation and oblique deposition process. In this field emitter, in spite of 3 µm diameter of initial mask size, we were able to obtain a 400 nm gap which is the distance between the gate electrode and the emitter tip. Therefore, the onset of emission was established at gate voltages as low as 10 V with Fowler-Nordheim-like emission characteristics. Then anode current was 2.5 µA at 25 V in one emitter and transconductance (g

m
=ΔIA/ΔVG) was 0.5 µS.
Fabrication of a New Pyroelectric Infrared Sensor Using MgO Surface Micromachining
Authors: Kotani Tokumi , Tsutomu Nakanishi Tsutomu Nakanishi , Koji Nomura Koji Nomura
Published: February 2005

A new La-modified PbTiO3 (PLT) pyroelectric infrared sensor with a microcavity has been successfully fabricated by MgO surface micromachining. A microcavity under the sensing element is formed by etching the front surface of the substrate in order to improve the thermal properties. To precisely control the fabrication of a microcavity, process conditions were investigated in detail. As the concentration in phosphoric acid decreased and Pt diffusion into MgO substrate increased, the side etch rate of the MgO substrate increased from 1.9 to 3.4 µm/min at 80°C. The sizes of the fabricated sensor, sensing area, and etching holes were 1×2 mm2, 200×240 µm2, and 60×120 µm2, respectively. Pyroelectric coefficients of 4.0×10-8C/cm2 K were obtained.
In Situ Formation of Ohmic Contact Electrodes of Cu and Ag onto the Fractured Surface of (Bi, Pb)-Sr-Ca-Cu-O Ceramics
Authors: Kusaka Tadaoki , Suzuki Yoshihiko , Yotsuya Tsutom , Aoki Akira , Ogawa Souichi , Miyake Shuji , Aoyama Takahiro
Published: February 2005

Ohmic contacts on (Bi, Pb)-Sr-Ca-Cu-O (BSCCO) superconductor ceramics have been studied. When the electrodes were formed on the as-sintered surface of a BSCCO pellet, nonohmic characteristics were observed. Analysis by X-ray photoelectron spectroscopy suggests that the surface layer of the BSCCO pellet is degraded. When the fractured section of a BSCCO pellet was used, both Cu and Ag electrodes were found to be ohmic without thermal annealing.
Large-Area ZnO Thin Films for Solar Cells Prepared by Photo-Induced Metalorganic Chemical Vapor Deposition
Authors: Yoshino Masahiro , Wenas Wilson W. , Yamada Akira , Konagai Makoto , Takahashi Kiyoshi
Published: February 2005

Textured ZnO films with low resistivity and high transparency in a wide wavelength range from 400 nm to 1400 nm have been successfully grown by the photo-induced metalorganic chemical vapor deposition (MOCVD) technique. It was found that ultraviolet irradiation during deposition was very effective in improving the electrical properties of the films, even with a low intensity. The obtained films have a good uniformity along the 10×10 cm2 substrate.
Oxidation-Induced Stacking Faults Dependent on Oxygen Concentration in Czochralski-Grown Silicon Wafers
Authors: Shimizu Hirofumi , Naganuma Takashi , Kanai Akira , Umemura Nobuaki
Published: February 2005

Oxidation-induced stacking faults at wafer surfaces (OSFs-S) of Czochralski-grown silicon are investigated as a function of dissolved oxygen concentration ([O
i]). In the wafers containing lower [O
i], OSFs-S frequently appear due to the reduction of the gettering ability. Considering the warpage due to thermal stresses, the optimum [O
i] required for suppression of crystal defects in device processing is determined to be 9-10×1023 atoms/m3.
GaInAsP/InP Multi-Quantum Barrier (MQB) Grown by Chemical Beam Epitaxy (CBE)
Authors: Inaba Yuichi , Uchida Takashi , Yokouchi Noriyuki , Miyamoto Tomoyuki , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

A multi-quantum barrier (MQB) using the GaInAsP/InP system has been demonstrated for the first time. n-i-n tunneling diodes consisting of MQB and bulk barriers were grown by chemical beam epitaxy (CBE). From the measurement of 77 K current-voltage characteristics, the effective potential barrier height of 1.3 times the classical conduction band offset was obtained in the MQB structure.
Role of Modulated Structure in High-Tc Superconductors
Authors: Seiichi Kuwata Seiichi Kuwata , Wataru Kinase Wataru Kinase
Published: February 2005

A modulated structure in many high-T
c superconductors is discussed by using a localized 2D electron-hole lattice system. Assuming that the formation of Cooper pairs mediated by the 2D electron-hole lattice oscillation is possible, the transition temperature and the carrier surface density are estimated to be on the order of 100 K and 1014/cm2, respectively.
Critical Current Distribution of In Situ Nb3Sn Wires
Authors: Masaichi Umeda Masaichi Umeda
Published: February 2005

Critical current distributions for analyzing nonlinear parts of voltage-current (V-I) characteristic curves of in situ Nb3Sn wires have been studied. With gradation of tin content from the outside toward the center of the wire during tin diffusion processing, critical current distribution curves became much broader and sometimes they showed double peaks. In contrast, when tin content of a matrix in a wire was uniform but the diameter of Nb3Sn filament in the wire was scattered, it was observed that the critical current distributions showed double peaks. Since Nb3Sn filaments in the matrix were ultrafine, superconducting properties such as the critical temperature, field and current were degraded. Furthermore, the interface area between Nb3Sn and the matrix in in situ wire increased, and grain boundary density in Nb3Sn filaments decreased such that the interface boundaries also made an effective contribution to the pinning mechanism.
Magnetic Properties and Structure of Co/Pt Multilayered Films Evaporated on Heated Substrates
Authors: Shiomi Shigeru , Nakabayashi Takaya , Okada Masanori , Tadashi Kobayashi Tadashi Kobayashi , Morio Masuda Morio Masuda
Published: February 2005

Co/Pt multilayered films were evaporated on glass substrates that were heated up to 500°C. Perpendicular magnetic anisotropy K
⊥ was found to increase with the elevation of substrate temperature T
s, reaching a maximum at T
s=300°C. The surface anisotropy component also increased with elevating T
s while the volume component hardly depended on T
s. The coercivity of the perpendicular magnetization curve, H
c⊥, greatly increased with the elevation of T
s, exceeding 4 kOe at T
s=300 and 400°C. The layered structure was found to deteriorate considerably at T
s=300°C, becoming indistinct at T
s=400°C and higher. On the other hand, the (111) preferred orientation normal to the film plane became more pronounced with the elevation of T
s. The average grain size <d

g
> was found to increase with the elevation of T
s. It was also found that H
c⊥ had a close relationship to <d

g
>, reaching a maximum at <d

g
>=250-300 Å.
Absorptive-Grating Gain-Coupled Distributed-Feedback MQW Lasers with Low Threshold Current and High Single-Longitudinal-Mode Yield
Authors: Nakano Yoshiaki , Cao Hong-Li , Tada Kunio , Luo Yi , Dobashi Machio , Hosomatsu Haruo
Published: February 2005

Although gain-coupled (GC) distributed-feedback (DFB) lasers of the absorptive-grating type have several merits over those of gain-grating type, there have been disadvantages which include threshold increase due to excess absorption, parasitic index coupling, and nonlinear operation. In this paper we describe some new concepts to cope with these problems, namely, grating duty-factor optimization, a conduction-type inverted absorptive grating, and an anti-phase index grating. We have applied these schemes to GaAlAs/GaAs multiple-quantum-well (MQW) GC DFB lasers. Consequently, low threshold current, high slope efficiency, high side-mode suppression railo, narrow linewidth, and high single-mode yield have been achieved concurrently in as-cleaved devices.
Experiential Solution of the Photon Transport Equation in Lossy Case
Authors: Noda Yoshitoshi , Nakai Katsutoshi Tanino
Published: February 2005

An experiential solution of the photon transport equation, which describes the behavior of light pulses incident on a lossy ruby laser amplifier, is given. Numerical analysis of the equation is performed for a ruby laser which has a loss coefficient of 0.02∼0.08 (cm-1). From the analysis, the experiential solution is derived and the error factor of the solution is typically less than 7 percent. The output waveform and total output energy of square pulse input are discussed for adapting the solution to a laboratory-size solid-state laser amplifier.
Relationship between Electrical Resistivity and Electrostatic Force of Alumina Electrostatic Chuck
Authors: Watanabe Toshiya , Tetuo Kitabayashi Tetuo Kitabayashi , Chiaki Nakayama Chiaki Nakayama
Published: February 2005

Alumina electrostatic chucks having various electrical resistivities were fabricated by changing the amount of TiO2 and heat treatment conditions. Experimental data on electrostatic force and its response time were obtained for the fabricated electrostatic chucks. The experimental results are compared with the theoretically predicted results utilizing the equivalent circuit model, and the relationship between electrical resistivity and electrostatic force characteristics is discussed.
Auger Electron Spectroscopy Study on the Stability and the Interfacial Reaction of Ta, Ta-N and TaN Films as a Diffusion Barrier between Cu9Al4 Film and Si
Authors: Noya Atsushi , Katsutaka Sasaki Katsutaka Sasaki , Mayumi Takeyama Mayumi Takeyama
Published: February 2005

The diffusion barrier properties of Ta, Ta-N and TaN films to Si and the Cu9Al4 compound have been studied by examining depth profiles obtained from Auger electron spectroscopy. The contact system degrades with the silicide formation at the interface between the barrier and the Si substrate. The silicide formation temperature of these films was 650°C for the Ta barrier and 700°C for the Ta-N one. The contact system using the TaN compound barrier tolerates a temperature of 750°C. Ta atoms are the diffusing species for silicide formation in the present study, which protects the contact system from catastrophic failure due to the intermixing of all elements at higher temperatures.
Estimation of Chemical Sputtering Rates of Carbon in He-H2 Glow Discharge Plasmas by Optical Emission Spectroscopy
Authors: Kouichi Tsuji Kouichi Tsuji , Kichinosuke Hirokawa Kichinosuke Hirokawa
Published: February 2005

The sputtering of cathode plates in glow discharge plasma with He-H2 gas mixtures has been investigated. The sputtering rate of the carbon plate alone increased with increasing H2 pressure. This enhancement in the sputtering rate of carbon can be explained by chemical sputtering with H+ ions dissociated from H2 molecules. The dependence of optical emission intensities of CH and C2 molecules on H2 pressure was very similar to that of the sputtering rate of carbon. Thus, correlation between the sputtering rate of carbon and the optical emission intensity was investigated. It has been found that the correlation between the sputtering rate of carbon and the intensity ratio I(CH 431.4 nm)/I(He I 501.6 nm) gave the best correlation coefficient. Therefore, it is possible to estimate the chemical sputtering rate of carbon by monitoring the emission intensities of CH 431.4 nm and He I 501.6 nm.
Measurement of Toroidal Plasma Current in RF Heated Helical Plasmas
Authors: Sakae Besshou Sakae Besshou
Published: February 2005

This report describes the measurement of toroidal plasma current by a semiflexible Rogowski coil in a helical vacuum chamber. A Rogowski coil measures the toroidal plasma current with a resolution of 0.1 kA, frequency range of up to 1 kHz and sensitivity of 6.5×10-9V·s/A. We measured the spontaneous toroidal plasma current (from -1.2 to +1.2 kA) under electron cyclotron resonance heating at 0.94 T toroidal field in the Heliotron-E device. We found that the measured direction of toroidal plasma current changes its sign as in the predicted behavior of a neoclassical diffusion-driven bootstrap current, depending on the horizontal position of the plasma column. We explain the observed plasma currents in terms of the compound phenomenon of an ohmic current and a neoclassical diffusion-driven current. The magnitude of the neoclassical current component is smaller than the value predicted by a collisionless neoclassical theory.