bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Foreign Gas on Gain and Rotational and Translational Temperatures for Regular and Sequence Band Transitions in Waveguide CO2 Laser
Authors: Shimizu Fumiko O. , Kawai Kenji , Minoh Hiroyuki Homma
Published: October 2002

From the measurement of small signal gain for the regular and sequence band transitions in a waveguide laser medium, the effect of foreign gas on the gain coefficient and rotational and translational temperatures is examined and compared with that in the ordinary laser medium. The rotational temperature is always well defined and is apparently higher than the translational temperature at any partial pressure of the foreign gas in the gas mixture. It is found that N2 and He cause opposite effects on the temperatures. The total and partial derivatives of the temperatures for the variables of the foreign gas pressure and the injected power are obtained. The processes of energy transfer and the relaxation mechanism are discussed.
Characterization of InSb Interface with Oxide Films
Authors: Takahashi Kenji , Arata Onozuka Arata Onozuka , Yasuhiro Tanaka Yasuhiro Tanaka
Published: October 2002

Metal insulator semiconductor (MIS) structures on InSb substrate, grown by an electron cyclotron resonance chemical vapor deposition (ECR-CVD) system, were studied. A high quality oxide film, deposited on the InSb substrate by ECR-CVD, was achieved. The minimum interface state density (min N
ss) value of 4×1011 cm-2 eV-1 was obtained. Auger electron spectroscopy (AES) and electron spectroscopy for chemical analysis (ESCA) were employed to clarify the MIS structure of these oxide films. It was found that the interface region between SiO2 and the InSb surface was wider for lower values of the surface state density and that the reduction reaction occurred at the InSb surface during the deposition of SiO2.
Photovoltaic Effect in Titanium Dioxide/Zinc Phthalocyanine Cell
Authors: Koichi Kajihara Koichi Kajihara , Katsuhisa Tanaka Katsuhisa Tanaka , Kazuyuki Hirao Kazuyuki Hirao , Naohiro Soga Naohiro Soga
Published: October 2002

The photovoltaic effect has been observed for a titanium dioxide (TiO2) and zinc phthalocyanine (ZnPc) composite cell which is denoted as ITO/TiO2/ZnPc/Au. The photocurrent flows from the ZnPc layer to the TiO2 layer in the external circuit when the cell is illuminated, and the photocurrent and photovoltage of the cell are directly and logarithmically proportional to the light intensity, respectively. A clear rectifying effect is observed in their current-voltage relationships. Not only the photovoltaic effect in the cell but also photoconduction in the TiO2 layer is observed under ultraviolet light illumination. The wavelength dependence of the photocurrent reveals that the collection efficiency of the cell at any wavelength is determined mainly by optical absorption in the ZnPc layer. This result also shows that the major part of incident light in the visible region effectively contributes to photocarrier generation because of the wide band gap of TiO2, and the excited ZnPc molecules play an important role in the photovoltaic effect.
Analysis of Modified Franz-Keldysh Effect under Influence of Electronic Intraband Relaxation Phenomena
Authors: Yuji Kuwamura Yuji Kuwamura , Minoru Yamada Minoru Yamada
Published: October 2002

Characteristics of the Franz-Keldysh effect were theoretically analyzed by taking into account electronic intraband relaxation. Theoretical analysis of optical absorption was performed basing on the density matrix formalism with the help of a stochastic model to include the intraband relaxation. The absorption tails observed in experiments were well explained by this theoretical analysis, together with the Franz-Keldysh effect itself.
Electronic and Vibrational Reflectivity and Absorption Spectra in ZrS2 Crystals
Authors: Syrbu Nicolae N. , Cebotari Vladimir Z. , Moldoveanu Nicolae P.
Published: October 2002

The study of both the absorption and λ-modulated absorption spectra have been investigated in the region of the lowest band gap. The reflectivity spectra of ZrS2 are presented in the region E>E
g (1.5 to 6.5 eV). The IR reflectivity spectra of ZrS2 for E⊥c polarization were investigated in the region from 50 to 4000 cm-1. The contours of vibrational spectra were calculated using multioscillator model and the parameters of phonons were determined. New data about the band structure were obtained in the region of the lowest band gap.
Study of Recovery in Plastically Deformed Al-Li-Based Alloy by Positron Annihilation
Authors: Mamdouh Abdelrahman Mamdouh Abdelrahman
Published: October 2002

Positron annihilation mean lifetime measurements have been performed on two samples of the commercial alloy [(8090) Al-Li-Cu-Mg-(Zr)]. One sample was deformed (37.5%) at room temperature and subjected to isochronal annealing. The temperature was varied from 300 K to 623 K. The other one was homogenized at 823 K and subjected to isothermal annealing at 873 K. The time of annealing varied from 0 to 12 h in steps of 2 h. Evidence of nonspurious lifetime component, in both cases, have been observed. The results of the plastically deformed samples (*BAR*τ*BAR* = 202±2 ps) are interpreted as trapping of positrons in dislocations and Li-rich zones. On the other hand the results of the homogenized sample (*BAR*τ*BAR* = 183±2 ps) are interpreted as trapping of positrons in Li-rich zones only.
Optimization of Surface-Acoustic-Wave Withdrawal-Weighted Filters Using Genetic Algorithms
Authors: Makoto Hirabayashi Makoto Hirabayashi
Published: October 2002

Instead of the conventional 0-1 sequence, a new sequence has been devised, which is appropriate for optimizing withdrawal-weighted filters, using genetic algorithms. The sequence consists of durational numbers of continuous 0s and 1s, and the search area is reduced to much smaller than the total configuration space. A filter whose relative 3 dB bandwidth is 0.5% is optimized. The method yields a maximum sidelobe level of -56.1 dB, while the level of the initially synthesized filter is -41.5 dB. The calculated results show that the method is effective for nonlinear optimization of withdrawal-weighted filters.
Imaging Two-dimensional Crystals of Catalase by Atomic Force Microscopy
Authors: Hara Satomi Ohnishi , Taiji Furuno Taiji Furuno , Hiroyuki Sasabe Hiroyuki Sasabe
Published: October 2002

Two-dimensional (2D) crystals of a water-soluble protein, catalase, were imaged in water using atomic force microscopy (AFM). The catalase molecules formed a 2D ordered monolayer by binding to a charged polypeptide monolayer of poly(1-benzyl-L-histidine) (PBLH) spread at the air-water interface. The film of PBLH, bound to catalase molecules, was horizontally transferred onto an alkylated silicon wafer for AFM imaging. The AFM images revealed that the 2D catalase crystal is composed of an array of tetramers. We also found that the pH of the sample during preparation strongly affected the quality of the AFM image because of the imaging resolution influence upon the force acting between the cantilever and the sample. The optimum sample pH was 6.0, at which a weak adhesive force in the range of 10-10–10-11 N was detected. From the results of investigation of the pH dependence of the sample during preparation on catalase-PBLH sample, it was demonstrated that the electrostatic force between the cantilever and the sample could be reduced as a result of charge cancellation at the catalase-PBLH interface (self-screening effect). We present 2D crystal images of catalase molecules acquired through AFM with molecular resolution, and demonstrate that sample preparation in which pH is optimized to induce the self-screening effect of surface charges is advantageous for AFM imaging of water-soluble protein molecules, because the electrostatic force can be controlled by changing the binding condition of the protein.
Mode Change of 1 MHz Discharge in O 2 Gas at Low Pressure
Authors: Kenji Aoyagi Kenji Aoyagi , Itsuo Ishikawa Itsuo Ishikawa , Yukinori Saito Yukinori Saito , Shinji Suganomata Shinji Suganomata
Published: October 2002

Radial distributions of plasma density change significantly at pressures above and below 0.2 Torr. At 0.5 Torr, the discharge is almost hollow with high density around the edge, and its color is almost white. At 0.1 Torr, the density distribution becomes high in the central region both axially and radially, and the discharge color becomes yellowish white. Two prominent lines of optical emission show different spatiotemporal profiles. The O2
+ 559.8 nm line is bright in the central region, while the O I 777.2 nm line is bright just in front of the instantaneous cathode.
Study of Optimum Annular Illumination Conditions by Evaluating the Resolution Limit and Pattern Image Contrast
Authors: Toshiyuki Horiuchi Toshiyuki Horiuchi
Published: October 2002

Annular illumination optical exposure systems are expected to reduce printable pattern sizes with only a slight change in the illumination source. However, in practice, the improvement in resolution is rather small, although the improvement in depth-of-focus is considerable. This limited improvement should be utilized as effectively as possible. This paper presents an analysis aimed at providing the minimum image contrast needed for replicating patterns onto resist and explains a method for determining the best annular illumination condition. It is clarified that the critical image contrast is about 0.6–0.75 for typical g-line or i-line resist processes. The best illumination condition is found to depend on the critical image contrast and how much depth-of-focus is expected. Assuming the critical image contrast is 0.6, the normalized annular source image radius σ m should be set at near 0.53 for beneficial printing.
A Complete System for Obtaining the Trap Parameters of Thermoluminescence Glow Peak
Authors: Mahmoud Said Rasheedy Mahmoud Said Rasheedy
Published: October 2002

Various experimental methods are currently employed for determining the trap parameters of an isolated thermoluminescence (TL) glow peak. In this work, a new method is described to obtain the trapping parameters in sequence of a TL glow peak starting with the order of kinetics b, the activation energy E (eV), the frequency factor S ( s-1) and finally the initial concentration of trapped electrons n
° ( cm-3). In the present work, an equation is suggested to estimate directly the order of kinetics b. Also, the possibility of obtaining S ( s-1) in the case of general-order kinetics is discussed. Finally, a simple analytical method is developed to obtain the relative value of n
° ( cm-3).
Enhancement of the Annular Illumination Effect Using a Printing Process Resolvable with Low Image Contrast
Authors: Horiuchi Toshiyuki , Marley Elisabeth Anne , Mimura Yoshiaki , Anzai Kazunori , Harada Katsuhiro , Kazuhiko Komatsu Kazuhiko Komatsu
Published: October 2002

Resolution enhancement by annular illumination is discussed. The image contrast of patterns on a wafer is improved by annular illumination in high spatial frequency regions. However, it is still less than 0.5, although the ordinary resist patterns can be resolved only when the image contrast is over about 0.6. Therefore, the actual resolution limit is hardly extended at all by the ordinary resist process. To utilize the small improvement of the image contrast and to realize a noticeable resolution enhancement, a special resist process, by which fine patterns can be printed with a low image contrast of less than 0.5, should be adopted. A large resolution enhancement is actually demonstrated by combining an extra-thin resist process with annular illumination. The optimum annular illumination conditions for low-image contrast printing are also investigated, and it is clarified that a large annular source radius is preferable. Since the resist process used is a matter of choice, various surface imaging techniques will also be applicable.
Contamination Charging up Effect in a Variably Shaped Electron Beam Writer
Authors: Ando Atsushi , Sunaoshi Hitoshi , Sato Shinji , Magoshi Shunko , Hattori Kiyoshi , Suenaga Machiko , Wada Hirotsugu , Housai Hiroaki , Hashimoto Susumu , Kazuyoshi Sugihara Kazuyoshi Sugihara
Published: October 2002

We investigated the beam drift on the second shaping aperture caused by the charging up of contamination layers on shaping deflector surfaces in an EX-8D variably shaped beam (VSB) writer. A surface charging model which is based on the movement of the secondary electron (SE) charge-up area in a deflector in response to the direction and strength of the field was adapted to explain the beam drift phenomenon. It was found that SE charge-up causes the beam drift and its amount depends on the amount of SEs moving between the electrodes. It was also found that by removing the contamination layers using a downflow cleaning process the beam drift is significantly reduced even if SEs move between the electrodes.
Assembly of Extreme Ultraviolet Lithography Optics Using At-Wavelength Foucault Testing
Authors: Tsuneyuki Haga Tsuneyuki Haga , Marcia C. K. Tinone Marcia C. K. Tinone
Published: October 2002

An on-line, at-wavelength, Foucault testing system has been developed to assemble the imaging optics for extreme ultraviolet lithography (EUVL). The relationship between Foucaultgrams and assembly errors was analyzed through the computer calculation of Foucaultgrams for each type of assembly error based on both a ray-tracing and a numerical approach. In addition, the assembly tolerance was estimated by calculating both the modulation transfer function (MTF) and the wave-front error (WFE) for diffraction-limited imaging performance. The calculated results indicate that a Foucault testing method is sufficiently sensitive to the various types of assembly error to enable the diffraction-limited imaging performance to be achieved.
Nanometer Electron Beam Lithography with Azide-Phenolic Resin Resist Systems
Authors: Yamamoto Jiro , Uchino Shou-ichi , Hattori Takashi , Toshiyuki Yoshimura Toshiyuki Yoshimura , Fumio Murai Fumio Murai
Published: October 2002

High resolution negative electron beam (EB) resists consisting of an aromatic azide and a phenolic resin have been developed for nanometer lithography. Bisazides which crosslink phenolic resins are more suitable for fine pattern fabrication than monoazides. Several phenolic resins such as novolak resin and polyhydroxystyrene were evaluated as resist matrix resins, and poly( p-hyroxystyrene) was selected as the best resin for nanofabrication. A resist composed of 3,3′-dimethoxy-4,4′-diazidobiphenyl and poly( p-hyroxystyrene) enables the definition of a 50 nm line-and-space pattern with an EB dose of 170 µ C/cm2 under optimum process conditions. The fine resist pattern obtained has sufficient dry etching resistance and can be applied to Si nanofabrication with good critical dimension control.
Radical Behavior in Fluorocarbon Plasma and Control of Silicon Oxide Etching by Injection of Radicals
Authors: Toshio Goto Toshio Goto , Masaru Hori Masaru Hori
Published: October 2002

In SiO2/Si selective etching processes using fluorocarbon plasmas, surface reactions of fluorocarbon radicals can affect the etching selectivity considerably. Therefore, information on radicals in plasmas and their surface reactions must be obtained. We developed an in-situ method of measuring various radicals in plasmas using infrared diode laser absorption spectroscopy (IRLAS) and have clarified the behaviors of the CF
x
(x=1–3) radicals in fluorocarbon plasmas for the first time. Moreover, we recently developed techniques of radical injection into plasma (RIT) and clarified the important radical in the plasma etching process. It is expected that these advances will contribute to the further developments in the semiconductor process field.
Rare-Earth Doping in SiC for Light-Emitting Devices
Authors: Pietsch Walter , Takeo Aramaki Takeo Aramaki , Teruaki Motooka Teruaki Motooka
Published: October 2002

Neodymium-doped SiC thin films are grown by means of supersonic free jets which are introduced into the vacuum chamber using a pulsed supersonic valve. Metal-organic complexes of Nd are mixed with a SiC film precursor, tetramethylsilane Si(CH3)4, to generate a molecular beam. Films were grown on p-type Si(100) substrates at 900° C from the molecular free jets for 90 min with different electron beam energies ranging from 25 to 75 eV. Cross-sectional transmission electron microscope images and diffraction patterns have shown that these SiC films were epitaxially grown zincblende or β-SiC (3C-SiC). Secondary ion mass spectrometry measurements of several doped SiC samples have revealed the depth profiles and doping concentrations of Nd ranging up to 5.8×1019 cm-3 depending on the electron beam energy. However, no appreciable photoluminescence corresponding to the Nd3+ ion was detected suggesting that neodymium is not incorporated as an optically active trivalent ion.
In Situ Observation of Oxidation and Etching of Silicon by Ultra-High-Vacuum Transmission Electron Microscopy
Authors: Toshinari Ichihashi Toshinari Ichihashi
Published: October 2002

O2–Si surface reaction processes, such as oxidation and etching, have been observed in situ with a new ultra-high-vacuum transmission electron microscope at atomic resolution. It was demonstrated that the etching occurs block by block and the oxidation starts from the terrace edge. Reconstructed Si surface structures appearing under clean vacuum conditions, such as Si(111)7×7 and Si(001)2×1 structures, have been also observed using this electron microscope on an atomic scale. We have demonstrated that this electron microscope is useful for studies of the dynamic behavior of surfaces.
Fabrication of Si Field Emitter Tip for a Three-Dimensional Vacuum Magnetic Sensor
Authors: Uemura Koji , Seigo Kanemaru Seigo Kanemaru , Junji Itoh Junji Itoh
Published: October 2002

A new Si field emitter tip generating a cross-shaped electron beam was fabricated for a three-dimensional vacuum magnetic sensor (VMS) application. The present tip is surrounded by a gate for field emission, and a focusing lens is made in the same plane as the gate. The beam current of about 50 nA was obtained with a single tip at the gate and lens voltages of 55 V and 10 V, respectively. The fabrication process and beam characteristics are described. Preliminary results such as linearity and sensitivity of VMS using the present tip are also discussed.
Fabrication of Si Nanostructures for Single Electron Device Applications by Anisotropic Etching
Authors: Hiramoto Toshiro , Ishikuro Hiroki , Saito Kenichi , Fujii Tomoyuki , Saraya Takuya , Ikoma Gen Hashiguchi
Published: October 2002

Si nanostructures for single electron device applications are successfully fabricated using a newly developed anisotropic etching technique . The minimum size of the Si nanostructures is about 10 nm, which is much smaller than the lithography limit. The novel process involves two anisotropic etching steps and one selective oxidation step, and is fully compatible with very large scale integration (VLSI) processes. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) observations indicate that the fabricated nanostructures are very uniform and atomically controlled. This process is promising for the future integration of single electron devices into VLSI chips.
Sub-10-nm Si Lines Fabricated Using Shifted Mask Patterns Controlled with Electron Beam Lithography and KOH Anisotropic Etching
Authors: Namatsu Kenji Kurihara , Masao Nagase Masao Nagase , Takahiro Makino Takahiro Makino
Published: October 2002

We developed a new method for Si nanofabrication that provides sub-10-nm resolution using electron beam lithography combined with KOH anisotropic etching of a Si(1\overline10) substrate. The method, called shifted mask pattern method, uses two shifted mask patterns to reduce the Si linewidth. The two shifted mask patterns delineated in the <11\overline2> direction are used as a KOH etching mask where the masks are shifted vertically to each other in the <11\overline2> direction. During KOH anisotropic etching, Si linewidth under the shifted part of the masks is reduced due to the etching's smoothing resulting from the low etching rate of the Si(111) plane. The linewidth can be controlled by changing the mask shift. An image reversal process using electron cyclotron resonance (ECR) plasma oxidation was used to form a plasma oxide mask for KOH etching. This mask was obtained by ECR oxygen plasma irradiation using a ZEP520 resist mask pattern. Highly accurate position and linewidth c ontrol was achieved with a 70-kV electron beam nanolithography system that has a minimum deflection step of 2 nm. The variation of pattern position and linewidth was about 1 nm. Using this method, we have been able to fabricate lines as narrow as 2 nm.
Single Atom Lithography and its Applications
Authors: Richard G. Woodham Richard G. Woodham , Haroon Ahmed Haroon Ahmed
Published: October 2002

A novel technique for single atom lithography has been developed for the fabrication of nanostructures. It is based on a focused ion-beam with a retarding field stage, which enables the ion impact energy to be reduced to any level down to 0 eV. An ion detector has been designed and incorporated in the system which has a quantum detector efficiency close to 100% for high energy ion impacts and is capable of detecting the arrival of single Au+ ions with energies as low as 30 eV. The system has been used to deposit nanostructures in the size range 1–5 nm in diameter. The relation of size to surface morphology and to beam parameters has been studied. A new system operating in UHV conditions has been commissioned to enhance the study, particularly with respect to nucleation of particles and surface mobility effects. Initial experiments on a Coulomb blockade device with islands fabricated with the system have been conducted.
Oxidation Characteristics of Al–Ta Thin Alloy Films as a Passivation Layer on Cu
Authors: Takeyama Mayumi , Noya Atsushi , Taguchi Masahiro , Sasaki Takaaki Ichikawa
Published: October 2002

The oxidation characteristics of Al and Al–Ta alloy films (500 Å) deposited as a passivation layer on Cu have been examined by depth profiling using Auger electron spectroscopy and X-ray photoelectron spectroscopy. Although alloying between Al and Cu takes place, the Al films prevent the oxidation of Cu up to the oxidation temperature of ∼300° C for 1 h in air, at which the surface-oxidized Al2O3 layer maintains the self-passivating ability. At more elevated oxidation temperatures, the further oxidation of Al and the formation of CuO in the Al–Cu alloy layer just beneath the oxide layer are confirmed to occur. On the contrary, the Al–Ta alloy films completely protect the Cu layer from oxidation even after oxidation at 500° C for 1 h in air. This is achieved due to the formation of the Ta buffer layer which separates the Cu layer from the surface-oxidized one, which is formed by the preferential oxidation of Al and the rejection of Cu from the Al2O3 during the oxidation.
Scanning Tunneling Spectroscopic Study of Bare and Iodine Modified Au(111) and Pt(111) in Aqueous Solution and in Vacuum
Authors: Nagatani Yasunori , Hayashi Toru , Itaya Taro Yamada
Published: October 2002

Tunneling current (I) versus tip height (s) profiles (I-s curves) have been measured on bare and iodine-modified surfaces of Au(111) and Pt(111) both in aqueous acid solutions and under ultrahigh vacuum (UHV) conditions to investigate the influence of these two environments. A mechanically stable electrochemical scanning tunneling microscope combined with a bi-potentiostat was constructed to measure the I-s curves accurately in aqueous solution under the N2 atmosphere. The tunneling barrier height energy was derived in each case from the I-s curve. Relatively large values for the tunneling barrier height were obtained on well-defined clean Au(111) (about 0.7 eV) and Pt(111) (about 1 eV) in solutions. It was found that the barrier heights obtained on the bare Au(111) and Pt(111) in solutions did not show significant dependence on the electrode potential, even when their surfaces were electrochemically oxidized. The iodine adlayers on Au(111) and Pt(111) were found to reduce the barrier heights compared with those observed on the bare surfaces in solution and in UHV. The barrier height on the iodine-modified Au(111) in 0.1 M HClO4 was far larger than that in UHV.
Analysis of Average Transport Critical Current Density of Oxide Superconductors Deposited on a Silver Base
Authors: Lee Win-Der , Yang Tzong-Jer , Bi-Shiou Chiou Bi-Shiou Chiou
Published: October 2002

Considering the resistivity of a silver base and the contact resistance of a silver base with a bulk superconductor, the dependence of average critical current density J
c(D, H
a) of a high-T
c oxide superconductor deposited on a silver base on the sample dimension D and the applied magnetic field H
a is calculated using a generalized critical-state model, which was recently extended to low field by Chen and Yang [Physica C 224 (1994) 345]. The self-field effect of the average critical current was also taken into account in the model. Based on the generalized critical-state model, new behaviors of J
c(D, H
a) in the low-field range of H
c1 ≤H
a≪H
c2 are obtained. In addition, a constant J
c(D, H
a) for 0≤H
a≤H
c1 is obtained, which is different from the results derived from a model that does not include the self-field effect. However, these theoretical results can be fitted to the experimental data to obtain some important macroscopic material parameters and may be used to interpret the dimension effect of transport J
c of a high-T
c oxide superconductor deposited on a silver base.
Effect of Degree of Coherence in Optical Lithography Using Dummy Diffraction Mask
Authors: Donggyu Yim Donggyu Yim , Seonbok Lee Seonbok Lee , Sungmuk Lee Sungmuk Lee , Yong Ho Oh Yong Ho Oh , Hai Bin Chung Hai Bin Chung , Hyung Joun Yoo Hyung Joun Yoo
Published: October 2002

The effects of degree of coherence in optical lithography using the dummy diffraction mask are investigated by simulation and experiment. Influences on resolution and depth of focus of the repeated and isolated patterns are simulated for the several coherence factors of the illumination. The process margins are also simulated through the exposure vs. defocus diagram. The lithographic performances of the complex periodic patterns are experimented. As degree of coherence (DOC) decreases, the contrast benefit is increased for line and space(L/S) patterns size less than 0.5 λ/NA where NA is the numerical aperture, and the depth of focus(DOF) benefit is increased for L/S patterns size less than 0.65 λ/NA. The smaller L/S patterns size is, the greater the influence of DOC is. In the isolated patterns of sub-resolution type, better lithographic performances could be obtained for the smaller coherence factor.
Impact of µA-ON-Current Gate-All-Around TFT (GAT) for Static RAM of 16Mb and beyond
Authors: Maegawa Shigeto , Ipposhi Takashi , Maeda Shigenobu , Kuriyama Hirotada , Kohno Yoshio , Inoue Yasuo , Hirokazu Miyoshi Hirokazu Miyoshi , Tadashi Hirao Tadashi Hirao
Published: October 2002

The gate-all-around thin-film transistor (TFT) (GAT) with thin channel poly-Si can suppress the individual performance variation induced by a poly-Si grain boundary in the channel, in addition to improving the average performance compared to the conventional single-gate TFT (SGT). This effect is attributed to the thinning of the effective channel poly-Si by half in the GAT. Poly-Si TFT simulation results clearly confirmed this effect in terms of the current(I)-voltage(V) characteristics and channel potential. The GAT also reduces the threshold voltage instability under negative bias temperature (-BT) stress because the GAT structure relaxes the stress electric field in the gate oxide. The high-performance GAT enables reduction of the size of the static random access memory (SRAM) cell by providing a large ON-current to the storage node and enhancing the data retention stability despite the low cell ratio. The GAT-SRAM cell is a strong candidate for SRAM of 16 Mb and beyond.
High-Efficiency Micromirrors and Branched Optical Waveguides on Si Chips
Authors: Namba Tohru , Uehara Akihito , Doi Takeshi , Nagata Takahiko , Kuroda Yasuhide , Miyazaki Seiichi , Shibahara Kentaro , Yokoyama Shin , Iwata Atushi , Masataka Hirose Masataka Hirose
Published: October 2002

High efficiency compact mirrors and branched waveguides which can be integrated on LSI chips have been developed. The Al capped bent optical waveguides efficiently change the light direction. The Al capping also reduces the light propagation loss of the optical waveguide from 1.8 to 0.6 dB/cm. Various micromirror shapes have been investigated and a reflectivity of 81% has been obtained for a double-reflection micromirror with a corner radius of 34 µm. Using the micromirrors, compact four-branch waveguides have also been designed and fabricated.
High-Speed SOI 1/8 Frequency Divider Using Field-Shield Body-Fixed Structure
Authors: Iwamatsu Toshiaki , Yamaguchi Yasuo , Ueda Kimio , Mashiko Koichiro , Yasuo Inoue Yasuo Inoue , Tadashi Hirao Tadashi Hirao
Published: October 2002

A high-speed silicon-on-insulator (SOI) 1/8 frequency divider with body-fixed structure was demonstrated using field-shield (FS) isolation. The maximum operation frequency is 2.1 GHz at 3.3 V. The SOI divider operates about 1.6 times faster than a bulk divider with the same dimensions. The normalized power consumption of the SOI divider at the maximum operating frequency is about 60% of that of the bulk divider. I
d-V
d transistor characteristics were improved, eliminating the kink in the saturation region, and the linearity of inverter characteristics was also improved with the body-fixed structure. The body contact collects excess carriers in the channel region, thereby preventing the parasitic bipolar action. From these results, it is suggested that devices using a field-shield body-fixed SOI structure have the potential for use in GHz-level systems containing analog circuits, and they are expected to be applied to portable communication systems and portable computers used in the multimedia era.
Theoretical and Experimental Estimations of Photon Recycling Effect in Light Emitting Devices with a Metal Mirror
Authors: Toshihiko Baba Toshihiko Baba , Ryoh Watanabe Ryoh Watanabe , Katsuhito Asano Katsuhito Asano , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

The photon recycling effect in light emitting devices was estimated theoretically and experimentally. It was shown from the rate equation analysis that this effect is marked when the injection carrier density is lower than 1×1018 cm-3 and the factor given by the average photon lifetime of spontaneous emission multiplied by the optical confinement factor inside the active region is larger than 100 fs. The external efficiency in light emitting diodes (LEDs) is improved by one order of magnitude if this factor is increased to 1 ps by the strong optical confinement around the active region. This theoretical estimation well agreed with the experimental result in fabricated GaInAsP/InP LEDs having a relatively wide emitting layer and a metal mirror; the efficiency became 1.6–1.8 times higher when the factor for fabricated LEDs was longer than 100 fs. An LED that exhibits a high efficiency comparable to those of laser diodes will be realized by improving the reflectivity of the metal mirror to higher than 99%.
Observation of Capacitance Hunching at the Flat-Band-Voltage in Boron-Doped Diamond Metal/Insulator/Semiconductor Structure
Authors: Suzuki Sei , Otsuka Yuzuru , Tetsuro Maki Tetsuro Maki , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

Metal/insulator ( CaF2)/semiconducting diamond (MIS) structures employing boron-doped homoepitaxial diamond films were prepared and their electrical properties were investigated. Al/ CaF2/diamond MIS diodes exhibited capacitance variation from accumulation to depletion values under the application of bias voltage from -4 to 4 V, and at the flat-band voltage, capacitance hunching always appeared in their capacitance-voltage ( C–V ) curves. These features coincide well with the prediction based on the theoretical analysis, and originate due to the presence of the deep boron level in the diamond energy gap.
Preparation of Superconducting Sr2CuO2(CO3)1-x(BO3)x Films by Metalorganic Chemical Vapor Deposition
Authors: Miyazaki Yuzuru , Yamane Hisanori , Hirai Toshio , Tsuyoshi Kajitani Tsuyoshi Kajitani
Published: October 2002

The growth conditions for Sr2CuO2(CO3)1-x
(BO3)x films using the metalorganic chemical vapor deposition (MOCVD) technique are determined. Superconducting films (T
c ∼ 30 K) with c-axis orientation are prepared on SrTiO3 (100) substrates using dipivaloylmethane (DPM) metal chelates of Sr and Cu, Sr(DPM)2, Cu(DPM)2 and [CH3(CH2)17O]3B source materials.
Basic Study on Multiplexed Superconducting Quantum Interference Device for Multichannel Biomagnetometer
Authors: Kunio Kazami Kunio Kazami , Jun Kawai Jun Kawai , Gen Uehara Gen Uehara
Published: October 2002

We have constructed a multiplexed 2-channel, 2-stage superconducting quantum interference device (SQUID) amplifier using double-washer SQUIDs and a 35-SQUID series array. The biasing current of the first-stage SQUIDs is switched by a complimentary metal oxide semiconductor (CMOS) analog multiplexer at liquid helium temperature, and an on-stage SQUID transfers the signal to the second-stage SQUID. Each SQUID has an additional negative feedback circuit to enlarge the linear input region and decrease distortion. Maximum input flux at the first-stage was 0.9Φ opp and the total harmonic distortion of the overall two-stage SQUID was 1% for a sinusoidal input flux of 0.1Φ opp. The voltage swings of the two channels were 1.1 and 1.3 mV.
Epitaxial Growth of Diamond on Iridium
Authors: Ohtsuka Kazuki , Suzuki Kazuhiro , Atsuhito Sawabe Atsuhito Sawabe , Tadao Inuzuka Tadao Inuzuka
Published: October 2002

Epitaxial growth of diamond on iridium thin films was performed by direct-current plasma chemical vapor deposition with ion irradiation pretreatment of the substrate. Pyramidal epitaxial diamond particles with a number density of ∼108cm-2were grown on the iridium film. The epitaxial relation is written as (100)diamond//(100)iridiumand [001]diamond//[001]iridium. Tilting of the epitaxial relation, as occasionally observed for diamond on silicon or beta silicon carbide, is scarcely observed. Erosion,as observed for diamond on nickel substrates, is not observed. The effect of the ion irradiation of the substrate is discussed briefly.
Balanced Inductive Plasma Sources
Authors: Georgy K. Vinogradov Georgy K. Vinogradov , Shimao Yoneyama Shimao Yoneyama
Published: October 2002

An approach is proposed for the design of powerful inductive sources with internally compensated anti-phase RF capacitive currents. It is shown that the total internal balance of both capacitive currents and RF magnetic field exist in a full wave helical resonator source. The new plasma source exhibits peculiar plasma phenomena having a clear physical interpretation.
Hydrogen Diffusion in C-Doped InGaAs
Authors: Hiroshi Ito Hiroshi Ito
Published: October 2002

The diffusion length of hydrogen in C-doped InGaAs has been estimated from the resistance variation in samples with n-type cap layers after annealing in N2 ambient. The obtained diffusion lengths are proportional to the square root of the annealing time, as in the normal diffusion process. The activation energy for the hydrogen diffusion is revealed to be 1.2 eV. The effective diffusion coefficients in InGaAs are found to be smaller than those in GaAs, implying that group-III atom species strongly affect the hydrogen diffusion behavior in C-doped III–V compound semiconductors.
Deep Level Transient Spectroscopy Depth Profile Measurements of Polycrystalline Zinc Oxide Ceramic
Authors: Lee Wei-I , Ruey-Ling Young Ruey-Ling Young , Wei-Kuo Chen Wei-Kuo Chen
Published: October 2002

A method is proposed for performing deep level transient spectroscopy depth profile measurements of defects in polycrystalline ZnO. A multilayer-chip ZnO varistor structure is adopted to minimize the number of grains connected in series. It is verified that the distributions of some defects near the ZnO grain boundary are highly nonuniform. Valuable information has been obtained from the measured defect distribution profiles.
Determination of Nematic Liquid Crystal (NLC) Orientation by Observing NLC Droplets on Alignment Surfaces
Authors: Rumiko Yamaguchi Rumiko Yamaguchi , Susumu Sato Susumu Sato
Published: October 2002

We have proposed a new and simple method for determination of nematic liquid crystal (NLC) orientation on alignment surfaces. NLC droplets on various alignment surfaces are observed using a polarizing microscope. The direction of the easy axis, the generation of pretilt angle and the tilt-up direction of NLC can easily be determined from disclination lines in the NLC droplets. The relationship between a flow-induced alignment effect and texture of the NLC on the alignment films with a weak azimuth anchoring strength is discussed.
Effect of Pressure on the Incommensurate Transition in ZrTiO4
Authors: Park Yung , Kim Ho-Gi , Kim Yoonho
Published: October 2002

An X-ray study of the effect of the pressure on the incommensurate phase transition in ZrTiO4 was performed in order to obtain the information concerning the nature of the competing forces that give rise to a structural instability at a general wave-vector. It was found that an increase in pressure lowers the transition temperature ( dT
i/ dP
i\cong-6.9 K/kbar). The pressure dependence of the incommensurate to commensurate transition was also investigated ( dT
c/ dP
c\cong-9.0 K/kbar).
Critical Thickness for the Solid Phase Epitaxy: Si/Sb/Si(001)
Authors: Kono Shozo , Goto Tadahiko , Yasushi Ogura Yasushi Ogura , Tadashi Abukawa Tadashi Abukawa
Published: October 2002

The early stages of solid-phase epitaxial (SPE) formation of Si/Sb(δ-layer)/Si(001) were studied using Auger electron spectroscopy. The Auger intensity ratio (Sb MNN)/(Si KLL) was measured as a function of the capping Si layer thickness. We found that there exists a critical capping Si thickness, ∼8–10 Si layers. Below this critical thickness, essentially all Sb atoms are segregated to the surface during the Si capping layer crystallization. Possible causes for this critical thickness are discussed and the need for further study under different SPE conditions is pointed out.
Application of Image Reconstruction Technique for the Measurement of Two-Dimensional Ion Energy Distributions Using a Retarding-Field Energy Analyzer
Authors: Fumiyoshi Tochikubo Fumiyoshi Tochikubo , Kenkoh Suemasa Kenkoh Suemasa , Tsuneo Watanabe Tsuneo Watanabe
Published: October 2002

A new measurement method of two-dimensional ion energy distribution impinging on a grounded electrode is developed for the conventional retarding-field energy analyzer, by means of the application of an image reconstruction technique. Electrically isolated multiple collectors are used for ion current measurement in the retarding-field energy analyzer. Two-dimensional ion energy distribution is reconstructed from the ion current by the algebraic reconstruction technique. As an example, the two-dimensional ion energy distribution in the capacitively coupled rf glow discharge at 13.56 MHz and 0.05 Torr in Ar is shown.
Adhesion Improvement of Photoresist on TiN/Al Multilayer by Ozone Treatment
Authors: Wakamiya Wataru , Hirayama Makoto , Kawai Akihiko Yasuoka
Published: October 2002

The effect of ozone treatment on photoresist adhesion is studied in terms of thermodynamics. The peeling strength of a photoresist-substrate joint is increased by a factor of about two by ozone treatment. An increase in the surface free energy of the substrate is responsible for this adhesion improvement.
Excess Arsenic in GaAs Grown at Low Temperatures by Molecular Beam Epitaxy
Authors: Chen NuoFu , Wang Yutian , Hongjia He Hongjia He , Lanying Lin Lanying Lin
Published: October 2002

The structural properties of GaAs grown at low temperatures by molecular beam epitaxy (LTMBE GaAs) were studied. The excess arsenic atoms in LTMBE GaAs exist in the form of arsenic interstitial couples (i.e. two As atoms share the one host site), and cause an increase in the lattice parameter of LTMBE GaAs. Annealing at above 300° C, the arsenic interstitial couples decomposed, and As precipitates formed, resulting in a decrease in the lattice parameter.
Virtual Point Source Pumped cw Nd:YAG Laser with 81 W Output from Linear Cavity and 22 W Output from Ring Cavity
Authors: Jie Song Jie Song , An Ping Liu An Ping Liu , Kazunori Okino Kazunori Okino , Kenichi Ueda Kenichi Ueda
Published: October 2002

Using a 32-diode-pumped virtual point source, we investigated the output characteristics of a cw Nd:YAG laser of both a linear cavity and a ring cavity. CW output power of 81 W was obtained from the linear-cavity laser under 291 W pumping power and 22 W cw output power was obtained from the ring-cavity laser under 149 W pumping power.
A Wavelength Tunable Q-Switched Erbium-Doped Fiber Laser with Fiber Bragg Grating Mirrors
Authors: Komukai Takeshi Imai , Takashi Yamamoto Takashi Yamamoto , Masataka Nakazawa Masataka Nakazawa
Published: October 2002

Q-switched operation of an erbium-doped fiber laser with fiber grating mirrors is demonstrated for the first time. The resonator was formed by splicing two fiber gratings to erbium-doped fiber ends. One of the fiber gratings was periodically stretched by a piezoelectric transducer for the Q-switching operation. An output pulse with a pulse width of 2.46 µ s and a peak power of 2.1 mW was obtained for a 1.48 µ m pump power of 26 mW. The oscillation wavelength was 1.552 µ m and the repetition rate was 1 kHz. The laser oscillation wavelength was tuned from 1.552 µ m to 1.556 µ m by applying lateral stress to one of the fiber grating mirrors.
Field Ion Microscope Observation of Mo Deposition with a Video System
Authors: Iwatsu Fumio , Hiroshi Morikawa Hiroshi Morikawa , Terumi Terao Terumi Terao
Published: October 2002

A sequential field ion microscope (FIM) observation of the progress of Mo deposition on a tungsten substrate at 55 K has been made, with the aid of a video system. Some of the image spots of deposited adatoms which appeared on the W(110) plane were found to disappear during further deposition, which suggests that an adatom is expelled from its adsorption site by an impinging atom, and acquires a mobility on the substrate surface even at cryogenic temperatures.
Relationship between Effective Work Functions and Noise Powers of Emission Currents in Nickel-Deposited Field Emitters
Authors: Yasuhito Gotoh Yasuhito Gotoh , Masayoshi Nagao Masayoshi Nagao , Motoki Matsubara Motoki Matsubara , Kazunori Inoue Kazunori Inoue , Hiroshi Tsuji Hiroshi Tsuji , Junzo Ishikawa Junzo Ishikawa
Published: October 2002

Low-frequency current fluctuations in nickel-deposited field emitters were evaluated quantitatively with normalized noise power which was obtained by integrating the spectral density of the current fluctuation between the frequencies of 0.2 and 2 Hz. The distance between the emitter and the collector was adjusted to 1.5 µm, in order to realize an electrode spacing similar to those of vacuum microelectronics devices. Measurements were performed under an ultrahigh-vacuum environment. The obtained noise powers were analyzed with the Seppen-Katamuki chart which indicates the effective work function and apex radius of the emitter. It was found that the emitters with higher effective work functions showed higher noise powers. The results were explained qualitatively from the differential of the Fowler-Nordheim equation.
Highly Sensitive and Stress-Free Chemically Amplified Negative Working Resist, TDUR-N9, for 0.1 µm Synchrotron Radiation (SR) Lithography
Authors: Shinji Tsuboi Shinji Tsuboi , Yoshio Yamashita Yoshio Yamashita , Soichiro Mitsui Soichiro Mitsui
Published: October 2002

A chemically amplified negative working resist, TDUR-N9 (Tokyo Ohka) for KrF excimer laser (248 nm) lithography, has been investigated for use in synchrotron radiation (SR) lithography. The resist shows high sensitivity and high resolution in SR lithography. Lines and spaces down to 0.1 µm are delineated at an exposure dose of 50 mJ/cm2. This high sensitivity will enable high-throughput SR lithography. In addition, the resist stress is less than 1 MPa, which is much smaller than those of other commercially available resists. It is found that this characteristic is essential for prevention of pattern deformation in pattern replication of around 0.1 µm.
Fabrication and Characterization of Diamond-Like Carbon Coated Knife Edge Field Emitter Array
Authors: Ko Chang Gi , Ju Byeong Kwon , Lee Yun Hi , Park Jung Ho , Myung Hwan Oh Myung Hwan Oh
Published: October 2002

We fabricated diamond-like carbon (DLC) coated knife edge-shaped field emitter array (KEFEA) on the (110) silicon wafer. The fabricated KEFEA has more than six hundreds times of aspect ratio and about two times higher electric field at tip-apex compared with the pyramid-shaped edge field emitter array (FEA). A high quality DLC film which has similar properties to the diamond film was coated on the silicon KEFEA by PECVD method in order to improve the stability and electrical characteristics. The turn-on field was lowered from 0.18 MV/cm to 0.14 MV/cm by the DLC film coating to the pure silicon KEFEA. More than 400% of the short-term emitted current fluctuation was observed from the measurement of the pure silicon KEFEA. The DLC film coating on the pure silicon KEFEA reduced the emission current fluctuation to 15%.
Room Temperature Pulsed Operation of Nitride Based Multi-Quantum-Well Laser Diodes with Cleaved Facets on Conventional C-Face Sapphire Substrates
Authors: Itaya Kazuhiko , Onomura Masaaki , Nishio Johji , Sugiura Lisa , Saito Shinji , Suzuki Mariko , Rennie John , Nunoue Shin-ya , Yamamoto Masahiro , Fujimoto Hidetoshi , Kokubun Yoshihiro , Ohba Yasuo , Gen-ichi Hatakoshi Gen-ichi Hatakoshi , Masayuki Ishikawa Masayuki Ishikawa
Published: October 2002

We demonstrate room temperature pulsed operation of nitride based multi-quantum-well (MQW) laser diodes with cleaved mirror facets grown on a conventional C-face sapphire substrate. Cleavage was performed along the <11*BAR*2*BAR*0> direction of the sapphire substrate, and the resultant facet was analyzed using an atomic force microscope (AFM) and theoretical calculation. A single peak emisson, at a wavelength of 417.5 nm, with a full width at half-maximum of 0.15 nm, was obtained. The threshold current density of the laser was 50 kA/cm2 and a voltage for the threshold current was 20 V.
Transmission Electron Microscopy of Sublimation-Grown GaN Single Crystal and GaN Homoepitaxial Film
Authors: Okada Tatsuya , Kurai Satoshi , Naoi Yoshiki , Nishino Katsushi , Sakai Fukuji Inoko
Published: October 2002

A GaN film with nominal thickness of 0.6 µ m was homoepitaxially deposited on a sublimation-grown GaN single-crystal substrate. An electron-transparent area of 10 µ m×10 µ m prepared by focused Ga ion beam machining was examined by transmission electron microscopy. In addition to the dislocations on the basal plane of the wurtzite unit cell, another type of dislocation, near pure edge in character and aligned close to the c-axis direction, was found in the GaN substrate crystal. Neither type of dislocation threaded to the top surface. Dislocation-free growth was achieved in the GaN homoepitaxial film.
Effect of Steady Bias Light on Carrier Lifetime in Silicon Wafers with Chemically Passivated Surfaces
Authors: Takao Maekawa Takao Maekawa , Yasushi Shima Yasushi Shima
Published: October 2002

We found that even a silicon surface chemically passivated with ethanol-iodine solution represents an active state in the recombination process of excess carriers. Hence, the decay of excess carriers is not a simple exponential decay and the time constant of decay depends strongly on the injection level of excess carriers. This injection-dependent nonexponential decay can be eliminated by illumination with a weak steady bias light. In other words, we recommend the use of a bias light illumination for measurements of bulk carrier lifetime with the technique of chemical passivation, since the illumination results in a low surface recombination velocity of below 5.5 cm/s in a wide range of injection level of 1–200%.