bluuebunny/crossref_metadata_2025 huggingface dataset:
Scaling of Edge Magnetic Fluctuations In DIII-D L-Mode
Authors: Neyatani Yuzuru , Shimada Michiya , Ohyabu Nobuyoshi , DIII-D Research Team DIII-D Research Team
Published: February 2005

Magnetic fluctuations at the divertor hit point were investigated during the L-mode near L-H transitions in DIII-D divertor discharges. These fluctuations show broad-band frequency spectra (15∼35 kHz) with toroidal coherency (0.4∼0.8) and rotate in the electron diamagnetic drift direction. The amplitude and the peak frequency follow different scalings. The parameter dependence of the amplitude is compared with the prediction of the microtearing and drift ballooning modes. Both modes are expected to be suppressed with increasing edge electron temperature gradient in the H-mode. The parameter scalings are more consistent with the prediction of drift ballooning modes than they are with the microtearing modes. The scaling of the frequency suggests that the peak frequency is the electron diamagnetic drift frequency forn=1 andm>5.
Photoluminescence in Sb-Doped ZnS
Authors: Nagano Masahiro , Kanie Hisashi , Yoshida Iwao , Aoki Masatoshi Sano
Published: February 2005

This paper describes the photoluminescence properties of cubic ZnS grown from three kinds of solution: Sb0.4S0.6, Sb and Zn0.6Sb0.4. The ZnS crystals grown from these three solutions showed n-type conduction. The concentration of Sb in the ZnS crystal grown from the Sb0.4S0.6 solution was 0.01 at.%. The emission band at 3.794 eV, which was first observed on the ZnS crystal from the Sb0.4S0.6 and Sb solutions, was due to the annihilation of excitons bound to neutral donors with a binding energy of 7 meV. It is considered that the Sb atom acts as the donor related to the 3.794 eV band. It seems that the Sb donor is also related to the band at 3.770 eV due to the transitions from the donor level to the valuence band.
Degradation and Recovery of Metal-Oxide-Semiconductor (MOS) Devices Stressed with Fowler-Nordheim (FN) Gate Current
Authors: Inokawa Hiroshi , Eric M. Ajimine Eric M. Ajimine , Cary Y. Yang Cary Y. Yang
Published: February 2005

Degradation and recovery behaviors of n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) and MOS capacitors are discussed based on the empirical power law. Devices with different gate oxide thicknesses, 10 and 33 nm, are stressed with Fowler-Nordheim (FN) gate current and the changes in subthreshold swing (S), drain current (I
D), transconductance (G
m), threshold voltage (V
th), interface trap density (D
it) above midgap, interface trapped charge (Q
it) above midgap, and effective oxide charge (Q
0) are measured during and after stressing. All parameters except V
th and Q
0 show recovery after degradation. After some stressing conditions, V
th and Q
0 show further degradation. It is found that the changes in parameters, during and after stressing, excluding those in V
th and Q
0 can be characterized by power laws. The behaviors of V
th and Q
0 are more complex, and the change in V
th is found to be influenced by changes in both Q
0 and Q
it.
An IR Study on the Stability of Y(DPM)3, Ba(DPM)2 and Cu(CPM)2 for UV Irradiation
Authors: Harima Hiroshi , Ohnishi Hiroshi , Hanaoka Ken-ichi , Goto Kunihide Tachibana
Published: February 2005

Ultraviolet-irradiation effects at 3∼8 eV (400∼150 nm) have been studied for Y(DPM)3, Ba(DPM)2 and Cu (DPM)2 (DPM: dipivaloylmethane) metalorganic chelates which are commonly used for YBa2Cu3O7-x
superconducting-film formation by metalorganic chemical vapor deposition (MOCVD). An IR spectral analysis shows that the chelate ring of Ba(DPM)2 is most sensitively affected when irradiated in a 200∼300 nm region through a π-π* transition of the ligand orbital, and Y(DPM)3 shows a similar, but much more modest reaction. On the contrary, Cu(DPM)2 is very stable for all the light sources used. Such a difference of stability is deeply related to the metal-oxygen bonding nature of these chelates.
Effect of Anion in Developer on Dissolution Characteristics of Photoresist
Authors: Yamaguchi Atsumi , Kishimura Shinji , Yoshiaki Yamada Yoshiaki Yamada , Hitoshi Nagata Hitoshi Nagata
Published: February 2005

The dissolution characteristics of photoresist in developers with added tetramethylammonium salts are discussed. It was observed that the dissolution rate of the photoresist was increased by adding tetramethylammonium salts to the developer. As the size of the anion of the added TMA salt becomes larger (I->Br->Cl-), the effect on the dissolution rate of the resist becomes greater. This “anion effect” is significant on unexposed and less exposed resists in which photoactive compound and novolak resin interact with each other strongly, while it becomes most negligible on fully exposed resists in which they interact weakly. It has also been found that the anion in the developer plays an important role in reducing the resist residue.
Properties of Large-Sized Nb-Based Superconducting TunnelJunctions for X-Ray Detection
Authors: Takeno Kazuhiko , Ishibashi Kenji , Mori Ken-ichi , Nagae Toshimitsu , Matsumoto Yuzuru , Katase Akira , Kinoshita Chiken , Nakai Kiyomichi , Takada Susumu , Nakagawa Hiroshi , Akoh Hiroshi , Aoyagi Masahiro , Kohjiro Satoshi
Published: February 2005

Niobium-based superconducting tunnel junctions are expected to be applicable to high-resolution X-ray measurements. Large-sized tunnel junctions with a Nb/Al/AlO
x
/Nb structure have been fabricated in order to study their performance in X-ray detection. The niobium layer which was sensitive to X-rays had a large size of 100 µm square ×1.2 µm thick. The junction detected 5.9 keV X-rays with an energy resolution of 1 keV. On the basis of the experimental data, the junction parameters were studied to produce a better energy resolution than that of silicon semiconductor detectors. The microstructure of the aluminum layer was observed by means of a transmission electron microscope.
Diagnosis of Surface Stability of 80K-Phase BiSrCaCuO Single Crystals with and without Li Doping
Authors: Hirata Satoshi , Sakuta Ken , Yasufumi Fujiwara Yasufumi Fujiwara , Takeshi Kobayashi Takeshi Kobayashi
Published: February 2005

The surface structure of 80 K-phase BiSrCaCuO single crystals with and without Li doping has been studied using low-energy electron diffraction (LEED) at elevated temperatures. Although the superconducting critical temperature rises slightly with Li doping, the cleaved surface becomes amorphous in vacuum at temperature ∼100 degrees lower than that of the undoped sample (600°C).
Coherency Dependence of Projection Printing Method Using a Phase-Shifting Mask
Authors: Asai Satoru , Isamu Hanyu Isamu Hanyu , Kohki Hikosaka Kohki Hikosaka
Published: February 2005

In a projection lithography system having fly-eye elements, a virtual source is created by an array of approximately mutually incoherent point sources. This paper describes a light-amplitude/phase simulation of the mask-projected image for a point source and discusses the dependence of the amplitude and phase on the point source's location. With the phase-shifting method, the mask images illuminated by point sources near the optical axis are better resolved, while point sources far from the optical axis blur small features. These results confirm that smaller-coherency-factor illumination is more effective for optical lithography using the phase-shifting method.
Reactive Ion Beam Etch of GaInAsP/InP Multilayer and Removal of Damaged Layer by Two-Step Etch
Authors: Matsutani Akihiro , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

Reactive ion beam etching (RIBE) is studied as a method to form a tiny reflector and microstructure for vertical cavity surface emitting lasers. Appropriate etching conditions with a chlorine gas for GaInAsP, InP, and GaAs have been obtained using RIBE. Microsized circular mesas including GaInAsP/InP multilayers with vertical side walls were fabricated. RIBE-induced damages in InP substrates were estimated to be localized within a depth of ∼1000 Å from the surface by capacitance-voltage (C-V) measurement. In addition, the removal of the induced damage by the second RIBE with different conditions for the InP wafer was proposed.
Development of New Imaging System for Chest Radiography: Investigation of Basic Imaging Properties and Improvement of Signal Detection
Authors: Kariya Yoshiharu Higashida
Published: February 2005

A new imaging system for chest radiography which has higher sensitivity in the mediastinum area than in the lung area has been developed. Through use of this new system for routine clinical examinations, the mediastinum area and lung areas are simultaneously displayed with a single exposure in optimal contrast. We investigated the fundamental physical properties of this system by comparing such items as its relative speed, modulation transfer functions (MTFs), density dependence on X-ray spectra, and low-contrast signal detections, with those of the conventional standard screen-film system.
Highly C-Axis-Oriented Pb(Zr, Ti)O3 Films Prepared by Sputtering
Authors: Fukami Tatsuo , Minemura Isamu , Yasushi Hiroshima Yasushi Hiroshima , Toshiyuki Osada Toshiyuki Osada
Published: February 2005

A newly developed tripole magnetron sputtering system, which has a third magnetic pole, has been applied to deposit PZT films in the atomic layer epitaxy mode. A set of experimental results revealed that the resultant films were highly c-axis orientated on (100) MgO substrates and that the deviation from stoichiometry in the films enhanced asymmetric properties of the P-E loop patterns.
PbTiO3 Thin Films Deposited by Laser Ablation
Authors: Imai Tadayuki , Masanori Okuyama Masanori Okuyama , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

PbTiO3 thin films have been deposited on Si or Pt substrates by the laser ablation method. The ArF excimer laser (193 nm) and YAG laser (1064 nm) were used. Systematic investigations on the film deposition rates with its spacial distributions as functions of laser fluence have been made. As a result, it is suggested that an excimer laser having a shorter wavelength is better for preparing PbTiO3 thin films. The perovskite phase is obtained in the films deposited using such an excimer laser and under suitable conditions. A substrate temperature of over 400°C and appropriate ambient O2 gas pressure are needed.
Fe and Al Concentrations in High Resistivity InP Layer Grown by Low-Temperature Liquid Phase Epitaxy
Authors: Ohtsuka Ken-ichi , Ohishi Toshiyuki , Abe Yuji , Sugimoto Hiroshi , Yoshiyasu Hajimu , Kuroki Hiroshi , Kuramoto Kazuo
Published: February 2005

High-resistivity InP layers grown by low-temperature liquid phase epitaxy from In-P-Fe-Al solutions were characterized by secondary ion mass spectrometry. Fe and Al concentrations in InP were found to be over 1016 cm-3. In the growth from In-P-Fe-Al solutions on S-doped InP substrates, the concentration of Fe and Al increased at the interface where electrical characteristics of the crystal drastically change.
Preparation of Lead-Based Perovskite Films by Sol-Gel Method and Their Properties
Authors: Kang Jian , Toshinobu Yoko Toshinobu Yoko , Sumio Sakka Sumio Sakka
Published: February 2005

Ferroelectric Pb(Fe0.5Nb0.5)O3(PFN)-PbTiO3(PT) thin films have been prepared on silica glass and silicon single crystal substrates by the sol-gel method using lead acetate, iron nitrate, niobium ethoxide and titanium tetraisopropoxide as precursors. It has been found that 38 mol% excess lead must be added to a starting solution to obtain single phase perovskite PFN coating films, while single phase perovskite 0.2PFN·0.8PT coating films can be prepared from the corresponding stoichiometric starting solution. The coating film shows a dielectric constant of about 500-1100 and dielectric loss of about 0.06-0.18 at 1000 Hz.
Preparation and Characterization of Pb-Based Ferroelectric Thin Films
Authors: Hayashi Shigenori , Kenji Iijima Kenji Iijima , Takashi Hirao Takashi Hirao
Published: February 2005

PbTiO3 thin films were prepared by newly developed “ion- and photoassisted evaporation”. The composition of the films was dependent on the substrate temperature and the evaporation rates of Pb and Ti. Controlling the evaporation rates to yield the stoichiometry, the perovskite phase formation took place merely at 500°C under the irradiation of oxygen ion. When an excimer laser beam was irradiated simultaneously with an oxygen ion beam, the perovskite phase formation took place at 325°C. This remarkable lowering of the deposition temperature was caused by ion- and photoactivation of the surface during the film growth.
Electrical Properties of (CaSr)F2/GaAs(111)B Interfaces Grown by Molecular Beam Epitaxy: Realization of Unpinning
Authors: Saeki Takao Waho
Published: February 2005

Electrical properties of lattice-matched (CaSr)F2/GaAs(111)B interfaces grown by molecular beam epitaxy (MBE) are investigated. C-V and ICTS results are presented that clearly indicate for the first time that the GaAs surface level is unpinned in metal/fluoride/GaAs (MIS) structures. The surface potential can be moved toward the conduction band edge up to E
c-0.1 eV. The minimum interface state density is estimated to be around 1×1011 eV-1 cm-2. In contrast, strong pinning is observed for MIS diodes using (100)-oriented substrates or lattice-mismatched fluorides. The realization of unpinning and accumulation is attributed to interface coherence and dangling bond termination. The present analysis demonstrates that pinning-free GaAs MIS structures can be successfully achieved if the interface is prepared properly.
Hydrothermal Synthesis of BaBe2Si2O7
Authors: Maeda Masaki , Uehara Toshio , Hidetaka Sato Hidetaka Sato , Takuro Ikeda Takuro Ikeda
Published: February 2005

The growth conditions of BaBe2Si2O7 crystals in the hydrothermal synthesis method were investigated. Experiments were carried out to determine P-T phase diagrams and reaction phase diagrams. The optimum conditions in the present experiments were 1) pressure: 500 bar, 2) temperature: 385°C, 3) temperature gradient: 15°C, 4) KOH concentration in water: 3 mol/l, 5) baffle-opening-area ratio: 15%, and 6) growth time: 60 h. Under these growth conditions, transparent single crystals of platelet shape (0.2 mm in edge) were obtained on the ceramic seeds.
Piezoelectric Properties at Polarization Reversal Process and Coercive Force of 0-3 Composite of Polymer and Ceramic Powder Mixture of PZT and PbTiO3
Authors: Hisao Banno Hisao Banno , Kohji Ogura Kohji Ogura
Published: February 2005

Piezoelectric d constants (d
33, d
h and d
31) of 0-3 composites of polymer and ceramic powder mixture of PZT and PbTiO3 at the polarization reversal process were measured at room temperature as a function of electric field after applying a reverse poling electric field to the prepoled composite specimens. Coercive force was obtained as a reverse poling field to make the piezoelectric d constants (d
33, d
h and d
31) of the specimens zero. Coercive forces for d
33, d
31 and d
h were different for the composites of polymer and ceramic powder mixture of PZT/PbTiO3 although they were identical for those of polymer and single ceramic powder (PZT or PbTiO3). These results are discussed theoretically based on a proposed model.
Properties of Hydrophone with Porous Piezoelectric Ceramics
Authors: Arai Toru , Ayusawa Kazutoshi , Sato Housaku , Miyata Tetsuji , Kobayashi Kazutami Kawamura
Published: February 2005

We constructed a hydrophone using porous piezoelectric ceramics and conducted a detailed investigation into hydrophone sensitivity under higher pressure and its acceleration sensitivity as vibrational noise. At a pressure of 7.85 MPa, the hydrophone sensitivity of the porous piezoelectric ceramic hydrophone was some 20 dB higher than that of the piesoelectric ceramic hydrophones. The difference in acceleration sensitivity between the porous piezoelectric ceramics and the piezoelectric ceramics was extremely minor. The hydrophone sensitivity is sufficiently high to allow us to consider vibrational noise as negligible.
Low-Hysteresis Actuator of Alkoxide-Prepared Pb0.96Sr0.04(Zr0.51Ti0.49)O3
Authors: Okada Nagaya , Ishikawa Kenji , Nomura Takashi , Murakami Kenji , Fukuoka Shuichi , Nishino Naoya , Kihara Utsuo
Published: February 2005

A PZT actuator is made of small particles synthesized by an alkoxide method. The small particles are calcined at 600°C for 5 h. The calcined powders are cold-pressed under 3×107 kg/m2. The pressed bodies are sintered in air for 3 h at a temperature between 600°C to 1100°C. The grain size is estimated to be around 1 µm by SEM observations. The hysteresis in the piezoelectric strain is about 1%, which is much smaller than that in an actuator of the same composition prepared by a conventional mixed oxide method and a conventional sintering technique, typically about 10%. Pinning effects of the ferroelectric domain by the grain boundaries and the reduction of 90° domains due to the decrease of the grain size explain the low hysteresis.
A Small-Size Ultrasonic Linear Motor
Authors: Murano Junichi Toyoda
Published: February 2005

A new structure for an ultrasonic linear motor using piezoelectric actuators has been developed. The ultrasonic vibrator consists of a metal bar with two legs. The direction of the slider's movement is controlled by changing the polarity of the drive voltage of the multilayered piezoelectric actuator. Typical performance characteristics of the linear motor are a velocity of 1 m/s and a static thrust of 100 gf.
Gap Structure Multilayer Piezoelectric Actuator
Authors: Kanayama Kouichi , Mase Hiroshi , Saigoh Hiroaki , Nagayama Hiroyuki , Hiroyasu Yamaoka Hiroyasu Yamaoka , Yoshihisa Ushida Yoshihisa Ushida
Published: February 2005

A new multilayer piezoelectric actuator (MPA), in which gaps were formed at the ends of the internal electrodes, was manufactured by a cofiring method. Its high endurance has been confirmed both by a 500-million-pulse driving test and by 120 VDC voltage-applying life test for 500 hours under high humidity. Large displacement was achieved in a wide temperature range up to 135°C by using newly developed piezoelectric ceramics.
Chemical Vapour Deposition of Amorphous Silicon with Silanes for Thin Film Transistors –The Influence of the Amorphous Silicon Deposition Temperature–
Authors: Breddels Paul A. , Kanoh Hiroshi , Osamu Sugiura Osamu Sugiura , Masakiyo Matsumura Masakiyo Matsumura
Published: February 2005

Amorphous silicon films have been prepared by low pressure chemical vapour deposition of monosilane, disilane and trisilane. The deposition temperatures ranged from 385°C to 555°C. The hydrogen content in the films was approximately 3 atomic percent and the optical band-gap was 1.6∼1.7 eV. Simple inverted staggered thin-film transistors were made with thermal silicon dioxide as the gate insulator. After annealing in a hydrogen radical rich ambient the field-effect mobilities for electrons were as high as 2.0 cm2/V·s and almost independent of temperature from 385°C to 500°C. At higher temperatures the mobility decreased rapidly and was less than 0.1 cm2/V·s at 555°C. These results appeared to be independent of the source gas.
Fabrication of Fine-Grained Positive Temperature Coefficient Ceramics from Chemically Prepared Powder
Authors: Deguchi Takeshi , Sumiyama Tomoko , Yamaguchi Iwao , Igarashi Masanori Kinugasa
Published: February 2005

Fine barium titanate powders were prepared by chemical synthesis to fabricate positive temperature coefficient ceramics. The calcining condition adapted for the chemical powder was experimentally determined to be a lower temperature than that for conventional powders. Microstructure and temperature dependence of resistivity of the fired samples were examined as a function of firing temperature. Niobium ions doped at a synthesizing stage of barium titanate were homogeneously diffused into a titanium lattice at a low temperature of 1150°C, and fine-grained PTC ceramics with grain sizes of 2∼3 µm were fabricated at that temperature.
The Effect of Mn Addition on Dielectric Properties and Microstructure of BaO-Nd2O3-TiO2 Ceramics
Authors: Yamada Akira , Yoshikazu Utsumi Yoshikazu Utsumi , Hisao Watarai Hisao Watarai
Published: February 2005

The dielectric properties and microstructures were investigated in ceramics of BaO·Nd2O3·5TiO2 to which various amounts of Mn were added. Although the behavior of the dielectric constant was independent of additional Mn, the temperature coefficient was improved considerably. The phases which were observed in these ceramics were characterized by means of electron probe microanalysis (EPMA) and X-ray diffraction method (XRD) in microareas. The shapes and areas of the phases varied with Mn content. The dielectric properties seemed to be mainly related to the properties of the matrix phase.
Dielectric Properties of Double-Oxide Ceramics in the System Ln2O3-TiO2 (Ln=La, Nd and Sm)
Authors: Takahashi Junichi , Kageyama Keisuke , Hayashi Takashi
Published: February 2005

A systematic investigation on dielectric property changes with compositional variation was carried out for binary compound ceramics which were fabricated by the chemical powder preparation method in the identical systems Ln2O3-TiO2 (Ln=La, Nd and Sm). The temperature coefficient of permittivity (TCεr) for those dielectrics was found to show a considerable deviation from a simple relation of TCεr=-εr·αL. It also found that the solubility limits of Sm3+ into the Nd3+ lattice were greatly extended in the binary compounds up to ∼80 or 90 mol%. Different dielectric property changes in the solid solutions with lanthanide substitution (La→Nd→Sm) were discussed on the basis of the different contributions of substituted ions to the polarization.
Simulations of Ferroelectric Characteristics Using a One-Dimensional Lattice Model
Authors: Omura Masayoshi , Ishibashi Hideo Adachi
Published: February 2005

Simulations of ferroelectric characteristics have been carried out using a one-dimensional model of polarization reversal in ferroelectrics in which latent nuclei are randomly distributed. Characteristics studied include pulse response, P-e hysteresis loops, differential electric susceptibility versus applied field (dP/de-e curves) and switching current versus applied field (i-e curves) in ferroelectrics. Results of simulations show that P-e hysteresis loops, dP/de-e curves and i-e curves depend on the viscosity which causes the delay in motion of the individual dipole moment, the interaction between neighboring atoms and the applied field.
Patterned Bi-Sr-Ca-Cu-O Films on Sr2Ca2Cu4Oy Substrates by Surface Diffusion of Metallic Bismuth
Authors: Kiejin Lee Kiejin Lee , Gwangseo Park Gwangseo Park
Published: February 2005

A technique which combines the fabrication and patterning of films 1 µm in thickness of the high T
c superconducting Bi2Sr2Ca1Cu2O
y
has been developed. Patterns are generated directly on the Sr-Ca-Cu-O (Sr:Ca:Cu=2:2:4) ceramic substrate using thermal evaporation of metallic bismuth through a mask followed by heat treatment at 830°C for 1 minute in air. Resistivity measurements for a patterned film show an onset to the superconducting state occurring at 85 K with zero resistivity at 79 K.
Crystal Orientation of BiSrCaCuO (11n) Thin Films Determined by X-ray Asymmetric Reflection
Authors: Kataoka Masayuki , Kuroda Ken'ichi , Tanimura Junji , Wada Osamu , Kojima Kazuyoshi , Takami Tetsuya , Hamanaka Koichi , Tetsuo Ogama Tetsuo Ogama
Published: February 2005

Tilt angles of the c-axes from the substrate surface of BiSrCaCuO (11n) thin films were precisely measured using a diffractometer method with X-ray asymmetric reflection. The preferred orientation was determined from the measurement of these angles. The high T
c phase composition film formed on a SrTiO3 (110) substrate had two tilt angles of 45.24° and 45.04°, and their preferred orientation was (1110), while the low T
c phase composition film had a tilt angle of 41.2° and the preferred orientation was (117). We also performed a precise measurement for a low T
c phase composition film formed on a SrTiO3 (110) 5° off substrate and found that its tilt angle was 45.4°.
Anion Vacancy States in the Insulator-ZnS Interface
Authors: Sohn Sang Ho , Hyun Dong Geul , Noma Mikihiro , Shinichi Hosomi Shinichi Hosomi , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

The ground state energy of a trapped electron in an anion vacancy near the insulator-ZnS interface is estimated in a point-ion lattice approximation including an interface image potential. Assuming the (111) interface to be the halfly intersected plane of a Zn-S bond growned to the (111) crystal orientation and the insulator as a classical dielectric medium, the interface Madelung constant which can be used in a point-ion lattice approximation is calculated as a function of the position of an anion vacancy from the interface and the permittivity of insulator by the Evjen method. Taking the appropriate value 1.033 for the effective charge, the estimation shows the ground state energy levels of anion vacancies whose positions are in the 1st and 3rd atomic layers from the interface arise in the range of 1.18±0.3∼1.55±0.3 eV below the lowest conduction band whereas, in the 2nd and 4th atomic layers, of 1.51±0.3∼2.46±0.3 eV.
Correlation Between Bulk Orderings and Anchoring Structures of Liquid Crystals Studied by Scanning Tunneling Microscopy
Authors: Iwakabe Yasushi , Hara Masahiko , Kondo Katumi , Tochigi Kenji , Mukoh Akio , Yamada Akira , Garito Anthony F. , Sasabe Hiroyuki
Published: February 2005

The anchoring structures of a homologous series of liquid crystals, n-alkylcyanobiphenyls (mCBs: m=7-12), on molybdenum disulfide (MoS2) are directly observed by scanning tunneling microscopy (STM) in order to analyze the alignment mechanism of liquid crystals. Based on highly reproducible STM images, the anchoring structures of mCBs are clearly divided into two categories, a monolayer (single-row) type (7CB, 8CB, 9CB and 11CB) and a bilayer (double-row) type (10CB and 12CB). Here we propose the monolayer is the anchoring structure of a nematic phase, while the bilayer is the anchoring structure of a smectic phase. The correlation between bulk phase orderings and anchoring structures of liquid crystals is discussed from the viewpoint of surface-phase formation for the mCBs and different solid substrates.
Structure of Amorphous SiNx:H Studied by Photoemission and Infrared Absorption
Authors: Ikurou Umezu Ikurou Umezu , Keiji Maeda Keiji Maeda
Published: February 2005

We present an X-ray photoemission (XPS) and infrared absorption (IR) study of hydrogenated amorphous silicon-nitride (SiN
x
:H) films which were prepared by plasma decomposition of SiH4 and NH3. Both Si 2p (XPS) and Si-H (IR) peaks are decomposed to contributions from Si-centered tetrahedrons. The peak shift in both XPS and IR can be divided into two compositional regions: below and above x=1.0. Peak energy increases gradually with x until it reaches 1.0. For x>1.0, the increment of peak shift is small. There are no particular features at around stoichiometric composition, x=1.33. The kink point at around x=1.0 and maximum composition of x=1.7 are discussed in terms of Si-centered tetrahedrons. The Si-Si bond, which decreased with increasing source gas ratio R (R=[NH3]/[SiH4]), did not disappear even though a large gas ratio R was given. This feature is important in accounting for the structure of the films.
Preparation of Metallic W Film by H2-Reduction of WO3 Electron-Resist Film
Authors: Baba Mamoru , Kiyoshi Ohta Kiyoshi Ohta , Toshio Ikeda Toshio Ikeda
Published: February 2005

A metallic W film was prepared from a WO3 electron-resist film by H2-reduction above 600°C, and the characteristics of the reduced W film have been investigated. It was found that the electric resistivity of the film decreases and the size of the constituent grains increases with increasing reduction temperature, while the film thickness decreases down to about 40% of the initial thickness above 600°C. The reduced W film had a discontinuous structure with many cracks and had random crystal orientation of the grains. A fine pattern of metallic W with high contrast and no crack was fabricated by the H2-reduction of a fine pattern of the WO3 electron resist.
Transient Temperature Profiles in Silicon Films during Pulsed Laser Annealing
Authors: Shimizu Kazuhiro , Imai Shigeru , Osamu Sugiura Osamu Sugiura , Masakiyo Matsumura Masakiyo Matsumura
Published: February 2005

Transient temperature profiles have been studied theoretically in silicon film heated by a single shot of a laser light pulse for several substrate structures. The molten silicon region is very shallow and disappears completely within a few tens of ns in (poly)crystalline silicon. It exists for more than a few hundred ns in amorphous silicon and also in silicon films on an oxide substrate. In silicon/oxide/conductive-substrate structures, the sustaining time of the molten silicon region is shortened by thinning the oxide film. Numerical results are compared with approximate relations derived from a simple physical picture.
Fine Epitaxial Growth of Monolayer-Stepped GaInAs/InP Quantum Wells by Metalorganic Molecular Beam Epitaxy
Authors: Hideo Kawanishi Hideo Kawanishi , Hirokazu Ikeda Hirokazu Ikeda
Published: February 2005

A possibility of monolayer-stepped GaInAs/InP multiple quantum wells was demonstrated by metalorganic molecular beam epitaxy (MOMBE). The 4.2 K PL spectra of these structures showed quantized energy shift which increased stepwise with decreasing growth time of the GaInAs well. The maximum energy shift was 0.467 eV for GaInAs growth time of 3 s, and the energy shift corresponded to 2-monolayer GaInAs quantum wells, by contrast with the calculated energy shift.
Theory of Relaxation of Frozen Defects in Doped Hydrogenated Amorphous Silicon
Authors: Yukio Osaka Yukio Osaka
Published: February 2005

The equilibration rate of frozen defects in phosphorus-doped hydrogenated amorphous silicon is described by the stretched-exponential time dependence exp (-(t/τ)β), where 0<β<1. Kakalios and Jackson have explained this phenomenon based on the assumptions that the neck hydrogen diffusion process to eliminate frozen defects is the diffusion between the interstitial sites, and the diffusion constant is dispersive in time, due to the distribution of hydrogen trapping sites on weak Si-Si bonds. In this paper, these assumptions are criticized and an alternative explanation is proposed based on the assumption that the neck hydrogen diffusion process is the jump process of hydrogen from the Si-H bond site into the interstitial site.
Electroluminescence in Perylene-Doped Anthracene Films: The Ambient Gas Effect in the Emission Process
Authors: Okii Hironori , Harada Ayako , Sunaga Kenji , Ohba Hiroshi Hara
Published: February 2005

Using an indium-tin-oxide (ITO) electrode and a powdered graphite electrode, electroluminescence (EL) in perylene-doped anthracene films was investigated under AC fields. In nitrogen ambient, the emission components consisted of both the recombination radiation by the injected charge carriers and the secondary emission by the glow discharge at the interface between the powdered graphite electrode and the film. Bright blue emission, which was clearly visible under the usual room lighting, was observed at the applied voltage of 100 V (50 Hz). The luminance of 110 cd/m2 and the radiant emittance of 0.5 mW/cm2 were obtained. The power conversion efficiency was approximately 0.03%(W/W).
Beam Profile Measurement of Vacuum Ultraviolet Lasers with Photostimulable Phosphor
Authors: Katto Masahito , Kurosawa Kou , Sasaki Wataru , Takigawa Yasuo , Masahiro Okuda Masahiro Okuda
Published: February 2005

The linear response of photostimulable phosphor material (BaFBr:Eu2+, imaging plate: IP) is confirmed for ArF and Ar2 excimer laser pulses whose wavelength and duration are 193 nm and 10 ns, and 126 nm and 5 ns, respectively. We demonstrate two-dimensional image recording on the IP with vacuum ultraviolet laser beams.
Anderson Localization and Universal Conductance Fluctuations with Spin-Orbit Interactions in δ-Doped GaAs Films and Wires
Authors: Taniguchi Hiroaki , Takahara Junichi , Takagaki Yukihiko , Gamo Kenji , Namba Susumu , Takaoka Sadao , Murase Kazuo
Published: February 2005

Weak localization and universal conductance fluctuations in Si-doped GaAs films and wires are investigated. A positive magnetoresistance due to antilocalization is observed in films of high carrier density. It disappears when the substrate is irradiated by an Ar ion beam. The spin-orbit scattering time τso is strongly dependent on the carrier density n
s. The ratio of the elastic scattering time τ0 to τso has a power-law dependence of (τ0/τso)\proptn
s
-2.9. The amplitude of the conductance fluctuations are discussed in terms of the phase breaking time deduced ffom the weak localization.
Magnetic Properties of Fe-Cu and Fe-P Electrodeposited Alumite Films
Authors: Daimon Hideo , Kitakami Osamu , Osamu Inagoya Osamu Inagoya , Akito Sakemoto Akito Sakemoto
Published: February 2005

Cu and P were examined as additives to decrease the perpendicular coercivity of Fe-electrodeposited alumite film. Addition of Cu and P to the Fe particles decreased the coercivity to less than 1000 Oe, and P was a more effective additive than Cu in decreasing the coercivity. In the Fe-Cu system, Cu atoms are considered to be dispersed uniformly in the Fe matrix because no drastic changes in the morphological, crystallographical and magnetic properties were observed. In the Fe-P system, P is considered to be precipitated between Fe microcrystallites because the crystallographic continuity of the Fe particles was deteriorated, and distinct microstructure was observed in the Fe particles when P was added. Drastic decrease in the coercivity of Fe-electrodeposited alumite film is considered to be mainly due to the discontinuity of the Fe particles in a system containing P.
The Defect Characterization of Heavily Si-doped Molecular Beam Epitaxy-Grown GaAs by the Monoenergetic Positron Method
Authors: Wei Long , Cho Yang-Koo , Dosho Chisei , Toshikazu Kurihara Toshikazu Kurihara , Shoichiro Tanigawa Shoichiro Tanigawa
Published: February 2005

Monoenergetic (100 eV-30 keV) positrons were used as a defect probe for heavily Si-doped GaAs with a thickness of 300nm grown by molecular beam epitaxy (MBE). The Doppler broadening parameters showed quite different profiles for two kinds of samples prepared at 450°C and 650°C, respectively. It is indicated that the surface states are quite different for preserved GaAs and the as-etched one. The high growth temperature introduced point defects with a higher concentration. It is assumed that the defect type of X in the Si-X complex should be a gallium vacancy or a vacancy complex which suppresses the free carrier concentration in heavily Si-doped GaAs.
Microscopic X-ray Photoelectron Spectroscopy Using a Wolter Type X-ray Mirror
Authors: Ninomiya Ken , Hasegawa Masaki , Aoki Sadao , Keizo Suzuki Keizo Suzuki
Published: February 2005

The possibility of µ-XPS (microscopic X-ray photoelectron spectroscopy) analysis using a focused X-ray has been demonstrated in a synchrotron radiation beamline. A Wolter type mirror produced a focused 150 eV X-ray with a beam size ranging from 23(sagittal)×36(meridional) µm2 to 1.4×20 µm2. The meridional beam size was always larger than the sagittal one due to the figure displacement of the mirror surface. When the focused beam was used for µ-XPS analysis of Si and Al samples, the Si(2p) and Al (2p) XPS spectra indicating native oxides on the sample surface could be clearly observed with energy resolutions of 1.7 to 2.8 eV. For practical µ-XPS analysis in the micrometer to sub-micrometer range, the fabrication accuracy of the mirror should be improved and the photon flux to the sample surface has to be increased.
Topography of the Ar+-Sputtered Si Surface
Authors: Chini Tapas Kumar , Bhattacharyya Satya Ranjan , Debabrata Ghose Debabrata Ghose , Debashis Basu Debashis Basu
Published: February 2005

The topography of Si surfaces after 30 keV Ar+ bombardment at oblique incidence is studied with and without seeding of high-melting-point W atoms. In both cases, the sputtered Si surfaces exhibit intense corrugated terrace morphology, the dimension of which increases with increasing ion dose. Also, a few cones characteristics for oblique ion incidence are formed and the seed material seems to have no influence on their development.
Depth Profiling of Hydrogen Implanted into Magnetic Bubble Garnet Films Using the 1H(15N, αγ)12C Reaction
Authors: Byoung-gon Yu , Imura Eiichi Arai
Published: February 2005

Using the 1H(15N, αγ)12C reaction, we have realized a high-resolution profiling of depth distribution of hydrogen implanted into the magnetic bubble garnet (MBG) films. The experimental results are compared with predictions from the Monte-Carlo simulation code (TRIM85). We have investigated two phenomena by observing the thermal behavior of hydrogen in the MBG films: 1) the efficiency of the SiO2 layer deposited onto the MBG film to suppress the hydrogen out-diffusion and 2) the effect of plasma exposure on MBG films that have been predamaged by Ne irradiation. We have obtained useful knowledge to achieve a large anisotropy field change that plays an important role for the production of the magnetic bubble memory devices with high storage density. New features are reported to understand the thermal behavior of hydrogen in the MBG films.
Estimation of Frequency Accuracy and Stability in a Diode Laser-Pumped Rubidium Beam Atomic Clock Using a Novel Microwave Resonant Method
Authors: Hiroyuki Furuta Hiroyuki Furuta , Motoichi Ohtsu Motoichi Ohtsu
Published: February 2005

Experiments on a diode laser-pumped rubidium (Rb) beam atomic clock are carried out. A novel microwave resonance method (HORR) with a conventional cylindrical cavity is used. On the basis of the experimental results, the expected frequency accuracy of 1.4×10-12 is theoretically estimated with this clock. A frequency stability as high as 7.8×10-13 τ-1/2 is also estimated.
Temperature Dependence of Electron-Beam-Induced Current Image of Semi-Insulating Undoped Liquid-Encapsulated Czochralski GaAs
Authors: Yozo Tokumaru Yozo Tokumaru
Published: February 2005

Semi-insulating undoped liquid-encapsulated Czochralski GaAs was investigated by the electron-beam-induced current method. It is found that defects which cannot be observed at room temperature become visible when the temperature is raised to about 350 K. A simple theoretical consideration on this experimental result was performed.
Soft X-Ray Reduction Lithography Using Multilayer Mirrors
Authors: Kinoshita Hiroo , Takenaka Kenji Kurihara
Published: February 2005

A feasibility study on soft X-ray reduction lithography using multilayer mirrors has been performed. An exposure wavelength range of 80 to 110 Å is proposed as the most suitable with current technology considering the optic design, the reflectivity of the multilayer, and the resist characteristics. With the aim of providing multilayers with very sharp interfaces and high reflectivity, we attempted to improve the multilayer fabrication process, with one result being the fabrication of an amorphous Mo/Si multilayer, by controlling substrate temperature. Experimental results of 0.2-µm pattern replication using a multilayer reflection mask are presented.
Electron Beam Lithography-Tools and Applications
Authors: Fritz J. Hohn Fritz J. Hohn
Published: February 2005

This paper describes the categories of electron beam lithography tools which to us seem to be of most importance. The first is a thermal field emission source gaussian round beam system. The overall performance to accomplish 0.05 µm imaging capability is presented. The second is a finely tuned variably shaped beam system which has the capability of delineating 0.15 µm dimensions at moderate throughput. Both systems have been integrated into a lithography sector with resist and process engineering as an integral part. We have applied this complete lithography sector to a variety of device runs ranging from 0.25 µm fully scaled all e-beam lithography, partially scaled mixed with optics, to mixed e-beam with e-beam lithography for less than 0.1 µm dimensions. Several non-direct write applications have been performed, such as the fabrication of 0.15 µm X-ray test masks and also phase shifting masks, for which we need the accuracy and registration capability of a high resolution direct write tool.
Electron Beam Block Exposure
Authors: Yasuda Hiroshi , Sakamoto Kiichi , Akio Yamada Akio Yamada , Ken-ichi Kawashima Ken-ichi Kawashima
Published: February 2005

A new exposure technique called block exposure was examined in order to increase the throughput of direct writing of memory LSI devices using an electron beam. With this technique, an electron beam is projected to a block of aperture patterns in the stencil mask to change the beam shape. Frequently used LSI pattern components are defined as blocks to be reused during the exposure. Patterns that are rarely used are exposed by using a variable-shape beam. With the demagnification ratio of one percent, masks are easy to fabricate and very reliable. The patterns with a 0.13-µm minimum feature size are well projected on a single-layer resist. With block exposure, any shape can be accurately transferred irrespective of the pattern shape or size. The throughput of about ten 8-in wafers per hour is estimated for several pattern layers of a 64-Mbit dynamic random-access memory (DRAM).
Determination of Acid Diffusion in Chemical Amplification Positive Deep-UV Resists
Authors: Schlegel Leo , Ueno Takumi , Nobuaki Hayashi Nobuaki Hayashi , Takao Iwayanagi Takao Iwayanagi
Published: February 2005

The diffusion of photogenerated acid in chemical amplification resist systems was examined by a newly developed method which allowed an estimation of the diffusion range by simple means. The acid mobility was investigated for various process conditions. It was found that prebake and post-exposure-bake conditions have strong influence on the mobility of acid. The diffusion range of acid is much larger than values estimated from the catalytic volume. Large differences in diffusion characteristics were found for two different resist systems. The diffusion of various sulfonic acids decreased strongly with increasing molecule size.
Dependence of Electron Cyclotron Resonance Plasma Characteristics on Magnetic Field Profiles
Authors: Nakamura Seiji Samukawa
Published: February 2005

Electron cyclotron resonance (ECR) plasma generation is influenced by the magnetic field profiles in ECR plasma. When an 875 G equimagnetic field and magnetic field gradient are nonuniform, the nonuniform plasma is generated around the ECR position (875 G position). Uneven plasma discharge causes ion acceleration and disturbs the ion flight directions due to the potential differences in ECR plasma. Therefore, a uniform magnetic field gradient at the ECR position and the flat 875 G equimagnetic field profile are necessary to achieve a precise pattern transfer without microloading effects.
400 kHz Radio-Frequency Biased Electron Cyclotron Resonance Position Etching
Authors: Seiji Samukawa Seiji Samukawa
Published: February 2005

A radio frequency (RF) biased electron cyclotron resonance plasma etching technology has been developed to realize efficient ion acceleration in high-density, uniform ECR plasma. 400 kHz RF-biased ECR position etching can achieve uniform and efficient ion acceleration, and prevents charge build-up damage to the thin gate oxide. Conversely, at frequency of more than 700 kHz, the plasma is disturbed by the local discharge between the grounded chamber wall and the substrate holder. Then, the gate oxide breakdown is caused by the stored charge due to the potential difference on the substrate.
Vacuum Ultraviolet Laser-Induced Surface Alteration of SiO2
Authors: Kurosawa Kou , Takigawa Yasuo , Sasaki Wataru , Katto Masahito , Inoue Yoshihide
Published: February 2005

Intense vacuum ultraviolet laser radiation is generated from rare gas excimer lasers. 9.8 eV photons from an argon excimer laser change surfaces of SiO2 to silicon. The reaction proceeds without the aid of reactive gas or solution and is thus called the “superdry process”. 9.8 eV photons create excitons via an efficient one-photon absorption process, and then these high-density excitons induce bond-breaking between Si and O.
Silicon Oxide Deposition into a Hole Using a Focused Ion Beam
Authors: Nakamura Hiroko , Komano Haruki , Norimatu Kenji , Yoshio Gomei Yoshio Gomei
Published: February 2005

Focused ion beam (FIB)-induced deposition of silicon oxide in terms of filling a hole is reported. It was found that a vacant space was formed when an ion beam was simply scanned through the hole area. To investigate the mechanism to form the vacancy, deposition on the sample, which has a step with a height of 0.8 µm, was carried out by using a Si2+ and a Be2+ ion beam. An extruded deposit resembling a pent roof was observed from the step ridge. The mechanism of the pent roof growth on the steplike sample was considered and the vacancy formation in the hole can be explained by the same mechanism. For silicon oxide, the high growth rate of the extruded deposit is thought to be the key to the vacancy formation. A useful way is proposed to fill the hole with silicon oxide with almost no vacancy.
Low-Energy Ion-Beam Irradiation Effects on Two-Dimensional Electron Gas in Modulation-Doped AlGaAs/GaAs Heterostructure
Authors: Yamazawa Masahiro , Matsumoto Toshiharu , Taniguchi Hiroaki , Sakamoto Toshitugu , Takagaki Yukihiko , Yuba Yoshihiko , Takaoka Sadao , Gamo Kenji , Murase Kazuo , Namba Susumu
Published: February 2005

Transport properties of a 2 dimensional electron gas (2DEG) system at low temperature have been investigated from Hall effect and magnetoresistance measurements to reveal the effects of irradiation-induced defects. Ar ions were irradiated at an energy between 20 and 100 eV with a dose up to 1016/cm2. The decreases in low temperature mobility and scattering time determined from magnetoresistance oscillation are observed in the 20 eV ion-irradiated sample where sheet carrier concentration is not affected. The induced defects are sensitively detected from the change in mobility in high-quality samples even for lightly damaged cases. A nearly complete recovery of mobility obtained after 400°C annealing suggests that defects induced by low-energy irradiation readily disappear.
Fabrication of 0.1 µm Complementary Metal-Oxide-Semiconductor Devices
Authors: Yoshimura Toshiyuki , Aoki Masaaki , Tatsuya Ishii Tatsuya Ishii , Shinji Okazaki Shinji Okazaki
Published: February 2005

CMOS devices with very short poly-Si gates of 0.1 µm are fabricated by electron beam lithography. A multilayer structure of a thin (160 nm) resist combined with a thin (15 nm) oxide layer above the poly-Si layer (100 nm) is introduced to define small patterns for the gates. The fabricated 0.1 µm devices with low-impurity-channel transistor (LICT) structures achieve normal I-V characteristics and fairly good subthreshold characteristics both at room and low temperatures.
Measurement of Sidewall Roughness by Scanning Tunneling Microscope
Authors: Sato Akinobu , Tsukamoto Yuji , Baba Masakazu , Matsui Shinji
Published: February 2005

A scanning tunneling microscope (STM) is a highly effective tool for observing a microfabricated pattern. However, it is difficult to measure sidewall roughness using a conventional STM because of the restriction of the tip shape and one-dimensional servo system. The main objective of this study is to develop a sidewall roughness characterization tool. The electron-beam deposition method is applied to preparing a novel STM tip shape. A two-dimensional servo system, with a subnano-vibration mode to provide vibrations below 1 nm for x- and z-directions to a tip during scanning, has been developed for sidewall roughness measurement.