bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Deposition Parameters on Laser Damage Threshold of 355-nm Scandium Oxide-Magnesium Fluoride High-Reflector Coatings
Authors: Tamura Shigeharu , Kimura Saburo , Sato Yoshiyuki , Motokoshi Shinji , Yoshida Hidetsugu , Yoshida Kunio
Published: February 2005

The experimental results of the laser-induced damage thresholds of Sc2O3/MgF2 high-reflector (HR) coatings for an UV (355-nm, 0.4-ns) pulsed laser have been shown. The deposition parameters have been optimized by use of 5-layer semitransparent coatings, with the distribution of the standing-wave electric-field being similar to that of the HR coatings. For the 5-layer coatings, their threshold values were found to depend on the deposition parameters and the absorption; the coatings with low absorption had high damage threshold. Based on these results, the HR coatings were fabricated on fused silica, BK7 and sapphire substrates, and their thresholds have been measured. The highest average threshold on each substrate have been 3.5, 4.2 and 3.8 J/cm2, respectively.
Luminescence and Energy Levels of Mn2+ in LnMB5O10 (Ln=La, Gd and Y; M=Mg, Zn and Cd)
Authors: Jagannathan R. , Manoharan S. P. , Rao R. P. , Kutty T. R. N.
Published: February 2005

Luminescence of Bi3+ or/and Mn2+ in LnMB5O10 system of phosphor has been studied. Bi3+ in LnMB5O10 leads to two types of emissions, viz. emission due to (i) Bi3+ isolated centres and (ii) Bi3+ clusters. In LaMB5O10, Bi3+ emission can cover longer distances (25 Å) for resonant transfer. In LaMgB5O10, replacement of Mg by Cd or Zn leads to considerable enhancement in Mn2+ emission intensity. In the case of GdMB5O10 system, this substitution leads to significant increase in the Gd3+→Mn2+ energy transfer rate. Energy levels of Mn2+ in LaMB5O10 and crystal field parameters (for the case of cubic field) have been calculated and the results based on these are discussed.
CaS:Eu, F Thin Film Electroluminescent Devices Prepared by RF Sputtering with Hydrogen-Argon Mixture Gas
Authors: Aozasa Masao , Kato Ken-ichi , Nakayama Tadaaki , Ando Keiichi
Published: February 2005

CaS:Eu, F electroluminescent devices with high luminous characteristics were prepared by rf-magnetron sputtering. The film quality of the active layer was improved by preparation with hydrogen-added argon sputtering gas. The active layer thus prepared has preferential (220) orientation and enhanced columnar structure with reduced incorporated fluorine atoms. The environment around the luminescent center was also affected to some extent by hydrogen addition to the argon sputtering gas. A device with the luminance of 250 cd/m2 and the luminous efficiency of 0.2 lm/W at a 1 kHz sine wave operation was prepared.
Temperature-Independent Internal Bias Field in L-α-Alanine-Doped Triglycine Sulfate Crystal
Authors: Nakatani Noriyuki
Published: February 2005

The temperature dependence of the internal bias field in L-α-alanine-doped triglycine sulfate (LATGS) crystal was investigated by P-E hysteresis loops and i-E curves under application of a triangular field. We could not observe any changes in the internal bias field at the Curie point. The internal bias field is almost independent of the temperature from 25 to 55°C. The strict equivalence between the internal bias field and the external applied field is demonstrated by the phenomenological consideration.
Behaviour of Ionic Effects on Response Times of Surface Stabilized Ferroelectric Liquid Crystal Devices
Authors: Saxena Kanchan , Bawa S. S. , Biradar A. M. , Chandra Subhas , Rup Raj
Published: February 2005

The response time measurements of a new room temperature ferroelectric liquid crystal have been done by using the field reversal method. The response time has been found to be frequency dependent and decreases considerably at frequencies above 10 kHz. The temperature dependence of response time showed the presence of ionic effects as is evident from the appearance of the second peak in the current response to an applied bipolar pulse.
A Simple Model for Pretilted Nematic Liquid Crystal Medium and Its Torsional Surface Coupling Strength
Authors: Sugiyama Takashi , Kuniyasu Seiyu , Seo Daeshik , Fukuro Hiroyoshi , Kobayashi Shunsuke
Published: February 2005

An explanation for the mechanism generating a pretilted nematic liquid crystal conformation aligned on rubbed alkylbranched-polyimide layers is given based on a steric interaction model. An analytical calculation using this model was shown to agree fairly well with the data of torsional coupling strength obtained in this work.
Relaxation and Aggregation Studies of Impurity-Vacancy Dipoles by Decomposition of Complex ITC Bands in KCl:Cd2+
Authors: Kawano Katsuyasu , Matsumoto Yukio , Nakata Rouhei , Sumita Minoru
Published: February 2005

Dipole relaxation and aggregation were investigated on Cd2+ ion doped into KCl crystal using an ionic thermocurrent (ITC) method in the temperature range from 180 to 280 K. Two ITC bands with the activation energies (E
R) of 0.57 and 0.50 eV were observed, in which the polarization temperatures were varied at 229, 232 and 235 K. The first intense band was attributed to the Cd2+–OH- dipole, in which OH- ion was probably formed by the decomposition of a water molecule intermixed during the crystal growth. After cleaning the second band, two new bands with E
R=0.64 and 0.52 eV appeared and were regarded as the Cd2+-vacancy dipole and its aggregate, respectively. Dipole relaxation and aggregation processes were discussed including the aggregate models.
Influence of Exposure to CO, CO2 and H2O on the Stability of GaAs Photocathodes
Authors: Wada Tatsuaki , Nitta Toshiyuki , Nomura Takashi , Miyao Masahiro , Hagino Minoru
Published: February 2005

The influence of CO, CO2 and H2O gases on the stability of negative-electron-affinity (NEA) GaAs photocathodes during operation is investigated in the present work. We have found that exposure both to H2O and CO2 decreases the photocurrent of the photocathode. However, exposure to CO, which is known as a harmful gas to various photocathodes, has little effect on the photocathode stability. Furthermore, the effects of these gases on the restoration of the photocurrent by additional cesium deposition are investigated. These results are discussed with regard to the Cs/O activation layer which plays an important role in NEA GaAs photocathodes.
Cu Electromigration Effect on Cu2-xSe Film Properties
Authors: Ema Yoshinori
Published: February 2005

Electrical and optical properties and structural change of vacuum-deposited Cu2-x
Se films due to electromigration have been investigated using Au/Cu2-x
Se/Cu(or Au) samples. DC voltages were applied to them to cause Cu migration. Under the bias in which the polarity of the Cu electrode was negative, Cu in Cu2-x
Se films decreased gradually, which increased Cu vacancies and carrier density. Under the bias in which the Cu electrode was positive, Cu ions were supplied to Cu2-x
Se films and Cu vacancies were filled, which decreased carrier density and changed the film structure to α-Cu2-x
Se. Small blocks of Cu accumulation were formed at the negative electrode edge.
Elastic Cross Section for Low-Energy-Proton Scattering in Copper with the Method of Partial Waves
Authors: Ohya Kaoru , Mori Ichiro
Published: February 2005

The differential cross section and the mean free path for the elastic collision of protons in a copper from the Fermi energy to the keV energy are calculated using the method of partial waves and the muffin-tin potential. For keV energies, the differential cross section is smaller than that with the Hartree-Fock-Slater single atom potential only for very small scattering angles of less than several degrees, and agrees with it for almost all the angles. The mean free path is close to the average atomic distance in copper and depends only slightly on primary proton energy from the Fermi energy to 5 keV, while the mean free path with the Hartree-Fock-Slater potential becomes much smaller than the atomic distance.
Influence of Water on Photochemical Reaction of Positive-Type Photoresist
Authors: Shibayama Yuko , Saito Masakatsu
Published: February 2005

Water content in a positive-type photoresist film has an important role in the photochemical reaction. We have studied how the water content influences the photochemical reaction of a positive-type photoresist. To proceed the reaction, a water supply was required for the positive-type resist film. This phenomenon is remarkably observed in the case of a thick film. The water usually had to be supplied by the moisture in the atmosphere by diffusion on the thin film. Even on a thick resist film, completeness of the reaction was obtained by some treatment of water absorption. By introducing a sufficicient amount of water into a resist film for the reaction while keeping it in air for a long time or soaking it in a water bath, a patterning of the thick resist film was accomplished.
Laboratory EXAFS by Fluorescence Detection
Authors: Tohji Kazuyuki , Mizushima Takanori , Udagawa Yasuo
Published: February 2005

It is demonstrated that a slight modification of a laboratory EXAFS (extended X-ray absorption fine structure) spectrometer for fluorescence detection can greatly lower the limit of dilution. It can also extend samples studied to thin films on X-ray opaque substrates. Basically the system consists of a laboratory EXAFS spectrometer eguipped with two NaI scintillation counters combined with filters, and an SSD (solid state detector). Optimum experimental conditions are chosen by monitoring the output of the SSD, and then scintillation counters are used for measurements by making use of the large aperture. The performance of this system was tested by dilute aqueous solutions of Fe(NO3)3, 1000 and 5000 A thick iron film deposited on glass substrates, a 6 mM solution of octaethylporphyrin iron (III) chloride (Fe(OEP)Cl).
Minimization of X-Ray Mask Distortion by Two-Dimensional Finite Element Method Simulation
Authors: Kishimoto Akihiko , Kuniyoshi Shinji , Saito Naoto , Soga Takashi , Mochiji Kozo , Kimura Takeshi
Published: February 2005

X-ray mask distortion caused by absorber stress is quantitatively analyzed by using two-dimensional simulation. Simulated results successfully predict the mask pattern distortion in practical mask structures. A square mask window is better than a circular one because the distortion for square windows can be minimized by reducing the pattern length. In addition, it is found that the maximum distortion is virtually the same regardless of the number of LSI chips within the square window mask.
Layer-By-Layer Controlled Digital Etching by Means of an Electron-Beam-Excited Plasma System
Authors: Meguro Takashi , Ishii Masashi , Kodama Hirokazu , Hamagaki Manabu , Hara Tamio , Yamamoto Yasuhiro , Aoyagi Yoshinobu
Published: February 2005

Characteristics o digital etching using an electron-beam-excited plasma system in GaAs are reported. In digital etching, etchant gas pulses and Ar ions are sequentially impinged onto the substrate surface to be etched. When the energy of Ar ion is -17 eV, etch rates which correspond to the 0.5 monolayer (ML) per cycle of GaAs (0.142 nm) are obtained between 0.3 and 0.5 seconds of Cl2 feed time by using Cl radicals as etchants. With these etching parameters, a rectangular cross-sectional etch profile with smooth surface is obtained. Damages induced in digital etching was characterized by current-voltage measurement of the diode fabricated after the etching.
Roles of Ions and Radicals in Silicon Oxide Etching
Authors: Ikegami Naokatsu , Ozawa Nobuo , Miyakawa Yasuhiro , Konishi Mamoru , Kanamori Jun
Published: February 2005

Thermally stimulated desorption and X-ray photoelectron spectroscopy were used to study the adsorptive condition of reactive-ion-etched SiO2 and PSG surfaces. Its relationship to the different reactivity between SiO2 and PSG under the condition of highly polymerized fluorocarbon plasma was discussed. The reaction process of radicals under the thermally excited condition was also investigated in a microwave-excited downstream reactor. The C, F molecules which covered the oxide surfaces as etching species during RIE were found to be chemisorbed, and as residues, they were adsorbed weakly. It was also found that oxygen atoms have the effect of decreasing the activation energy of the spontaneous reaction with the oxide surfaces in the fluorocarbon plasma.
Experimental and Theoretical Study of the Charge Build-Up in an ECR Etcher
Authors: Namura Takashi , Okada Hiroyuki , Naitoh Yasushi , Todokoro Yoshihiro , Inoue Morio
Published: February 2005

The charge build-up in an electron cyclotron resonance (ECR) etcher has been studied experimentally and theoretically. The experimental results show that the charge build-up profiles of the wafer are convex and positive, and are detected only when the RF bias exists. We have derived a simplified equivalent circuit model for the wafer in an ECR etcher. The charge build-up profile predicted with the simplified equivalent circuit model shows a good agreement with the experimental results. It is concluded that the variation of plasma potential caused by the radial RF current across the magnetic field results in the charge build-up.
Effect of In Impurity on the Electrical Properties of Amorphous Se80Te20
Authors: Tripathi S. K. , Arora R. , Kumar A.
Published: February 2005

Temperature and intensity dependence of photoconductivity (σph) is studied in vacuum evaporated thin films of Se80Te20-x
In
x
where x=0, 0.5 and 10 with a view to determining the effect of In impurity on the photoconductive behaviour of a binary amorphous Se80Te20 alloy. Temperature dependence of dark conductivity (σd) is also studied and it is observed that dark conductivity increases and activation energy decreases with the addition of In in binary Se80Te20 alloy. σph also increases upon In incorporation. However, photosensitivity (σph/σd) decreases with an increase in In concentration. The results are explained in terms of the increase in the defect density on In incorporation in the Se80Te20 binary system.
Etching Rate Control by MeV O+ Implantation for Laser-Chemical Reaction of Ferrite
Authors: Lu Yong Feng , Takai Mikio , Chayahara Akiyoshi , Satou Mamoru , Sanda Hiroyuki , Nagatomo Syohei , Namba Susumu
Published: February 2005

The control of etching rate in laser-induced chemical reaction of Mn–Zn ferrite in H3PO4 solution by MeV O+ implantation has been investigated. The etching induced by Ar+-ion laser irradiation in a H3PO4 solution was suppressed by implantating 3 MeV O+ to a dose of 1×1017 cm-2 when the laser power was low. The etching suppression disappeared when the O+-implanted sample was thermally annealed at 850°C for 30 min. The suppression is found to be related to the crystallinity change induced by ion implantation instead of surface reflectivity change.
Positive Charges and E' Centers Formed by Vacuum Ultraviolet Radiation in SiO2 Grown on Si
Authors: Yokogawa Ken'etsu , Yajima Yusuke , Mizutani Tatsumi , Nishimatsu Shigeru , Suzuki Keizo
Published: February 2005

Silicon dioxide films thermally grown on Si are irradiated with vacuum ultravioulet (VUV) photons (16.7 and 16.8 eV) as the films are supplied with bias voltages between -10 and 10 V. The resultant positive charges and E' centers in the films are studied by C-V (capacitance-voltage) and ESR measurements, respectively. The observed E' centers are distributed near the SiO2 surface, while the positive charges are localized at or very near the SiO2/Si interface. The positive charges and the E' centers show different characteristics in their bias and irradiation time dipendencies as well as in their depth distributions. These results indicate that the detected positive charges are different from holes trapped at oxygen vacancy sites between weak Si–Si bonds.
Amorphous Silicon Thin-Film Transistors with SiOxNy/SiNx Gate Insulators
Authors: Hiranaka Kouichi , Yamaguchi Tadahisa
Published: February 2005

A double layer of plasma chemical vapor deposition SiO
x
N
y
and SiN
x
was applied to the gate insulator of an amorphous silicon (a-Si) thin-film transistor (TFT). When a thin SiN
x
layer is inserted between the a-Si of an a-Si TFT and the SiO
x
N
y
gate insulator, the density of trapped charges is found to decrease less than for a gate insulator with only SiN
x
, when the thickness of SiN
x
is decreased. No deterioration was observed in the switching characteristics of an a-Si TFT with a SiO
x
N
y
/SiN
x
gate insulator, compared with a-Si TFTs with SiN
x
gate insulators commonly used in liquid crystal displays. The density of trapped charges is related to the threshold voltage shift.
E-Beam Direct-Write in a Dry-Etched Recess Gate HEMT Process for GaAs/AlGaAs Circuits
Authors: Hülsmann A. , Kaufel G. , Köhler K. , Raynor B. , Schneider J. , Jakobus T.
Published: February 2005

We developed a technology to fabricate enhancement and depletion high electron mobility transistors (E- and D-HEMTs) with sub-0.5 µm gatelengths using e-beam direct-write lithography. The gates are recessed by dry etching. The recess is stopped on 30 Å AlGaAs layers for E- and D-field effect transistors (FETs) respectively. We have extensively investigated the double layer resist technique for direct-write to improve the reliability of 0.3 µm electron-beam (E-beam) lithography. Ring oscillators using direct coupled FET logic (DCFL) have been measured indicating delay times of 16 ps per stage.
Preparation of High-Quality n-Type Poly-Si Films by the Solid Phase Crystallization (SPC) Method
Authors: Matsuyama Takao , Wakisaka Kenichiro , Kameda Masaaki , Tanaka Makoto , Matsuoka Tsugufumi , Tsuda Shinya , Nakano Shoichi , Kishi Yasuo , Kuwano Yukinori
Published: February 2005

For further improvement of conversion efficiency in a-Si solar cells, it is necessary to develop materials with high photosensitivity in the long-wavelength region. A new solid phase crystallization (SPC) method was developed to grow a Si crystal at temperatures as low as 600°C. Using this method, high-quality thin-film polycrystalline silicon (poly-Si) with a Hall mobility of 70 cm2/V·s was obtained. Quantum efficiency in the range of 800 nm ∼ 1000 nm was achieved up to 80% in an experimental solar cell using the n-type poly-Si with a grain size of about 1.5 µm. Therefore, it was found that our SPC method was suitable as a new technique to prepare high-quality solar cell materials.
Optimization of Chemical Vapor Deposition Conditions of Amorphous-Silicon Films for Thin-Film Transistor Application
Authors: Kanoh Hiroshi , Sugiura Osamu , Breddels Paul A. , Matsumura Masakiyo
Published: February 2005

The optimum condition has been investigated for chemical vapor deposition (CVD) of amorphous-silicon (a-Si) films to form high-performance a-Si thin-film transistors (TFTs) by a fully plasma-free process. It was found that hydrogen annealings improve the TFT characteristics a great deal and that there is an optimum deposition temperature and gas flow rate. The maximum field-effect mobility of electrons and on/off current-ratio were more than 0.8 cm2V-1s-1 and 106, respectively.
Circuit Applications of the Negative Differential Resistances in Heterojunction GaAs MISFET's
Authors: Delhaye Etienne , Aguila Thierry , Wolny Michel , Boissenot Philippe
Published: February 2005

Circuit applications of the negative differential resistance existing in the I-V characteristics of WN gate GaAlAs-GaAs MISFET's are presented for the first time. Both negative drain conductance and negative transconductance are used to implement a bistable flip-flop, frequency multiplication circuit and exclusive NOR gate, thus offering an interesting alternative to resonant tunnelling devices with the advantage of a much simpler epitaxial structure.
Flux Line Dynamics Crossover in the Tl-Ba-Ca-Cu-O Thin Film
Authors: Wang Chungyung , Chang Hung-Lun , Chu Ming-Lee , Juang Jenh-Yih , Gou Yih-Shun , Uen Tzeng-Ming
Published: February 2005

By extending the observation of the current-voltage characteristics to a much higher dissipative state, the flux-line motion experiences at least two stages of crossover, namely, from glassy hopping to creep-dominating, and finally an abrupt transition into the flow regime.
Resonance Phenomenon in a Self-Terminating Metal Vapor Laser
Authors: Taniguchi Hiroshi , Saito Hiroshi
Published: February 2005

A resonance phenomenon is found from the small-signal analysis of the characteristics in a self-terminating metal vapor laser based on the rate equations in the laser system.
Gas Evaporation of Zn by Means of the Top-Heating Vertical Furnace
Authors: Dohi Minoru , Sawai Shinya , Kato Manabu , Wada Nobuhiko
Published: February 2005

Gas evaporation of Zn without convection was carried out in the top-heating furnace. The temperature distribution and the pressure of He gas in the furnace were controlled and the particles deposited at various places of temperature in the furnace were observed by scanning electron microscope. The conditions of nucleation and growth mechanisms of the evaporated Zn vapors were discussed.
AES and XPS Studies of Surface of AlxGa1-xAs (110) Treated by Ammonium Sulfide
Authors: Ohno Hirotaka , Kawanishi Hidenori , Akagi Yoshiro , Nakajima Yoshiharu , Hijikata Toshiki
Published: February 2005

We applied the technique of ammonium sulfide treatment to Al
x
Ga1-x
As (110) surfaces and investigated the atomic composition of a surface by Auger electron spectroscopy and X-ray photoelectron spectroscopy. It was found that surface oxidation was significantly reduced by the sulfur treatment and that sulfur atoms were mainly bonded to Al atoms in an Al-enriched sample of Al
x
Ga1-x
As (x=0.78). The surface compositions of the Al-enriched specimen (x=0.43, 0.78) were also found to be As-riched as a result of both sulfur treatment and the preferential etching of metallic atoms by an acidic solution, which prevents the initial oxidation of the surface of Al
x
Ga1-x
As.
Quantum Size Effect and HRTEM Observation of CdSe Microcrystallites Doped into SiO2-Glass Films Prepared by Rf-Sputtering
Authors: Tsunetomo Keiji , Kawabuchi Akira , Kitayama Haruyuki , Osaka Yukio , Nasu Hiroyuki
Published: February 2005

CdSe microcrystallite-doped SiO2 glass films were prepared by the magnetron rf-sputtering technique. High resolution transmission electron microscopy (HRTEM) observation was carried out to determine the shape and the average size of the microcrystallites. The microcrystallites had a spherical configuration and they seemed to have a wurtzite structure. The optical band gap of the films clearly exhibited the blue shift compared to bulk CdSe. The shape of optical absorption spectra also changed as the microcrystallite size decreased. A simple model of the size quantization on interband absorption in a semiconductor sphere was used to explain the change of the optical absorption spectra. Taking into account the particle size distribution, the calculated absorption spectra successfully agreed with the real absorption spectra. The observed blue shifts of optical absorption were consistent with theoretical values calculated using the mean microcrystallite radii estimated from the HRTEM observations.
Time-Averaged Electric Field Profiles in a Capacitive Coupling Parallel Plate Electrode RF Discharge Helium Plasma
Authors: Kaneda Teruo , Kubota Tadahiro , Ohuchi Mikio , Chang Jen-Shih
Published: February 2005

Time-averaged electric field profiles in a capacitive coupling parallel plate electrode RF discharge with Balun circuit have been measured for a helium plasma. The experiment was conducted at a gas pressure from 0.3 to 3 Torr and RF power from 10 to 30 W. The results show that the time-averaged electric field in the central region of the discharge tube is observed to be relatively uniform for the present range of experimentation except for the gas pressure near 0.7 Torr for higher RF power conditions, where nonmonotonic potential profiles are observed.
Precise Pressure-Temperature Control System for Electrical Measurements down to 4.2 K Using Helium Gas as a Pressure Transmitting Medium
Authors: Hikita Tomoyuki , Maruyama Taketoki , Yamada Noboru
Published: February 2005

A system in which electric measurements can be performed under a good hydrostatic condition (up to 7 kbar in helium gas environment) and under very precisely controlled temperature has been developed. This system is especially suitable for the very low temperature measurements (down to 4.2 K) where most pressure transmitting materials solidify. The system has been utilized for the measurements of dielectric constant and the spontaneous polarization of a quantum ferroelectric, tris-sarcosine calcium bromide ((CH3NHCH2COOH)3CaBr2; TSCB).
Ion Channeling Study of Epitaxially Grown HoBa2Cu3OxThin Films on MgO(001)
Authors: Watamori Michio , Shoji Fumiya , Itozaki Hideo , Hanawa Teruo , Oura Kenjiro
Published: February 2005

The crystalline quality of high-Tcsuperconducting HoBa2Cu3Oxthin films formed on MgO(001) has been investigated by a high-energy ion channeling technique. Analysis was performed at 3 depth regions (surface, inside, and interface), and the degree of crystalline quality at each depth was estimated. Based on ion channeling measurements carried out with the normal <001> and off-normal <101> and <011> directions, it has been found that (1) the crystalline quality at the film surface is much better than that at the interface, (2) the crystalline disorder can be seen mainly along thec-axis, and (3) the film consists of two domains, 90° rotated from each other about thec-axis of the film. The crystalline quality of the MgO substrates has also been investigated.
X-Ray Photoacoustic Spectroscopy of Brass
Authors: Toyoda Taro , Masujima Tsutomu , Shiwaku Hideaki , Iida Atsuo , Ando Masami
Published: February 2005

The X-ray photoacoustic spectrum of brass has been measured at EXAFS regions (K-edges of Cu and Zn) using synchrotron radiation. It is shown that the information derived from EXAFS is also included in the X-ray photoacoustic spectrum which reflects the heat production processes in brass. However, the result showed that the increases and changes of the photoacoustic signal were different from those of the X-ray absorption coefficient at EXAFS regions.
Nanometer Pattern Transfer by VUV Lithography with a D2 Lamp
Authors: Mutoh Katsuhiko , Iwabuchi Takashi , Kudo Kazuhiro , Watanabe Hisashi , Todokoro Yoshihiro , Miyata Takeo , Sano Reiji
Published: February 2005

Vacuum-ultraviolet lithography of a trilayer resist system which consists of polymethyl methacrylate (PMMA), Si and polyimide has been studied using a deuterium lamp. The exposure dose needed for a 0.1-µm-thick PMMA film is less than 1 mJ/cm2, and a high etch rate ratio of 40 for polyimide to Si is obtained with the reactive ion beam etching (RIBE) technique. Using a simple contact exposure system and RIBE, photomask patterns are accurately transferred in the polyimide down to a linewidth of 0.2 µm, and 50-nm line patterns of polyimide are obtained.
A Consideration of the Deformation of Rectangular Pattern
Authors: Tanaka Hidehito , Ota Tsuneo , Tanimoto Keisuke , Kawabata Ryohei , Shibayama Hikou
Published: February 2005

The mechanism of rectangular pattern deformation is studied and methods to realize precise pattern definition are presented. We observed that rectangular pattern deformation strongly depends on the absorbed energy distribution within the resist due to defocusing. Resist thickness thinning and surface image techniques such as DESIRE show promise in realizing precise pattern definition.
Study of Hydrogen Vacuum-Ultraviolet Light Sources for Submicron Lithography
Authors: Kudo Kazuhiro , Iwabuchi Takashi , Mutoh Katsuhiko , Miyata Takeo , Sano Reiji , Tanaka Kuniaki
Published: February 2005

The output properties of hydrogen light sources and the resist parameters, such as spectral sensitivity and absorption coefficient, in the vacuum-ultraviolet (VUV) region were investigated. A very low exposure energy of about 1 mJ/cm2 was obtained by employing a very thin polymethyl methacrylate film and the VUV light of hydrogen microwave discharge. Contact photolithography using a Si/MgF2 mask and a trilayer resist system showed that submicron patterns as small as 0.2 µm had been replicated at an exposure time of under 30 s.
119Sn-Mössbauer Spectroscopic Study of High-Tc Superconducting YBa2(Cu0.995Sn0.005)3O7-y and the Gamma-Ray Irradiation Effect
Authors: Nishida Tetsuaki , Katada Motomi , Matsumoto Yasukuni
Published: February 2005

119Sn-Mössbauer measurement of the superconducting Y-Ba-Cu(Sn)-O system has been made at temperatures between 18 and 298 K. All the spectra show a superposition of an intensive singlet and a weak doublet peaks due to Sn4+ species located at different Cu(1) sites; the singlet is assigned to a square planar Cu(Sn)O4 and the doublet to a triangular Cu(Sn)O3. 60Co-γ ray (∼108 R) irradiation results in an increased fraction of the Cu(Sn)O3 species. Isomer shift (δ) and absorption area (A) increase linearly with decreasing temperature and become constant at temperatures lower than 95-100 K, which is comparable to the onset temperature of superconducting transition (94.8 K). This finding indicates that softening of lattice vibration at the Cu(1) sites, followed by a strong electron-phonon coupling, is closely concerned with the superconductivity in Cu(2)O4 layer.
The Application of the Correlation Method for the EB (Electron Beam) Exposure System
Authors: Kawamura Ichiro , Okino Teruaki , Handa Nobuo , Sato Hitosi , Goto Nobuo
Published: February 2005

In EB direct wafer writing, we have applied the correlation method to detecting the position of the registration mark and we also applied it to detecting the width of the mark, the size of the beam and the degree of focusing for the calibration of the EB exposure system. This method is less influenced by random noises and has wide capability for the signal forms. We have also developed a detection hardware unit and applied it to our variable shaped EB exposure system JBX-8600DV with satisfactory results. The reliability of detection of the mark position is 0.05 µmpp by single scanning; that of the beam size is 0.02 µmpp. We can adjust the focus to within ±3 µm.
Magnetic Field Dependence of Voltage Noise in Y1Ba2Cu3O7-x Ceramic Superconductor Film
Authors: Nojima Hideo , Shintaku Hidetaka , Nagata Masaya , Ohno Eizo , Koba Masayoshi , Kataoka Shoei
Published: February 2005

Magnetic field dependence of voltage noise in a ceramic superconductor Y1Ba2Cu3O7-x
film has been investigated. We have observed a maximum of the noise at about 10 Oe for the perpendicular field to the film surface. For the parallel field to the film surface, the noise increases slightly with the increase of the field. These noise characteristics are considered due to a motion of magnetic flux in the film.
Atomic Layer Controlled Digital Etching of Silicon
Authors: Sakaue Hiroyuki , Iseda Seiji , Asami Kazushi , Yamamoto Jirou , Hirose Masataka , Horiike Yasuhiro
Published: February 2005

Layer-by-layer etching of silicon on atomic scale has been achieved by repeating the reaction cycles of fluorine (F) atom adsorption on a cooled Si surface and subsequent Ar+ ion (≃20 eV) irradiation which induces fluorine/Si surface reactions. The digital etch rate first increases and reaches a plateau region with an increase of Ar+ ion irradiation time. For the case of CF4/O2 downstream plasma as a fluorine source, CF
x
radical accumulation appears to be a self-limiting stop of the F/Si reaction to promote atomic layer etching, while F atoms produced by a remote NF3 plasma or an F2/95%He discharge also cause similar atomic layer etching in which the amount of physiosorbed fluorine molecules on Si surfaces controls the etch rate. The etching in the plateau region exhibits no microloading effect because the fluorine coverage is independent of pattern size. Anisotropic etching of Si with a 20 nm PMMA mask pattern and an aspect ratio of 5 is attained.
High-Power and High-Efficiency P-GaAlAs/N-GaAs:Si Single-Heterostructure Infrared Emitting Diodes
Authors: Nakamura Shuji , Takagi Hironori
Published: February 2005

P-GaAlAs/N-GaAs:Si single-heterostructure infrared emitting diodes (SH-IREDs) whose emission can be confined only to the n-GaAs layer have been developed. The external efficiency and the output power are increased more than 70%, the interface of p-n junction becomes much smoother, and the number of thyrister characteristics of SH-IREDs becomes smaller in comparison with those of conventional P-GaAs/N-GaAs:Si homostructure infrared emitting diodes (HOMO-IREDs).
Low-Temperature Crystallization of Hydrogenated Amorphous Silicon Induced by Nickel Silicide Formation
Authors: Kawazu Yunosuke , Kudo Hiroshi , Onari Seinosuke , Arai Toshihiro
Published: February 2005

We have investigated the silicidation process of the Ni/a-Si:H system on a fused silica substrate mainly by in situ electric resistance measurement. A rise of the resistance is observed in the temperature range of 480–510°C of the resistance curve at a heating rate of 2 K/min. The results of the RBS measurements and the XRD measurements show that the rise of the resistance originates from the diffusion of Ni from the NiSi2 layer to a-Si:H film, and that the a-Si:H crystallizes during the diffusion. Noting that the crystallization temperature of a-Si:H film is higher than 700°C, the present crystallization occurs at a much lower temperature. It is suggested that this low-temperature crystallization is induced by heterogeneous nucleation, where the NiSi2 becomes the nucleus for Si crystallization.
The Melt Process of Tl–Ba(Sr)–Ca–Cu–O Tape-Shaped Wire
Authors: Okada Michiya , Yuasa Toyotaka , Matsumoto Toshimi , Aihara Katsuzo , Seido Masahiro , Matsuda Shinpei
Published: February 2005

The melt process effectively improves crystal orientation, and introduces pinning centers in high-T
c oxide superconductors. It is, however, very difficult to apply the melt process to compounds containing volatile elements such as thallium oxide. In this paper, an extremely high-speed zone-melting process (HIZM) of tape-shaped wire in the Tl–Ba(Sr)–Ca–Cu–O system is presented. The HIZM was successfully performed on the Tl-2223 tape with little vaporization of thallium. After solidification, the Tl-2223 matrix transformed to the nonequilibrium phase of 2212 with fine CaO and Cu0 particles. A postannealing was undertaken to retransform the nonequilibrium phases to the equilibrium 2223-phase. It would be possible to control the nonequilibrium CaO phase as pinning center during HIZM and subsequent annealing process.
Photocarrier Generation in a Layered Organic Photoreceptor Containing Azo Pigment
Authors: Umeda Minoru , Niimi Tatsuya , Hashimoto Mitsuru
Published: February 2005

Studies have been made on photocarrier generation which is caused in a highly sensitive layered organic photoreceptor for electrophotography and produces a photoinduced discharge. A series of experiments has been carried out on a layered photoreceptor which has a carrier generation layer (CGL) containing a fluorenone bisazo pigment as the main component. As a result, we have found that (1) excitons are produced in the bulk of the CGL by photon absorption, (2) the excitons dissociate into free carriers (negative electrons and positive holes) at the interface between the CGL and a carrier transport layer (CTL), and (3) the positive holes are immediately injected into the CTL, so that few free carriers recombine.
Numerical Simulation of Elongating the Pulse Duration of a TEA CO2 Laser
Authors: Sasaki Koichi , Tsukishima Takashige
Published: February 2005

The results of numerical simulations of elongating the pulse duration of a TEA CO2 laser are reported. It is shown that neither relative increase of N2 gas in the N2:He:CO2 gas mixture nor elongation of the pulse duration of the discharge current is very effective. A significant result is obtained with the pulse injection locking method, when the following two conditions are satisfied: 1) the detuning angle is less than 0.1π, and 2) the initiation of discharge of the main laser is synchronized with the injected laser pulse within about 200 ns.
CW and Pulse Response of a Mechanical Resonator: Numerical Evaluation and Experimental Observations
Authors: Pal Barnana , Sinha S. K.
Published: February 2005

The response of a finite size mechanical resonator under acoustic excitation has been studied in the “propagating wave” model. The results give a good understanding of the experimental patterns observed in standard `pulse echo' and CW experiments. The formation of modulated pulse echo pattern, observed in coherent pulse/CW technique, has also been analysed in detail and the analysis supports the method of detection of the mechanical resonance frequencies by vanishing the modulation pattern. Moreover, the analysis suggests a method of measuring ultrasonic attenuation constant from the modulated pulse echo pattern. The acoustic velocity and attenuation constants have been measured experimentally using the above technique for Al and Cu single crystal and also for polycrystalline Cu. The measured values of acoustic velocities have been compared with other measurements where available.
Fabrication of Periodic Structures in GaAs by Focused-Ion-Beam Implantation
Authors: Shiokawa Takao , Ishibashi Koji , Kim Pil Hyon , Aoyagi Yoshinobu , Toyoda Koichi , Namba Susumu
Published: February 2005

The characteristics of the ion bombardment-enhanced etching for a GaAs substrate using Ga focused-ion-beam implantation and selective etching of HCl have been investigated. The contrast and sensitivity of the etching as a positivetype resist were estimated to be 2.87 and 7.4×1013 cm-2, respectively. The microstructure of a 63 nm period was fabricated by the maskless process.
A DUV-Defined-Negative Resist/EB-Defined-Positive Resist Two-Layer Resist System for the Fabrication of T-Shaped Gate
Authors: Takenaka Hiroshi , Watanabe Hisashi , Todokoro Yoshihiro , Inoue Morio
Published: February 2005

We have developed a DUV-defined-negative resist/EB-defined-positive resist two-layer resist system to fabricate T-shaped gates of GaAs MESFET devices. In this resist system, the head of the T-shaped gate is fabricated in the top layer negative resist using a deep-UV exposure and the foot of the T-shaped gate is fabricated in the bottom layer positive resist using an e-beam exposure. Resist profiles are easily controlled because exposures and developments of the top and bottom layers are completely separated. A sub quarter-micron T-shaped gate with the head of the width of more than one micron was successfully fabricated by using this two-layer resist system. This two-layer resist system has wide applicablity for the fabrication of GaAs MESFET devices.
Intensity Noise of GaAlAs / GaAs Surface Emitting Laser
Authors: Morito Ken , Koyama Fumio , Iga Kenichi
Published: February 2005

The relative intensity noise (RIN) of a vertical cavity surface emitting (SE) laser diode was measured for the first time. We found that the relative intensity noise was - 135 dB/Hz at the injection current 1.1×I
th which is comparable to that of a low noise edge emitting laser.
Nature of the Anomalous Shape Change in Loss Permittivity versus Frequency Curve of Polymers above and near the Glass Transition Temperature
Authors: Anada Yuichi , Kakizaki Maeko , Hideshima Teruo
Published: February 2005

A simple theory has shown that loss permittivity due to the micro-Brownian motion of macromolecules in amorphous region of crystalline polymers is governed by the distribution of fractional free volume as well as that of relaxation times at a constant fractional free volume. Further investigation is carried out to clarify the roles of these two types of distribution. For this purpose, Γ-distribution is used for the distribution of fractional free volume, while the Debye-type decay function and the Williams-Watts' decay function are employed for the distribution of relaxation times. The comparison between the calculated and experimental values reveals that the former distribution determines substantially the shape of loss permittivity versus frequency curve nearTg, while the latter plays an essential role for the shape of this curve at temperatures much higher thanTg.
Measurement of Elastic Constant and Intrinsic Twist of Ferroelectric SmC* Liquid Crystal
Authors: Kawaida Masahiro , Akahane Tadashi
Published: February 2005

The elastic constant B
3 and the intrinsic twist D of a ferroelectric SmC* liquid crystal and their temperature dependences were measured by making use of the selective reflection in a homeotropically aligned cell, and the critical electric field E
c needed to unwind the helix was also estimated. E
c was much smaller than a critical electric field when the dechiralization lines disappear in a homogeneously aligned cell. The constants determined here are considered not to be influenced by the wall anchoring of the glass plate. When we apply a simple power law, α(1-T/T
c)γ, to the temperature dependences of B
3, D and E
c, the exponents γ will be 0.44, 0.81 and 0.95, respectively, where T
c is the SmC*-SmA transition point.
The Influence of Oxygen on KCl:Pb2+ Annealed for a Long Time at High Temperature
Authors: Asada Hiroshi
Published: February 2005

The effect of annealing for a long time at high temperature was investigated on KCl:Pb2+ crystal in an atmosphere of air. When the crystal was annealed at 600°C, A and B bands decayed with annealing time and two new bands appearing at 246 nm and 253 nm grew. This phenomenon is considered to be described by a model in which one dipole is combined with one oxygen to form an oxide molecule.
Static Charge Elimination of Charged Matter by Vacuum UV Irradiation
Authors: Gosho Yasushichi , Saeki Masamori
Published: February 2005

Air is photoionized by the irradiation of vacuum UV light emitted from a deuterium lamp with a MgF2 window. The short wavelength transmission limit of this lamp is 112 nm, which corresponds to the photon energy of 11 eV, and nitric oxide is firstly produced by photochemical reaction and photoionized by those photons having an energy of 11 eV. The lamp behaves like a radio isotope, and its irradiation accelerates the charge elimination of charged matter in air.
Measurement of Electron Density and Temperature of Plasma with RF Current Drive by Alfvén Wave
Authors: Lin Jing , Matsumoto Keigo , Hotta Eiki , Suzuki Mitsuaki
Published: February 2005

Alfvén waves were excited in a toroidal plasma. The experimental data show that the Alfvén wave heats the plasma mainly in the central region. It is found that the decrease of loop voltage observed when the radio frequency (rf) is turned on, is mainly caused by electron heating.
Enhancement of Proton Stopping Power on Two-Dimensionally Focused “Plasma Focus Diode”
Authors: Jiang Weihua , Zhang Chi , Masugata Katsumi , Yatsui Kiyoshi
Published: February 2005

Ion beam-target interaction experiments were performed by using a two-dimensionally focused “plasma focus diode”. The proton energy losses in different targets were measured with an improved time-resolvable Thomsonparabola energy spectrometer. With the beam power density of ∼0.1 TW/cm2 at a beam energy of ∼1.5 MeV, enhanced energy deposition has been observed for aluminium targets 7 µm thick. Theoretical calculations show that the experimental data are in good agreement with those given by the simulation model based on free and bound electron stopping terms.
The Use of Three Hamon Devices to Realize High-Accuracy Resistance Ratios
Authors: Sasaki Hitoshi
Published: February 2005

Precise measurement of a ratio of resistance, 6453.2 to 1, is required to calibrate 1-Ω standard resistors against the quantized Hall resistance. In this paper, a novel technique is proposed which can measure this ratio with an accuracy of 0.01 ppm by using three Hamon devices and a high-precision Wheatstone bridge. In addition, the ratio 6453.2:10000 is obtained as a by-product.
Calibration of Pyranometers for the Photovoltaic Device Field
Authors: Nagamine Fumiaki , Shimokawa Ryuichi , Miyake Yukiharu , Nakata Minoru , Fujisawa Kazuya
Published: February 2005

We have established the standard calibration method of reference pyranometers for the photovoltaic (PV) device field. We carried out the calibration of pyranometers by three different calibration methods (ASTM shading, IEC shading and JMI hood methods) for the first time, and found that the calibration values were in good agreement within ±1% except for the values which deviated by errors due to the temperature dependence and the incident angle dependence which were particular to the pyranometer itself. The calibration was based on the absolute cavity radiometer conforming to WRR. Each calibration method employed, including our original JMI hood method, was introduced and assessed, and the causes of the calibration errors and the accuracy of pyranometers were discussed.
Characterization of Diamond Films Synthesized on Si from a Gas Phase in Microwave Plasma by Slow Positrons
Authors: Uedono Akira , Tanigawa Shoichiro , Funamoto Hiroyuki , Nishikawa Akira , Takahashi Kouji
Published: February 2005

Variable-energy positrons were used as a nondestructive probe for diamond films synthesized on the Si substrate from a gas phase of a CH4/H2 mixture by microwave plasma chemical vapor deposition. The Doppler broadening of the annihilation photons was found to be strongly influenced by the concentration of CH4. The values of mean positron diffusion length in the diamond films were found to be decreased by increasing the concentration of CH4. The concentration of defects, C, was estimated as follows: 4×10-4<C<4×10^-3. A
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Studies on the Dynamic Behavior of Fatty Acid Monolayers at the Air-Water Interface by a Current-Measuring Technique
Authors: Majima Yutaka , Iwamoto Mitsumasa
Published: February 2005

Dynamic behavior of fatty acid monolayers at the air-water interface was investigated using a current-measuring technique, where a current-area (I-A) isotherms was monitored together with a surface pressure-area (π-A) isotherm during the compression of a monolayer at the air-water interface. In liquid phase, current I decreased at a constant rate with compression, due to a change in the vertical component of the dipole moment of fatty acid molecules. At the liquid-solid phase transition, a striking feature in the present current measurement was observed; the I-A isotherm for a stearic acid monolayer has a sharp bend. Current I increased abruptly when a monolayer collapsed. Dynamic behavior of monolayers in the presence of an external electric field was also investigated using the current-measuring technique.
SiH3 Radical Density in Pulsed Silane Plasma
Authors: Itabashi Naoshi , Nishiwaki Nobuki , Magane Mitsuo , Goto Toshio , Matsuda Akihisa , Yamada Chikashi , Hirota Eizi
Published: February 2005

The SiH3 radical density in pulsed silane discharge plasma was measured by infrared diode laser absorption spectroscopy (IRLAS) for three buffer gases and also as functions of the sample pressure and the pulse width. They were compared with the SiH and SiH2 radical densities. The growth rate of a-Si:H thin film was compared with the SiH3 radical density on various plasma conditions. These data were employed to discuss the contribution of SiH3 to a-Si:H thin-film growth.