bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous 3-D Imaging Using Chirped Ultrashort Optical Pulses
Authors: Minoshima Kaoru , Matsumoto Hirokazu , Zhang Zhigang , Yagi Takashi
Published: October 2002

A novel method for simultaneous 3-D imaging using chirped ultrashort light pulses is proposed. Simultaneous imaging without scanning is possible by means of the conversion between the time and the color axes mediated by the chirped pulse. The theoretical limitation of the spatial resolution is discussed. We proved the efficacy of this method by measuring an area composing three flat steps made of three gauge blocks of different lengths with an accuracy of better than 0.3 mm. This technique is applicable for imaging of the shape of moving objects, or surface testing or inspection.
Direct Imaging of Spatial Distribution of Ions Generated by Nonresonant Multiphoton Ionization of H2 Gas
Authors: Ichimura Shingo , Sekine Shigeyuki , Steffen Hans Joachim , Kiyohide Kokubun Kiyohide Kokubun , Hazime Shimizu Hazime Shimizu
Published: October 2002

The spatial distribution of ions generated by nonresonant multiphoton ionization (NRMPI) of H2 gas with a picosecond YAG laser was clearly observed with a new detection system consisted of a static lens, a microchannel plate (MCP) intensifier, a charge-coupled device (CCD) camera, and an image processor. The ions were distributed along a straight line, reflecting the ion generation along the laser beam path. The ionization region had a spindle shape with the maximum diameter at the focal point of a spherical lens used for laser beam focussing. The size of the ionization region was about 2.5 mm in length and 0.05 mm in diameter when the gas pressure was 1×10-5 Pa and incident laser energy was 12 mJ/pulse. The laser power density at the focal point was about 2×1013 W/cm2.
Wetting Failure of Photoresist on Spin-On-Glass (SOG) Substrate by Spin Coating
Authors: Akira Kawai Akira Kawai , Hitoshi Nagata Hitoshi Nagata
Published: October 2002

The wetting failure of photoresist occurs during the spin-coating process on the spin-on-glass (SOG) surface. The SOG surface has relatively low surface free energy. By treating the SOG surface with an alkaline aqueous solution prior to the photoresist coating, wetting failure can be prevented. The alkali treatment has the effect of increasing the surface free energy of SOG film, especially in its polar component. The spreading work W
S changed from a positive to negative value by the alkali treatment, which can explain the prevention of the wetting failure.
H-Atom Incorporation in Mg-Doped GaN Grown by Metalorganic Chemical Vapor Deposition
Authors: Yasuo Ohba Yasuo Ohba , Ako Hatano Ako Hatano
Published: October 2002

H-atom incorporation was studied for Mg-doped GaN grown by metalorganic chemical vapor deposition. H-atom incorporation was found to increase linearly with Mg concentration, suggesting the formation of simple complex between Mg and H atoms in GaN. Decrease of H-atom concentration was observed after thermal treatment in Ar, supporting the hypothesis that H-atom extraction plays an important role in obtaining low-resistivity p-type conduction.
Magnetoresistance in Co–Cu Alloy Films Formed by Electrodeposition Method
Authors: Yuji Ueda Yuji Ueda , Masaki Ito Masaki Ito
Published: October 2002

Giant magnetoresistance (GMR) in Co-Cu alloys prepared by the electrodeposition method has been investigated. The formation of solid solution in the as-deposited samples has been confirmed by X-ray diffraction. For Co17Cu83 alloy, the values of the MR ratio at room temperature of as-deposited sample and sample annealed at 400°C for 25 h are 1.3% and 6.3%, respectively. With an increase in the annealing temperature from 400°C to 500°C, the annealing time showing the maximum MR ratio is shifted toward shorter time.
Dependences of Coercivity and Remanence on Co Layer Thickness in (111)Pt/Co and Pt/Co/Ag Superlattices
Authors: Toshiki Kingetsu Toshiki Kingetsu
Published: October 2002

The magnetic and structural properties of (111)Pt/Co and Pt/Co/Ag superlattices were studied. The samples were grown at 373 K on Ag buffer layers preformed on 7×7-(111)Si substrates by molecular-beam epitaxy. The superlattices with Co layer thickness ( t) smaller than 1.5 nm exhibited perpendicular magnetic anisotropy. The dependence of the coercivity (H
c) of the Pt/Co superlattices on t is presented in detail. The H
c exhibited a t
-5/2 dependence that was previously reported not to be demonstrated in an epitaxial Pt/Co/Pt wedge-shaped sandwich structure.
Unified Model for Structure Transition and Electrical Properties of InAs (001) Surfaces Studied by Scanning Tunneling Microscopy
Authors: Hiroshi Yamaguchi Hiroshi Yamaguchi , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

Thermal stability of the ( 2×4) structures
on InAs and GaAs (001) surfaces is studied
by using scanning tunneling microscopy with atomic resolution.
Even just before the transition to a ( 4×2) structure,
the annealed InAs surface has much lower density of kinks
in the dimer vacancy rows than the annealed GaAs.
This difference leads to a unified model that can explain
both the 1st order phase transition
and the peculiar electric properties of an InAs (001) surface.
<011>-Oriented Tungsten Field Emitter Coated with Liquid Lithium Thin Film
Authors: Hata Koichi , Kumamura Masayuki , Yasuda Tsukasa , Yahachi Saito Yahachi Saito , Akinori Ohshita Akinori Ohshita
Published: October 2002

Field electron emission patterns from a <011>-oriented tungsten tip coated with liquid lithium film were observed. For the film thickness between 5 and 30 nm, emission patterns showed the formation of liquid lithium cones on the facets of the tungsten surface. The Fowler-Nordheim plots showed the presence of the space charge effect. The increase of the number of liquid cones with tip voltage was qualitatively explained in terms of the space charge effect. For the film thickness more than 30 nm, only pulsed explosive emission was observed.
Method to Obtain Low-Dislocation-Density Regions by Patterning with SiO2 on GaAs/Si Followed by Annealing
Authors: Yamaichi Eiji , Ueda Takashi , Gao Qingzhu , Chouho Yamagishi Chouho Yamagishi , Masahiro Akiyama Masahiro Akiyama
Published: October 2002

A method to obtain low-dislocation-density regions in GaAs on Si has been proposed. The method comprises performing the thermal cycle for GaAs, which is partially covered by SiO2 patterning, on Si. Dislocations in the GaAs layer on Si are gathered at the periphery of the SiO2 pattern due to surface stress modulation. This method yields the dislocation density of less than 105 cm-2 in the uncovered region.
Water Diffusivity of Dielectric Films Evaluated with Use of D2O
Authors: Fukuda Kenji , Nakano Tadashi , Fujishima Masaaki , Mura Naomi , Ichinose Kyoji Tokunaga
Published: October 2002

Diffusion coefficients of D2O in dielectric films are studied through the analysis of deuterium depth profiles by secondary ion mass spectrometry (SIMS). The films investigated are atmospheric chemical vapor deposition (CVD) SiO2 (LTO), borophosphosilicate glass (BPSG), plasma-CVD SiO2, tetra-ethoxy-silicate (TEOS)-based plasma-enhanced CVD SiO2 (P-TEOS), O3- and TEOS-based SiO2 ( O3-TEOS), and organic spin-on glass (SOG) films. The diffusion coefficient of D2O in the plasma-CVD SiO2 film is less than one-fifth those in the other films.
Radiolysis of Solid CO2 and Future Electron Spin Resonance Dating on Outer Planets
Authors: Makoto Hirai Makoto Hirai , Motoji Ikeya Motoji Ikeya , Yoshiaki Tsukamoto Yoshiaki Tsukamoto , Chihiro Yamanaka Chihiro Yamanaka
Published: October 2002

Paramagnetic radicals have been detected in solid CO2 with gamma irradiation at 77 K
with the measurement of electron spin resonance (ESR). Species of O3
-,
CO3
-, CH3, SO3
- and HO2 are identified. The lifetimes of
O3
-, CH3 and HO2 at several temperatures were obtained by isothermal
annealing experiments. Their stability at the ambient temperature of Mars and icy
satellites was estimated from the Arrhenius plot of the lifetime for the future
possibility of ESR dating of solid CO2.
Tunable Twin-Guide Laser with Integrated Waveguide
Authors: Illek Stefan , Wolf Thomas , Michael Schier Michael Schier , Charlotte Raetzel Charlotte Raetzel
Published: October 2002

As a step towards an integrated heterodyne receiver the tunable twin-guide (TTG) laser has been integrated with a waveguide on semi-insulating substrate using the butt-coupling and the integrated twin-guide (ITG) coupling scheme. An output power of 4 mW from the waveguide and a tuning range of 2.2 nm has been achieved.
Dynamic Properties of Soluble Monolayer of Sodium Dodecyl Sulfate (SDS) on Aqueous Solution
Authors: Ozawa Atsumi , Minamisawa Akiko , Sakai Keiji , Takagi Kenshiro
Published: October 2002

The relaxation phenomenon of the surface elasticity was investigated for a soluble mono-molecular layer of sodium dodecyl sulfate (SDS) on aqueous solution. Two kinds of experiments, induced surface wave measurement and ripplon light scattering, were performed at frequencies of 1 kHz and 40 kHz, respectively. In the dilute region below the critical micellar concentration (CMC), the concentration dependence of the surface elasticity obtained at 1 kHz is well explained by the theory of diffusion-dominated relaxation, while the surface elasticity at 40 kHz was found to exceed the low-frequency value, which suggests another relaxation mechanism. The results obtained above the CMC were also presented.
Liquid Crystalline Behavior and Optical Properties of Poly(2,5-dinonyloxy-p-phenylenevinylene)
Authors: Maki Hamaguchi Maki Hamaguchi , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Poly(2,5-dinonyloxy- p-phenylenevinylene) prepared by dehydrochlorination polymerization of 2,5-dinonyloxy- p-xylylenedichloride has been found to begin to soften at about 463 K, and to be in the nematic liquid crystalline state upon melting. By cooling the polymer at a liquid crystalline state to room temperature, an oriented thin film was obtained, whose band-gap energy was substantially lower than that of the (amorphous) film prepared by casting chloroform solution of the same polymer. Anomalous temperature dependences of absorption and photoluminescence spectra of the polymer were also revealed.
Epitaxial Growth of GaSe Films by Molecular Beam Epitaxy on GaAs(111), (001) and (112) Substrates
Authors: Kojima Nobuaki , Sato Kei , Yamada Akira , Konagai Makoto , Kiyoshi Takahashi Kiyoshi Takahashi
Published: October 2002

We have successfully grown epitaxial GaSe films on GaAs(111), (001) and (112) by molecular beam epitaxy. On the GaAs(111) substrate, the c-axis of the GaSe layer was perpendicular to the substrate surface, while each unit layer of GaSe was inclined on GaAs(001) and (112) substrates when the growth temperatures were higher than 500°C at high beam fluxes of Ga and Se. Furthermore, we could detect strong photoluminescence (PL) emission from the GaSe films grown on GaAs(001) and (112) substrates. This result suggests that crystal quality was improved by growth through chemical bonding at a higher growth temperature.
Low-Temperature Chemical Vapor Deposition of Silicon Dioxide Using Tetra-isocyanate-silane (Si(NCO)4)
Authors: Hitoshi Taniguchi Hitoshi Taniguchi , Osamu Sugiura Osamu Sugiura
Published: October 2002

Deposition characteristics and step coverage of low-temperature
chemical vapor deposition
silicon dioxide (CVD SiO2) using tetra-isocyanate-silane
( Si(NCO)4; TICS) and H2O
have been investigated for application to interlayer
dielectric films for advanced VLSI.
The deposition rate was 13 nm/min at 100°C.
The rate rapidly decreased with the
increasing deposition temperature.
It was determined by partial pressure rather than
by flow rate of material gases.
The step coverage showed a conformal profile.
Positron Reemission from Thin W(100) Foil in 10-6 Torr Pressure
Authors: Bi Jin Bi Jin , Osamu Sueoka Osamu Sueoka , Akira Hamada Akira Hamada
Published: October 2002

The production of low-energy positron beams for positron-gas scattering experiments has been tested using thin W(100) foils in high-vacuum pressure ( 10-6 Torr).
The W foil was baked for cleaning and used as a positron moderator in situ.
The efficiency of positrons reemitted from the thin foil was 14±2% for a 1000-Å-thick foil and 10±2% for a 2000-Å-thick one.
The positron work function of the W(100) surface in 10-6 Torr was -1.9±0.3 eV.
The energy width in situ was 1.5±0.2 eV, narrower than that exposed to air.
The feasibility of the brightness-enhancement method in 10-6 Torr for positron-gas scattering experiments was discussed.
Growth Process of Polyhedral Oxide Precipitates in Czochralski Silicon Crystals Annealed at 1100°C
Authors: Sueoka Koji , Ikeda Naoki , Toshiro Yamamoto Toshiro Yamamoto , Sumio Kobayashi Sumio Kobayashi
Published: October 2002

The growth process of polyhedral oxide precipitates in Czochralski (CZ) silicon crystals has been studied with annealing at 1100°C from 4 h to 16 h, after preannealing at 900°C for 4 h. It was found, from transmission electron microscopy (TEM) observations, that the growth of polyhedral precipitates follows a t
1/2 law. At 1100°C, the concentration of oxygen interstitials at the interface (C

i

O
) is estimated to be 1.2 times the thermal equilibrium concentration (C

O

*) on the basis of a theoretical model of oxygen precipitation in silicon. The growth of polyhedral precipitates is explained quantitatively by a diffusion-limited growth model of a spherical precipitate, using the estimated C

i

O
.
Fabrication of High-Quality Nb/Al-AlOx-Al/Nb Junctions by a Simple Process
Authors: Mizutani Naoki , Uehara Gen , Yamasaki Shuichi , Adachi Akira , Kado Youichi Takada
Published: October 2002

We have fabricated Nb/Al–AlO

x

–Al/Nb junctions that have extremely low leakage currents by a simple process using only two mask levels. Reducing the thickness of the Al layer under the AlO

x

improved the quality. For a 20 µm2 junction, the current at 0.5 mV at 0.5 K was 4 or more orders of magnitude lower than that at 4.2 K. For 0.70 µm2 junctions, the current at 0.5 mV below 1.5 K was 3 or more orders of magnitude lower than that at 4.2 K. We have also fabricated ultra small junctions of high quality. These high-quality junctions can be fabricated by a simple process, hence they are appropriate for various applications.
Energy Transfer from Tm3+ to bfEr3+ in Zirconiumfluoride Glasses Pumped by a 786 nm Laser Diode
Authors: Cho Woon Jo , Kim Myong Wook , Cheol Jo Jae , Park Sang Sam Choi
Published: October 2002

The upconversion of 786 nm to visible fluorescence was studied for Tm3+ and Er3+ in both Tm3+-Er3+-codoped and Er3+ singly doped ZrF4-based fluoride glasses for several dopant concentrations. It was found that the addition of Tm3+ enhanced the upconversion efficiencies of the green and the red emission corresponding to the transitions from the 4S3/2 and 4F9/2 levels of the Er3+ ion. The increase in the emission of samples containing 2 mol% TmF3 and 1.5 mol% ErF3 amounted to a factor of about 3 for the green emission and a factor of 300 for the red emission. The 1.48 µm emission from the transition of 3F4 to 3H4 for the Tm3+ ion decreased with increasing Er3+ concentration. The mechanism of the energy transfer from Tm3+ to Er3+ was discussed.
Effect of Overcoat Layer on Highly Reflective Coating for High-Average-Power Lasers
Authors: Motokoshi Shinji , Yoshida Hidetsugu , Yoshida Kunio , Tatsuhiko Yamanaka Tatsuhiko Yamanaka , Sadao Nakai Sadao Nakai
Published: October 2002

The effect of an overcoat layer on highly reflective coatings used for high-average-power lasers is presented. For high-average-power lasers, it is important to diffuse temperature localized due to such factors as impurity absorption in the coating. It was predicted from the calculation of thermal diffusion that the temperature rise was considerably relaxed in the radial direction by use of an overcoat layer which had high thermal conductivity. The damage threshold at a pulse repetition rate of 30 Hz was increased to about 20 J/cm2 from about 12 J/cm2 by adding an Al2O3 overcoat layer to a highly reflective coating.
New Class of Amorphous and Icosahedral Phases in Zn–Mg–Rare-Earth Metal Alloys
Authors: Niikura Akio , Tsai An-Pang , Akihisa Inoue Akihisa Inoue , Tsuyoshi Masumoto Tsuyoshi Masumoto
Published: October 2002

A new class of amorphous and icosahedral phases has been obtained in rapidly solidified Zn-Mg-Rare-Earth Metal (RE) ternary alloys. The rapidly solidified alloy structure exhibits the amorphous phase when it contains the RE elements of La, Ce, Pr or Eu with large atomic size. On the other hand, it exhibits the icosahedral phase when it contains Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu or Y. The tendency for the formation of amorphous or icosahedral phase is mainly dominated by the atomic size of RE elements.
Electrical Double-Layer Forces Measured with an Atomic Force Microscope while Electrochemically Controlling Surface Potential of the Cantilever
Authors: Ishino Takashi , Hieda Hiroyuki , Kuniyoshi Tanaka Kuniyoshi Tanaka , Nobuhiro Gemma Nobuhiro Gemma
Published: October 2002

The atomic force microscope was used to detect electrostatic forces and estimate surface potentials of samples in aqueous solution by applying voltage to a conducting tip. We controlled surface potential of a Au-coated cantilever electrochemically, and measured force vs distance curves on monolayers with different kinds of functional groups. As a result, we detected force variation with applied voltage to the tip, and the direction of force variation was found to agree with the polarity of surface charges due to the dissociation of the functional groups.
Thickness Dependence of the Epitaxial Structure of Vanadyl Phthalocyanine Film
Authors: Hoshi Hajime , Hamamoto Kenichi , Yamada Toshiki , Ishikawa Ken , Takezoe Hideo , Fukuda Atsuo , Fang Shaoli , Kohama Keiichi , Maruyama Yusei
Published: October 2002

We have studied the thickness dependence of the crystal structure in vanadyl phthalocyanine (VOPc) films epitaxially grown on KBr(100) surface. Optical second-harmonic generation observed in oblique incidence increases nearly quadratically with film thickness up to at least 64 nm and saturates, indicating a structural change from an epitaxial polar VO orientation to a nonpolar bulk crystal structure. The latter was assigned to monoclinic structure based on X-ray diffraction. Optical absorption spectra in visible and infrared regions and scanning electron microscopy also show the structural difference between the films thicker and thinner than about 80 nm.
Potentiometry Combined with Atomic Force Microscope
Authors: Uchihashi Takayuki , Fukano Yoshinobu , Sugawara Yasuhiro , Morita Seizo , Nakano Akihiko , Ida Tohru , Okada Takao
Published: October 2002

We have presented a novel method for surface potential measurement based on an atomic force microscope operating under the contact mode. This method is precise and exhibits sub-mV accuracy for potential measurement as well as nanometer-order spatial resolution. We show, for the first time, simultaneous measurements of the surface potential and surface actual topography on an ion-implanted silicon substrate with inhomogeneity of surface conductance.
Colored Shadow Moiré Topography Using Colored Light Sources: Red, Green, and Blue
Authors: Jo Jae Heung , Yuk Keun Cheol , Soo Chang Soo Chang
Published: October 2002

We present a simple method of determining the absolute order of fringes and the depression or elevation of the surface using colored moiré patterns (red, green, and blue). This technique is based on the various color patterns generated by the superposition of the three differently colored moiré fringes.
Observation of Atomic Structure by Scanning Tunneling Microscopy of Vicinal Si(100) Surface Annealed in Hydrogen Gas
Authors: Kuninori Kitahara Kuninori Kitahara , Osamu Ueda Osamu Ueda
Published: October 2002

This paper reports on the atomic structure and adsorbed species on a vicinal Si(100) surface annealed in H2. Annealing was carried out at 1000–1200°C under the H2 pressure of 4–7 Torr. The annealing in ultrahigh vacuum (UHV) was also carried out for comparison. Reconstruction structures of 2×1 and 1×2 were found by scanning tunneling microscopy (STM) for the surface annealed in H2 as well as that in UHV. The most obvious difference of the H2-annealed surface from the UHV-annealed one is a large retreat of S
A
steps resulting in promotion of a biatomic step formation. Thermal desorption spectroscopy indicated the presence of a monohydride phase on the H2-annealed surface, which is consistent with the 2×1 structure observed by STM.
Silicon-Hydrogen (SiHn, (n= 1, 2, 3)) Bonding Configurations in Very Thin Hydrogenated Amorphous Silicon Films Deposited on Various Kinds of Substrates under Different SiH4 Dilution Conditions
Authors: Drevillon Hajime Shirai
Published: October 2002

Silicon-hydrogen ( SiH

n

, ( n=1, 2, 3)) bonding configurations in the very thin hydrogenated amorphous silicon (a-Si:H) films ( <1000 Å) fabricated on various kinds of substrates under different SiH4 dilution conditions have been investigated by means of infrared phase-modulated ellipsometry (IRPME). The silicon-hydrogen configurations are monitored as a function of film thickness for a variety of substrates and the various SiH4 dilution conditions of H2, Ar and He. The deposition thickness for SiH stretching mode become dominant is strongly influenced by the nature of the substrate and the SiH4 dilution conditions.
Reverse Biased Annealing Studies in Hydrogenated Amorphous Silicon Solar Cells
Authors: Murthy R. V. R. , Singh V. Dutta
Published: October 2002

The effect of reverse biased annealing treatment in a-Si:H solar cells has been studied by using reverse current-voltage and forward capacitance-voltage measurements. The increase in reverse current at higher reverse biases in current-voltage characteristics and the anomalous peak in forward capacitance-voltage characteristics are attributed to the defect state at p-i interface. On the reverse biased annealing treatments, the reverse current as well as the peak in the forward capacitance decreases. This behaviour has been explained by passivation of the interface states, presumably due to hydrogen ions which are assisted by the applied electric field while annealing.
The Effect of Oxygen and Supply Rate of Mist on the Preparation of Y–Ba–Cu–O Superconducting Thin Films by the Mist Microwave-Plasma Chemical Vapor Deposition Method
Authors: Takahashi Naoyuki , Kosaka Akinori , Akinori Koukitu Akinori Koukitu , Hisashi Seki Hisashi Seki
Published: October 2002

The effect of the input molar ratio of oxygen (O
R) and supply rate of mist on the preparation of Y–Ba–Cu–O superconducting thin films by the MPCVD method have been investigated. Although the preparation of Y–Ba–Cu–O superconducting thin films was attempted at the input molar ratio of oxygen O
R=F
O2/(F
O2+ total F
Ar) from 0.1 to 0.8, the Y–Ba–Cu–O superconducting phase was formed only in the narrow range of O
R from 0.1 to 0.3. In addition, the formation of the Y–Ba–Cu–O superconducting phase was limited not only by the input molar ratio of oxygen but by the supply rate of mist.
310-Femtosecond Optical Pulse Generation from a Gain-Switched Laser Diode Using Soliton Compression
Authors: Hiroshi Ohta Hiroshi Ohta , Tokukoh Oki Tokukoh Oki
Published: October 2002

Stable subpicosecond optical pulses are generated from a gain-switched laser diode using soliton compression. The pulse width is 310 femtoseconds, which is adjusted by the input peak power and finely tuned by the DC bias to optimize the soliton condition. As a result, the experimental results agree well with theory, and the pulse width and peak power are very stable according to the estimation of temporal stability by the second-harmonic generator scheme. This indicates that fine tuning reduces the nonsoliton element.
Tunable Picosecond Pulse Generation from an Actively Mode-Locked Laser Diode Array with Intracavity Chirp Compensation
Authors: Chi-Luen Wang Chi-Luen Wang , Ci-Ling Pan Ci-Ling Pan
Published: October 2002

Wavelength-tunable picosecond pulses have been generated from an actively mode-locked laser diode array in an external cavity. The cavity incorporated a folded dispersive delay line which provided functions of pulse compression, wavelength tuning and spatial mode control. By varying the group velocity dispersion inside the cavity, the laser pulse width was intra-cavity compressed from 44 to 25 ps. The laser wavelength was tuned from 794 to 806 nm by translating a stripe end mirror horizontally with respect to the optical axis. The side mode suppression ratio was better than 10 dB over the entire tuning range. The spatial mode was a quasi-single-lobe.
Surface Potential of Polyimide Langmuir-Blodgett Films Induced by Photoirradiation
Authors: Mitsumasa Iwamoto Mitsumasa Iwamoto , Eiji Itoh Eiji Itoh
Published: October 2002

Surface potentials in two kinds of polyimide (PI and TRIPI) Langmuir-Blodgett films on various metal electrodes were examined before and after photoirradiation. Linear relationships between the saturated surface potential and the work function of metals were obtained before photoirradiation, suggesting that excess charges were transferred from metals into heat-treated PI LB films until thermodynamic equilibrium was attained at the interface. The heat-treated PI LB films were charged positively with photoirradiation, whereas the heat-treated TRIPI LB films were charged negatively. It was found that the linear relationships between the saturated surface potential and the work function of metals were again obtained after photoirradiation.
Anomalous Ferromagnetic and Antiferromagnetic Properties of Polyaniline Derivatives Depending on Acidic Treatment
Authors: Yoshino Katsumi , Mizobuchi Hiroshi , Araki Hisashi , Sakamoto Tsuyoshi Kawai
Published: October 2002

Optical and magnetic properties of a polyaniline derivative, copolymer prepared from aniline and 5-amino-2-naphthalene sulfonic acid, have been studied. These properties reflect protonation and deprotonation reactions in the polymer main chain, similarly to polyaniline. Temperature dependence of electron spin resonance (ESR) spectra shows characteristic antiferromagnetic and ferro- or ferrimagnetic behavior depending on acidic treatment. Preliminary results of tracing of magnetization curves have also been mentioned.
Phonon Softening in Au–49.5 at%Cd Alloy
Authors: Ohba Takuya , Shapiro S. M. , Aoki Shingo , Otsuka Kazuhiro
Published: October 2002

Phonon softening was observed in the parent phase of a AuCd alloy which transforms from the β2(B2) parent to ζ2′(trigonal) martensite atMs=304 K. Since Cd strongly absorbs neutrons, the isotope114Cd was used in preparing the single crystal for the measurements. The [ζζ0]TA2( u//[1\bar0]) phonon branch was measured and found to be anomalously low. A minimum is present at ζ=0.35 which softens asMsapproaches from above. The results are consistent with the model proposed by Ohbaet al. [Materials Trans. JIM 33 (1992) 29] based upon a crystallographic study of the ζ2′phase.
Passivation of GaAs Power Field-Effect Transistor Using Electron Cyclotron Resonance Chemical Vapor Deposition Silicon Nitride Technique
Authors: Chang Edward Yi , Lin Kun-Chun , Wu Janne-Wha , Chen Tzu-Hung , Chen John-Sea , Wang Sheng-Ping
Published: October 2002

Monolithic microwave integrated circuit (MMIC) chips are typically passivated with dielectric films to improve their long-term environmental reliability. Improper passivation generally degrades chip performance and reduces wafer yield. This paper reports the change of metal-semiconductor field-effect transistor (MESFET) parameters after silicon nitride passivation using electron cyclotron resonance chemical vapor deposition (ECR-CVD). In general, the changes in the electrical parameters after passivation are small. Gate-drain breakdown voltage of the MESFET's after ECR-CVD passivation is significantly improved compared to that after PECVD. The microwave characteristics of the high-powered MESFET's passivated using ECR-CVD silicon nitride are also reported in this paper.
Spin-Valve Effect in [{Co–Pt/Cu/Ni–Fe–Co}/Cu] Multilayers
Authors: Hiroshi Sakakima Hiroshi Sakakima , Mitsuo Satomi Mitsuo Satomi
Published: October 2002

Spin-valve multilayers using hard magnetic layers such as Co–Pt, instead of antiferromagnetic layers such as Fe–Mn, were proposed. [Co–Pt/Cu/Ni–Fe–Co/Cu]
N
multilayers were prepared by RF sputtering. The multilayers showed typical spin-valve type magnetoresistance (MR) characteristics with a considerably large MR ratio ( ∼4%) and a small switching field ( ∼5 Oe). The MR ratio increased with the repetition number N and showed a saturation tendency for N ≥5.
Second-Order Optical Nonlinearities of an Electrooptic Polymer Containing a Thiazole Ring and Its Use in Single-Mode Waveguide Fabrication
Authors: Watanabe Toshio , Michiyuki Amano Michiyuki Amano , Satoru Tomaru Satoru Tomaru
Published: October 2002

A new electrooptic (EO) polymer synthesized for optical waveguide devices contains a thiazole ring in a nonlinear optical (NLO) chromophore. The introduction of the thiazole ring results in a charge transfer (CT) band shift towards the near IR region, so this EO polymer has a large second-order nonlinearity even in the near IR region. Its d
33 and r
33 values at 1.3 µm are estimated to be 44 pm/V and 12 pm/V, respectively. Using this EO polymer as the core channel, we successfully fabricate single-mode waveguides by the reactive ion etching (RIE) technique.
Lyotropic Behavior of Poly(2,5-dinonyloxy-p-phenylenevinylene)
Authors: Maki Hamaguchi Maki Hamaguchi , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

It has been revealed that a concentrated chloroform solution of poly(2,5-dinonyloxy- p-phenylenevinylene) (NO-PPV) can be in a lyotropic liquid crystalline state at room temperature. The lyotropic NO-PPV solution exhibits redshift of optical absorption compared with the isotropic solution. X-ray diffraction analysis of an NO-PPV film cast from the chloroform solution suggested that a so-called sanidic (boardlike) mesophase formed in the solution state: i.e. the polymer main chains are extended, aligned side-by-side, and stacked parallel to each other. Preparation of fibers and films with preferred orientation from the NO-PPV solution was also described.
Highly Transparent and Conductive Zinc-Stannate Thin Films Prepared by RF Magnetron Sputtering
Authors: Minami Tadatsugu , Sonohara Hideo , Shinzo Takata Shinzo Takata , Hirotoshi Sato Hirotoshi Sato
Published: October 2002

Highly transparent and conductive zinc-stannate thin films, ZnSnO3, have been prepared by rf magnetron sputtering using a target composed of ZnO–SnO2 ( SnO2, 78 wt%). A resistivity as low as 4×10-3 Ω·cm and an average transmittance above 80% in the visible range were obtained for undoped zinc-stannate films deposited with substrate temperatures ranging from room temperature to 300°C. The zinc-stannate films were relatively more stable in an oxidizing environment at high temperatures than either ZnO or SnO2 films. In addition, thermal stability in a hydrogen environment was improved over SnO2 films, and chemical stability in both acidic and basic solutions was improved over ZnO films.
Influence of Electrode Contacts on Leakage Current of SrTiO3 Capacitors
Authors: Tamura Tetsuro , Takai Kazuaki , Noshiro Hideyuki , Kimura Mami , Seigen Otani Seigen Otani , Masao Yamada Masao Yamada
Published: October 2002

The current-voltage (I-V) characteristics of capacitors using SrTiO3 film were investigated. Rectification characteristics were observed, either when oxygen gas was introduced during sputter deposition of top electrodes, or when the SrTiO3 film was annealed in oxygen. These I-V characteristics are attributed to blocking contacts between SrTiO3 and the electrodes. It is considered that such contacts are formed because of the reduction of the crystal defects in SrTiO3 films, and they have decisive influence on the leakage current of the capacitor.
Raman Spectroscopic Study of Nb/AlOx–Al/Nb Josephson Junctions
Authors: Shin'ichi Morohashi Shin'ichi Morohashi
Published: October 2002

We have studied the AlO

x

barrier composition of niobium (Nb) Josephson junctions with a Nb/AlO

x

-Al/Nb structure using Raman spectroscopy at 10 K. We have observed both Al-O and Al-OH modes of an AlO

x

barrier with a few nm thickness in the Raman spectra through Nb counter electrode. For a structure annealed at 300°C, the Al-O mode intensity increases and the Al-OH mode intensity decreases. This contributes to a change in the critical current of the junction after annealing.
Origin of Depolarization in Sol-Gel Ferroelectric Pb(Zr0.4Ti0.6)O3 Thin-Film Capacitors
Authors: Mihara Takashi , Yoshimori Hiroyuki , Paz de Araujo Hitoshi Watanabe
Published: October 2002

We evaluated depolarization characteristics of sol-gel Pb(Zr0.4Ti0.6)O3 ferroelectric thin-film capacitors. The depolarization characteristics were strongly dependent upon the capacitance of the load capacitor. The newly obtained hysteresis loop during the pulse response indicates that significant voltage of opposite direction is generated on the ferroelectric capacitor at the moment the read pulse becomes zero. We experimentally found that the mechanism of depolarization is based on depoling (or partial switching) by an opposite-direction voltage arising from accumulated switching charge on a load capacitor. This mechanism can be easily extended to the internal depolarization effect due to the interfacial linear capacitor between the ferroelectric region and electrode.
Self-Formed In0.5Ga0.5As Quantum Dots on GaAs Substrates Emitting at 1.3 µm
Authors: Mukai Kohki , Ohtsuka Nobuyuki , Mitsuru Sugawara Mitsuru Sugawara , Susumu Yamazaki Susumu Yamazaki
Published: October 2002

We grew 1.3-µm emitting self-formed In0.5Ga0.5As quantum dots on GaAs substrates by supplying InAs and GaAs monolayers alternately during atomic layer epitaxy. The dots were 20 nm in diameter and 10 nm in height, and were surrounded by In0.1Ga0.9As in the lateral direction and by GaAs perpendicular to the dots. Diamagnetic energy shifts of excitons in the dots clearly demonstrated three-dimensional quantum confinement.
Photoresist Characteristics of Polyurea Films Prepared by Vapor Deposition Polymerization
Authors: Sato Masatoshi , Masayuki Iijima Masayuki Iijima , Yoshikazu Takahashi Yoshikazu Takahashi
Published: October 2002

Aromatic polyurea was prepared by vapor deposition polymerization of 4,4′-diaminodiphenyl methane and 4,4′-diphenylmethane diisocyanate, and the mass spectra of the gases obtained from the polyurea by heating were measured. Mass spectrum analysis revealed depolymerization, which is a distinctive feature of polyurea. The polyurea finally evaporated completely at 300°C or lower in a vacuum. A Fourier transform infrared (FT-IR) analysis indicated that polymerization and cross-linking took place between unreacted end groups or urea bonds in the polyurea that was exposed to ultraviolet light. As a consequence, the exposed polyurea did not evaporated even at temperatures greater than 300°C. Exploiting the difference in thermal resistance between the exposed and unexposed polyurea, films were developed by heating, yielding a resolution of 5-micron lines and spaces. It was found that the polyurea can be used as a negative resist material, and that an all-dry lithographic process could be accomplished. In addition, the dielectric strength of the exposed polyurea is 2.5 times as much as that of unexposed polyurea.
Low-Temperature Surface Cleaning of GaAs Using Trisdimethylaminoarsine
Authors: Nomura Yasuhiko , Shigeo Goto Shigeo Goto , Yoshitaka Morishita Yoshitaka Morishita
Published: October 2002

We applied trisdimethylaminoarsine (TDMAAs) to the surface cleaning of GaAs (111)B substrates in a high-vacuum environment in order to lower the treatment temperature. The native oxide formed on the substrate was removed at substrate temperatures as low as 400°C under TDMAAs pressure. Characterizations by atomic force microscopy and secondary ion mass spectrometry showed that TDMAAs cleaning markedly improves the surface smoothness and reduces residual impurities (carbon and oxygen) compared to conventional thermal cleaning using As4. The photoluminescence spectra (77 K) of GaAs/AlGaAs quantum wells grown by molecular beam epitaxy directly (without a GaAs buffer layer) on a TDMAAs-cleaned substrate were comparable to those on a 500-nm-thick GaAs buffer layer after thermal cleaning.
Thin-Film Polycrystalline Si Solar Cell on Glass Substrate Fabricated by a Novel Low Temperature Process
Authors: Yamamoto Kenji , Nakashima Akihiko , Suzuki Takayuki , Yoshimi Masashi , Hitoshi Nishio Hitoshi Nishio , Masanobu Izumina Masanobu Izumina
Published: October 2002

Thin film polycrystalline Si solar cells on glass substrates were fabricated by the excimer laser annealing of heavily boron doped a-Si and the subsequent deposition of polycrystalline Si on them by plasma-enhanced chemical vapor deposition at low temperature. The resistivity of the heavily boron doped laser annealed polycrystalline Si film is as low as 2×10-4 Ω·cm. The structure of the solar cell presented here is ITO/n µc-Si:H (30 nm)/p poly-Si (2 µm)/p+ poly-Si (300 nm)/glass substrate, which shows reasonably high current density despite the low-temperature fabrication. The effective diffusion length of this solar cell estimated from the evaluation of the inverse quantum efficiency is more than or equal to the thickness ( 2 µm) of the solar cell.
Accurate Determination of the Urbach Energy of a-Si:H Thin Films by Correction for the Interference Effect
Authors: Leblanc François , Maeda Yoshihito , Ando Masahiko , Masatoshi Wakagi Masatoshi Wakagi , Tetsuroh Minemura Tetsuroh Minemura
Published: October 2002

The absorptance spectra of a-Si:H films thinner than 0.5 µm are distorted by the presence of only a few interference fringes, which makes the determination of the Urbach energy (UE) difficult. The interference effect is analyzed by computing the absorptance spectrum as a function of the film's thickness t. The difference between the UE derived by exponential interpolation and the actual UE reaches a maximum of 17 meV for t ≈220 nm, and it can not be neglected even for films thinner than 100 nm. We measured the photothermal deflection spectroscopy spectra for several film thicknesses and corrected the UE by numerically fitting the spectra.
DC and AC Characteristics of ZnSe/Ge/GaAs and ZnSe/InGaAs/GaAs Lattice-Matched Heterojunction Bipolar Transistors Grown by Metal-Organic Chemical Vapor Deposition
Authors: Tseng Hsien Cheng , Ji Lung Shen Ji Lung Shen , Ru Chu Hsieh Ru Chu Hsieh
Published: October 2002

We report the first demonstration of ZnSe/Ge/GaAs and ZnSe/InGaAs/GaAs closely lattice-matched heterojunction bipolar transistors (HBTs) grown by the low-pressure metal-organic chemical vapor deposition (MOCVD) system. Both ZnSe/Ge/GaAs and ZnSe/lnGaAs/GaAs HBTs have advantages of larger valence band offset (ΔE
v), lower base resistance, and lower contact resistance compared with the AlGaAs/GaAs HBT for high-speed digital circuits. Based on S-parameter measurements at 77 K, a unity-gain cutoff frequency f
T=6 GHz and a maximum oscillation frequency f
max=13 GHz at a collector current density of 1.8 kA/cm2 were obtained for the ZnSe/Ge/GaAs HBT. To our knowledge, this is the first II-VI/IV/III-V compound-semiconductor HBT ever reported to operate at such a high frequency.
Lattice Constants of the Proton-Exchanged Waveguides Formed on Domain-Inverted LiTaO3
Authors: Kondo Yukiko , Li Yu-Shan , Onoe Atsushi , Tada Kunio , Yoichi Fuji Yoichi Fuji
Published: October 2002

The lattice constants in the proton-exchanged waveguide layers formed on the LiTaO3 substrate with and without the domain-inverted structure are determined with the X-ray rocking curve method. The increase in lattice constant caused by the proton-exchange process (Δ
c/ c
) is 0.53%. The values Δ
c/ c
measured in the annealed proton-exchanged waveguides with domain-inverted slab structure, with the periodically domain-inverted structure, and without the domain-inverted structure are 0.19%, 0.21% and 0.23%, respectively.
Organic Electroluminescent Devices Using a Mixed Single Layer
Authors: Naka Shigeki , Shinno Kazuhisa , Okada Hiroyuki , Miyashita Hiroyoshi Onnagawa
Published: October 2002

Electroluminescent devices with mixed single-layer organic materials that consist of hole transport meterial,
electron transport material and dopant material are studied. High luminance could be obtained by optimizing
the weight ratios of hole and electron transport materials.
Isolated Nanometer-Size Si Dot Arrays Fabricated Using Electron-Beam Lithography, Reactive Ion Etching, and Wet Etching in NH4OH/H2O2/H2O
Authors: Nakajima Anri , Hajime Aoyama Hajime Aoyama , Kazuo Kawamura Kazuo Kawamura
Published: October 2002

A simple technique for fabricating an array of isolated nanometer-size Si dots is reported. The processing procedures consist of electron beam lithography and reactive ion etching followed by wet etching in NH4OH/H2O2/H2O. The resulting array has isolated crystalline Si dots, each 10 nm in diameter and 10 nm high. To our knowledge, these are the smallest isolated crystalline Si dots reported to date.
Implanted Antimony Precipitation in Silicon Studied by Medium-Energy Ion Scattering
Authors: Hashimoto Makoto , Deguchi Tadayoshi , Yokoyama Shin , Masataka Hirose Masataka Hirose
Published: October 2002

Implantation of 50 keV Sb+ ions has been accomplished into silicon through 10 nm thermal oxides with doses ranging from 1×1014 cm-2 to 1×1015 cm-2. The Sb precipitation process at different annealing temperatures has been evaluated by medium-energy ion scattering (MEIS) and Raman scattering. Annealing at 900°C for 30 min causes Sb precipitation in the bulk Si at concentrations above ∼2×1020 cm-3, while at the SiO2/Si interface the precipitation occurs above 5×1019 cm-3. The bulk precipitation limit is about one order of magnitude larger than that of the thermal equilibrium solid solubility of Sb ( 3×1019 cm-3), while the precipitation at the Si surface or the SiO2/Si interface occurs at concentrations over the thermal equilibrium value.
Prevention of Resist Pattern Collapse by Flood Exposure during Rinse Process
Authors: Tanaka Toshihiko , Morigami Mitsuaki , Oizumi Hiroaki , Taro Ogawa Taro Ogawa , Shou-ichi Uchino Shou-ichi Uchino
Published: October 2002

A resist hardening method that prevents resist pattern bending is described. In this method, a photo-crosslinking resist is flood exposed during rinsing. This exposure increases the crosslinking ratio of the resist, thus hardening the resist pattern before drying. Using this method, a 1.6-µm-thick 0.25-µm line-and-space pattern can be delineated without resist bending.
Plasma-Enhanced Diamond Nucleation on Si
Authors: Katoh Masahiro , Makoto Aoki Makoto Aoki , Hiroshi Kawarada Hiroshi Kawarada
Published: October 2002

Both positive and negative bias effects on the nucleation of chemical vapor deposition (CVD) diamond have been investigated thoroughly in microwave plasma. Prior to the conventional microwave plasma CVD growth of diamond, positive or negative biasing pretreatment has been performed. The pretreatment conditions were varied in terms of substrate bias voltage ( -100∼+100 V), pretreatment pressure ( 0.2∼15 Torr), and methane fraction ( 2∼40%) in hydrogen source gas. It is found that the positive substrate bias as well as the negative bias are effective for the nucleation of diamond.
Suppression of Precipitate Formation in Heteroepitaxial Growth of YBa2Cu3O7-δ Film on Misoriented SrTiO3 Substrates
Authors: Gong Jianping , Kawasaki Masashi , Fujito Kenji , Tsuchiya Ryuta , Yoshimoto Mamoru , Koinuma Hideomi
Published: October 2002

We have investigated the effect of misoriented substrates on precipitate formation in c-axis-oriented YBa2Cu3O7-δ films grown by the pulsed laser deposition technique. The films grown on exact SrTiO3(100) substrates had precipitate densities as high as 107–108/cm2, whereas the films on substrates with surfaces misoriented from (100) by 0.5°–1° had fewer precipitates by two to three orders of magnitude. A film surface of 105/cm2 precipitates can give 90% probability of a precipitate-free practical device size area (10 µ m×10 µ m), providing a high possibility of successful fabrication of a Josephson tunnel junction.
Effect of Mg-mixing on Band Offsets in ZnCdSSe Superlattices
Authors: Takashi Nakayama Takashi Nakayama
Published: October 2002

The band offsets of Mg-mixed ZnSSe strained superlattices are calculated by the first-principles pseudopotential method in the local density approximation. It is shown that Mg-mixing into the barrier layers increases the band offsets for both the heavy-hole and electron states, thus strengthening the carrier confinement, which is in agreement with experiments. A chemical trend of the offset among various II-VI superlattices is discussed using the atomic orbital energies and radii.
Preparation of γ-Iron Ultrafine Particles Using a Transversely Excited Atmospheric CO2 Laser
Authors: Majima Tetsuro , Miyahara Tesshu , Haneda Koichi , Michio Takami Michio Takami
Published: October 2002

γ-Iron ultrafine particles which are stable at room temperature have been prepared in a high yield of maximum 90% by the SF6-sensitized infrared photodecomposition of Fe(CO)5 using a transversely excited atmospheric (TEA) CO2 laser. The obtained γ-iron particles are isotropic in shape, having an uniform size of 6.5–8.5 nm with a mean size of 7.6 nm and fcc structure, and are paramagnetic at 1.8–295 K The paramagnetic fcc γ-iron particles begin to transform into ferromagnetic bcc α-iron above 473 K with almost complete conversion to α-iron at 653–693 K.
Influence of Deformation of Smectic Layer Structure on Dielectric Behavior of Ferroelectric Liquid Crystal
Authors: Itoh Nobuyuki , Koden Mitsuhiro , Miyoshi Shuji , Akahane Tomio Wada
Published: October 2002

The dielectric permittivity of a surface stabilized ferroelectric liquid crystal (SSFLC) cell was found to be influenced by the electric field treatment, which changed the smectic layer structure and the cell texture. The relationship between the dielectric permittivity and the texture change was studied, considering the effect of the deformation of the smectic layer structure on the dielectric behavior of SSFLC.
Optical Study of Intermixing in CdTe/CdMgTe Quantum Wells
Authors: Tönnies Dietrich , Bacher Gerd , Forchel Alfred , Waag Andreas , Litz Thomas , Landwehr Gottfried
Published: October 2002

CdTe/CdMgTe quantum wells were processed by rapid thermal annealing (RTA) at temperatures between 390° C and 550° C. Due to the interdiffusion of Cd and Mg ions the photoluminescence of the quantum wells exhibits strong blue shifts up to 360 meV at the highest annealing temperature. This energy shift is close to the total discontinuity of the quantum well structures, indicating an almost perfect interdiffusion of barrier and well material. By using a simple model for the quantum well potential changes due to interdiffusion we derive the interdiffusion length as a function of the annealing temperature. The interdiffusion is characterized by an activation energy of 2.8 eV.
Polymer Light-Emitting Diodes with Single- and Double-Layer Structures Using Poly(2,3-diphenylquinoxaline-5,8-diyl)
Authors: Yamamoto Takakazu , Tetsuji Inoue Tetsuji Inoue , Takaki Kanbara Takaki Kanbara
Published: October 2002

A light-emitting diode (LED) using poly(2,3-diphenylquinoxaline-5,8-diyl) (PdPhQx) as the light-emitting material, ITO/PdPhQx/MgAg, emits blue-green (490 nm) light. Introduction of hole transporting layers such as vacuum-deposited or spin-coated thin layers of poly(thiophene-2,5-diyl), poly( p-phenylene), and poly(N-vinylcarbazole) between ITO and PdPhQx in the LED enhances electroluminescence efficiency by about two orders of magnitude. Addition of a diaryldiamine (TPD) in the PdPhQx layer causes a red shift of the emitted light to 565 nm due to formation of an exciplex between PdPhQx and TPD.