bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Study of Direct Measurement of Nonlinear Response Time of Conjugated Polymer Based on Cross-Phase-Modulation
Authors: Zhao Ying-Qiao , Zhu He-Yuan , Liu Jian-Hua , Die-Chi Sun Die-Chi Sun , Fu-Ming Li Fu-Ming Li
Published: October 2002

In this paper, we present a time-resolved pump-probe method based on cross- phase-modulation (XPM) to measure nonlinear response time. The nonlinear response time can be determined by comparing the self-frequency-shift curve obtained from the numerical calculation with the experimental results.
Characterization of Thin-Film Electroluminescent Devices with Multiple Ta2O5 Interlayers Incorporated into SrS:Pr,Ce Phosphor
Authors: Horng Ray-Hua , Kung Dong-Sing Wuu
Published: October 2002

A thin-film electroluminescent device (ELD) has been fabricated by incorporating multiple Ta2O5 interlayers into the SrS:Pr,Ce phosphor layer using rf-magnetron sputtering. X-ray measurement results confirm the enhanced crystallinity of the phosphor layer and can be explained by the extra thermal-cycle annealing due to the different deposition temperatures for Ta2O5 (100° C) and SrS (500° C). The inclusion of thin barrier films is expected to redistribute the internal field and introduce additional interface states in the ELD structure. Based on the results of Sawyer-Tower circuit measurements, it is found that the transferred charge density in the active layer can increase with the number of intermediate layers. This contributes to an increase in brightness and the reduction of the threshold voltage. Moreover, a stacked structure for SrS:Pr and SrS:Ce phosphor layers with window effects is proposed to alleviate the absorption problem in the SrS:Pr,Ce multi-barrier ELD structure. Details of the mechanism and the improvement in the chromaticity will also be described.
Hole Transport in Hydrazone Doped Polymers
Authors: Sinicropi J. A. , Lin L.-B. , P. M. Borsenberger P. M. Borsenberger , E. H. Magin E. H. Magin
Published: October 2002

Hole mobilities have been measured in poly(styrene) doped with a series of hydrazone (HDZ) molecules with different dipole moments. The results are described by a formalism based on disorder. The formalism is premised on the argument that charge transport occurs by hopping through a manifold of localized states that are distributed in energy. The parameters of the formalism are σ, the energy width of the hopping site manifold or DOS (density-of-states), µ0a prefactor mobility, and Σ the degree of positional disorder. The results show that the widths are between 0.098 and 0.113 eV, increasing with increasing dipole moment. The widths are described by an argument based on dipolar disorder. The argument is that the total width of the DOS is comprised of a dipolar component and a van der Waals component. Describing the dipolar component by the model of Young leads to the conclusion that the van der Waals components are approximately 0.091 eV. The prefactor mobilities are between 6 and 9×10-3cm2/ Vs. Values of Σ are approximately 1.5. Compared to other classes of doped polymers with similar dipole moments, the relatively low mobilities of these materials are attributed to the high values of the van der Waals components and the low prefactor mobilities. The degree of positional disorder is similar to literature values reported for a wide range of doped polymers.
Impurity Gettering Effect in Pr2O3- Added InGaAs Liquid Phase Epitaxy
Authors: Chang Liann-Be , Wang Tung-Win , Liu Cheng-Chung , Wu Yao-Hwa , Yi-Chang Cheng Yi-Chang Cheng
Published: October 2002

InGaAs epilayers were grown on semi-insulating (SI) InP substrates by liquid phase epitaxy (LPE) with a rare-earth (RE) compound Pr2O3 added into the growth melt during the epitaxial process for the first time. Without the growth melt baking process, the corresponding Hall measurements indicate that the background concentration of these InGaAs-grown layers will decrease from a value of 1.6×1016 cm-3 to 2.0×1015 cm-3. Their corresponding 77 K mobility also increases significantly from a value of 15321 cm2/ V·s to 32171 cm2/ V·s. The X-ray diffraction measurements, secondary ion mass measurements (SIMS) and photoluminescence (PL) spectra of Pr2O3- added InGaAs epitaxial layers all demonstrate that the grown layers exhibit pure crystalline quality. Finally, InGaAs/InGaAs/InP pin diodes were fabricated, and a smaller leakage current and better response for the Pr2O3- added samples were reported.
Preparation of Cu 10Zr 7 Intermetallic Compound Film and Its Application as a Diffusion Barrier in Cu/Cu 10Zr 7/ZrN/Si Contact System
Authors: Ken-ichi Yoshimoto Ken-ichi Yoshimoto , Hideto Yanagisawa Hideto Yanagisawa , Katsutaka Sasaki Katsutaka Sasaki
Published: October 2002

We investigated the diffusion barrier properties of Cu10Zr7 intermetallic compound film for possible application to Cu metallization technology. First, a Cu/Zr bilayered film was heat-treated in vacuum at various temperatures for 1h, to confirm the most stable Cu–Zr compound formed by solid-phase reaction. It was found that a single phase of Cu10Zr7 compound can be obtained at temperatures above 550°C and that this compound film is stable up to 600°C. On the other hand, by the co-sputtering method, although CuZr2–Cu10Zr7 mixture alloy film was prepared, no Cu10Zr7 single-phase compound film was obtained. We heat-treated the Cu/CuZr2–Cu10Zr7 bilayered film for 2h at 500°C, which was lower than the temperature necessary for the formation of Cu10Zr7 by solid-phase reaction. In this way, we prepared the stoichiometric Cu10Zr7 film. Then, we produced the Cu/Cu10Zr7/ZrN/Si contact system using this Cu10Zr7 film as a diffusion barrier and investigated its thermal stability. We found that the system is satisfactorily stable up to 650°C without any Si diffusion, although a slight diffusion of Cu was observed at the interface of Cu/Cu10Zr7.
Effects of Sodium on Cu(In, Ga)Se2-Based Thin Films and Solar Cells
Authors: Nakada Tokio , Iga Daisuke , Hiroki Ohbo Hiroki Ohbo , Akio Kunioka Akio Kunioka
Published: October 2002

Cu(In, Ga)Se2 (CIGS) films were deposited with intentionally incorporated Na2Se by a multi-step process onto SiO

x

/soda-lime glass substrates at elevated temperatures. The effects of sodium on film properties were investigated using X-ray diffraction, X-ray photoelectron spectroscopy and Hall effect measurements. By the addition of Na2Se, the hole concentration of the CIGS-based films (Ga/(In+Ga) ratio=0.37–0.39) increased dramatically to the 1016–1017
c
m
-3 range for a wide range of Cu/(In+Ga) ratios from 0.4 to 0.8. The increased hole concentration resulted in improved CIGS-based solar cells with efficiencies of 10–13.5% over an extremely wide Cu/(In+Ga) ratio range of 0.51–0.96. P-type Cu(In, Ga)3Se5 phase films with hole concentrations high enough to be used as absorber layers of photovoltaic devices were obtained for the first time by the Na control technique. The possibility of a new type of solar cell with a ZnO:Al/buffer/ p-Cu(In, Ga)3Se5 heterojunction structure is suggested.
Kinetics and Depth Distributions of Oxygen Implanted into Si Analyzed by the Monte Carlo Simulation of Extended TRIM
Authors: Yoneda Tomoaki , Kajiyama Kenji , Tohjou Fumiyo , Yoshioka Yoshiaki , Ikeda Atsushi , Kisaka Yoshiaki , Nishimura Tomoaki , Kido Yoshiaki
Published: October 2002

We precisely measure the depth profiles of 50–200 keV 18O+ implanted into Si and
SiO2 by secondary ion mass spectrometry (SIMS) and then best-fit the on. The O-profiles derived from the RBS
analysis are compared with those calculated by the extended TRIM. The present analysis
revealed that the O-atoms implanted at 550° C migrated toward the surface before reaching
the stoichiometry ( SiO2). The diffusion coefficient was estimated to be about 1×10-14 cm2/ s, which was about 2 orders of magnitude larger than the value for 16O in crystalline Si
at 550° C. This is possibly due to the induced dense defects distributed from the mean
depth of 16O toward the surface (enhanced diffusion).
Impedance of Metal–Gel Derived Film Interface
Authors: Banerjee S. , Chakravorty D.
Published: October 2002

Gel films of different compositions were grown on stainless steel and copper electrodes with varying degrees of roughness. The gel systems chosen were xM2O–(100- x)SiO2 (mole%) with M=Li, Na or K and x having values 10, 20 and 30 respectively. AC impedance of cells comprising the above with a counter electrode of the same type was measured over the frequency range 5 Hz to 1000 kHz. Constant Phase Angle (CPA) impedance characterizing the electrode–electrolyte interface shows a variation with frequency with the exponent n having values in the range 0.30 to 0.48. The fractal dimensions d of the electrode surfaces were determined from the self affine surface profile measurements. The ac impedance deduced n values are found to be in reasonable agreement with those calculated from the fractal dimensions of the electrode surfaces.
Structural, Electrical and Optical Properties of Sol–Gel Processed Lead Titanate Thin Films
Authors: Reji Thomas Reji Thomas , D. C. Dube D. C. Dube
Published: October 2002

Polycrystalline PbTiO3 thin films having layered perovskite structure were fabricated by a sol–gel (spin coating) processing method. The substrates used were fused silica and stainless-steel. Surface morphology of the films was studied with scanning electron microscopy (SEM). The effect of post-deposition annealing on the electrical and structural properties were analyzed. Crystalline phase of PbTiO3 can only be obtained when the annealing temperature is higher than 500°C. The electrical measurements were conducted on metal–film–metal capacitors. Films annealed at 600°C exhibited crystallinity with perovskite phase, a dielectric constant of 132 and a dissipation factor of 0.039 at 1 kHz. I-V characteristics were found to be ohmic at low fields and space charge limited, controlled by traps at high fields. Transmission spectra of the films deposited on fused silica were recorded and from this, refractive index, extinction coefficient and thickness of the films were calculated. The standard deviation of the thickness was found to be 18.8 nm. The dispersion curve for the refractive index `n' is fairly flat beyond 500 nm and rises rapidly towards shorter wavelength region, showing the typical shape of dispersion curve near an interband transition. The refractive index was found to be in the range 2.00–2.20 for different wavelengths (300 to 900 nm).
Formation of a New Phase in Ru Films by Sputtering Based on Band Calculation Prediction
Authors: Kazuo Shiiki Kazuo Shiiki , Okitoshi Hio Okitoshi Hio
Published: October 2002

The formation of the metastable Ru films sputtered onto a glass substrate and single crystals with different lattice constants was studied. X-ray diffraction(XRD) and electron beam diffraction(EBD) analyses revealed a new phase that grew on Mo single crystal, which appears to be a single-crystal-like body centered tetragonal structure, although the equilibrium phase is hexagonal close-packed structure. Such phase formation is reasonable considering the total energy calculated by band calculation.
Analyses of Nonlinear Circuits with Nonlinear Impedances and Generators
Authors: Hiroshi Orihara Hiroshi Orihara , Yoshihiro Ishibashi Yoshihiro Ishibashi
Published: October 2002

Nonlinear circuits consisting of passive impedances and generators are analyzed on the basis of inversion formulae and Kirchhoff's rules. We derived formulae giving nonlinear voltages and currents in any network.
Study on Chaotic Characteristics of Incidence Data of Measles
Authors: Sumi Ayako , Ohtomo Norio , Tanaka Yukio
Published: October 2002

In this paper, the chaotic characteristics of time series data of monthly number reported cases of measles in New York City from January 1928 to December 1963 were investigated using the computing program “MemCalc”. Power spectral densities (PSDs) were calculated for the measles data, two types of time series numerically calculated from the SEIR epidemic model (the chaotic and periodic time series) and the noisy time series. Exponential characteristics were observed in the PSDs for the measles data and the chaotic and periodic time series, but not observed in the PSDs for the noisy time series. For the measles data and the chaotic time series, the PSDs exhibit the broad continuous peaks peculiar to the chaotic state. The behavior of the three-dimensional spectral array obtained from segment time series analysis is distinguishable from the cases of the periodic and noisy time series. It was concluded that the dynamics of the measles data is chaotic. The present method was used to extract the chaotic characteristics from measles data having a short time period.
Simulation-Based Automatic Optical Proximity Effect Correction Adaptive for Device Fabrication
Authors: Tsudaka Keisuke , Furumi Koji , Hidetoshi Ohnuma Hidetoshi Ohnuma , Hiroichi Kawahira Hiroichi Kawahira
Published: October 2002

A new optical proximity effect correction (OPC) method adaptive for device fabrication has been developed, focusing on the evaluation method of printed images through simulation. The evaluation procedure of this method is consist of not only measurement of edge placement error of the printed image but analysis of the shape of the printed image. Automatic correction which is flexible for various pattern shapes is available, and distortion via overcorrection is prevented. By using this method for 0.28 µ m static random access memory (SRAM) poly-Si patterns, an excellent distortion-free printed image adequate for actual device fabrication processing has been obtained with simple mask patterns. The SRAM cell size was reduced to as small as 5 µ m2.
Site-Specific Chemical-Bond Scission in Poly(Methyl Methacrylate) by Inner Shell Excitation
Authors: Ueno Nobuo , Tanaka Kenichiro
Published: October 2002

The results of photon-stimulated ion desorption (PSID) from thin solid films of poly(methyl methacrylate) (PMMA) and corresponding polymers, poly(methyl acrylate) (PMA) and poly(methacrylic acid) (PMAA), owing to inner-shell excitation, are briefly reviewed. The results show that an enhancement of PSID takes place effectively upon electron excitation to a particular antibonding molecular orbital, indicating that the excitation to the antibonding state plays a major role in PSID enhancement. As a typical example, CH3+desorptionviaoxygen 1s electron excitation was shown as a function of photon energy. By comparison of the photon energy dependences of PSID yields of CH3+from the three polymers, it was found that the excitation of oxygen 1s electron at OCH3to the σ*state localized at COCH3in PMMA results in the enhanced emission of CH3+by bond scission at the side chain ( O–CH3), not at the main chain. The results indicate that there is a strong correlation between the sites of excitation and the following chemical-bond rupture. It is pointed out that monochromatic synchrotron radiation can be used as a “scalpel” to cut a chemical bond selectively in a molecular solid.
Application of a New Adhesion Promoter to Stable Chemically Amplified Resist Pattern Fabrication on Boron Phosphorus Silicate Glass Substrates
Authors: Masayuki Endo Masayuki Endo , Akiko Katsuyama Akiko Katsuyama
Published: October 2002

We have developed a new, non-ammonia generating adhesion promoter, 4-trimethylsiloxy-3-pentene-2-one. Its adhesion ability to a substrate is superior to the conventional adhesion promoter, hexamethyldisilazane, due to its high reactivity. We obtained high-aspect-ratio and precise chemically amplified resist patterns on boron phosphorus silicate glass (BPSG) substrates using this new adhesion promoter.
Annealing of Silica Glasses Implanted with High-Energy Copper Ions
Authors: Nakao Setsuo , Miyagawa Yoshiko , Saitoh Kazuo , Ikeyama Masami , Niwa Hiroaki , Tanemura Seita , Soji Miyagawa Soji Miyagawa , Masato Tazawa Masato Tazawa
Published: October 2002

Silica glasses were implanted with 1.8 MeV Cu ions at a dose of 0.32–1.3×1017 ions/cm2 at a temperature of less than 300° C. The thermal annealing of the samples was carried out in air in the range of 300–1100° C, and the effects on the formation and growth of Cu nanoparticles were examined as a function of ion dose and annealing temperature using Rutherford backscattering spectrometry and optical absorption measurements. It was found that the broad absorption band between 250–400 nm was increased and the average radius of Cu particles was slightly decreased where the total concentration of Cu was not changed up to 700° C. This suggests that small Cu precipitates were generated. The surface plasmon resonance absorption at approximately 570 nm was clearly developed at 800° C. In addition, the average radius of Cu particles increased as the annealing temperature increased from 800–1000° C. However, the concentration of Cu began to decrease at temperatures above 800° C. The plasmon absorption also decreased in intensity with increasing temperature, which indicated that the amount of Cu particles had decreased. The decrease of the amount of Cu particles was affected by ion dose.
Ion Beam Modification of a Photoresist and Its Application to Field Emitters
Authors: Tanemasa Asano Tanemasa Asano , Daisuke Sasaguri Daisuke Sasaguri , Eiji Shibata Eiji Shibata , Katsuya Higa Katsuya Higa
Published: October 2002

Ion beam irradiation effects on a novolac positive-tone photoresist and its application to micron-size field emitters have been investigated. Irradiation of Ar and P ions was examined. The electrical resistivity of the photoresist film is found to decrease after Ar ion implantation at doses on the order of 1016 cm-2. Baking of the photoresist prior to irradation at a high temperature is preferred to produce electrical conductivity. P ions show weaker effects than Ar ions. Raman spectroscopy shows that carbon-carbon bonds such as the graphite bond are produced due to ion bombardment. The field emission of electrons is observed from emitters made of the ion-irradiated photoresist. The emission current is shown to be fairly stable when it is compared with an emission characteristic of synthesized diamond. Fabrication of field emitter arrays using a mold technique is demonstrated. The field emitter array shows emission at a current level of about 40 µA.
Calixarene Electron Beam Resist for Nano-Lithography
Authors: Fujita Jun-ichi , Ohnishi Yoshitake , Manako Shoko , Ochiai Yukinori , Nomura Eiichi , Toshitsugu Sakamoto Toshitsugu Sakamoto , Shiniji Matsui Shiniji Matsui
Published: October 2002

New electron beam (EB) resists made of calixarene resists are introduced. Typical sensitivities of calixarene resists range from 700 µ C/cm2 to 7 mC/cm2. High-density dot arrays with 15 nm diameter constructed using calixarene resist were easily delineated using a point EB lithography system. Our results suggest that the resolution limit of calixarene resists is dominated by a development process such as adhesion to a substrate rather than by the EB profile. Calixarene resists are resistant to etching by halide plasma. We also demonstrated nanoscale devices processed by using calixarene resists. Calixarene resists are promising materials for nanofabrication.
Analysis of Columnar Microstructure in Fe–N Thin Films Prepared by an Ion-Assisted Vapor Deposition Method
Authors: Yoshida Osamu , Ishikawa Junko , Katsumi Endo Katsumi Endo , Noriyuki Kitaori Noriyuki Kitaori
Published: October 2002

Iron nitride thin film was produced through an ion-assisted evaporation process. After structural and elemental analyses using X-ray diffraction and energy dispersion X-ray spectroscopy it was judged that the film is ε-Fe3N. It was found that this film consists of straight columns. Moreover, an X-ray line analysis across the columnar direction clarified that the sides of the columns are oxidized. In addition, the electron diffraction patterns obtained suggest that the c-axis of ε-Fe3N (hexagonal) is in line with the direction of the columns.
Coulomb-Blockade Dominated Transport in Patterned Gold-Cluster Structures
Authors: Wybourne Martin N. , Clarke Laura , Yan Mingdi , Cai Sui X. , Brown Leif O. , Hutchison James , Keana John F.W.
Published: October 2002

In this paper we present the fabrication and near-room temperature electrical transport properties of structures made from the gold-cluster material Au55[P(C6H5)3]12Cl6. We discuss the use of electron-beam lithography to define the structures laterally and compare the direct current-voltage characteristics of non-patterned and patterned structures. In both cases non-linear behavior is observed with features that are consistent with Coulomb blockade dominated transport in disordered arrays of clusters. Radio frequency induced plateaus in the current-voltage characteristics demonstrate coherent tunneling. Finally, we show that other ligand stabilized gold-cluster materials can be used to form ordered gold-cluster arrays.
Low Temperature Synthesis of Diamond Films in Thermoassisted RF Plasma Chemical Vapor Deposition. II
Authors: Ichiro Watanabe Ichiro Watanabe , Koushin Yoshie Koushin Yoshie
Published: October 2002

Diamond films are synthesized using a radio-frequency (13.56 MHz) plasma and external heating by infrared radiation. A film without nondiamond carbon is deposited at temperatures of 350–600°C from a mixture of C2H5OH and H2. Diamond quality at low temperature is improved by changing the impedance-matching condition of the radio-frequency system, incorporation of O2, or incorporation of CF4. In these trials, the incorporation of CF4 is most effective for the improvement of diamond quality. A high-quality film is deposited even at 350°C from a mixture of 0.5% C2H5OH, 0.5% CF4 and 99% H2 without using external heating. The quality improves as the temperature is increased up to 550°C.
Fast Calculation Method for the Rate Equations of Plasma
Authors: Oda Utaro Furukane
Published: October 2002

The rate equations for the plasmas in which the electron or ion density and the temperature changes substantially in a finite time are solved by using a fast numerical calculation method. The scheme of the method is presented. A recombining plasma mixed with cooling gases is investigated, and some other cases in which the effect of the electron temperature change on \dotneis significant are briefly discussed.
Particle Transport Study with an Electron Beam in the Tohoku University Heliac
Authors: Nakamura Eiji , Kitajima Sumio , Takayama Masakazu , Inagaki Shigeru , Takeo Yoshida Takeo Yoshida , Hiroshige Watanabe Hiroshige Watanabe
Published: October 2002

The particle transport of low density ( ∼1012 m-3) and low energy ( <20 eV) electrons is studied with a directed electron beam in the Tohoku University Heliac. The particle diffusion coefficient is estimated experimentally using the emissive filament technique. We investigate the coefficient's dependence on magnetic field strength, collision frequency and electron beam energy. The measured dependence is similar to the dependence calculated using the neoclassical transport theory.
Dynamic Selective Reflection from a Low-Density Atomic Vapor
Authors: Takahisa Mitsui Takahisa Mitsui , Katsumi Sakurai Katsumi Sakurai
Published: October 2002

The dynamics of selective reflection when atomic vapor density is modulated are studied. In our theoretical work, we found a new type of light emission in selectively reflected light, which differs from that of ordinary selective reflection. It is understood to be backscattering from a moving dynamic grating created in density-modulated atomic vapor. Experimentally, the dynamics of the selective reflection are studied by analyzing the intensity spectrum of the reflected light intensity.
Improvement of Sensor for Noncontact Capacitance/Voltage Measurement and Lifetime Measurement of Bare Silicon(100)
Authors: Sakai Takamasa , Kohno Motohiro , Okada Hiroshi , Hideaki Matsubara Hideaki Matsubara , Sadao Hirae Sadao Hirae
Published: October 2002

In order to develop a new field of application and to improve the measurement accuracy, a new sensor for the noncontact capacitance/voltage system [metal-air-insulator-semiconducter method (MAIS method)] was successfully developed. The new sensor fulfilled the guard ring function and eliminated the stray capacitance which influenced the measurement accuracy. The bare silicon wafer just after buffered HF cleaning was measured as an application example and the accumulation and quasi inversion were verified. The apacitance/voltage ( C–V) and capacitance/time ( C–t) curve beheviors of the bare silicon wafer were closely related to the high-density interface states localized in the vicinty of the midgap within the energy gap. Moreover, it was confirmed that the generation lifetime of the bare p-type silicon wafer could be measured by the MAIS method using the new sensor.
Characterization of Graded Pulse-Doped Channel AlGaAs/InGaAs/GaAs Heterojunction Field-Effect Transistors
Authors: Lour Wen-Shiung , Chen H. R. , Ling-Tze Hung Ling-Tze Hung
Published: October 2002

This paper reports on the fabrication and characterization of graded pulse-doped channel AlGaAs/InGaAs/ GaAs heterojunction field-effect transistors (HFET's). Triple pulse-doped sheets, δ(n
1)=1.2×1012, δ(n
2)=4×1011, δ(n
3)=1×1011 cm-2 from buffer to gate is used as an active channel. Typical drain-to-source and gate-to-drain breakdown voltages are larger than 25 V. The further enhancement in breakdown voltage is using the following methodology: 1) a strained AlGaAs insulator, 2) an InGaAs quantum-well like channel, and 3) less impurity scattering in the graded pulse-doped channel. The maximum transconductance is 160 mS/mm with an available current density of 250 mA/mm. Further increasing the δ(n
1) to 4×1012 cm-2, the maximum transconductance is 165 mS/mm. The available current density is increased to 480 mA/mm. Moreover, their transconductance vs. gate voltage profiles display broad plateaus. The fabricated devices exhibit a small output conductance of 0.3 mS/mm. The evaluated open-drain voltage gain is as high as 500. These results have better performances than those of i-AlGaAs/n+-InGaAs HFET's fabricated by our system.
Novel Method for Monitoring the Surface Roughness during Molecular Beam Epitaxy
Authors: Ray-Ming Lin Ray-Ming Lin , Si-Chen Lee Si-Chen Lee
Published: October 2002

A novel in situ method to monitor the InAs epilayer surface roughness by using pyrometer reading is proposed. The variation of pyrometer reading can be related to the surface morphology of the InAs epilayer deposited on GaAs, and provides an easy way for rapid calibration of growth conditions. The atomic force microscope is applied to measure the surface roughness which verifies the correlation between InAs epilayer morphology and the pyrometer reading.
Light-Induced Annealing of Dangling Bonds in a-Si:H
Authors: Takeda Kosei , Hikita Harumi , Kimura Yutaka , Yokomichi Haruo , Yamaguchi Masaaki , Morigaki Kazuo
Published: October 2002

We have investigated the kinetics of light-induced defect (dangling bond) creation and annealing processes in a-Si:H containing a large amount of hydrogen at 300 K and 77 K using the ESR technique. We have obtained direct evidence for the light-induced annealing of dangling bonds at 300 K. A model, in which nonradiative recombination of electrons and holes at hydrogen-related dangling bonds is taken into account, is presented to interpret the experimental results.
On the Possibility of High Density Data Storage Based on Modulation-Doped Electron Trapping Materials
Authors: Chong Yihong Wu , Beh Chee Yang
Published: October 2002

The possibility of achieving high density two- and three-dimensional data storage based on modulation-doped electron trapping materials is discussed. The key component of the proposed memory is a modulation-doped structure of electron trapping materials in which the information storing and releasing atoms are spatially separated to such a distance that the charge transfer rate between the two types of dopants is negligibly low at zero electric field but can be either greatly increased or further reduced by an external electric field, depending on polarity of the field. A high density memory both in the two- and three-dimensional forms is suggested by using this technique, and in particular limiting performance of the two-dimensional case is discussed in detail based on the signal-to-noise ratio analysis.
Phase Change Cycling for Erasable Optical Storage Driven by Ultrashort Laser Pulses
Authors: Morilla M. C. , J. Solís J. Solís , C. N. Afonso C. N. Afonso
Published: October 2002

Reversible phase transitions between the amorphous and the crystalline states have been induced in Sb0.93Ge0.07 thin films by irradiation with picosecond laser pulses of different energy densities. It is shown for the first time that a material can be repetitively cycled between both states by means of ultrashort pulsed laser irradiation. The phase transformation involves optical contrast thus demonstrating that erasable phase change optical storage driven by ultrashort laser pulses is feasible.
Control of Organic Interfaces with a Thin Film of Silicon Monoxide between 8-Hydroxyquinoline Aluminum and Diamine Layers in an Organic EL Diode
Authors: Yutaka Ohmori Yutaka Ohmori , Yoshitaka Kurosaka Yoshitaka Kurosaka , Norio Tada Norio Tada , Akihiko Fujii Akihiko Fujii , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

The insertion of a thin film of silicon monoxide (SiO) at the interface of the 8-hydroxyquinoline aluminum (Alq3) and the diamine derivative (TPD) layers in the electroluminescent (EL) diode enhances the emission from the Alq3 layer. The mechanism of emission enhancement from the hetero interfaces has been discussed with respect to the emission spectra of the diodes containing a thin film of a marker layer which was inserted into the emissive layer near the interface. The SiO layer thickness dependence on EL intensity in the diode with the SiO layer has been discussed.
Morphology and X-Ray Diffraction Peak Widths of Aluminum Nitride Single Crystals Prepared by the Sublimation Method
Authors: Tanaka Motoyuki , Nakahata Seiji , Sogabe Kouichi , Hirohiko Nakata Hirohiko Nakata , Masaaki Tobioka Masaaki Tobioka
Published: October 2002

AlN single crystal is one of the promising materials for substrates of GaN-based laser diodes. We prepared aluminum nitride single crystals by the sublimation method and characterized them. The crystals are transparent and slightly yellow. Some crystals are needle-shaped with a hexagonal cross section, diameter of 0.5 mm and length of 3 mm, grown parallel to |001|. Other crystals are plate-shaped with a maximum width of 3 mm, 5 mm length and 0.5 mm thickness, grown with a large (001) face. Also, other crystals are needle-shaped with a rectangular cross section, width of 1 mm, 7 mm length and 0.3 mm thickness, grown with a large (101) face. Their widths of X-ray rocking curves is about 39 arcsec, with a full width at half-maximum, 203 arcsec and 12 arcsec, respectively. The orientation of AlN single crystal axis is sufficient for use in substrates for GaN-based diodes.
Substrate-Orientation Dependence on Structure and Magnetic Properties of MnAs Epitaxial Layers
Authors: Morishita Yoshitaka , Iida Koichi , Junya Abe Junya Abe , Katsuaki Sato Katsuaki Sato
Published: October 2002

Ferromagnetic MnAs layers were grown on (001), (111)A, and (111)B GaAs substrates by molecular-beam epitaxy at substrate temperatures (T
s) in the range from 150 to 400° C. The crystal structure of the MnAs was NiAs type and its orientation was found to change depending on the substrate, (1101) for the (001) GaAs substrate and (0001) for the (111)A and (111)B substrates at T
s between 300 and 400° C. Polar magneto-optical Kerr-effect measurement demonstrated a crystal-orientation dependence of Kerr rotation and Kerr ellipticity spectra of the MnAs epitaxial layers.
Light Point Defects on Hydrogen Annealed Silicon Wafer
Authors: Izunome Koji , Miyashita Maki , Ichikawa Akihiko , Kirino Yoshio , Arita Jiro , Ueki Akira
Published: October 2002

In observing 0.1 µ m in size light point defects (LPDs) in Czochralski-grown silicon wafers in hydrogen annealing by scatterometer (Surfscan\circR SP1 and Surfscan 6200 from Tencor Instrument), we have found that the hydrogen annealed wafer has fewer defects on the surface, compared with a polished wafer. Assuming that LPDs are equal to Crystal Originated Particles (COPs) which are oxygen precipitates and/or vacancy-type defects, LPDs can therefore be reduced by evaporating oxygen from the surface, and migrating silicon-atoms onto the surface during hydrogen annealing at 1200° C for 1 h.
Real Time Analysis of Liquid Crystal Surface Orientation Dynamics Using Polarization Modulated Spectroellipsometry
Authors: Tadokoro Toshiyasu , Toriumi Tomoyuki Fukazawa
Published: October 2002

Polarization modulated spectroellipsometry (PMSE) with the time resolution of 1 ms was used to analyze the dynamic response of 4-n-pentyl-4′-cyanobiphenyl (5CB) liquid crystals. The surface dynamics of 5CB in the vicinity of polyimide orienting layer were isolated using the reflection PMSE. Information about bulk reorientation dynamics was obtained from transmission PMSE experiments. Comparison of the results of two experiments indicates that the surface molecules require a higher electric field for reorientation and decay occurs much faster (3 ms) than the bulk molecules (100 ms). These observations clearly indicate the presence of an anchoring effect and illustrate the advantage of the reflection PMSE for the study of surface reorientation dynamics of liquid crystals.
Direct Observation of Helical Polysilane Nanostructures by Atomic Force Microscopy
Authors: Kenzo Ebihara Kenzo Ebihara , Shin-ya Koshihara Shin-ya Koshihara , Mamoru Yoshimoto Mamoru Yoshimoto , Tatsuro Maeda Tatsuro Maeda , Tsuyoshi Ohnishi Tsuyoshi Ohnishi , Hideomi Koinuma Hideomi Koinuma , Michiya Fujiki Michiya Fujiki
Published: October 2002

The nanostructure of a single quantum wire of the silicon: poly[n-decyl-(S)-2-methylbutylsilane] molecule on a hydrophobic ultrasmooth sapphire plate has been observed by atomic force microscopy (AFM). The backbone structure of this molecule is considered to be a rigid rodlike helix and to be fixed securely into a preferential single-screw-sense. The obtained result of the AFM shows that the polysilane molecule, with a length of about 2 µm, consists of very long rod-like segments linked by kinks as expected for this backbone structure. Network-like aggregated nanostructures of these molecules were also observed for the sample prepared from concentrated solvents.
Oxygen Diffusion in Pt Bottom Electrodes of Ferroelectric Capacitors
Authors: Suga Yuichi Matsui , Hiratani Masahiko , Hiroshi Miki Hiroshi Miki , Yoshihisa Fujisaki Yoshihisa Fujisaki
Published: October 2002

Oxygen diffusion through the grain boundaries of Pt films during the crystallization annealing of Pb(Zr, Ti)O3 (PZT) was investigated for the stacked structure of PZT/Pt/TiN. If the Pt film was sputtered on the TiN film by an in-vacuum process, then columnar (111)-oriented grains were grown with continuous grain boundaries normal to the substrate. On the other hand, a Pt film deposited on a TiN film exposed to air after the TiN deposition consisted of granular grains with a random orientation, because the Pt film was grown on the native oxide surface of the TiN film. The degree of oxygen diffusion in the Pt film deposited on the exposed TiN film was lower than that on the nonexposed TiN film after the PZT was crystallized at 650° C in O2. Differences in the grain boundary structure, such as the diffusion length, are considered to determine the oxygen diffusion rate.
Theoretical Composition Calibration and Thickness Measurement in the Analysis of Multielement Thin Films Using Wavelength Dispersive Spectroscopy: Applications to Lead Zirconate Titanate Thin Films
Authors: Kyung-Mun Byun Kyung-Mun Byun , Jae-Whan Kim Jae-Whan Kim , Won-Jong Lee Won-Jong Lee
Published: October 2002

The composition of a thin film measured by wavelength dipersive spectroscopy (WDS) deviates from the actual value if the film thickness is less than the X-ray generation depth of the elements measured. For multielement films, the measured concentration of the element with a shallow X-ray generation range is overestimated compared with that of the element with a deep X-ray generation range. In the case of lead zirconate titanate (PZT) films, the deviation of the measured composition ratio Pb/(Zr+Ti) from the actual value becomes more pronounced as the films become thinner. Accordingly, the composition measured by WDS needs to be calibrated for the film thickness. In this study, composition correction factors were derived theoretically as a function of the film thickness in order to calibrate the composition of thin PZT films obtained by WDS analysis. The thicknesses of films were calculated from the sum of [ ZAF] k of each element obtained in WDS analysis, and those values were compared with the experimental results.
Optical Absorption and Photoluminescence of Self-Assembled Silicon Quantum Dots
Authors: Shiba Kazutoshi , Nakagawa Kazuyuki , Ikeda Mitsuhisa , Kohno Atsushi , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: October 2002

Hemispherical silicon quantum dots with an average height of 6.3, 3.3 or 1–2 nm covered with an ultrathin SiO2 layer have been spontaneously formed on SiO2/Si(100) and quartz substrates by the thermal decomposition of pure silane at low pressure. It is found that the optical absorption edge determined from photothermal deflection spectroscopy exhibits blue shifts from 1.9 to 2.5 eV when the average dot size was decreased from 6.3 to 1–2 nm and correspondingly, the luminescence peak energy increases from 1.2 to 1.4 eV at room temperature. The large Stokes shift suggests that the localized, radiative recombination centers existing presumably in the SiO2/Si dot interface are responsible for the efficient, room-temperature luminescence from the silicon quantum dots.
Nonlinear Phase Shift and Detuning by Second- and Third-Order Nonlinearities
Authors: Zhang Lei , Shirakawa Akira , Shigeki Morita Shigeki Morita , Takayoshi Kobayashi Takayoshi Kobayashi
Published: October 2002

We have analyzed the nonlinear phase shift and the wave-number detuning induced by the second- and third-order nonlinearities. Analytical expressions were obtained under the fixed intensity approximation. With a strong pump intensity, the conversion efficiency curve plotted against the phase-mismatch narrows. Due to the detuning effect, the conversion efficiency at perfect phase-matching saturates with the increase of the pump intensity. The experimental result confirms our theory and shows an asymmetric effect caused by the third-order nonlinearity at higher intensity.
Tip-induced Electron Occupation of an Unoccupied Surface State in Scanning Tunneling Microscopy Imaging of a GaAs(110) Surface with Ag Clusters
Authors: Nakayama Chun-Sheng Jiang , Masakazu Aono Masakazu Aono
Published: October 2002

Scanning tunneling microscopy (STM) images of a GaAs(110) surface with Ag clusters show that a Ga dangling bond state of this surface is occupied or unoccupied depending on the polarity of sample bias, in certain local regions of the surface. These results, which appear to be strange at first glance, can be interpreted by taking the electric field due to the STM tip into consideration. All other details of observed STM images can also be interpreted on the basis of this tip-induced field effect.
Bias-enhanced Nucleation of Oriented Diamond on Singlecrystalline 6H-SiC Substrates
Authors: Xi Li Xi Li , Yasuaki Hayashi Yasuaki Hayashi , Stanislav Lilov Stanislav Lilov , Shigehiro Nishino Shigehiro Nishino
Published: October 2002

A bias-enhanced nucleation (BEN) technique in hot-filament chemical vapor deposition (HF-CVD) has been applied to single-crystalline 6H-SiC substrates for the deposition of oriented diamond films. The results of scanning electron microscopy (SEM) showed that on the (000\overline1) face not only oriented diamond films with the relationship (111) Dia.//(000\overline1) 6H-SiC and <110> Dia. // <11\overline20> 6H-SiC, but also that high nucleation density (\symbol"3E109 cm-2) has been achieved. In the case of deposition on the (0001) face of the 6H-SiC under the same experimental conditions, although the nucleation density of diamond was enhanced (above 109 cm-2), however, oriented diamond was not observed. The diamond nucleation density is greater on the (0001) face than on the (000\overline1) face. The differences in oriented nucleation and nucleation density on these two faces are attributed to the difference of their specific free surface energy and chemical bonds.
High-Oxygen-Pressure Synthesis of Superconducting Y0.8Pr0.2Ba2Cu3O8
Authors: Kato Bin Okai
Published: October 2002

Heat treatment of Y0.8Pr0.2Ba2Cu3O7 under high oxygen pressure produces overdoped Y0.8Pr0.2Ba2Cu3O7+
y

. The oxygen content 7+y is saturated at 8. Through overdoping, T
c fluctuates somewhat but does not change greatly, and Y0.8Pr0.2Ba2Cu3O8 remains superconducting with T
c=64 K. The fact that T
c of overdoped Y0.8Pr0.2Ba2Cu3O7+
y

does not increase to ∼90 K is consistent with the model of Pr hybridization with neighboring oxygen atoms.
Surface Morphology of YBa2Cu3O7-y Films Prepared by Metalorganic Chemical Vapor Deposition Using Liquid Sources
Authors: Yoshida Yutaka , Ito Yoshiaki , Yamada Yasuji , Nagai Hisashi , Takai Yoshiaki , Hirabayashi Izumi
Published: October 2002

We have prepared c-axis oriented YBa2Cu3O7-
y

thin films by metalorganic chemical vapor deposition (MOCVD) on MgO(100) substrates using newly developed liquid-state sources with and without fluorine and studied the surface morphology of the films using atomic force microscopy (AFM). Spiral steps accompanied by screw dislocations were observed on the surface of films prepared with both fluorinated and nonfluorinated sources in the AFM image. The shape of growth steps for the former is rounded, whereas the latter is polygonal, suggesting that the lateral bonding force between the growth units, which is represented by the Jackson's α factor, varies for each case. The kinetic roughening effect on the spiral shape is a minor effect compared to the α factor effect.
Subnanosecond Tunable Ultraviolet Pulse Generation from a Low-Q, Short-Cavity Ce:LiCAF Laser
Authors: Liu Zhenlin , Ohtake Hideyuki , Sarukura Nobuhiko , Dubinskii Mark A. , Semashko Vadim V. , Naumov Alexander K. , Korableva Stella L. , Abdulsabirov Ravil Yu.
Published: October 2002

We have developed an all-solid-state tunable ultraviolet laser system employing recently developed Ce:LiCAF, a new degradation-free tunable ultraviolet laser medium pumped by the fourth harmonic of a conventional Q-switched Nd:YAG laser. The low-Q, short-cavity Ce:LiCAF laser produced satellite-free subnanosecond pulses in a tuning range of 281 nm to 297 nm under appropriate pumping-fluence control.
Radial Thermal Expansion of Purified Multiwall Carbon Nanotubes Measured by X-ray Diffraction
Authors: Shunji Bandow Shunji Bandow
Published: October 2002

The thermal expansion in the radial direction (stacking axis of graphene sheets) of multiwall carbon nanotubes (MWNTs) is measured in the temperature range from 10 to 320 K. The sample includes in excess of 85% by weight of MWNTs. The radial thermal expansion of MWNTs is found to be almost the same with the c-axis thermal expansion of graphite. This result strongly challenges the concentric structural model for MWNTs, suggesting the appropriateness of the scroll type model instead of the concentric one.
Persistent Mode Operation of Bi2Sr2CaCu2Ox/Ag Stacked Double Pancake Coils with Superconducting Joints
Authors: Fukushima Keiji , Okada Michiya , Sato Junichi , Kiyoshi Tsukasa , Kumakura Hiroaki , Togano Kazumasa , Wada Hitoshi
Published: October 2002

A persistent current mode magnet was successfully fabricated using Bi2Sr2CaCu2O

x

/Ag tapes. The magnet system consisted of four Bi2Sr2CaCu2O

x

/Ag double pancake coils as a magnet and a noninductively wound Bi2Sr2CaCu2O

x

/Ag–Au single pancake coil as a persistent current switch. The pancakes were stacked and jointed using a butt-jointing method to form a superconducting closed loop. Persistent current mode operation of the magnet was initiated in liquid helium, trapping a magnetic field of 1 T which corresponds to a loop current of 134 A. The voltage-current ( V–I) characteristic of the closed loop was estimated from the decay of the trapped field. An index number in the V–I curve, n, above 30 and a loop resistance of 2×10-10 Ω were observed for the loop current above 30 A after 116 hours.
Frequency Stabilization of a Visible Laser Diode to an Enhanced Saturated Absorption Signal of Molecular Iodine in an External Cavity
Authors: Masuda Tomonori , Kimura Tetsuya , Toshiharu Tako Toshiharu Tako , Atsuo Morinaga Atsuo Morinaga
Published: October 2002

A small saturated absorption signal of molecular iodine was enhanced by placing an iodine cell inside an external cavity. Using the third derivative signal of the enhanced saturated absorption signal, the diode laser was frequency stabilized to a hyperfine component of molecular iodine.
Growth of p-type Zinc Oxide Films by Chemical Vapor Deposition
Authors: Kazunori Minegishi Kazunori Minegishi , Yasushi Koiwai Yasushi Koiwai , Yukinobu Kikuchi Yukinobu Kikuchi , Koji Yano Koji Yano , Masanobu Kasuga Masanobu Kasuga , Azuma Shimizu Azuma Shimizu
Published: October 2002

The growth of p-type ZnO film was realized for the first time by the simultaneous addition of NH3 in carrier hydrogen and excess Zn in source ZnO powder. The resistivity was typically 100 Ω·cm. A model showing nitrogen incorporation suggests the possibility of realizing p-type ZnO film of low resistivity by optimizing thermal annealing.
Resolution Correction for Time-of-Flight Neutron Scattering Experiments Using the Monte Carlo Method
Authors: Yoshiei Todate Yoshiei Todate , Satoru Taniguchi Satoru Taniguchi , Keisuke Tajima Keisuke Tajima
Published: October 2002

A new efficient method has been proposed for convolution of the neutron scattering cross section with instrumental resolution of the inelastic time-of-flight spectrometer at pulsed neutron sources. This method has several advantages over the conventional analytical formulation of the resolution function commonly used for the triple-axis spectrometers at steady reactors, not only because of its flexibility and capability for more realistic representation of the origin of the instrumental broadening, but also because of its higher efficiency of computation.
Photoluminescence Characterization of High-Purity Synthesized Diamond
Authors: Horiuchi Kenji , Nakamura Kazuo , Kuwata-Gonokami Satoshi Yamashita
Published: October 2002

Photoluminescence (PL) properties of high-purity synthesized diamond are studied using the 5th-harmonic of a Nd:YAG laser. Free-exciton related emissions are dominant even at room temperature, which confirms high crystal perfection of the sample. The intensity of the FE-related peaks decreases at temperatures below 150 K, and existence of shallow trap centers is suggested. Also there exists a long-lived broad band in the visible region. These features cannot be observed by cathodoluminescence, and PL characterization is proved to be effective for characterization of such high-quality diamond.
Quasibound States of Electric Field-Induced Quantum Wells in Silicon Subsurfaces
Authors: Khairurrijal Khairurrijal , Seiichi Miyazaki Seiichi Miyazaki , Masataka Hirose Masataka Hirose
Published: October 2002

Quasibound states of a nontriangular quantum well in the silicon subsurface layer induced by an intense surface electric field are directly calculated on the basis of generalized Airy functions to obtain the field emission current from the silicon surface. The subband energy level and the resonance width of the quasibound state can be simultaneously derived from the complex eigenenergy of the system. By comparing the results for the nontriangular quantum well to those for the triangular quantum well with a finite depth obtained using the Blatt-Weisskopf approximation, it is shown that the triangular quantum well model is not valid under intense surface electric fields.