bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Relationship between Directivity and Linewidth of a Planar Microcavity Laser
Authors: Kikuo Ujihara Kikuo Ujihara
Published: October 2002

On the basis of the analysis of the cavity quasimode structure, the relationship between the directivity and the linewidth of the output beam from a laser with a planar microcavity is examined assuming a narrow spectral width of the laser medium. A simple relation is obtained which implies that, in a planar laser, the directivity is determined by the net loss of the laser similarly to the laser linewidth.
Resistivity Response to Oxygen of Transition Metal Dichalcogenide TiS2
Authors: Kishiro Koichi , Takemoto Satoshi , Hisao Kuriyaki Hisao Kuriyaki , Kazuyoshi Hirakawa Kazuyoshi Hirakawa
Published: October 2002

The resistivity responses of layered compound TiS2 to oxygen and nitrogen gases were measured around room temperature. The resistivity showed a selective and reversible response to oxygen. This may be due to the fact that oxygen intercalates into van der Waals gaps in the layered structure of TiS2. The resistivity showed an increment of 1% oxygen partial pressure in 10 min at 50°C. From the comparison with a commercial oxygen gas sensor, it was shown to operate at a lower temperature with the response time as short as the commercial one.
Pyroelectricity of Noncentrosymmetric Langmuir-Blodgett Films of Phenylpyrazine Derivatives
Authors: Kamata Toshihide , Umemura Junzo , Takenaka Tohru , Koizumi Naokazu , Takehara Kenji , Isomura Kazuaki , Taniguchi Hiroshi
Published: October 2002

Pyroelectricity of alternating Langmuir-Blodgett (LB) films consisting of phenylpyrazine derivatives and stearic acid was measured by the static method at various temperatures. It was found that the LB films consisting of a compound with highly conjugated π-electron system showed large pyroelectricity which was greatly dependent on the temperature of the sample films. The sign of the pyroelectric coefficients changed at a temperature characteristic of the films. In the high-temperature range, a dull pyroelectric response was observed. The pyroelectricity of LB films with various ion complexes was also examined. The films of polyion complex which had more spatial freedom showed larger pyroelectricity. However, an extremely sparse molecular packing gave a low degree of molecular orientation in the film resulting in small pyroelectricity.
Damage and Its Rapid Thermal Annealing Behavior of 1 MeV Ar+-Ion-Implanted Silicon
Authors: Kim Kwang Il , Kuwano Hiroshi , Kwon Young Kyu , Hahn Soo Kap
Published: October 2002

The formation of the buried amorphous layer and its annealing behavior during rapid thermal annealing in 1 MeV Ar+-implanted (100) silicon at a dose of 1×1015 cm-2 have been investigated by cross-sectional transmission electron microscopy. Rutherford backscattering spectroscopy and the thermal-wave-modulated optical reflectance technique. The buried amorphous layer is completely recovered, but forms a closure dislocation at 675°C. The regrowth rate of solid phase epitaxy from the upper (closer to the surface) amorphous/crystalline (a/c) interface is found to be higher than that from the lower (in the bulk) a/c interface. Closure dislocations coalesce into V-shaped dislocations which are observed mainly in the upper regrown region and evolve into extended defects such as the dislocation loops and lines at higher temperature. However, they persist with the end-of-range dislocations even at the temperature of 1100°C.
Electroplated and Dry-Released Metallic Microstructures for a Lateral Tunneling Unit Application
Authors: Toshiki Hirano Toshiki Hirano , Dai Kobayashi Dai Kobayashi , Tomotake Furuhata Tomotake Furuhata , Hiroyuki Fujita Hiroyuki Fujita
Published: October 2002

This paper presents a new method of fabricating a lateral tunneling unit (LTU), by dry releasing of electroplated structures. An LTU is an integrated tunneling current sensing unit that has a tunneling tip and a linear actuator for moving the tip. The new fabrication method has many advantages over the existing polycrystalline silicon structure and hydrofluoric acid (HF) wet release method, namely, use of a metallic material, thicker structure, higher yield, and a safer, easier, and faster process. New LTUs and LTU-AFM probes were successfully fabricated by this method. Gold and nickel were used as alternative structural materials. The electrolytic polishing method was proposed as a new post-release processing and was used to fabricate sharp needles. The comb-drive actuator of an LTU was operated and the characteristics were measured; the results showed that this actuator has good linearity.
Calibration Method for Displacement Characteristics of Tube Scanners in Scanning Probe Microscopy using Coupled-Cavity Laser Diode Sensor
Authors: Yokohata Toru , Hara Shigeji , Kaneko Reizo , Koji Kato Koji Kato
Published: October 2002

A handy and precise calibration method for the displacement characteristics of a tube scanner in the submicrometer scale is proposed. A coupled-cavity laser diode sensor, which acts as a submicrometer gauge with subnanometer accuracy, is used to calibrate a displacement sensor. This sensor is then used to measure the displacement sensitivity. A problem of precise measurement by scanning probe microscopy is also discussed.
Activity Coefficients of Electrons and Holes in Degenerate Semiconductors with Nonuniform Composition
Authors: Chang Kow-Ming , Yeh Ta-Hsun , Shih-Wei Wang Shih-Wei Wang , Chi-Hung Lee Chi-Hung Lee
Published: October 2002

A new simple, general and rigorous analytic expression for the equilibrium activity coefficients of electrons and holes in degenerate semiconductors with nonuniform composition is presented. These activity coefficients are functions of the carrier degeneracy (Fermi-Dirac statistics), the band gap, the electron affinity and the density of states which vary with position. The calculation of carrier activity coefficients requires the selection of chemical potential and electrostatic potential references. The choice of these reference states is addressed. The relationships between purely thermodynamic quantities and parameters of the band theory are also presented. Emphasis is also placed on formulating an equation in a simple, Boltzmann-like form in which the nonideal behavior is described by two parameters, the effective band-gap shrinkage, ΔE
g, and the effective asymmetry factor, A. In this form the working equations for the carrier densities and activity coefficients are convenient for use in computer-aided analysis and design. The approach presented here allows convenient treatment of nonuniform degenerate semiconductors in a manner that is consistent with thermodynamics as well as with the Poisson-Boltzmann equation for the electrostatic potential.
Optimum Electrode Materials for Ta2O5 Capacitors for High- and Low-Temperature Processes
Authors: Hideaki Matsuhashi Hideaki Matsuhashi , Satoshi Nishikawa Satoshi Nishikawa
Published: October 2002

In this paper, we describe the effects of electrode materials on the leakage current of Ta2O5 films, and show optimum electrode materials for high- and low-temperature processes. The leakage current depends on the electrode material and varies with the annealing temperature. The leakage current is mainly determined by the work function of the electrode before and after low-temperature annealing (400° C). On the other hand, after high-temperature annealing (800° C), the leakage current is also affected by the reaction between Ta2O5 and the electrode. From the viewpoint of the leakage current, TiN and Mo (or MoN) are optimum materials for low- and high-temperature processes, respectively.
Transformation of Amorphous SnOx Films Studied by Electrical Resistivity and Optical Transmission
Authors: Muranaka Shigetoshi , Tamada Yoshio Oka
Published: October 2002

The electrical resistivity and optical transmission of reactively evaporated amorphous SnO

x

films were measured as a function of the temperature. The films showed two drastic changes in both the electrical resistivity and optical transmission. The results indicated that the films were oxidized at about 250° C and then crystallized at about 400° C.
Generation and Flux-Pinning Effect of High-Density Dislocation in High-Tc Superconductor YBa2Cu3O7-δ
Authors: Zheng Xuguang , Nishioka Shido , Hisao Kuriyaki Hisao Kuriyaki , Kazuyoshi Hirakawa Kazuyoshi Hirakawa
Published: October 2002

High-density dislocations accompanied by stacking faults are introduced into YBa2Cu3O7-δ ceramics using a solid-state reaction method. Investigation on transmission electron microscopy reveals that these dislocations are created during crushing of ceramics presintered at a temperature near their melting point. A high intragrain critical current density is obtained for the superconductor, which shows that this kind of dislocation serves as a pinning force for the magnetic flux.
Characteristic High-Field Dependence and Composition Variation of Giant Magnetoresistance in Fe/Ag Granular Materials
Authors: Makhlouf Salah Ahmed , Sumiyama Kenji , Kimio Wakoh Kimio Wakoh , Kenji Suzuki Kenji Suzuki
Published: October 2002

Magnetoresistance (MR) measurements of Fe-cluster-dispersed Fe–Ag films fabricated by using the ion-cluster-beam technique display the following features. (1) The giant magnetoresistance (GMR) effect is observed in the Fe/Ag granular alloys with 12 to 45 at.% Fe, whereas it is suppressed in the Fe-rich region. (2) The MR curves display both saturation- and nonsaturation-type behavior even in a high magnetic field of 140 kOe, whereas the corresponding magnetization curves easily saturate at very low fields. The salient point here is that the GMR is optimized without any heat treatment of the specimens, and the results display some unique features of the GMR in this system.
Squeezed Light Generation with 1.064 µm Nd:YAG Laser and 0.85 µm Single-Mode Fiber
Authors: Norihiko Nishizawa Norihiko Nishizawa , Satoshi Kume Satoshi Kume , Masakazu Mori Masakazu Mori , Toshio Goto Toshio Goto , Akira Miyauchi Akira Miyauchi
Published: October 2002

Efficient squeezing at low pump light power is demonstrated with a mode-locked 1.064 µm Nd:YAG laser and a fiber ring reflector made of 0.85 µm single-mode fiber. Noise reduction of about 2.0 dB below the shot noise level is observed. The squeezing process by the optical Kerr effect is calculated with a simple model. The experimental results are in good agreement with the calculated ones.
Direct Observation of Domain Structures in Triglycine Sulfate by Atomic Force Microscope
Authors: Bae Min-Kun , Horiuchi Toshihisa , Hara Kazuhiro , Ishibashi Yoshihiro , Matsushige Kazumi
Published: October 2002

Direct observations of domain structures on a cleavage (010) plane of TGS [triglycine sulfate; (NH2CH2COOH)3-H2SO4] are conducted using an atomic force microscope (AFM). The domain structure immediately after a cleavage treatment and its relaxed one are analyzed in detail, especially for the height of domain wall and the transition layer at antiparallel domain walls. Moreover, the positions of glycine and sulfate groups are determined by comparing the observed highly resolved molecular images with the electron-density function obtained from the reported X-ray diffraction data.
Influence of Manganese on Lanthanum-Doped BaTiO3
Authors: Chen Ying-Chung , Lo Gun-Man , Shih Chi-Ren , Wu Long , Mao-Hsiung Chen Mao-Hsiung Chen , Kuang-Chih Huang Kuang-Chih Huang
Published: October 2002

The minimum room-temperature resistivity for La–Mn–codoped BaTiO3 occurred at [La+3]-5/3[Mn+
x

]∼0.35 mol%. Most of the Mn acceptors were in the bulk regions, existing as Mn+2 ions. The others, existing as Mn+3 ions, cause the grain growth inhibition effect and should exist at the grain boundaries, similar to an acceptor level. The slope of the positive temperature coefficient resistance (PTCR) effect (ρ160° C/ρ120° C) was increased with increasing Mn content. However, the maximum order of PTCR (ρ max/ρ min) existed at [Mn+
x

]∼0.06 mol%.
Study of Scratch-Induced Mechanical Damage on Silicon (111) Surfaces
Authors: Takashi Iizuka Takashi Iizuka , Yasumasa Okada Yasumasa Okada
Published: October 2002

Scratch-induced mechanical damage on silicon (111) surfaces, in particular the fractures, residual strain fields and anneal-induced dislocations generated by <112> and <110> direction scratches, is investigated by optical microscopy, X-ray diffraction topography and the copper decoration method. The asymmetry in this damage in the [112̄] and reverse [1̄1̄2] directions is observed. The asymmetries are correlated with each other and are discussed in terms of the inclined (111̄) cleavage plane whose intersection with the (111) surface is perpendicular to the <112> direction.
Electron Cyclotron Emission from Optically Thin Plasma in Compact Helical System
Authors: Hiroshi Idei Hiroshi Idei , Shin Kubo Shin Kubo , Minoru Hosokawa Minoru Hosokawa , Harukazu Iguchi Harukazu Iguchi , Kunizo Ohkubo Kunizo Ohkubo , Teruyuki Sato Teruyuki Sato
Published: October 2002

A frequency spectrum of second harmonic electron cyclotron emission was observed for an optically thin plasma produced by fundamental electron cyclotron heating in a compact helical system. A radial electron temperature profile deduced from this spectrum neglecting the multiple reflections effect shows a clear difference from that measured by Thomson scattering. We relate the spectrum with the electron temperature profile by the modified emission model including the scrambling effect. The scrambling effect results from both mode conversion and change in the trajectory due to multiple reflections of the emitting ray at the vessel wall. The difference between the two temperature profiles is explained well by using the modified emission model. Reconstruction of the electron temperature profile from the spectrum using this model is also discussed.
Performance of AgGaS2 Crystal Filter for Raman Spectroscopy
Authors: Susaki Masami , Yamamoto Nobuyuki , Horinaka Hiromichi , Huang Wen Zheng , Cho Yoshio
Published: October 2002

The performance of a AgGaS2 crystal filter combined with a single monochromator is described for the use of Raman spectroscopy. The filter can be utilized in both band-pass mode and band-elimination mode near 497 nm with a narrow band width of 1.5 nm. A dye laser tuned at 497.3 nm can be used as an excitor since the center wavelength of the filter is located exactly at the wavelength. On the other hand, the precise center wavelength of the filter can be easily adjusted to the 496.5 nm line of an Ar+ laser excitor by temperature tuning at -23.5° C. High rejection of laser lines of both excitors is proved in the Raman spectroscopy performance test.
A Derivation of the Schödinger Equation from the Bayesian Estimation
Authors: Masahiro Agu Masahiro Agu
Published: October 2002

It is shown on the basis of the detailed balance condition in thermal equilibrium that the Schrödinger equation is derived from the Bayesian estimation concerning the stochastic system following the Fokker-Planck equation. Here the square of the modulus of wave function is shown to correspond to the Bayes' probability densitywith imaginary time. A generalized form of Schrödinger's equation is also derived from the Bayesian estimation in an off-equilibrium steady state.
Short-Term Frequency Stability Estimation of an Optically Pumped Cesium Beam Frequency Standard
Authors: Kenji Hisadome Kenji Hisadome , Masami Kihara Masami Kihara
Published: October 2002

A theory is proposed for the calculation of the short-term frequency stabiliry of any optically pumped Cs beam frequency standard. This theory takes into account the influence of fluorescence photon statistics and laser linewidths. The accuracy of the theory is confirmed by measuring the signal to noise ratio of an optically pumped Cs beam resonator and then estimating the short-term frequency stability of the standard based on the resonator. The theory predicts the observed performance well.
Optogalvanic Double-Resonance Spectrum of Kr Detected Using Frequency-Modulated GaAs Semiconductor Lasers
Authors: Nishimiya Nobuo , Masayasu Endo Masayasu Endo , Masao Suzuki Masao Suzuki
Published: October 2002

State-selective optogalvanic spectroscopy has been performed using frequency-modulated GaAs semiconductor lasers. The first laser beam modulated by the sine wave of frequencyf1irradiated a laser galvatron filled with Kr of natural abundance and generated the signal corresponding to the 2p4-1s3transition. The second one modulated byf2was introduced along the first beam, which was frequency-locked to one of the hyperfine components of83Kr. The intermodulated optogalvanic signal detected by a lock-in amplifier with the reference off1+f2was the second derivative and those by 2f1+f2was the third derivative of the double-resonance line profile. The signals split by the nuclear hyperfine effect were clearly isolated from the strong signal of the even-mass Kr.
Spectroscopic Study on ZnTBP/CA/PhR Film by Photon-Gated Hole Burning
Authors: Chen Lingbing , Li Jianzhao , Zhao Youyuan , Li Fuming , Zhang Manhua , Yao Shaoming
Published: October 2002

Spectroscopic study was carried out on a highly efficient photon-gated persistent hole-burning material, Zn-tetrabenzoporphyrin/crotonic acid/phenoxy resin film, at liquid helium temperature. Deep holes were burnt displaying a relative change of transmittance of 2000% and that of optical density of 0.94. Hole erasing caused by Ar+ laser irradiation was observed. Laser-induced donor-acceptor electron transfer was determined to be responsible for the hole formation. The photoproduct was found to be rather stable against room-temperature cycling.
High-Resolution Temperature Measurement Using Phase-Compensating Interferometer and Frequency-Monitoring Interferometer
Authors: Murakami Fumio , Nakano Taketoshi , Ohta Tatehisa , Ichinose Takumi
Published: October 2002

A noncontact interferometric thermometry method based on phase-compensating interferometry is described. Direct frequency monitoring by the reference interferometer connected in parallel to the sensing interferometer provides temperature measurement of high accuracy.
Metal Impurity Trapping Effect by Stress at Edges of Local Oxidation of Silicon Structure
Authors: Ishigami Shun-ichiro , Ishii Satoru , Shinyashiki Hiroshi , Hisashi Furuya Hisashi Furuya , Takayuki Shingyouji Takayuki Shingyouji
Published: October 2002

In this study, the direct relationship between stress at edges of the local oxidation of silicon (LOCOS) structure and Fe atoms was investigated employing secondary ion mass spectroscopy (SIMS), total reflection X-ray fluorescence (TXRF), transmission electron microscopy (TEM), and optical microscopy. Fe atoms contaminated from the back of the wafer diffused to the front surface during the drive-in annealing and became trapped by the stress generated at LOCOS edges and aggregated to form some kinds of defect. TXRF analysis suggested that even the lowest stress generated at LOCOS edges in practical LSI fabrication processes must gain sufficient ability to trap Fe atoms once contamination occurs. There seemed to be a critical Fe concentration to form these defects.
Optical Properties of High-Quality Ga1-xInxAs1-ySby/InAs Grown by Liquid-Phase Epitaxy
Authors: Gong Xiuying , Kan Hirofumi , Yamaguchi Tomuo , Suzuki Isao , Aoyama Mitsuru , Kumagawa Masashi , Rowell Nelson L. , Wang Aiguo , Rinfret Robert
Published: October 2002

The photoluminescence (PL) of InAs and GaInAsSb/InAs epilayers grown by Gd-doped liquid-phase epitaxy (LPE) has been investigated using a double-modulation Fourier transform infrared spectrometer (FTIR). The spectra were composed of peaks due to band-to-band, band-to-impurities, and exciton recombinations. The excitation power, temperature and Gd concentration dependences of these features were studied. The temperature dependence of the band-to-band transition energies was examined by measuring FTIR transmission spectra and by comparing experimental results with those obtained with an empirical formula. A PL full width at half-maximum (FWHM) as narrow as 4.35 meV has been achieved for GaInAsSb epilayers grown from Gd-doped melt indicating high purity of epilayers. Raman scattering measurements of GaInAsSb epilayers showed a two-mode behavior for the optical phonons, indicating that homogeneous, high-quality epilayers were achieved.
Homoepitaxial Growth of Cubic GaN by Hydride Vapor Phase Epitaxy on Cubic GaN/GaAs Substrates Prepared with Gas Source Molecular Beam Epitaxy
Authors: Tsuchiya Harutoshi , Okahisa Takuji , Hasegawa Fumio , Okumura Hajime , Yoshida Sadafumi
Published: October 2002

Thick cubic GaN (c-GaN) layers were homoepitaxially grown on c-GaN/(100)GaAs by hydride vapor phase epitaxy (HVPE). The c-GaN crystals used as substrates in this work were prepared by gas source molecular beam epitaxy (GSMBE). When the growth temperature was too low (∼700° C) or too high (∼1000° C), hexagonal GaN (h-GaN) was included in the grown layer, but pure c-GaN was obtained at 900° C. The growth rate of c-GaN by HVPE in this work was about 1.6 µ m/h, which was 4–10 times higher than that of GSMBE or metalorganic vapor phase epitaxy (MOVPE), and an about 5 µ m thick c-GaN film was obtained by 3-h growth. The X-ray diffraction (XRD) patterns showed only the (200) and (400) c-GaN peaks but no h-GaN one. The cathodoluminescence (CL) spectra exhibited a strong peak at about 365 nm, which corresponds to the band edge emission. No emission due to deep levels was observed.
Modulation Molecular Beam Epitaxy under Constant Low As Pressure
Authors: Takashi Suzuki Takashi Suzuki , Tatau Nishinaga Tatau Nishinaga
Published: October 2002

A new method of molecular beam epitaxy for III–V compounds called modulation molecular beam epitaxy (M-MBE) is proposed. In this method, group III flux modulated in pulse is introduced under a continuous supply of low-pressure As4flux. This causes a persistent and periodic change of the surface reconstruction and associated intensity oscillation of reflection high-energy electron diffraction. The growth mechanism in this method is discussed in detail for homo- and heteroepitaxy. The optical property of the AlAs-GaAs single quantum well (SQW) structure is investigated to evaluate a heterointerface grown by this method. SQWs grown at 300° C show a good characteristic almost equal to those grown at high temperature by the conventional MBE method with growth interruptions. In contrast, SQWs grown at 580° C have rather poor characteristics.
Effect of Ge Concentration on Static and Microwave Performances in GexSi1-x Heterojunction Bipolar Transistors under High-Level Injection
Authors: Chyan Yih-Feng , Sze Simon Ming , Reif Chun-Yen Chang
Published: October 2002

We report the theoretical investigation of the effect of Ge concentration on both static and high-frequency performances in polycrystalline silicon emitter Ge

x

Si1-
x

heterojunction bipolar transistors (HBTs). The calculation is carried out up to 0.95 V, before the onset of the Kirk effect [C. T. Kirk: IEEE Trans. Electron Devices ED-9 (1962) 164]. From this model, we find that the current gain, transconductance, cutoff frequency, and maximum oscillation frequency increase with increasing Ge concentration. In addition, the base transit time and the switching delay time in the emitter-coupled logic circuit slightly decrease as Ge content increases. Furthermore, it shows that the high-level injection effect becomes more pronounced in the Ge

x

Si1-
x

HBT as Ge concentration increases. Compared with the conventional low-level injection model, the improved model provides much more accurate expressions for electrical characteristics of Ge

x

Si1-
x

HBTs operating under high-level injection.
Optical Properties of (AlxGa1-x)0.5In0.5P Quaternary Alloys
Authors: Kato Hirokazu , Adachi Sadao , Nakanishi Hiroshi , Ohtsuka Kouji
Published: October 2002

The dielectric function spectraε(E) of (AlxGa1-x)0.5In0.5P quaternary alloys lattice-matched to GaAs have been measured at room temperature in the 1.2–5.5-eV photon-energy range using spectroscopic ellipsometry (SE). The measured SE spectra show distinct structures at energies of theE0,E1andE2critical points. These spectra are analyzed on the basis of a simplified model of interband transitions. This model enables us to obtain the, optical response in (AlxGa1-x)0.5In0.5P alloys of arbitrary compositionxand photon energyE=\hbarω. Results are presented for the complex refractive index (n*=n+ ik), absorption coefficient (α) and normal-incidence reflectivity (R) of these alloys.
Trainable Pattern Classifier Using a Computer-Generated Hologram
Authors: Hsu Ken Yuh , Hsieh Chau-Jern Cheng
Published: October 2002

A novel technique for pattern classification is proposed and demonstrated. The perceptron learning algorithm is used for training, and the trained interconnection weight matrix is transferred into a computer-generated hologram. The hologram is used as a correlation filter in the optical system for pattern classification. Both computer simulation and optical experiment results are presented.
Photoluminescence of Heavily p-Type-Doped GaAs: Temperature and Concentration Dependences
Authors: Chen Horng Dar , Feng Ming Shiann , Chen Po An , Kun Chuan Lin Kun Chuan Lin , Janne Wha Wu Janne Wha Wu
Published: October 2002

Photoluminescent (PL) properties of heavily carbon- and zinc-doped GaAs were investigated for concentration from 8×1017 to 2.3×1020 cm-3 and temperature from 300 K to 20 K. Both a band-to-band (B, B) peak and a band-to-acceptor (e, A) peak appeared at 300 K for the heavily p-type-doped GaAs PL spectra, even in degenerated GaAs. The variation of the intensities of the (e, A) peak and (B, B) peak with concentration and temperature was investigated, and the change in position of the two peaks at various concentrations and temperatures was observed. The rapid increase in linewidth with increasing concentration due to the appearance of a shoulder peak was also studied; this behavior is different from that of the shoulder peak in the PL spectrum from Zn-doped crystal.
Optical Properties of PbTe
Authors: Norihiro Suzuki Norihiro Suzuki , Sadao Adachi Sadao Adachi
Published: October 2002

The real (ε
1) and imaginary (ε
2) parts of the dielectric function, ε(E)=ε
1(E)+ iε
2(E), of PbTe have been measured by spectroscopic ellipsometry (SE) in the 1.15–5.4 eV photon-energy range at room temperature. The measured SE spectra reveal distinct structures at energies of E
1, E
2 and E
3 critical points. These data are analyzed using two theoretical models, namely, the model dielectric function (MDF) and standard critical-point (SCP) model. It is found that the SCP model can provide a satisfactory fit to the second derivatives of ε(E) spectra [ d2
ε(E)/ dE
2], but does not yield good fits to ε(E) spectra. The MDF, on the other hand, results in excellent agreement with the experimental data for both ε(E) spectra and their derivatives. Dielectric-related optical constants, such as the complex refractive index (n
*=n+ ik), absorption coefficient (α) and normal-incidence reflectivity (R), of PbTe are also presented.
Electric Field Effect on the Emission of Electron-Irradiation-Induced Defects in n-GaAs
Authors: Goodman Stewart A. , F. Danie Auret F. Danie Auret , Walter E. Meyer Walter E. Meyer
Published: October 2002

The enhancement of the emission rate of electron-irradiation-induced defects in the presence of an electric field in n-type GaAs with carrier concentrations ranging from 1×1014to 1×1016cm-3has been investigated using deep level transient spectroscopy (DLTS). The relationship between the electric field strength and the emission rate of the three major electron traps (E1, E2 and E3) in electron-irradiated n-type GaAs material is presented. Using the models for phonon-assisted tunnel emission of electrons from deep levels developed by Ponset al.. and the enhancement due to Poole-Frenkel potential barrier lowering a correlation was attempted between the experimental results and those predicted by the above-mentioned two models. From these results an estimate of the Franck-Condon shift for the three defects is presented.
Optical Deep-Level Transient Conductance Characterisation of Semi-Insulating Gallium Arsenide Treated with Hydrogen Plasma
Authors: Teng Lai Say , Douglas Nener Brett , Alexander Butcher Dimitri Alexiev
Published: October 2002

Optical deep-level transient conductance spectroscopy (ODLTCS) has been employed to characterise Schottky devices fabricated on liquid encapsulation Czochralski (LEC) semi-insulating (SI) GaAs material which has been exposed to low-pressure microwave (2.42 GHz) H2plasma. A range of substrate temperatures and exposure times to the plasma were tested. An increase in device conductance spectra amplitudes were observed after 60 min of H2plasma treatment at 100° C, 300° C, and 400° C. In devices exposed to H2plasma at 200° C, the conductance spectra decreased in magnitude with time and after 60 min and 120 min treatments, the spectra were identical to that of the control device. The change in device conductance under the above conditions suggests that there is (i) an optimal plasma condition for the passivation of defects by atomic H with the formation of neutral defect-H (DH) complexes, (ii) the reaction between defects and atomic H is time dependent, and (iii) the LEC SI GaAs materials are contaminated with H during the growth process. In contrast, the increase in magnitude of ODLTC spectrum after 200° C treatment with molecular H for 60 min confirms the role of passivation by the atomic H.
A Model Analysis of the Thermal Conductivity of Ag-doped Bi–Sr–Ca–Cu–O Superconducting Oxide
Authors: Ikebe Manabu , Fujishiro Hiroyuki , Matsukawa Michiaki , Tatezaki Fumiaki , Ogasawara Hiromitsu , Noto Koshichi , Michishita Kazuo , Kubo Yukio
Published: October 2002

A phenomenological model to analyze the transport phenomena in inhomogeneous materials is proposed and applied to the measured thermal conductivity of Ag-doped Bi–Sr–Ca–Cu–O (Bi2212) superconducting oxide. Based on the model, the effective ratios of the doped Ag amount in the grain boundary to that inside of the grain are determined to be 0.75:1.0 for a Bi2212+15 wt%Ag specimen and 0.85:1.0 for a Bi2212+10 wt%Ag specimen. The model analyses indicate that doped Ag particles preferentially occupy the grain boundaries, contributing to the formation of the linked Ag heat path in the oxides.
Characteristics of Chlorine-Doped ZnSe Films and ZnSe–ZnS Superlattices Grown by Hot Wall Epitaxy
Authors: Sakakibara Shingo , Fujimoto Kouki , Amano Noriyasu , Ishino Kenei , Akihiro Ishida Akihiro Ishida , Hiroshi Fujiyasu Hiroshi Fujiyasu
Published: October 2002

Chlorine-doped (Cl-doped) n-type ZnSe films were prepared on GaAs(100) substrates by hot wall epitaxy (HWE) using ZnCl2 as a doping source. The electron concentration could be controlled from 8.4×1014 cm-3 to 2.8×1019 cm-3 by varying the ZnCl2 temperature. ZnSe films with an electron concentration above 1019 cm-3, having a donor-bound excitonic photoluminescence emission (I
2) without deep level emission were obtained for the first time. The activation energy of the chlorine donor was estimated to be 26.7 meV from the photon energy of I
2. The existence of Cl in the films was confirmed by SIMS. Moreover, the Cl-doped ZnSe–ZnS superlattices with high electron concentration on the order of 1017 cm-3 and excitonic PL emissions associated with the free exciton, were obtained for the first time.
Surface and Interface Study of Titanium Nitride on Si Substrate Produced by Dynamic Ion Beam Mixing Method
Authors: Beag Young Whoan , Tarutani Masayoshi , Min Kyung-youl , Kiuchi Masato , Ryuichi Shimizu Ryuichi Shimizu
Published: October 2002

Crystal growth of TiN on Si substrate under dynamic ion beam mixing (DIBM) processing was monitored by reflection high-energy electron diffraction (RHEED) and the interface was studied by transmission electron microscope (TEM). The TEM observation has revealed that the intermixed layer between the Si substrate and TiN film is composed of three different types of sublayers. The thicknesses of the first and the second sublayers were same as ∼7–8 nm and ∼3–4 nm, respectively, independent of different arrival ratios of Ti/N. The thickness of the third layer, however, was ∼6 nm for the arrival ratio of nearly unity whereas it was ∼14 nm for the arrival ratio greater than unity. Characterization of these sublayers with a field-emission analytical electron microscope (AEM) has revealed that these three sublayers are of an amorphous structure, composed of a mixture of Si and N, of a mixture of Si, N and small amount of recoil-implanted Ti, and of a mixture of Si, N, and Ti, for the 1st, 2nd and 3rd sublayers, respectively. TiN (001) is epitaxially grown on Si (001) along the incident direction of nitrogen ions even though the intermixed layer exists inbetween the TiN film and Si substrate.
Photoionization Spectra of High Rydberg Series and Ionization Potential of Ag
Authors: Toshiaki Ishikawa Toshiaki Ishikawa
Published: October 2002

A series of the Rydberg states of Ag in quantum numbers n=22 to 60 produced by a three-step selective excitation process using three tunable dye lasers is measured. It is found that the least squares fitting of the Rydberg formula to the observed Rydberg series yields the ionization potential of E
i=61104.3 cm-1±0.06 cm-1.
Scanning Laser Microscopy of Magneto-Optic Storage Media
Authors: Wright C. David , Clegg Warwick W. , Attia Boudjemline Attia Boudjemline , Nicholas A. E. Heyes Nicholas A. E. Heyes
Published: October 2002

The application of scanning laser microscopy to the evaluation of the properties and performance of magneto-optic storage media and magneto-optic record/replay systems is described. It is shown that scanning laser microscopy provides a most powerful tool for the investigation of such media and systems. Not only can fundamental properties, such as Kerr rotation, reflectivity, coercivity, and hysteresis loop shape of the storage material itself be investigated, but a quantitative measure of recording and overwrite performance can be obtained. Furthermore, the evaluation of important record/replay system parameters such as noise performance and read head resolution is straightforward. Finally, it is shown that the scanning laser microscope provides an ideal instrument base with which to investigate novel record and replay methods, such as direct overwrite and phase contrast and super-resolution read techniques.
Three-Dimensional Electric Field Vector Measurements in Nitrobenzene Using Kerr Effect
Authors: Takechi Haruo Ihori , Arii Kiyomitsu
Published: October 2002

We have been investigating a nonuniform electric field measurement method in dielectric liquids using the Kerr electrooptic effect. Three-dimensional electric field vectors were measured as the first step in determining the three-dimensional nonuniform electric field distributions. The electric field vector to be measured was produced in a pair of inclined parallel-plane electrodes. Negative high-voltage pulses were applied to the electrode system. Nitrobenzene with large Kerr constant was used in the experiments. A He-Ne laser beam passed through nitrobenzene between the electrodes along two different orthogonal directions. The magnitude and the direction of the electric field vector were calculated from the light intensity measured by a photodiode. Maximum errors of measured electric field strength and direction were 9.3% and 4.3°, respectively.
Application of Focused Ion Beam Implantation to Produce Gallium Arsenide Metal Semiconductor Field-Effect Transistors with a Novel Doping Profile
Authors: Hussain Tahir , John Richard Adrian Cleaver John Richard Adrian Cleaver , Haroon Ahmed Haroon Ahmed
Published: October 2002

We report the fabrication and performance of a new gallium arsenide (GaAs) metal semiconductor field-effect transistor (MESFET) device. The new device combines the concept of step-doping, where the doping of the channel is changed in a step, from high towards the source to low towards the drain, of the MESFET channels with that using a buried p-layer under the channel. Focused ion beams (FIBs) of silicon (Si) and beryllium (Be) were used, respectively, to implant the n-layer for the stepped channel and the p-layer at the channel substrate interface. A range of Be co-implantation doses and energies were studied for 150 keV channel implantation. The Be co-implanted layer improves the transconductance and pinch-off voltage of the devices by increasing the abruptness of the channel layer and reducing the substrate current. The available power from a step-doped device is high compared to uniform-channel devices with either low or high dopant concentration.
Optimized Welding of Stainless Steel Tubings for Corrosion Free Exposure to HBr Gas
Authors: Hattori Taeko , Takagi Hideki , Boireau Alain , Chevrel Henri , Eiichi Ozawa Eiichi Ozawa , Jean M. Friedt Jean M. Friedt
Published: October 2002

Hydrogen bromide gas phase corrosion of welded 316L electropolished stainless steel tubings to be used for the distribution of ultra clean gases has been investigated by using two techniques: one is leaching of the corroded tubings and subsequent chemical analysis of the dissolved metallic elements, the other one is bromine penetration depth at the stainless steel surface by Auger spectroscopy. These test procedures were applied to optimize the back shielding gas used for orbital welding of such tubings. A correlation is found between the oxygen concentration in the back shielding gas and the gas phase corrosion. Purified argon as back shielding gas insures best corrosion resistance due to the minimum thickness of superficial iron oxide, and maximal chromium concentration underlying the top iron/manganese oxide layer. Tubings made of stainless steel containing very small concentration of manganese exhibit lower level of corrosion. A corrosion enhancement mechanism by manganese is proposed.
Fluorescence from Wing of Morpho sulkowskyi Butterfly
Authors: Kumazawa Kinya , Tanaka Shingo , Keishi Negita Keishi Negita , Hiroshi Tabata Hiroshi Tabata
Published: October 2002

Fluorescence from various parts of a wing of a male butterfly,Morpho sulkowskyi(Morphospecies), was investigated using a microspectrophotometer. From the central (blue color) region of the wing, fluorescence was observed for the first time in this species when irradiated with ultraviolet (UV) or visible light. On the other hand, the distal tip (black color) of the wing was not fluorescent. Further microscopic studies also showed that the fluorescence spectra of the upper (dorsal) and the lower (ventral) surfaces of scales, which were obtained from the fluorescent central region of the wing, were different, having fluorescence peaks at 520 nm and 470 nm, respectively.
Mechanism of Reactive Ion Etching Lag in WSi2 Etching Using Electron Cyclotron Resonance Plasma
Authors: Maruyama Takahiro , Fujiwara Nobuo , Yoneda Masahiro , Tsukamoto Katsuhiro , Banjo Toshinobu
Published: October 2002

The electron cyclotron resonance (ECR) plasma is one of the suitable methods to generate plasma at a low pressure; however, unprecedented low pressure (<0.1 Pa) and smaller feature size have created unexpected problems. We study the relationship between ion energy and WSi2 etching products in order to discuss the mechanism of the reactive ion etching (RIE) lag observed in the WSi2 etching results. We investigate the dependence of WSi2 etch rate and RIE lag on etching parameters at low pressures (4×10-2 Pa). The RIE lag of WSi2 etching is stronger than that of poly-Si etching. Also, the RIE lag increases as rf power increases. Two possible reasons for the RIE lag can be suggested. One is the decrease of the flux ratio of a high-aspect-ratio pattern. Another is that partial pressure of the etch products at the bottom of a narrow space pattern is higher than that at the wide space pattern.
Quasi-Static and Dynamic Density Fluctuations in the Glassy State III. Isotropic Scattering Related to Isothermal Compressibility of Glass and Anisotropic Scattering
Authors: Tomoyoshi Yamashita Tomoyoshi Yamashita , Kensuke Kamada Kensuke Kamada
Published: October 2002

For expressions of isotropic and anisotropic scattering, V
v
iso and H
v, in a glass, V
v
iso=V
v
dyn
so+V
v
qst
iso and H
v=H
v
dyn+H
v
qst were introduced from the viewpoint of dynamic and quasi-static density fluctuations. The V
v
dyn
iso, which is an isotropic scattering due to the dynamic density fluctuation, can be associated with an isothermal compressibility of glass measured on a comparable time scale. The isothermal compressibility estimated from the V
v
dyn
iso was in good agreement with that measured by dilatometry for the PC and PMMA. Therefore, it was clarified experimentally for the first time that the isothermal compressibility of glass is dominated thermodynamically by the dynamic density fluctuation largely remaining in the glassy state. Both polycarbonate (PC) and polymethylmethacrylate (PMMA) have large V
v
dyn
iso, and an organic polymer has much dynamic density fluctuation, irrespective of whether it has side-chains for its molecule structure. Furthermore, it is important to note that H
v
dyn/H
v of PC is very small in the glassy state. Therefore, optical anisotropy of PC is attributed primarily to the quasi-static density fluctuation rather than the dynamic density fluctuation.
Native Oxide Removal on Si Surfaces by NF3-Added Hydrogen and Water Vapor Plasma Downstream Treatment
Authors: Kikuchi Jun , Iga Masao , Ogawa Hiroki , Fujimura Shuzo , Hiroshi Yano Hiroshi Yano
Published: October 2002

NF3 was injected into the downstream of hydrogen and water vapor plasma to produce etching species without generating fluorine atoms, and native oxides on Si(111) surfaces formed in H2SO4/H2O2 solution were removed. The absence of fluorine atoms in the plasma and the downstream was confirmed by monitoring with a monochromator and an ESR spectrometer, respectively. Thus, etching of the quartz surface of a chamber which led to particle generation was not observed. The Si surfaces after the downstream treatment were investigated and compared with that after HF wet cleaning using attenuated total reflection Fourier transform infrared (FT-IR ATR) spectroscopy and X-ray photoelectron spectroscopy (XPS).
Temperature Dependence of Etching with Molecular Fluorine on Si(111) Surface
Authors: Masayuki Hiroi Masayuki Hiroi , Toru Tatsumi Toru Tatsumi
Published: October 2002

Etching with molecular fluorine on a Si(111) surface was studied in an ultrahigh vacuum reactor. Reflection high-energy electron diffraction intensity oscillation during the etching was successfully observed only below 580° C. Drastic improvement of surface morphology and disappearance of the oscillation indicate an etching mode variation with increasing temperatures. An activation energy of 108 kcal/mol for the etching on flat (111) surface was estimated from the periods of the oscillations.
Study of the Etching Reaction by Atomic Chlorine Using Molecular Beam Scattering
Authors: Karahashi Kazuhiro , Jiro Matsuo Jiro Matsuo , Kei Horiuchi Kei Horiuchi
Published: October 2002

We studied the interaction of atomic chlorine with Si(100)2×1 surfaces using atomic chlorine beams. Above 600° C, the etching reactions with molecular or atomic chlorine were the same, therefore we studied reactions below 600° C. Most of the desorption products were SiCl2, but some higher silicon chlorides, such as SiCl4 or Si2Cl6, also desorbed from the surface. Our study of the temperature dependence of the SiCl2 desorption reaction showed that the activation energy is 0.08 eV at 0.4 monolayers (ML) and 0.2 eV at 0.8 ML. These extremely low activation energies suggest that the surface reaction is mainly driven by the kinetic or chemical potential energy of incident atomic chlorine instead of thermal excitation from the Si(100) surface. The reaction depends on the surface chlorine coverage, with the reaction occurring above 0.3 ML, reaching a maximum at 0.4 ML, and decreasing as the coverage increases further.
Comparison of Relaxation Process of Compressive and Tensile Strains in InGaAs Lattice-Mismatched Layers on InP Substrates
Authors: Tsuchiya Tomonobu , Taniwatari Tsuyoshi , Komori Masaaki , Ruriko Tsuneta Ruriko Tsuneta , Hiroshi Kakibayashi Hiroshi Kakibayashi
Published: October 2002

This paper investigates the difference in crystal quality between strained-layer multiple quantum wells with compressive (+0.5%) and tensile strains (-0.5 %). For the compressive strain, the photoluminescence intensity decreased and the length of fringe bending increased from 250 Å to 500 Å when the number of periods increased from 5 to 15. The amount of fringe bending increased when the InP thickness decreased, especially when the strain was compressive. We also investigated the relaxation process in an InGaAs layer as a function of the layer thickness (from 25 nm to 2 µ m). For a compressive strain (+1.1%), misfit dislocations were observed near the interface between InGaAs and InP substrate. On the other hand, for a tensile strain (-1.1 %), we observed cracks instead of misfit dislocations. Moreover, the cracks were considered to increase the X-ray full width at half maximum of both the InGaAs lattice-mismatched layer and the InP substrate.
Photoluminescence of Si1-xGex/Si Quantum Wells with Abrupt Interfaces Formed by Segregant-Assisted Growth
Authors: Usami Noritaka , Susumu Fukatsu Susumu Fukatsu , Yasuhiro Shiraki Yasuhiro Shiraki
Published: October 2002

Photoluminescence (PL) of Si1-
x

Ge

x

/Si quantum wells with abrupt interfaces formed by segregant-assisted growth (SAG) is reported. It was found that SAG-grown samples show spectral red-shift compared to those grown by conventional solid-source molecular beam epitaxy due to the suppression of Ge surface segregation during growth. Crystal quality of SAG-grown samples is discussed based on the excitation variation of PL intensity.
Photoluminescence from Localized Excitons in Si/Ge Superlattices
Authors: Joachim Hartung Joachim Hartung , Victor Higgs Victor Higgs , Gordon Davies Gordon Davies , E. C. Lightowlers E. C. Lightowlers , Vincent Arbet-Engels Vincent Arbet-Engels , K. L. Wang K. L. Wang
Published: October 2002

Short period strained-layer Si/Ge superlattices grown by molecular beam epitaxy have been investigated by photoluminescence spectroscopy. In 16×4, 15×4 and 12×4 superlattices with 80 or 120 periods two new luminescence peaks appear. From their separation in photon energy, the two peaks are assigned to a no-phonon transition and its silicon transverse optical phonon replica. Detailed photoluminescence investigations have confirmed that the new peaks which appear at energies between 0.85 and 1.05 eV give evidence for radiative recombination in the superlattices. From their luminescence intensity as well as lineshape dependence on the excitation power we attribute the new peaks to localized excitons.
Optical Detection of Interdiffusion in Strained Si1-xGex/Si Quantum Well Structures
Authors: Sunamura Hiroshi , Fukatsu Susumu , Noritaka Usami Noritaka Usami , Yasuhiro Shiraki Yasuhiro Shiraki
Published: October 2002

An extended optical study on interdiffusion in strained Si1-
x

Ge

x

/Si quantum well structures grown by gas-source molecular beam epitaxy is presented. Using photoluminescence (PL) spectroscopy, diffusion coefficients are derived from the luminescence peak energy blue shifts observed in vacuum-annealed samples. Here, growth temperature dependence of the diffusion coefficients is systematically investigated and it is found that the activation energy associated with interdiffusion is rather constant at ∼3 eV. In addition, extended results are presented to support the oxidation-induced band gap shrinkage observed as the anomalous red shift in samples annealed in N2 or O2 ambient. The strain originating from the oxidation of the capping layer is estimated from the energy shifts. Excitation power dependence of PL intensity is investigated to study the effect of thermal treatment on the crystal quality. It is found here that surface oxidation in QWs with thin capping layer degrade their optical quality.