bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Ni and Zn Substitutions for Cu in the 25 K Phase of Bi–Sr–La–Cu–O Superconductors
Authors: Mao Zhiqiang , Xu Cunyi , Tian Mingliang , Xu Gaojie , Wang Yu , Zhang Yuheng , Durbin Stephen M. , Li Shi , McElfresh Mike
Published: October 2002

We investigate the effect of Ni and Zn substitutions for Cu on the lattice parameters, phonon vibrational feature, electronic structure, as well as transport properties in Bi2Sr1.8La0.2CuO

y

. The experimental data show that both Ni and Zn are soluble in the Bi2Sr1.8La0.2CuO

y

material up to about 10% of the Cu content. In Bi2Sr1.8La0.2Cu1-
x

Ni

x

O

y

system, the superconducting critical temperature T
c decreases linearly with Ni concentration and the rate of T
c decrease is around 2.5 K/at.%, while for Bi2Sr1.8La0.2Cu1-
x

Zn

x

O

y

system the dependence of T
c on the Zn dopant concentration deviates from a linear behavior and the Zn substitution suppresses the T
c much stronger than the Ni substitution. The comparison of the phonon vibrational feature of the apical oxygen atoms in the CuO6 octahedron between the Bi2Sr1.8La0.2Cu1-
x

Ni

x

O

y

and Bi2Sr1.8La0.2Cu1-
x

Zn

x

O

y

systems shows that the Zn substitution leads to a more serious structure distortion than the Ni substitution. In addition, the electronic structures of the two doped systems were compared using XPS spectrum. The results show that the Zn substitution reduces Cu oxidation level more remarkably than the Ni substitution. Some possible explanations for the stronger suppression of T
c by the Zn substitution than by the Ni substitution are provided, based on these experimental results.
Logarithmic AC Response in Rb3C60 Crystals
Authors: Lee Ming-Way , Shi Jen-Bin , Shyh-Chyu Luo Shyh-Chyu Luo
Published: October 2002

AC susceptibility measurements were performed on Rb3C60 crystals. Two peaks are observed in the imaginary part of the susceptibility χ′′(T) and the peak near the transition temperature T
c is more pronounced. This is interpreted in terms of weak links in the fullerene superconductors. The temperature associated with the intragranular χ′′ maximum T
m exhibits extremely weak dependence on ac frequency f; T
m shifts to higher temperature with increasing f and the effect is enhanced by increasing dc magnetic-field amplitude H
dc or ac amplitude h
ac. The inverse temperature 1/T
m is found to depend roughly linearly on logarithmic frequency. This result is consistent with the prediction of the thermally activated flux creep model. This implies that the ac power dissipation in the Rb3C60 superconductors is predominantly due to hysteretic losses and therefore that magnetic flux is in the irreversible regime of the magnetic phase diagram. The thermal activation energy for flux lines U
0 is estimated to be ≈6.1 eV at H
dc=1 kOe and h
ac=1 Oe. Finally, (1-T
m/T
c)3/2 is found to depend linearly on ln
f.
Crystallinity of Ce Substituted YIG Films Prepared by RF Sputtering
Authors: Tate Akiyuki , Uno Takehiko , Mino Shinji , Atushi Shibukawa Atushi Shibukawa , Toshihiro Shintaku Toshihiro Shintaku
Published: October 2002

The crystallinity of Ce-substituted yttrium iron garnet ( Ce1\colonYIG) film was studied by measuring X-ray diffraction (XRD) and deformation and by transmission electron microscope (TEM) observation. The Ce1\colonYIG films were prepared on anisotropic etched or unetched GGG and cation doped GGG (GCGMZG) substrates by RF sputtering. They have a narrow crystallization region as regards substrate temperature and this region becomes narrower as the O2 gas flow rate is increased. The XRD measurements and TEM observation revealed that crystallized Ce1\colonYIG films have a multilayered structure except for those on GCGMZG substrates. Their layered structure was dependent on their thickness, the substrate treatment, the lattice constant difference between the film and the substrate and the O2 flow rate. They also exhibited compressive deformation which originated mainly from the lattice constant difference between the film and the substrate. The crystal growth mechanism of Ce1\colonYIG films was considered on the basis of recent work on the growth mechanism of compressively deformed strained semiconductor film.
A High-Power Q-Switched CO2 Laser Using Intense Pulsed RF Discharge Excitation
Authors: Tatsuhiko Sakai Tatsuhiko Sakai , Naoya Hamada Naoya Hamada
Published: October 2002

A compact high-power Q-switched CO2 laser has been developed using a combination of intense pulsed rf (13.56 MHz) discharge excitation and a high-speed rotating Q-switch chopper. Performance characteristics have been investigated as functions of Q-switching velocity, input discharge energy density and laser gas composition. A pulse peak power of 300 kW and an average power of 740 W at 10 kHz pulse repetition frequency have been obtained simultaneously for a Q-switched laser based on a CO2 laser with 1.1 kW average power. By decreasing the repetition frequency to 4 kHz, the peak power was enhanced to above 500 kW. An analytical model describing the unique features of the Q-switched CO2 laser has also been developed for quantitative evaluation of the laser performance. Good agreement was obtained between the theoretical model and experimental results.
Bandwidth Narrowing of an All-Solid-State Optical Parametric Oscillator Amplifier System
Authors: Srinivasan Narayanan , Kimura Takashi , Kiriyama Hiromitsu , Yamanaka Masanobu , Izawa Yasukazu , Yamanaka Sadao Nakai
Published: October 2002

An all-solid-state narrow-bandwidth tunable near-infrared KTP optical parametric oscillator amplifier (OPOA) is presented. The bandwidth at 960 nm was reduced from the free running mode ( >100 GHz) to less than 150 MHz by the simultaneous injection seeding of the pump laser and the OPOA, which is close to the Fourier transform limit of the 4 ns output pulses. The OPOA has a potential tunability of over 60 nm from 915–975 nm determined by its external cavity grating tuned diode seed laser.
Spatial Resolutions and Polarization Analysis in Raman Microprobe Technique
Authors: Tsutomu Ishioka Tsutomu Ishioka
Published: October 2002

The spatial resolutions and polarization analysis in the Raman microprobe technique were dealt with. The spatial resolutions for the axial and the horizontal directions of high-numerical-aperture objectives in vacuum were estimated theoretically by the analysis of the spatial distribution of the incident electric field near the focal point. Based on the results, a method of correction for the polarization scrambling effect caused by the sharp focusing objective in the polarization analysis, which is a modification of the method derived by Turrell, was derived. This was applied successfully to the analysis of spectral change due to the shift of the focus in a specimen such as α-quartz.
Effects of the External Electric Field from a Substrate on Conductance Changes of SnO2 Thin Films by CO Gas
Authors: Kunishima Yoshiko Niki , Yanagida Masaru Miyayama
Published: October 2002

Thin SnO2 films were sputtered on SiO2/Si substrates. The effects of the external electric field from the substrate on the film conductance and on CO gas reactions at the film surface were studied. The conductance of the film increased with a positive substrate bias, and decreased with a negative substrate bias. A gradual increase in conductance was observed at 250 and 300° C in air, which suggested a change in the amount of adsorbed oxygen ions on the film surface. A positive substrate bias induced a larger increase in conductance due to CO gas at 250 and 300° C, which indicates enhancement of the adsorption of negatively charged oxygen ions and subsequent CO oxidation. In contrast, a negative bias induced a larger increase in conductance due to CO gas at 47° C, which indicates enhancement of the adsorption of positively charged CO. The results suggest that it is possible to control surface gas reactions and gas sensitivity using this external electric field.
Temperature Dependence of Quantized States in a GaAs/Al 0.23)Ga 0.77)As Asymmetric Triangular Quantum Well Heterostructure
Authors: Lin Der-Yuh , Chi-Feng Li Chi-Feng Li , Ying-Sheng Huang Ying-Sheng Huang
Published: October 2002

The piezoreflectance (PzR) measurements of a GaAs/Al0.23)Ga0.77)As asymmetric triangular quantum well heterostructure as a function of temperature in the range of 20 to 300 K have been carried out. The structure was fabricated by molecular beam epitaxy using a digital alloy compositional grading method. A comparison of the PzR and photoreflectance spectra allows us to identify the features associated with the heavy- and light-hole valence bands unambiguously. The detailed study of the temperature variation of excitonic transition energies indicates that the main influence of temperature on quantized transitions is through the temperature dependence of the band gap of the constituent material in the well. The anomalous behavior of the temperature dependence of the linewidth of 11H excitonic feature is discussed.
Dilution-Gas Effect on Electron Density and Temperature in RF SiH 4 Plasma Based on Microwave Cavity Resonance Measurement
Authors: Hideshi Nomura Hideshi Nomura , Akihiro Kono Akihiro Kono , Toshio Goto Toshio Goto
Published: October 2002

Using a microwave cavity resonance technique, the electron density (n
e) in a low-pressure (40–100 mTorr) RF (13.56 MHz) SiH4 plasma and the electron loss rate in the afterglow were measured with varying SiH4 fractions in the SiH4/Xe, /Ar, /He and /H2 mixture gases. The behavior of electron temperature (T
e) was estimated from the relative variations of the excitation rate constants (k
em) for emissive rare-gas excited states, which were derived by combining the results of electron density measurements with optical emission measurements. The product k
em
n
e generally increased with increasing dilution but the behaviors of the individual k
em and n
e differ considerably for different mixture gases. The results were discussed in terms of energy and particle balance consideration. It was found that the dominant electron loss process in the afterglow is attachment and that the major attaching species is not SiH
x
(x=0–4) but some larger molecules produced in the plasma, even under the low-power (< about 5 W) conditions studied. The same attachment process was shown to have a significant role in determining T
e and n
e in the active plasma.
Compact Magneto-Optical Head Module Integrated with Chip Elements using Double Holograms
Authors: Katayama Ryuichi , Komatsu Yuichi , Nagano Tsuyoshi , Watanabe Akira , Tada Kentaro , Hotta Hitoshi , Yuzo Ono Yuzo Ono
Published: October 2002

A compact magneto-optical head module integrated with chip elements, which uses a polarizing grating and a holographic optical element, has been developed. The module size is W14.4 mm×D5.6 mm×H13 mm. A readout experiment for a magneto-optical disk has been carried out employing a 685 nm laser diode. Carrier-to-noise ratio of more than 45 dB has been obtained under quadruple capacity conditions compared with the first-generation ISO (International Organization for Standardization) standard. Alignment tolerance was also investigated.
Construction and Performance of a Fourier-Transform Infrared Phase-Modulated Ellipsometer for In-Process Surface Diagnostics
Authors: Tachibana Kunihide , Shirafuji Tatsuru , Muraishi Shuichi
Published: October 2002

A Fourier-transform infrared phase-modulated spectroscopic ellipsometer (FT-IR PMSE) has been constructed by insertion of a grid polarizer as an analyzer in front of an infrared detector in addition to a conventional setup for phase-modulated reflection absorption spectroscopy (PMRAS). Although ellipsometric parameters Ψ and Δ are subject to the effect of mirrors placed between a photoelastic modulator and the analyzer, this can be canceled out in the derivation of optical density of the measured surface. The performance of the ellipsometer has been demonstrated in the characterization of thermally oxidized Si surfaces. It is shown that the imaginary part of the optical density spectrum has a higher signal-to-noise ratio than the real part, which corresponds to the spectrum obtained by PMRAS, and a linear relationship with SiO2 thickness. By this method the presence of a fluorinated layer has been detected on CF4 plasma-treated Si surface.
Determination of Interatomic Potential by Ab-Initio Periodic Calculation for MgO
Authors: Toshio Kamiya Toshio Kamiya
Published: October 2002

Interatomic potentials between Mg–O and O–O in MgO crystal are determined using the crystal energy surface obtained by an ab-initio periodic calculation. A flexible form of the interatomic potential is proposed and applied to the determination of the interatomic potentials. The dielectric constant, bulk modulus and temperature dependence of the crystal structure are calculated by lattice dynamics and molecular dynamics (MD) methods using the interatomic potential obtained. It is found that the obtained interatomic potential well reproduces these properties for MgO. Phase transition from rocksalt structure to CsCl structure is observed under an isostatic pressure of 80 GPa at 300 K in the MD simulation.
Monolithic Integration of Waveguide Gratings and Quantum-Well Distributed-Feedback Laser for Implementation of Subminiature Optical-Disc Pickup Head
Authors: Suhara Toshiaki , Taniguchi Takehiro , Uemukai Masahiro , Yoshimoto Akihiro , Nishihara Hiroshi , Hirata Takaaki , Iio Shinji , Suehiro Masayuki
Published: October 2002

We propose a subminiature optical-disc pickup head implementation by monolithic integration of wave- guide grating components, a graded-index separate-confinement heterostructure single-quantum-well distributed-feedback laser and photodiodes. Fabrication of a prototype device and the results of a preliminary experiment are presented.
Element-Specific Contrast in Scanning Tunneling Microscopy via Resonant Tunneling
Authors: Himpsel Franz J. , Jung Thomas , Schlittler Reto , Gimzewski Jim K.
Published: October 2002

An element-specific version of scanning tunneling spectroscopy for metals is presented. Contrast between two metals is achieved by resonant tunneling via surface states and image states. These states are characterized independently by inverse photoemission. Image states provide elemental identification via the work function, since their energy is correlated with the local work function. Element-specific surface states produce contrast at higher spatial resolution, but the contrast is smaller than that for image states. These imaging techniques are used to study the growth modes of Cu stripes on stepped W(110) and Mo(110) surfaces.
Interpretation of Frictional-Force Microscopy Images Based on the Two-Dimensional Stick-Slip Motion of the Tip Atom
Authors: Naruo Sasaki Naruo Sasaki , Katsuyoshi Kobayashi Katsuyoshi Kobayashi , Masaru Tsukada Masaru Tsukada
Published: October 2002

Frictional-force microscopy (FFM) images of graphite are calculated by a numerical simulation using a static model. We find that a remarkable transition of the FFM image pattern occurs depending on the cantilever stiffness. This image transition is interpreted based on the two-dimensional stick-slip motion of the tip atom. It is clarified that the frictional force image pattern reflects two kinds of tip atom motion: 1) straight motion and 2) zigzag motion.
Reversible Tip-induced Structural Modifications in Scanning Tip Microscopy
Authors: Kyeongjae Cho Kyeongjae Cho , John D. Joannopoulos John D. Joannopoulos
Published: October 2002

Tip-induced structural modifications of the Si(100) surface in scanning tunneling microscopy (STM) and atomic force microscopy (AFM) are investigated with first-principles total energy pseudopotential calculations. The atoms of the tungsten tip and the surface are fully relaxed according to the tip-surface interactions. At tip-surface distances relevant to STM measurements, the tip is found to significantly influence the dynamics of the surface atoms leading a new understanding of the microscopic STM measurement process. At smaller tip-surface distances, the tip-surface interactions can be used to directly manipulate the geometry of the surface atoms. At very low temperature, the theory predicts the existence of micromechanical hysteresis on an atomic scale which can be measured in low temperature AFM. The theory also leads to the discovery of a specific protocol of tip movements with implications towards a novel design for an ultra-high density memory storage device.
Cross-Sectional Scanning Tunneling Microscopy on Cleaved Si(111): Observation of Novel Reconstruction and Structural and Electrical Properties of MOS Interface
Authors: Komeda Tadahiro , Tokumoto Shangjr Gwo
Published: October 2002

Cross-sectional scanning tunneling microscopy (XSTM) measurements revealed two types of reconstructions on Si(111) surfaces depending on the cleaving conditions. The first one is a 2×1 structure consistent with previous reports. The second one is a novel 8×1 structure, which shows a missing-row structure where one row is missing in every four rows in the 2×1 structure. We propose a model for the missing-row reconstruction seen on the Si(110) surface. XSTM observation of the metal-oxide-semiconductor (MOS) interface structure clearly showed a fractured metal layer and cleaved Si areas which demonstrated the possibility of observing the interface with atomic resolution. Scanning tunneling spectroscopy (STS) measurement of the Si part showed systematic shifts of the spectra with the application of bias voltage between the metal and the Si, which agreed well with the expected band bending in the Si.
Si Dimer Chain on Si(100)-2×1:H Surface Fabricated by Scanning Tunneling Microscope
Authors: Huang Dehuan , Yamamoto Yoshihisa
Published: October 2002

In order to fabricate an atomic chain with metal, semiconductor and insulator phases on an atomically flat insulating surface by manipulating single atoms one by one with an ultrahigh-vacuum scanning tunneling microscope (UHV STM), we investigated the Si(100)-2×1 surface and its hydrogen termination. The obtained STM images show that the Si(100)-2×1 surface will have fewer defects when appropriate preparation is employed. We successfully prepared the monohydride Si(100)-2×1:H surface using the dry etching process. Hydrogen atoms on the Si(100)-2×1:H surface can be extracted by applying both positive and negative voltage pulses between the STM tip and the sample surface with a certain tunneling current. This implies that the mechanism for extracting hydrogen atoms on the monohydride surface is due to not only electron excitation but also field evaporation. There is a pairing effect to force extracted hydrogen atoms in pairs from dimers. Using this technique, we fabricated a Si dimer chain on the Si(100)-2×1:H surface by removing pairs of hydrogen atoms.
Fabrication of Buried Metal Dot Structure in Split-Gate Wire by Scanning Tunneling Microscope
Authors: Aoki Nobuyuki , Fukuhara Keizo , Kikutani Tomoyuki , Oki Akio , Hidenobu Hori Hidenobu Hori , Syoji Yamada Syoji Yamada
Published: October 2002

Fabrication of a new class of quantum structure which has a buried nickel (Ni) dot in a split-gate quantum wire using a scanning tunneling microscope (STM) is described. In order to fabricate small structures at the desired wire surface position, we employ a combined STM/scanning electron microscope (SEM) system in high vacuum. The fabrication methods are those based on simple electrical evaporation with a tungsten (W) tip. On the free surface far from the split-gate electrodes, the structure produced after applying a single voltage pulse is a small mesa (150 nm diameter, 20 nm high). However near the gates, large holes (150 nm diameter at half-depth, 85 nm deep) are created. Such large holes act as the pinpoint antidot for the two-dimensional electron gas (2DEG) lying at a depth of 60 nm from the wafer surface. As a metallic material, we adopted a Ni. For burying Ni into the hole, we moved the Ni-coated W tip to the hole bottom by observing the SEM image and created a Ni dot in the hole by applying a single voltage pulse.
Scanning Tunneling Microscopy/Scanning Tunneling Spectroscopy Observation of III–V Compound Semiconductor Nanostructures
Authors: Noh Joo-Hyong , Asahi Hajime , Kim Seong-Jin , Minori Takemoto Minori Takemoto , Shun-ichi Gonda Shun-ichi Gonda
Published: October 2002

InAs submonolayer samples grown on the vicinal (100) GaAs substrates and the self-organized quantum wire structures formed in the (GaP)2(InP)2 short-period superlattices (SLs) on the nominally (100) GaAs substrates by gas-source molecular beam epitaxy (GS-MBE) are studied by scanning tunneling microscopy (STM) and spectroscopy (STS). In the former nanostructures, the STM images show alternating bright stripes (InAs area) and dark stripes (GaAs area), and the bright stripe width increases with the amount of In supplied during growth. A difference is also observed in the I–V curve; the slope dI/ dV is different between the bright and dark areas and shows the same value in each area, although the onset voltage for the current rise is the same in all areas independent of InAs and GaAs areas. In the latter nanostructures, the STM images show alternating bright and dark stripes corresponding to the self-organized wire structures. In this case the onset voltage for the current rise as well as the slope dI/ dV varies depending on the lateral alloy composition modulation in the wire structures.
Scanning Probe Lithography Using a Trimethylsilyl Organosilane Monolayer Resist
Authors: Sugimura Hiroyuki , Keiko Okiguchi Keiko Okiguchi , Nobuyuki Nakagiri Nobuyuki Nakagiri
Published: October 2002

A trimethylsilyl organosilane monolayer was applied as a self-developing resist for scanning probe microscope (SPM) lithography under ambient conditions. Both a scanning tunneling microscope and an atomic force microscope with a conductive probe were applied and shown to be effective for this lithography. The resist was prepared on a silicon (Si) substrate by chemical vapor deposition, and was patterned through the localized degradation of the organosilane monolayer induced by scanning an SPM tip while positively (+5∼+10 V) biasing the substrate. The degradation rate was enhanced by increasing the concentration of atmospheric water vapor or oxygen. The patterning mechanism was identified as tip-induced anodic oxidation, i.e., scanning probe anodization. The pattern was transferred to the Si substrate through selective chemical etching in which the degraded monolayer regions served as etching windows. Consequently, fine grooves as narrow as 30 nm could be fabricated.
SiO2/Si System Studied by Scanning Capacitance Microscopy
Authors: Yamamoto Takuma , Suzuki Yoshihiko , Hiroyuki Sugimura Hiroyuki Sugimura , Nobuyuki Nakagiri Nobuyuki Nakagiri
Published: October 2002

The applicability of scanning capacitance microscopy (SCaM) in the characterization of SiO2/Si systems was demonstrated. Our SCaM, which is combined with a contact AFM, measures the capacitance derivative against the bias voltage applied to the sample ( dC/ dV). Line-shaped grooves etched into a SiO2 layer were imaged by SCaM based on the differences in the SiO2 thickness. AFM images were simultaneously obtained. The acquired SCaM and AFM images showed good agreement. SCaM images of the sample were obtained at different dc bias voltages. The contrasts of the SCaM images varied with the dc bias. The bias dependence of the image contrasts was compared with the dC/ dV-V differences between the thick SiO2 regions and the thin SiO2 regions and with calculated results. The results of this comparison showed good agreement.
In-Situ Selective Area Etching of GaAs in Metalorganic Molecular Beam Epitaxy Chamber using Trisdimethylaminoarsenic
Authors: Hayashi Toshihiko , Asahi Hajime , Yamamoto Kazuhiko , Ken-ichi Hidaka Ken-ichi Hidaka , Shun-ichi Gonda Shun-ichi Gonda
Published: October 2002

Selective area etching of GaAs using the metalorganic precursor, trisdimethylaminoarsenic (TDMAAs), is investigated under various etching conditions. The (100)-GaAs surface is partly masked using stripe shaped SiO2 films along the [011] and [0*BAR*1*BAR*1] directions. Cross-sectional scanning electron microscopy (SEM) observation shows that the etched shapes depend on both the stripe mask orientation and the substrate temperature, while they are almost independent of the TDMAAs flow rate and the stripe window width. Excellent mirror surface morphology is achieved at substrate temperatures below 500° C and high TDMAAs flow rates. It is possible to control the etched profiles by choosing etching conditions. TDMAAs is not only a promising arsenic source for growth but is also a quite useful in-situ etching gas source in metalorganic molecular beam epitaxy (MOMBE).
Time-Dependent Temperature Calculation of Aluminum Line Applied with Electrical-Overstress Pulses
Authors: Keiji Yamamoto Keiji Yamamoto , Takahiro Tsuru Takahiro Tsuru
Published: October 2002

When electrical-overstress (EOS) pulses are applied to an aluminum line, the temperature of the aluminum line will increase due to Joule heating. Since aluminum is a good conductor of heat, some of the heat generated will escape. This causes the deviation of the aluminum-line temperature from that predicted adiabatically. A computer simulation program, which employs the two-dimensional finite-element method, was developed to calculate transient aluminum-line temperature. In this program, the heat transfer coefficient α c is introduced to simulate heat escape. EOS pulse experiments were performed to determine the value of α c of an aluminum line. Using this value, the transient temperature of the aluminum line applied with EOS pulses was simulated. The threshold energy for fusing, which increases the peak temperature of the aluminum line to the fully vaporized point, was calculated for aluminum lines having various widths.
Second-Harmonic Properties of Horizontally Polarized Shear Modes in an Isotropic Plate
Authors: Deng Ming Xi Deng Ming Xi
Published: October 2002

The second harmonics of SH modes that occur within an isotropic plate with two free boundaries are investigated by applying second-order perturbation theory. The results show that the second harmonics include two types of waves. One is driven waves produced by the fundamental waves due to the nonlinearity of an elastic medium, and the other is free waves introduced to satisfy the second-harmonic boundary conditions. It is also found that the second-harmonic field patterns are symmetric, and the second-harmonic amplitudes are independent of propagation distance and one of the third-order elastic constants, C. The second-harmonic resonant phenomena occur and the second harmonics possess the characteristics of two-dimensional spatial accumulation once the phase velocities of SH modes equal the longitudinal velocity of the elastic medium. Moreover, the analytical expressions of the second harmonics are obtained. Numerical results show the distortions of the second-harmonic field patterns.
Magnetostatic Coupling MSR with In-Plane Magnetization Films
Authors: Nishimura Naoki , Hiroki Tomoyuki , Tsunashima Takeshi Okada
Published: October 2002

Magnetically induced super resolution (MSR) with double (front and rear) masks was achieved using GdFeCo/GdFe/TbFeCo (readout/intermediate/memory) triple layer films. The duplication of information from the memory layer to the readout layer is done through the magnetostatic coupling. The front mask and the rear mask are formed by in-plane magnetization and by collapsing written domains, respectively, without applying external fields. The transition from in-plane to perpendicular magnetization was made sharper by introducing the intermediate layer. Using this MSR medium and a conventional optical head (λ=780 nm), carrier-to-noise ratio (C/N) of over 45 dB for a mark length of 0.40 µm and crosstalk of -38 dB for a 0.8 µm track pitch were achieved. However, during the readout process, the magnetostatically coupled MSR medium is much more sensitive to the disturbance of external fields than exchange-coupled MSR medium.
High-Beta Operation with Enhanced Axial and Radial Confinement in the HIEI Tandem Mirror
Authors: Sakai Osamu , Kenichi Iwami Kenichi Iwami , Yasuyoshi Yasaka Yasuyoshi Yasaka
Published: October 2002

The operation of a tandem mirror using Ion Cyclotron Range of Frequencies (ICRF) waves and limiter biasing is performed in the HIEI tandem mirror. An ion confining potential is formed in the plug cell by high-field-side injection of the fast magnetosonic wave. Limiter biasing is simultaneously imposed with formation of a confining potential and minority heating in the central cell, and both axial and radial confinement are enhanced by a factor of 4. As a result, a high-beta plasma (∼14%) is produced in the central cell. The high-beta plasma is sustained magnetohydrodynamically by ponderomotive force of ICRF electric fields.
Measurement of Fast Electron Velocity Distribution Function in a Reversed Field Pinch Plasma
Authors: Yagi Yasuyuki , Hirano Yoichi , Toshio Shimada Toshio Shimada , Yoshiki Maejima Yoshiki Maejima
Published: October 2002

Fast electrons in the edge region of the reversed field pinch (RFP) device, TPE-1RM20 are studied using an electron energy analyzer (EEA) in the energy range below 1 keV. Results show that the fast electron velocity distribution function can be approximated either by a drift Maxwellian distribution function or two asymmetric half-Maxwellian distribution functions. The fast electron temperature is comparable to or slightly less than the central electron temperature depending on the fitting functions. The temperature obtained using the EEA is more than one order of magnitude lower than the characteristic fast electron energy estimated from soft X-ray emissions from the inserted materials at 2–8 keV. These observations indicate that fast electrons mainly have a Maxwellian distribution function with a temperature comparable to the central electron temperature and that the distribution function may have a higher energy tail in the keV region.
Doppler-Free Saturated Selective Reflection with Copropagating Pump-Probe Method
Authors: Takahisa Mitsui Takahisa Mitsui , Hidetoshi Numata Hidetoshi Numata , Katsumi Sakurai Katsumi Sakurai
Published: October 2002

Doppler-free spectroscopy of high density atomic vapor has been demonstrated using copropagating pump-probe selective reflection. The observed narrow resonance has been interpreted theoretically taking account of the saturation of the atomic vapor. Our theory predicts that the saturation effect due to optical pumping is not uniform over the Doppler-broadened transition and is prominent at zero velocity.
Kinetics of CFX (x=1 –3) Radicals and Electrons in RF CF4-H2, CHF3-H2 and CHF3-O2 Plasmas
Authors: Koji Maruyama Koji Maruyama , Katsunori Ohkouchi Katsunori Ohkouchi , Toshio Goto Toshio Goto
Published: October 2002

The densities of CF, CF2, and CF3 radicals have been measured in RF CF4-H2, CHF3-H2 and CHF3-O2 plasmas using infrared diode laser absorption spectroscopy. In H2 additive fluorocarbon plasmas, it was found that fluorocarbon film formation on the electrodes increases the radical densities in the plasma by reducing the surface loss probability and producing the radicals through sputtering of the fluorocarbon film. In CHF3-O2 plasma, the CF radical density decreased rapidly when a small amount of O2 gas was added due to the removal of fluorocarbon film, whereas an increase in the density of CF3 was observed. The spatially averaged electron density has also been measured using a microwave interferometer together with the Ar* emission intensity under the same conditions as the radical measurements. The variations in the electron temperature and density are explained qualitatively by the change in the electron loss process in the gas phase induced by H2 or O2 admixture.
Magnetically Induced Superresolution Using Domain Stability
Authors: Hirokane Junji , Akira Takahashi Akira Takahashi , Shigeo Terashima Shigeo Terashima
Published: October 2002

Two types of magnetically induced superresolution (MSR) readout methods were investigated. In one MSR method, triple-layered films in which the readout layer was coupled magnetostatically with the recording layer were used. In another MSR method, exchange-coupled triple-layered magnetic films were used. We utilized the phenomena of domain nucleation and domain collapse in readout layers in these MSR readout methods, and obtained a short rise time with domain nucleation and a short fall time with domain collapse in their readout layers.
Critical Dimension Measurement in Nanometer Scale by Using Scanning Probe Microscopy
Authors: Masao Nagase Masao Nagase , Hideo Namatsu Hideo Namatsu , Kenji Kurihara Kenji Kurihara , Takahiro Makino Takahiro Makino
Published: October 2002

This paper describes and demonstrates a new method using scanning probe microscopy for nanometer-order measurements of critical dimensions. The modeling equation, which includes the critical dimensions of both the sample and the probe, is derived from a mathematical relationship between the sample, probe, and image. The dimensions, which are the fitting parameters of the modeling equation, can be calculated from the height dependence of apparent width in SPM images. The feasibility of this method was confirmed by measuring several structures fabricated by nanofabrication.
Cathodoluminescence Imaging of n-Type Porous Silicon
Authors: Itoh Masashi , Yamamoto Naoki , Takemoto Kuniko , Nittono Osamu
Published: October 2002

Cathodoluminescence (CL) from n-type porous silicon (PS) was studied using a transmission electron microscope (TEM) equipped with the CL detection system. Two luminescence peaks at wavelengths of 660 nm and 420 nm were observed from a cross-sectional sample. The monochromatic CL images clearly reveal the spatial distribution of these luminescences along the depth direction; the 660 nm luminescence is mainly from near the top surface of the PS layer and the 420 nm luminescence the interface between the PS layer and Si substrate. The increase of the 420 nm luminescence intensity upon removal of the Si substrate suggests that the excited carriers in the residual Si matrix of the PS take part in the 420 nm luminescence.
Fabrication of c-Axis Oriented Pb(Zr, Ti)O3 Thin Films on Si(100) Substrates Using MgO Intermediate Layer
Authors: Senzaki Junji , Mitsunaga Osamu , Uchida Takahito , Tomo Ueno Tomo Ueno , Koichi Kuroiwa Koichi Kuroiwa
Published: October 2002

Tetragonal perovskite Pb(Zr

x

Ti1-
x

)O3 (PZT) ferroelectric thin films with single c-axis orientation were successfully fabricated on Si(100) substrates using an intermediate layer of MgO thin film. The (100) oriented MgO intermediate layers can be prepared on Si(100) substrates with low growth rate during RF magnetron sputtering at a substrate temperature of 300° C. On the (100) oriented MgO intermediate layer, PZT can be deposited using a digital Metalorganic chemical vapor deposition (MOCVD) method at 480° C. By analysis of cross sections of the PZT/MgO/Si(100) stacked structure using focused ion beam observation, it is clearly shown that a uniform MgO layer causes the deposited PZT film to consist of a uniform tetragonal perovskite phase. However, a nonuniform MgO layer causes the PZT film to contain an additional phase because of direct contact between PZT and the Si substrate.
Photoreflectance Study on the Effect of Lattice Defects in InP on (001) Si
Authors: Mo Shaobai , Peiner Erwin , Bartels Arne , Tang Guang-Ping , Schlachetzki Andreas , Kuzmenko Roman , Hildebrandt Stefan , Schreiber Jürgen
Published: October 2002

The residual stress in epitaxial InP on (001) Si was investigated by photoreflectance spectroscopy. Depending on doping concentration, low-field and intermediate-field spectra were measured which were quantitatively analysed by a third-derivative approximation or by a multilayer model, respectively. In both cases, transitions only from the heavy-hole and the split-off valence subbands into the conduction band contributed to the spectra, while the light-hole to conduction-band transition was absent. In addition to the energy shift due to tensile strain caused by the different thermal expansion coefficients of InP and Si, a signal component originating from compressive strain in the InP was observed. This effect is attributed to the clustering of dislocations at twin defects. As a result, a model of the defect distribution in the heteroepitaxial InP layers was presented.
Identification of Water Molecules in Low Humidity and Possibility of Quantitative Gas Analysis using Porous Silicon Gas Sensor
Authors: Akira Motohashi Akira Motohashi , Masatoshi Ruike Masatoshi Ruike , Manabu Kawakami Manabu Kawakami , Hidekazu Aoyagi Hidekazu Aoyagi , Akira Kinoshita Akira Kinoshita , Akinobu Satou Akinobu Satou
Published: October 2002

In a previous experiment, it was shown that a gas identification sensor using porous silicon necessitated more than 60% concentration for identification. In the present study, it was shown by means of an experiment using water vapor that the concentration limit for gas identification may be controlled by changing the sensor temperature. In addition, the possibility of quantitative analysis of gas identification in which the sensor temperature is taken as a new parameter was proposed.
Improvement of Responsivity of Antenna-Coupled Warm Carrier Device Using Polycrystalline Ge Thin Films
Authors: Uchida Takashi , Takashi Shimizu Takashi Shimizu , Yoshizumi Yasuoka Yoshizumi Yasuoka
Published: October 2002

Electrical properties of Ge thin films evaporated on Si3N4 substrates were improved by introducing a heat treatment after the deposition. The Hall mobility of the deposited films increased with increasing heat-treatment temperature and was 280 cm2/V·s for a hole concentration of 6×1017 cm-3 at a heat-treatment temperature of 900° C. This value of the Hall mobility was about three times larger than that obtained for Ge films without heat treatment. A point-contact warm carrier device was also fabricated using evaporated Ge film with heat treatment, and the detected voltage induced by CO2 laser radiation was measured. The fabricated device operated as an antenna-coupled device and the detected voltage was about ten times higher than that obtained using a device without heat treatment.
Nanoscale SiO2 Particles Placed Upon the Crystalline Silicon
Authors: Victor G. Zavodinsky Victor G. Zavodinsky , Igor A. Kuyanov Igor A. Kuyanov
Published: October 2002

Using ab initio local-density approach we have studied the electronic structure of the free n-fold SiO2 rings as well as the rings placed upon the surface of the silicon cluster. For the free planar rings the best agreement of theoretical results and the experimental ultraviolet photoemission spectrum of the amorphous silica was obtained for the 6-fold ring. The interaction of the 6- and 4-fold planar SiO2 rings with the silicon surface change the electronic structure of the silica particle very weakly. The electronic structure of the 3-fold planar ring, which contacted the silicon surface undergoes a significant reconstruction.
New Disc Format for Land/Groove Recording on Magnetically Induced Super-Resolution Disc
Authors: Mieda Michinobu , Takemori Hirotoshi , Murakami Yoshiteru , Akira Takahashi Akira Takahashi , Shigeo Terashima Shigeo Terashima
Published: October 2002

We developed a new disc format for land/groove recording. The new disc had grooves wobbled on one side to obtain address information. We examined characteristics of signals reproduced from the wobbled grooves and a suitable groove shape for a double-layered magnetically induced super-resolution disc. By the use of the new disc format, good signal quality of address information is obtained on both lands and grooves. At a groove shape with 40 nm depth and 0.7 µm track pitch, a CNR of 47 dB and a crosstalk of -32 dB were obtained at the recorded mark length of 0.55 µm in magnetic field modulation recording.
Preparation of TB(S)CCO Superconductor Coating by Electrophoretic Deposition Method
Authors: Negishi Hideyuki , Koura Nobuyuki , Yasushi Idemoto Yasushi Idemoto , Makoto Ishikawa Makoto Ishikawa
Published: October 2002

The preparation of Tl2Ba2Ca2Cu3O10+
x

(TBCCO) superconducting oxide coating on Ag wire by the electrophoretic deposition method was investigated. Because it was the TBCCO powder is chemically stable in cyclohexanone, and a cyclohexanone bath (20 m l cyclohexanone+2.0 mg iodine+0.4 g TBCCO powder) was used. The deposited sample dried by hot air was sintered at 785° C for 10 min in Tl atmosphere, and T
c,zero was 104 K. The superconductivity of the Tl2Ba1.6Sr0.4Ca2Cu3O10+
x

(TBSCCO) coating was improved if the deposited sample was completely covered with a large quantity of TBSCCO powder to control the evaporation of Tl from the sample. When the sample was sintered at 815° C for 6 h, a uniform and approximately single high-T
c phase coating was obtained with a T
c,zero of 113 K.
Effect of Ar+O2 Plasma Etching on Microwave Characteristics of YBa2Cu3O7-x Based Resonators
Authors: Ban Masahito , Takenaka Tsuyoshi , Hayashi Kunihiko , Katsumi Suzuki Katsumi Suzuki , Youichi Enomoto Youichi Enomoto
Published: October 2002

We present an improvement in the patterning process of microwave devices by suppressing the oxygen effusion from the patterning edge of YBa2Cu3O7-
x

(YBCO) thin film. The damage in the edge is estimated from unloaded Q factors of YBCO-based micro-stripline resonators, because the high frequency current is limited along the edge. The unloaded Q factors increase with the oxygen content during the plasma etching. This result suggests that oxygen radicals in the Ar+O2 plasma restore the oxygen in the edge and reduce the loss of microwave devices.
Coaxing the Maximum Performance out of an Ordinary Structured MO Disk
Authors: Aratani Katsuhisa , Narahara Tatsuya , Fukumoto Atsushi , Masuhara Shin , Arakawa Nobuyuki , Yoshihiro Takemoto Yoshihiro Takemoto , Yasuyuki Takeshita Yasuyuki Takeshita
Published: October 2002

An ordinary structured magneto-optical disk was improved and optimized to achieve high areal recording density using the magnetic field modulation recording technique. After studying film material/thickness, groove geometry, and birefringence in a poly-carbonate substrate, a track pitch of 0.85 µm with a linear recording density of 0.31 µm/bit is determined to be a good combination for a wavelength of 690 nm and an objective lens with a numerical aperture of 0.55, which results in an areal density of 3.8 bit/µm2 or 2.4 Gbit/inch2.
Absorption Lines of O2 and HF in KrF Laser Spectrum
Authors: Shimauchi Midori , Miura Tokiwa , Hiroshi Takuma Hiroshi Takuma , Da Xing Da Xing
Published: October 2002

Absorption lines in the KrF laser spectrum corresponding to impurities produced by shots of pulsed discharge are investigated. Wavelengths of strong absorption lines of the O2 Schumann-Runge, B–X, system (2–7) band are revised taking the effects of triplet structures into account. Rotational lines of (0–6), (7–9) and (4–8) bands of O2
B–X are newly assigned. Rotational lines of the HF B–X system (0–15), (1–16) and (3–18) bands are confirmed by their decreasing intensity with increasing number of shots. Relative intensities of rotational lines of the (2–7) band give the rotational temperature of 400±50 K. Spectra observed using a multichannel detector in the 7th order of the 6.65-m grating spectrograph (FWHM 3.37 pm) are used to obtain the absorption cross section, σ, of the (2–7) band. The population in v
′′=7 obtained from the σ value is consistent with the results previously obtained for the ArF laser.
Reflector Parameters for High Reflectance and High Contrast Ratio with White-Taylor Reflective Display
Authors: Yoshida Hidefumi , Sasaki Takanori , Kimiaki Nakamura Kimiaki Nakamura , Makoto Ohashi Makoto Ohashi
Published: October 2002

We have calculated the appropriate reflector parameters for high white-state reflectivity. First, we studied the reflector with and without a refractive layer. With a refractive layer on the reflector, the appropriate average reflector slope is smaller than that without, because the incident light refracts at the air interface and the incident angle to the reflector is small. Next, we investigated the appropriate reflector for a White-Taylor display. We found that the optimum shape of the reflector for reflective display depends on the type of light source, i.e., a diffused light source or a point light source. The optimum average slope of the reflector (K) for the White-Taylor display is between 7° and 10°. With this value of K, we can achieve both high reflectivity and a high contrast ratio with both a diffused light source and a point light source.
Calculation of Crystal Structures, Dielectric Constants and Piezoelectric Properties of Wurtzite-Type Crystals Using Ab-Initio Periodic Hartree-Fock Method
Authors: Toshio Kamiya Toshio Kamiya
Published: October 2002

Methods to calculate the dielectric constant, piezoelectric constant, and electromechanical coupling factor are proposed based on ab-initio Hartree-Fock periodic calculation. Crystal structures, dielectric constants and piezoelectric properties are calculated for the wurtzite-type compounds AlN and ZnO. Calculated structures well reproduce the experimental ones within an error of 1%. The present calculations tend to overestimate both effective charges and transverse optical phonon frequencies. The dielectric constants at constant stress and strain, piezoelectric constants and electromechanical coupling factors are also calculated, and the nature of piezoelectric properties is discussed.
Fabrication of CdSe/ZnSe Quantum well Structures on Glass Substrates by Vacuum Evaporation
Authors: Hanaoka Atsusi , Sumio Sano Sumio Sano , Junji Saraie Junji Saraie
Published: October 2002

We fabricated CdSe/ZnSe polycrystalline quantum well structures on glass substrates by vacuum evaporation. The ZnSe buffer layers had columnar structures along the [111] axis. A sharp emission peak due to the recombination of quantized electrons and holes in the well was observed at 11 K for the first time. The peak shifted as the thickness of the CdSe well changed. The results of heat treatments are also reported.
On the Reynolds Number in Laser Experiments
Authors: Didier Galmiche Didier Galmiche , Serge Gauthier Serge Gauthier
Published: October 2002

To characterize the hydrodynamic flows in laser accelerated targets, we define two Reynolds numbers. Transport coefficients are computed within the frameworks of the One Component Plasma model for strongly correlated plasmas, and of the Braginskii formula for plasmas dominated by small angle scattering. Configurations with laser energies ranging from 100 J to 2 MJ are investigated. It appears that flows are generally in non-linear regimes except for a target imploded with a 2 MJ laser where turbulence probably occurs. Natural diffusion effects appear to be small.
Nonlinear IR Generation in AgGaS2
Authors: Kiyoshi Kato Kiyoshi Kato , Hiromichi Shirahata Hiromichi Shirahata
Published: October 2002

AgGaS2 has been found to be phase matchable for type-1 SHG from 0.884 to 5.55 µ m at 20.0° C. The improved Sellmeier's equations, which correctly reproduce much of the nonlinear experiments thus far reported in the literature, are presented.
Dependence of Optical Properties on the Device and Material Parameters in Liquid Crystal Microlenses
Authors: Shin Masuda Shin Masuda , Shogo Fujioka Shogo Fujioka , Michinori Honma Michinori Honma , Toshiaki Nose Toshiaki Nose , Susumu Sato Susumu Sato
Published: October 2002

Liquid crystal microlenses are prepared using various liquid crystals and dependence of the optical properties on device and material parameters is investigated experimentally. Numerical apertures of the liquid crystal microlenses for different combinations of the structure parameters and the material parameters are measured. The numerical aperture of the LC microlens is maximum value when the ratio of the diameter and thickness is 3 and its spot size is less than 2 µm. Optical properties of the LC microlenses are mainly dominated by the birefringence property and dielectric anisotropy of liquid crystal materials. It is necessary to use a LC material with a large birefringence and a large dielectric anisotropy to design the LC microlens with a large numerical aperture and a low driving voltage performance.