bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanostructure Formation on Amorphous WO3 Thin Films in Air by Scanning Tunneling Microscopy
Authors: Qiu Hong , Lu Yong-Feng , Mai Zhi-Hong
Published: October 2002

Scanning tunnelling microscope (STM) modifications on α-WO3-x
thin films were carried out in air. Holes and bumps were produced. Two mechanisms were clarified with respect to the water layer attached more or less in modifications. By applying voltage pulses, the high humidity (>60%) raised the probability of hole formations. Connection lines were formed between the holes, confirming a dominant electrochemical nature. The low humidity (<20%) raised the probability of bump formations. Similar heights in both STM and atomic force microscopy (AFM) images imply a physical transformation in the process. Depressed sides near the bumps strongly manifested the diffusion of surface molecules to the tip induced by the electric field gradient. In the intermediate humidity (20–60%), there was a higher voltage threshold for bump formations than for hole formations, as well as for positive voltage pulses than for negative voltage pulses. The discrepancies were reasonably attributed to the different tip-sample distances and the consequently induced electric fields.
A Novel P-Channel Flash Electrically-Erasable Programmable Read-Only Memory (EEPROM) Cell with Oxide-Nitride-Oxide (ONO) as Split Gate Channel Dielectric
Authors: Huang Chih-Jen , Liu Yun-Chang , Wang Mu-Chun , Caywood John , Hong Shi-Fang , Wu Auter , Hsia Liang-Chu , Chang Yi-Jao , Liu Fu-Tai
Published: October 2002

A novel p-channel flash electrically-erasable programmable read-only memory (EEPROM) cell, which is programmed/erased via channel Fowler-Nordheim (FN) tunneling, is described in this paper. Channel FN tunneling is a high efficiency and low-power-consumption approach to flash cell operation. High endurance up to 1 M cycles was demonstrated with small window closure. The new flash cell exhibits good reliability which is quite insensitive to disturb or over program. In order to simplify the process, the interpoly dielectric and select gate dielectrics are fabricated using the same oxide-nitride-oxide (ONO) stack during formation of this cell. Hence, this cell shows good potential for achieving simple processing, low power consumption and negligible disturbance during operation.
A New Dual Floating Gate Flash Cell for Multilevel Operation
Authors: Lin Hongchin , Chen Jack Tai-Yuan , Wong Shyh-Chyi
Published: October 2002

A new dual floating gate flash memory cell using constant bias voltages for multilevel operation is proposed to increase memory density. Channel hot electrons (CHE) and drain avalanche hot electrons (DAHE) are used to store different amounts of charge in different floating gates. To erase the data, channel fowler-nordheim (FN) tunneling is applied first, and then substrate hot electron (SHE) injection is utilized to prevent from over erase and tighten the threshold voltage spread. The simulation results indicate that the multilevel flash memory cell with slight modifications of triple well technology is a promising device for future multilevel operation devices.
Passivation of Deep Levels in 3C-SiC on Si by a Hydrogen Plasma Treatment
Authors: Kato Masashi , Sobue Fumitaka , Ichimura Masaya , Arai Eisuke , Yamada Noboru , Tokuda Yutaka , Okumura Tsugunori
Published: October 2002

It is discovered for the first time that deep levels in n-type 3C-SiC/Si are passivated by hydrogen. Hydrogen is introduced by a plasma treatment, and its effects are investigated by deep level transient spectroscopy (DLTS). 3C-SiC grown on Si using silane and propane has a deep level with an activation energy of 0.3 eV. This defect is passivated by hydrogen, and its majority is reactivated by annealing at a temperature above 500°C. The plasma treatment forms new deep levels in the near-surface region of the sample. Although these levels are almost annealed out at 400°C, different kinds of deep levels appear after annealing in the near-surface region. The concentration is low (<1014 cm-3) for annealing at 400°C, and rapidly increases with increasing annealing temperature up to 600°C. Thus, the concentration of the deep levels in 3C-SiC is decreased by the hydrogen plasma treatment and subsequent annealing at 400°C without the introduction of high densities of plasma-induced deep levels.
Performance Improvement in Vertical Surface Tunneling Transistors by a Boron Surface Phase
Authors: Hansch Walter , Borthen Peter , Schulze Jörg , Fink Christoph , Sulima Torsten , Eisele Ignaz
Published: October 2002

The fabrication and characteristics of silicon tunneling transistors based on vertical metal-oxide-semiconductor (MOS) gated pin-diodes are shown. In these devices the tunnel junction is formed between an influenced MOS-channel and an abrupt, ultra-highly doped boron layer. The ultra-high doping amount of about 2.6×1014 cm-2 is achieved by the formation of a √3×√3-R30° boron surface phase. The tunneling transport and the influence of the boron surface phase on the transistor behavior is investigated. The transistor performance is characterized by a current gain between 3 and 5 orders of magnitude at a low supply voltage of -0.2 V with saturation behavior.
High-Frequency Characteristics of Quantum Well Infrared Photodetectors with Blocking Barrier
Authors: Ryzhii Victor , Khmyrova Irina , Ishibashi Tadao , Sumith V. Bandara Sumith V. Bandara , Sarath D. Gunapala Sarath D. Gunapala
Published: October 2002

We have developed an analytical model for quantum well infrared photodetectors (QWIPs) with a superlattice serving as the absorption region and a blocking barrier. The explicit analytical expression for the frequency-dependent responsivity is derived as a function of the QWIP structural parameters. Using this expression we calculate the 3 dB cut-off frequency and bandwidth-response efficiency. The bandwidth of QWIPs with a moderate number of QWs can exceed 100 GHz exhibiting fairly large responsivity. We show that a fast tunneling filling of the absorption region by the electrons injected from the emitter contact results in a significant modification of the high-frequency properties of the QWIP under consideration compared to the standard QWIPs, in particular, in the elimination of the low-frequency peak of the responsivity.
Annealing Effect and Measurement of Magnetostriction in Fe49Co49V2 Alloy using the Michelson Laser Interferometer
Authors: Ahn Seung Joon , Kim Dae Wook , Kim Ho Seob , Kim Cheol Gi , Lee Yong San , Cho Jaewon
Published: October 2002

We investigate the annealing effects of microstructure, magnetostriction in Fe49Co49V2 and soft magnetic properties of B–H hysteresis loops. Fe49Co49V2 alloy samples are prepared in a thermal annealing furnace at temperatures between 500 and 900°C. A Michelson laser interferometer with a feedback signal of optical path length (OPL) variation is employed for measuring magnetostriction of the samples. As the annealing temperature increases, the grain size related to texture of the alloy samples increases due to recrystallization. After annealing at a high temperature of 900°C, the magnetostriction value increases from 2 ×10-6 to 33 ×10-6 at H=60 Oe. The results suggest that the magnetostrictive characteristics are improved by the microstructural modification.
Optimized Oxygen Plasma Etching of Polycarbonate for Low-Loss Optical Waveguide Fabrication
Authors: Kang Jae-Wook , Kim Joon-Sung , Kim Jang-Joo
Published: October 2002

The oxygen plasma etching condition of polycarbonate was characterized in detail to fabricate low-loss optical waveguides. The effects of etching parameters such as rf power and chamber pressure were systematically studied and the parameters were optimized to minimize the surface roughness in etched areas. Buried channel waveguides with thermally stable polycarbonate were fabricated using the optimized conditions, resulting in smooth and almost vertical etched patterns. The waveguides showed an optical loss of less than 0.8 dB/cm and 1.4 dB/cm at the wavelength of 1.3 µm for TE and TM polarizations, respectively. The refractive index of polycarbonate after being stored at 190–230°C for 1 h remains almost constant, demonstrating the thermal stability of polycarbonate waveguides.
Molecular Weight Dependence of Ion-Mode Relaxation and DC Conduction in Polypropylene Oxide Complexed with LiClO4
Authors: Kano Kenji , Takahashi Yoshiyuki , Furukawa Takeo
Published: October 2002

Broadband dielectric spectroscopy has been employed to investigate the ion dynamics in polypropylene oxide (PPO) complexed with 0.1% LiClO4 over a molecular weight range of M=425–3500. It is found that ions undergo two types of motions: local fluctuation (ion-mode relaxation) and long-range diffusion (dc conduction). The dc conductivity σdc decreases markedly with increasing molecular weight (∝M
-2) whereas the ion-mode relaxation time τion and its strength Δε
ion are nearly independent of M. The ion-mode relaxation is an indication of some structural inhomogeneity that confines ions temporarily in a certain domain. Analyses of these experimental results based on a dynamic percolation model lead us to propose the following ionic processes in PPO/LiClO4 systems. The ionic motion originates in the elementary jumps for a distance equivalent to a monomer length at a frequency of segmental mode molecular motion. Due to structural inhomogeneity, such an elementary motion is confined in a domain of approximately 1.2 nm in diameter to result in a relaxational nature specified by the time constant τf. Structural renewal occurring at a rate of 1/τr allows ions to jump into adjacent domains and to undergo long-range diffusion. Below M=400, τr equals τf. In a high M range, τr becomes much larger than τf to control σdc according to σdc=Δε
ion/τr. Structural renewal is suggested to occur in association with a large-scale molecular motion.
Microstructural, Electrical Properties and Temperature Stability of Resonant Frequency in Pb(Ni1/2W1/2)O3–Pb(Mn1/3Nb2/3)O3–Pb(Zr, Ti)O3 Ceramics for High-Power Piezoelectric Transformer
Authors: Yoo Juhyun , Lee Yongwoo , Yoon Kwanghee , Hwang Sangmo , Suh Sungjiae , Kim Jongsun , Yoo Chungsik
Published: October 2002

Piezoelectric properties of Pb1-a
Sr
a
(Ni1/2W1/2)0.02(Mn1/3Nb2/3)
b
(Zr
x
, Ti
y
)1-0.02-b
O3) ceramics, to which 0.5 wt% PbO, 0.3 wt% Fe2O3 and 0.25 wt% CeO2 were added, were investigated at different compositions of a=0–0.06, b=0.05–0.09, x=0.49–0.51, and y=0.49–0.51. In the ceramics with a constant composition of a=0 and b=0.07, mechanical quality factor, coercive field and Curie temperature increased with the decrease in Zr/Ti ratio due to the increase in tetragonality. With the increase of PMN mol% at a=0, x=0.51, and y=0.49 composition, grain size decreased and coercive field increased. At the composition of b=0.07, x=0.51, and y=0.49, the dielectric constant and mechanical quality factor increased while the Curie temperature and coercive field decreased with the amount of Sr. Taking into consideration the dielectric constant of 1,680, the mechanical quality factor of 1,814, and the temperature stability of the resonant frequency TCfr of 88, it was concluded that the ceramics with the composition of a=0.06, b=0.07, x=0.51, and y=0.49 were best for the high-power piezoelectric transformer application.
Study on Helical Structure of the B4 Phase Formed from Achiral Banana-Shaped Molecule
Authors: Thisayukta Jirakorn , Takezoe Hideo , Watanabe Junji
Published: October 2002

The helical structure of the B4 phase in the banana-shaped molecules, the 1,3-benzene bis[4-(4-n-alkoxyphenyliminomethyl) benzoate] (P-n-O-PIMB) series, has been studied by means of optical microscopy, X-ray diffraction and circular dichroism for homogeneously and homeotropically aligned cells. The homogeneously aligned cells showed a transparent blue color and a circular dichroism at about 400 nm, indicating the existence of a helical structure. Detailed texture observation also reveals the existence of two helical domains with opposite helical senses. The two helical domains are formed with equal probability, and with the helical axes parallel to the layers similar to the twist grain boundary (TGB) phase. This helical structure is also supported by X-ray diffraction. The balance between the two domain areas is broken by doping P-n-O-PIMB with its chiral analogue. The texture of the homeotropically aligned cells suggests two different helical axes, both of which are parallel to the layer but with one parallel and the other perpendicular to the bent-core plane.
Carbazole-based Photorefractive Organic Glass Showing High Diffraction Efficiency at Low External Electric Field
Authors: Sohn Jiwon , Hwang Jaehoon , Park Soo Young , Lee Geon Joon
Published: October 2002

Photorefractive organic glass, 9-(2-ethyl-hexyl)-3-[2-(4-nitro-phenyl)-vinyl]-9H-carbazole (EHCN), showing large coupling gain and high diffraction efficiency at low external electric field was synthesized and characterized. EHCN showed the glass transition at 25°C and the good thermal stability up to 400°C. Photorefractivity of EHCN was investigated by using 100 µm thick films (S1, S2, S3) doped with 0%, 0.5%, and 1% 2,4,7-trinitrofluorenone (TNF), respectively. Two-beam coupling net gain of 50.8 cm-1 was obtained for the 0.5% TNF-doped EHCN sample (S2) at 40 V/µm field. The highest internal diffraction efficiency, obtained from the degenerate four-wave mixing at 30 V/µm field, reached 90% for the 1% TNF-doped EHCN sample (S3).
Formation and Deformation of Multiwall Carbon Nanotubes in Arc Discharge
Authors: Takikawa Hirofumi , Tao Yoshitaka , Miyano Ryuichi , Sakakibara Tateki , Zhao Xinluo , Ando Yoshinori
Published: October 2002

Running arcs under both vacuum and low pressure and a jumping arc under vacuum were generated with a pure graphite cathode for 1–3 s upon applying a magnetic field. For the running arcs under both vacuum and low pressure, multiwall carbon nanotubes (MWNTs) were observed only at the cathode spot craters where the arcs were extinguished by switching the power off. At the crater where the cathode spot had run over, nanotubes were hardly observed. For the jumping arc in vacuum that was self-extinguished, only a few nanotubes were observed at the cathode spot craters. No nanotubes were observed on the surface outside the cathode spot crater for all arcs. These results revealed that the nanotubes are formed, as well as destroyed, by the cathode spot. The process of nanotube formation and deformation is discussed, taking into account the cathode spot activity and electron emission.
Well-size-controlled Colloidal Gold Nanoparticles Dispersed in Organic Solvents
Authors: Gen Tsutsui Gen Tsutsui , Shujuan Huang Shujuan Huang , Hiroyuki Sakaue Hiroyuki Sakaue , Shoso Shingubara Shoso Shingubara , Takayuki Takahagi Takayuki Takahagi
Published: October 2002

The preparation of well-size-controlled colloidal gold nanoparticles in organic solvent is presented. After the preparation of well-size-controlled aqueous colloidal gold particles, we changed the solvent to an organic one. This technique is required to enable a chemical reaction between gold particles and hydrophobic molecules, since a colloidal gold solution is typically prepared in water using a reduction process. We also investigated the stability of the gold particle suspension, and found that the stability decreases in the sequence of water, ethanol, chloroform, and benzene solution.
Mode Shape Measurement of Piezoelectric Resonators Using Image Processing Technique
Authors: Watanabe Yasuaki , Shikama Yuji , Goka Shigeyoshi , Sato Takayuki , Sekimoto Hitoshi
Published: October 2002

An image processing technique for measuring the mode shapes of piezoelectric resonators is described. Laser speckle interference, a periodic resonator excitation and charge coupled device (CCD) image captures are effectively combined in this method. The experimental results for three kinds of AT-cut quartz resonators demonstrate the applicability of the proposed method.
Finite Element Method Simulation of Double-T Type Vibrators for Flatly Supported Piezoelectric Vibratory Gyro-Sensor
Authors: Kikuchi Takayuki , Tomikawa Yoshiro , Soma Takao
Published: October 2002

In this study we deal with a flexural vibrating resonator for flatly supported vibratory gyro-sensors in parallel with the rotating plane. This type of gyro-sensor uses two vibration modes in only one plane of single crystal quartz, and therefore can be constructed to be very stable under operating conditions. The double-T type vibrator that has two T-type resonating arms and two resonant arms is designed for improving the quality factor Q of both driving and detecting vibration modes for this vibratory gyro-sensor. The result of finite element analysis of the double-T type vibrators shows the small influence of its vibration mode with the support at the center of gravity of the vibrator.
PSpice Simulation on Piezoelectric Vibrator with Negative Impedance Converter Circuit
Authors: Ko Young-In , Kim Moo-Joon , Ha Kang-Lyeol , Tomikawa Yoshiro
Published: October 2002

To simulate the electromechanical characteristics of a piezoelectric transverse mode vibrator with negative impedance converter (NIC) circuit, we propose a new simulation model for Pspice implementation, which is coupled to the distributed constant equivalent circuit for a piezoelectric vibrator with divided electrodes and the NIC circuit including an active device, such as operational amplifier. The usefulness of the model is demonstrated by comparing the simulation results with experimental ones.
Longitudinally Coupled Resonator Filter Using Edge Reflection of Bleustein-Gulyaev-Shimizu and Shear Horizontal Waves with Various Bandwidths Realized by Selecting Substrates
Authors: Michio Kadota Michio Kadota , Junya Ago Junya Ago , Hideya Horiuchi Hideya Horiuchi , Mamoru Ikeura Mamoru Ikeura
Published: October 2002

A conventional surface acoustic wave (SAW) resonator filter requires reflectors with many grating fingers at both sides of the interdigital transducers (IDTs). On the other hand, a small-sized low-loss resonator filter without grating fingers can be realized by utilizing the reflection of a Bleustein-Gulyaev-Shimizu (BGS) wave or a shear horizontal (SH) wave at the edge of a substrate. As a result, the authors have developed longitudinally coupled resonator filters using the reflection of BGS and SH waves at the edges of a substrate. Longitudinally coupled resonator filters on piezoelectric ceramic substrates for the first intermediate frequency (IF) stage have been realized to be low-loss, small-sized and extremely wide bandwidth (fractional bandwidth of 15%) filters as compared to the ordinary resonator filters, and they can have various kinds of bandwidths (2 to 15%) by employing ceramic substrates with various electromechanical coupling factors. On the other hand, the edge-reflection-type resonator filters on LiTaO3 single crystal for various first IF stages have also been realized to be low-loss and small-sized filters. In spite of being a wire-bonding type of IF filter, the package size of this filter is the same as that of the radio frequency (RF) SAW filter.
Analysis of an Electrode-Width-Difference-Reversal-of-Directivity Transducer on a La3Ga5.5Nb0.5O14 Substrate
Authors: Inagawa Kiyoshi , Hasegawa Koji , Koshiba Masanori
Published: October 2002

The parameters included in coupling-of-modes equations such as coupling coefficients, transduction coefficients and electrostatic capacitances are theoretically determined for an electrode-width-difference-reversal-of-directivity transducer (EWD-RDT) on a La3Ga5.5Nb0.5O14 substrate with Euler angles of (108°, 148°, 144°). In the hybrid finite-element method (HFEM), used for determining these parameters, all the effects of anisotropy of the substrate, piezoelectric perturbation, mechanical perturbation and energy storage are taken into account. Numerical results for the frequency characteristics of insertion loss and for the directivity are compared to the experimental data, and the validity and usefulness of the present method are demonstrated. Furthermore, the electrode height dependence of the parameters and the directivity of EWD-RDT are investigated in detail.
Estimation of the Stability of Acoustic Multipath in Long-Range Propagation
Authors: Miyakawa Yutaka , Hachiya Hiroyuki , Nakamura Toshiaki , Nakano Iwao
Published: October 2002

We present the stability estimation results of the data collected during the sound transmission experiment performed by Japan Marine Science and Technology Center (JAMSTEC) in 1996 in the western equatorial Pacific Ocean. The combined information of the amplitude and the phase was effective for identifying a ray and observing the ocean-structure change. The phases of correlated signals were very stable within 50 s not only for the paths propagated near the sound fixing and ranging (SOFAR) axis but for ones turning at about 2500 m depth. The travel time could be estimated within an error of less than 0.3 ms.
Influences of Temperature and Stress on Transmission Characteristics of Multilayer Thin-Film Narrow Bandpass Filters
Authors: Chen Tei-Chen , Kuo Jing-I , Lee Wei-Lung , Lee Cheng-Chung
Published: October 2002

In this study, an analytical model is developed to evaluate the effects of uniform and nonuniform temperature increases, as well as stress level, on the optical characteristics of three-cavity sub-nanometer bandpass filters fabricated using TiO2 and SiO2 film materials through ion-assisted deposition (IAD), taking into account the coupled photoelastic and thermo-optical effects. A more realistic stress analysis, which is capable of considering the effects of intrinsic and thermal stresses, bending moment as well as nonuniform temperature increase, is proposed and formulated for the first time. Various factors, including errors in film thickness, changes of refractive index and film thickness due to temperature increase and stress as well as the delamination gap along the layer interface, are then considered to evaluate their individual influence on optical characteristics of bandpass filters. The results show that the change of film thickness due to temperature increase and stress has a significant effect on center wavelength shift. Moreover, a significant degradation of the transmission curve due to nonuniform temperature increase was observed.
Phases and Domain Structures in Relaxor-Based Ferroelectric (PbMg1/3Nb2/3O3)0.69(PbTiO3)0.31 Single Crystal
Authors: Tu Chi-Shun , Chen Li-Fang , Schmidt V. Hugo , Tsai Chih-Long
Published: October 2002

The Brillouin back-scattering spectra, dielectric permittivities, polarization–electric field (P–E) hysteresis loops and domain structures have been measured as a function of temperature in a relaxor-based ferroelectric single crystal (PbMg1/3Nb2/3O3)0.69(PbTiO3)0.31 (PMN–31%PT). In order of increasing temperature, PMN–31%PT undergoes successive phase transitions: rhombohedral phase (below ∼370 K) →coexistence of rhombohedral and tetragonal phases (between ∼370 and ∼380 K) →tetragonal phase (between ∼380 and ∼400 K) →coexistence of tetragonal and cubic phases (betwee ∼400 and ∼420 K) →cubic phase (above ∼420 K). An extra ferroelectric anomaly of the dielectric permittivity appears at 370 K possibly due to the percolating polar cluster induced by an external electric field. It was found that different individual domain regions have different transition temperatures. This phenomenon suggests an inhomogeneous distribution of Ti4+ concentration in the PMN–31%PT crystal. The dielectric permittivity ε
′ of PMN–31%PT obeys the empirical relation, ε
′
m/ε
γ(f,T)=1+[T-T
m(f)]′/2δγ
2, above the temperature of permittivity maximum T
m.
Study of the Characteristics of Defects in the Oxidation-induced Stacking Fault-Ring Area in Czochralski Silicon Crystals by Multi-chroic Infrared Light Scattering Tomography and Transmission Electron Microscopy
Authors: Ma Minya , Irisawa Toshiharu , Ogawa Tomoya , Frigeri Cesare
Published: October 2002

A new defect morphology of dark stripes was observed in both as-grown and annealed Czochralski silicon (CZ-Si) crystals by photoluminescence (PL) mapping of a multi-chroic infrared light scattering tomography (MC-IR-LST) system. The dark stripes in the as-grown CZ-Si crystal are believed to be highly decorated striations, where grown-in defects have inhomogeneously segregated during the crystal growth. When this crystal was annealed at 1150°C for 16 h in an O2 atmosphere, defects such as stacking faults, oxygen-precipitate-related polyhedral defects, impurities and dislocation loops were observed around the dark stripes in the oxidation-induced stacking fault (OSF)-ring region using transmission electron microscopy (TEM) and the MC-IR-LST system. Investigation results suggested that the main grown-in defects around dark stripes were oxygen precipitate nuclei and vacancy-related nuclei, which resulted in the formation of such defects during the thermal oxidation process.
Crystallinity of Thin Silicon Films Deposited at Low Temperatures: Combined Effect of Biasing and Structuring the Substrate
Authors: Birkholz Mario , Conrad Erhard , Fuhs Walther
Published: October 2002

The improvement of crystallinity of thin silicon films by (i) controlling the ion flux to the substrate and (ii) structuring the substrate surface is demonstrated. Films were deposited by electron-cyclotron resonance chemical-vapor deposition (ECR CVD) at 600 K on grooved substrates that were located on a dc-biased susceptor. The degree of crystallinity as determined by Raman spectroscopy and electron microscopy improved with increasing susceptor bias V
S, which is explained in terms of the local heating of the film surface during initial growth. For V
S=15 V a pronounced increase of grain size was observed by X-ray diffraction that is accompanied by a texture inversion from (110)- to (111)-preferred orientation. The effect is discussed in terms of an ion-assisted reaction step on the surface of the growing film.
Effect of Interference-Fringe Noises in Numerical Analysis of Sinusoidally Phase-Modulated Holographic Interferograms: Theoretical Investigation
Authors: Miyazaki Takeshi , Toki Masato , Gotoh Hideaki , Kitamura Makoto
Published: October 2002

In this paper, we present a numerical analysis of the effect of random noises contained in interferograms of a vibrating object. We theoretically investigated the case where several Bessel-function arguments are used to determine object-vibration phasors. The value of each argument can be calculated from holographic interferograms with phase-modulation phasors of the same magnitude but of different phases. The root-mean-square (rms) error values of object-vibration amplitudes are different for the two algorithms, called synchronous and sum algorithms. At smaller object-vibration amplitudes, values determined by the former have higher accuracies, while for larger amplitudes, those determined by the latter have higher accuracies. Averaging these values by weights, which are the square reciprocals of the respective rms errors gives higher accuracies. The rms error values depend on the phase-modulation magnitude. These values in the cases of the former and latter algorithms are minimum at phase-modulation magnitudes of 0.640π and 0, respectively.
Decoherence of Beam Oscillation in a 2 TeV × 2 TeV Muon-Collider Ring
Authors: Kim Eun-San , Yoon Moohyun
Published: October 2002

The decoherence behavior of betatron-oscillation motion of a beam after a transverse kick is examined by a multiparticle tracking method. When a beam is displaced transversely, it undergoes a betatron oscillation and the oscillation decays in time because of decoherence among the oscillations of different particles. The rate of decoherence depends on the spread of betatron frequencies as well as the strength of wakefields. The impedances of a broad-band resonator model and rf cavity are adopted. Operation of the ring with a slippage factor η1 ≃-10-6 in the 2 TeV × 2 TeV muon-collider ring may lead to beam breakup-like instability. It is explicitly shown that the decoherence due to betatron-tune spreads results in a transition from beam breakup-like instability to stable beam oscillation. Emittance growth due to a strong wakefield is also shown to be suppressed by tune spreads.
Proposal of a New Multifunctional Measurement Method Using Piezoelectric Vibrator
Authors: Akira Kimoto Akira Kimoto , Katsunori Shida Katsunori Shida
Published: October 2002

In this paper, we propose a new multifunctional sensing method by which the sound speed and impedance are measured using piezoelectric ceramics. An experiment was conducted to estimate the NaCl concentration and temperature by measuring the sound speed and conductivity using a pair of the piezoelectric ceramics. As a result, the usefulness of the proposed technique is demonstrated.
Kelvin Probe Force Microscopy Imaging Using Carbon Nanotube Probe
Authors: Takahashi Satoru , Kishida Takayoshi , Seiji Akita Seiji Akita , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

We have measured the potential profiles of the contact potential difference (CPD) between Al-evaporated substrates and dispersed carbon nanotubes (CNTs) by Kelvin probe force microscopy (KFM) using both a conventional Au-coated Si (Au–Si) probe and a CNT probe. The lateral resolutions of both topography and the potential distribution image were improved by using the CNT probe. The CPD has been measured for CNTs with various diameters. We observed that the CPD increases with an increase in the diameter. This indicates that the work function of CNTs increases with an increase in the diameter.
Carbon Nanotube Tip for Scanning Tunneling Microscope
Authors: Wataru Mizutani Wataru Mizutani , Nami Choi Nami Choi , Takayuki Uchihashi Takayuki Uchihashi , Hiroshi Tokumoto Hiroshi Tokumoto
Published: October 2002

We attached multiwall carbon nanotubes (CNTs) to the top of a Au tip using a manipulation system, and used the tip as a probe for a scanning tunneling microscope (STM). We measured Au(111) surfaces using an ultrahigh-vacuum-STM with an electrochemically etched Au tip and a multiwall CNT tip attached to the top of the Au tip. When the CNT tip was cleaned by heating in a coil filament, we observed the 22×√3 reconstruction of clean Au(111). With an uncleaned CNT tip, many adsorbates were observed along the reconstruction, which may be contaminants desorbed from the CNT tip. The stability of the CNT tip depends on its length, diameter and the contact to the base material. Thus far, we have obtained good resolution using a CNT with a length of less than 200 nm. We found that when the CNT was not vertical to the sample surfaces, the tip-surface interaction increased the stability of the CNT tip.
Laser-Scanning Probe Microscope Based Nanoprocessing of Electronics Materials
Authors: Lu Yong-Feng , Hu Bing , Mai Zhi-Hong , Wang Wei-Jie , Chim Wai-Kin , Chong Tow-Chong
Published: October 2002

Recently, scanning probe microscope (SPM) has become a promising technique for nanofabrication. In this paper, we present a novel method of nano-fabrication, namely, nano-fabrication by atomic force microscope (AFM) tips under laser irradiation. The SPM was operated as an AFM. During imaging and nano-fabrication, the AFM is in constant force mode. The tip is fixed with the sample moving via a tube scanner. Nano-lithography software controls the scanner motion in x and y directions. The SPM has an open architecture allowing an external laser beam incident on the tip at an incident angle between 0 to 45°. A vertically-polarized Nd:YAG pulsed laser with a pulse duration of 7 ns was focused on the tip. An electrical shutter was introduced to switch the laser irradiation. Alignment between the laser beam and the tip was performed under a high-power charge coupled device (CCD) microscope. The kinetics of the nanostructure fabrication has been studied. Craters were created in air ambient under different laser pulse numbers, pulse energies and tip force. The feature size of the craters, which are in the nanometer scale, increases with the pulse number, pulse energy and the tip force. This technique has potential applications in nano-lithography and high-density data storage.
Interactive Force between Cyclodextrin Inclusion Complexes Studied by Atomic Force Microscopy
Authors: Norimi Futaba Shigeo Oyama , Ryuji Morita Ryuji Morita , Mikio Yamashita Mikio Yamashita , Hidemi Shigekawa Hidemi Shigekawa
Published: October 2002

Change in the intermolecular interaction between cyclodextrins (CyDs) with guest materials was observed by measuring the adhesion force using atomic force microscopy (AFM) in air. The observed adhesion force with water as the guest material is weaker for α-CyD (composed of 6 glucose) than β-CyD (7 glucose), contrary to the fact that α-CyD is more hydrophilic than β-CyD, indicating that the intrinsic interaction of molecules could be obtained separately from the meniscus force even in air. In addition, the adhesion force depends on the type of guest molecules (H2O, para-nitrophenol, and triethylendiamine) for α-CyDs, but not for β-CyDs. The observed change was explained well by the change in the dipole moment induced by the structural deformation due to the guest materials.
Electrical Characterization of Al/SiNx:H/n and p-In0.53Ga0.47As Structures by Deep-Level Transient Spectroscopy and Conductance Transient Techniques
Authors: Castán Helena , Dueñas Salvador , Barbolla Juan , Blanco Nieves , Mártil Ignacio , González-Díaz German
Published: October 2002

We have analyzed the influence of the dielectric composition and the post deposition rapid thermal annealing (RTA) treatment on the electrical characteristics of electron-cyclotron-resonance plasma-deposited SiN
x
:H/n and p-In0.53Ga0.47As interfaces. The devices are characterized by means of capacitance–voltage (C–V), deep-level transient spectroscopy (DLTS) and conductance transient analyses. Our results show that a simple cleaning step of the semiconductor surface prior to insulator deposition, and a post deposition RTA process are sufficient to obtain good-quality structures, the n-type being better than the p-type. In both cases, we conclude that a dielectric composition of x=1.50 seems to be the best choice, and that the most adequate RTA temperature is between 500°C and 600°C.
Magnetic Properties and Recording Characteristics of High Magnetization Exchange-Coupled Double-Layer TbFeCo for Magnetic Flux Reading Optical Recording
Authors: Chen Bing-Mau , Lai Chih-Huang , Shieh Han-Ping D.
Published: October 2002

The magnetic properties and recording characteristics of exchange-coupled double-layer (ECDL) disks consisting of a transition metal-rich TbFeCo readout layer with high magnetization and a recording layer were studied for magnetic flux reading optical recording. The effective coercivity of ECDL with rare-earth (recording)/transition metal-rich (readout) films could be greatly enhanced from 1.7 to 7.6 kOe through exchange coupling between two active layers. Moreover, ECDL disks possess a lower recording bias field (100 Oe) and a lower onset field (-150 Oe) for thermomagnetic writing. The enhanced effective coercivity was explained by the Kobayashi model, and the lower bias field and onset field of ECDL disks were analyzed by the modified nucleation field model. The ECDL disks with magnetization over 300 emu/cm3, high stability and low recording bias field are potentially applicable for magnetic flux readout toward high density recording at a high writing rate.
Theoretical Study of Temperature Tuning and Anisotropy of Liquid Crystal Infiltrated Synthetic Opal as Photonic Crystal
Authors: Johri Gajendra K. , Tiwari Akhilesh , Johri Manoj , Yoshino Katsumi
Published: October 2002

We have theoretically studied the occurrence of photonic band gap. Calculated values of relative width and lattice size for nematic liquid crystal ZLI-1132 and smectic ferroelectric liquid crystal (R)-4′-(1-methoxycarbonyl-ethoxy)-phenyl-4-[4-(n-octyloxy)phenyl]benzoate (1MC1EPOPB) synthetic opal (SiO2) infiltrated with liquid crystal as a function of temperature using a model of strong localization for the occurrence of pseudogap are reported for the W-point in the Brillouin zone. A new expression for refractive index calculation for synthetic opal infiltrated with liquid crystal is proposed. Central wavelength is also calculated and compared with the observed ones. The structure parameter and opal size are also given. This work is important for temperature tuning and anisotropy of photonic crystal.
Lasing Characteristics of 1.2 µm Highly Strained GaInAs/GaAs Quantum Well Lasers
Authors: Kondo Takashi , Schlenker Dietmar , Miyamoto Tomoyuki , Chen Zhibiao , Kawaguchi Masao , Gouardes Eric , Koyama Fumio , Iga Kenichi
Published: October 2002

In this study, we demonstrate a highly strained 1.2 µm GaInAs/GaAs quantum well laser which may be used in high-speed local area networks. Edge emitting lasers with either a GaInP or AlGaAs cladding layer have been fabricated. We have achieved a threshold current density as low as 170 A/cm2 for GaInP-cladding-layer lasers and a high characteristic temperature T
0 as high as 211 K from 30°C to 120°C for AlGaAs-cladding-layer lasers. The material gain coefficient g
0 was estimated to be 1550 cm-1 which is comparable to that of 0.98 µm GaInAs lasers. A preliminary lifetime test under heatsink-free CW condition was carried out, which shows no notable degradation after 300 h. We also demonstrated an AlAs oxide confinement laser in a 1.2 µm wavelength band.
Thickness Dependence of Properties of Plasma-Deposited Amorphous SiO2 Films
Authors: He Le-Nian , Hasegawa Seiichi
Published: October 2002

Amorphous SiO2 (a-SiO2) films were deposited at 300°C by plasma-enhanced chemical vapor deposition using SiH4–O2 mixtures. The [O2]/[SiH4] ratio was maintained at 1.5, in which oxide films having a stoichiometric composition could be obtained. The Si–O–Si stretching mode, stress, the density of Si dangling bonds and buffered HF (BHF) etch rate were investigated as a function of film thickness. It was found that the peak frequency of Si–O–Si stretching mode centered at around 1050 cm-1 increased from 1050 to 1075 cm-1 with increasing film thickness from 0.1 to 1.1 µm. By comparison with calculations based on the effect of multiple reflections in film/substrate system, it was found that the shift of the Si–O–Si stretching mode to high frequencies was due not only to the effect of multiple reflections, but also to the physical effect of thermal heating and/or ion bombardment during film growth, which would contribute to rearrangement of the Si–O–Si bonding network. The experimental results for the stress behavior, the density of Si dangling bonds and BHF etch rate confirmed this finding.
Effects of Chemical Changes in Electron-Reflecting Coating of a Shadow-Mask's on the Life Characteristics of the Cathode Ray Tube
Authors: Yamamoto Morio , Koitabashi Masayasu , Kimura Hiroshi
Published: October 2002

To improve the life characteristics of the cathode ray tube (CRT) with an electron-reflecting coating (ERC) on the shadow mask, the chemical and thermal behaviors of ERC were studied during the CRT manufacturing process. The ERC, being a mixture of Bi2O3 powder and water glass, reacted with CO2 of the air to form carbonates such as bismuth oxy carbonate (Bi2O2CO3) and alkali carbonate (K2CO3) when the ERC was kept in room air. During the subsequent baking process these carbonates partly decomposed to bismuth silicates such as Bi12SiO20. The carbonates remaining after the manufacturing process caused the CO2 and H2O gases to be released from the ERC during the CRT operation. The lifetime of the cathode in the CRT was found to be related inversely to the relative amount of carbonates present in the ERC. For achieving a longer lifetime of the CRT, it is necessary to reduce the carbonates in the ERC by controlling the humidity in room air during the manufacturing process.
Depth-Resolved Cathodoluminescence of III–V Nitride Films Grown by Plasma-Assisted Molecular Beam Epitaxy
Authors: Jae-Min Myoung Jae-Min Myoung , Kyu-Hwan Shim Kyu-Hwan Shim , Sangsig Kim Sangsig Kim
Published: October 2002

The luminescence properties of III–V nitride films (an undoped GaN, an undoped GaN/Al0.2Ga0.8N multiquantum well, and a p-type Mg-doped GaN films) were investigated using the depth-resolved cathodoluminescence (CL) spectroscopy. From the low- and room-temperature CL of the undoped GaN and GaN/AlGaN MQW films, an emission at 2.9 eV was found with the longer penetration depth and is attributed to the higher density of dislocations at the interface between the film and the substrate. In order to explain the depth-resolved CL of the Mg-doped GaN film, the configuration coordinate model is proposed on the basis of the local strain near the Mg impurities. This model demonstrates that local strain may play a crucial role in controlling the radiative efficiency, line width, and peak position of the luminescence from the film.
Passivation of Bulk and Surface Defects in GaAs Grown on Si Substrate by Radio Frequency Phosphine/Hydrogen Plasma Exposure
Authors: Wang Gang , Ogawa Takashi , Murase Kosuke , Hori Kengo , Soga Tetsuo , Zhang Baijun , Zhao Guangyuan , Ishikawa Hiroyasu , Egawa Takasi , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

The effects of PH3/H2 plasma exposure on GaAs grown on Si substrate (GaAs/Si) were investigated. It was found that incorporation of P atoms in H2 plasma not only hydrogenated the defect-related recombination centers of GaAs/Si epilayer, but also phosphidized the surface region of GaAs/Si epilayer by forming a phosphidized layer. Electron beam-induced current measurement directly proved that the defect-related dark spot density was effectively reduced by adding P atoms into the pure H2 plasma. In addition, PH3/H2 plasma exposure greatly increased the minority carrier lifetime properties and decreased the saturation current of the GaAs p+–n junction structure grown on Si substrate.
Evaluation of Organic Monolayers Formed on Si(111): Exploring the Possibilities for Application in Electron Beam Nanoscale Patterning
Authors: Yamada Taro , Takano Nao , Yamada Keiko , Yoshitomi Shuhei , Inoue Tomoyuki , Osaka Tetsuya
Published: October 2002

The methods of preparing organic monolayers on Si(111), the effects of electron-beam irradiation onto these monolayers, and the deposition of metal atoms over the irradiated areas have been investigated in order to develop a process of mass-scale production of nanometer-scale patterns on Si(111) wafer surfaces. The organic monolayers were fabricated on hydrogen-terminated Si(111) wafer surfaces using previously reported methods for the electrolysis of para-substituted benzenediazonium salts and the Grignard reaction with various alkyl moieties and reaction procedures. Using these electrolysis methods, partially well-defined two-dimensional monolayers were formed, which were, however, obscured by precipitated by-products. The Grignard reaction deposited homogeneous monolayer moieties of alkyl groups which were randomly arranged and are suitable for surface passivation. Electron-beam bombardment of the organic monolayers on Si(111) was performed in an atmosphere of O2 or H2O. The bombarded area was effectively oxidized in a well-controlled manner. By immersing the bombarded specimen into an aqueous NiSO4+(NH4)2SO4 solution, Ni was selectively impregnated only within the area of electron bombardment. Based on these results, application of organic monolayers for fabricating nanometer-scale monolayer patterns is proposed.
Preparation of Epitaxial YBa2Cu3O7-y/CeO2 Multilayer Films on Yttria-stabilized Zirconia (100) by All-Coating-Pyrolysis Process
Authors: Manabe Takaaki , Yamaguchi Iwao , Tsuchiya Tetsuo , Kondo Wakichi , Mizuta Susumu , Kumagai Toshiya
Published: October 2002

Epitaxial YBa2Cu3O7-y
(Y123)/CeO2 multilayer films were prepared on yttria-stabilized zirconia (YSZ) (100) by the all-coating-pyrolysis (All-CP) process, i.e., both an epitaxial Y123 film and a CeO2 buffer layer were fabricated by a coating-pyrolysis process without using any high vacuum apparatus. A CeO2 buffer layer with smooth surface morphology and excellent in-plane alignment was successfully prepared on YSZ(100) by the CP process through pyrolysis at 500°C and crystallization at 1200°C in air. Subsequently, heteroepitaxial growth of Y123 on the CeO2-buffered YSZ(100) with an in-plane alignment relationship, Y123[100]∥CeO2[011]∥YSZ[011], was also achieved by CP process through a two-step [low-p(O2) of 10-4 atm/pure O2] annealing at 740°C. The dc-resistance of the epitaxial Y123/CeO2 film on YSZ(100) showed metallic behavior in the normal state and exhibited T
c,zero of 89.5 K by the conventional four probe method.
SiO2 Insulation Layer Fabricated using RF Magnetron Facing Target Sputtering and Conventional RF Magnetron Sputtering
Authors: Morohashi Shin'ichi , Matsuo Atsunori , Hara Toshihiro , Tsujimura Shogo , Kawanishi Masanori
Published: October 2002

We have investigated the deposition conditions for a SiO2 insulation layer, such as the substrate-target length, Ar pressure and applied RF power density, using both RF magnetron facing target sputtering and the conventional RF sputtering techniques. We have fabricated an SiO2 layer having with a good surface smoothness under the high deposition rate condition using the RF magnetron facing target sputtering technique.
Device Simulation of Grain Boundaries in Lightly Doped Polysilicon Films and Analysis of Dependence on Defect Density
Authors: Kimura Mutsumi , Inoue Satoshi , Shimoda Tatsuya , Sameshima Toshiyuki
Published: October 2002

Device simulations of grain boundaries in lightly doped polysilicon films have been performed. Dependence of the energy band, carrier density, potential barrier and electric conductivity on the defect density and grain size was carefully investigated. As a result, the mechanism of the carrier transportation has been clarified. The boundary defects not only trap and reduce free carriers, but also form the potential barrier and interfere with the carrier movement. As the defect density increases, in the case of the small grain size, first, the space-charge regions spread over the entire grain. Next, while the potential barrier remains the same, the lowest energy of the conduction band from the Fermi level (E
c-E
f) increases, and the carrier density decreases. Finally, E
c-E
f becomes the highest and remains the same. On the other hand, in the case of the large grain size, before the space-charge regions spread over the entire grain, E
c-E
f at the grain boundary reaches its maximum. Therefore, even if the defect density increases further, the potential barrier remains the same, and the carrier density remains high. By comparing the experimental and simulated electric conductivity, the defect density can be extracted.
Phases of the Initialized AgInSbTe Phase Change Optical Recording Films
Authors: Chou Lih-Hsin , Chang Yem-Yeu , Chai Yeong-Cherng , Wang Shiunn-Yeong
Published: October 2002

The Ag–In–Sb–Te active layer transformed into different phases after applying different initialization powers ranging from 150 mW to 900 mW. With an initialization power of 250 mW, the rhombohedral Sb crystalline phase was formed. For higher initialization powers, i.e., 350 mW or 450 mW, the AgSbTe2 crystalline phase and the newly proposed fcc Sb crystalline phase started to form. For initialization powers higher than or equal to 550 mW, no rhombohedral Sb phase was observed.
Photocarrier Transport in Nonuniform Field Based on Schottky Cell for the Time of Flight Measurement in Poly(3-alkylthiopehene) Films
Authors: S. Pandey Keiichi Kaneto , Wataru Takashima Wataru Takashima
Published: October 2002

The photocarrier transport measured by the time of flight (TOF) method in the Schottky junction cell of poly(3-alkylthiophene) (PAT) films/Al are studied taking the nonuniform field into consideration. The cell exhibits an excellent rectification characteristic, indicating the formation of a Schottky-type junction. When photocarriers are assumed to transit under a uniform field the mobility shows negative field dependence at the low field region. A simple model of nonuniform field distribution accounting for the apparent negative field dependence is proposed. The model is based on the finding that the bias is dominantly applied to the thin insulating depletion layer, and that the transit time is determined by the carrier migration at the low field bulk region.