bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of Pb(Zrx, Ti1-x)O3 Thin Films by Source Gas Pulse-Introduced Metalorganic Chemical Vapor Deposition
Authors: Aratani Masanori , Nagashima Kuniharu , Funakubo Hiroshi
Published: October 2002

We prepared Pb(Zr
x
, Ti1-x
)O3 [PZT] thin films on (111)Pt/Ti/SiO2/Si substrates at 620°C by metalorganic chemical vapor deposition (MOCVD). PZT [Zr/(Zr+Ti)=0.68] thin films of different thicknesses prepared by the conventional continuous source gas introduction MOCVD (continuous-MOCVD) and by pulsed gas introduction MOCVD (pulse-MOCVD) were compared to investigate the growth mechanism of these films. Stoichiometric PZT films were obtained for a wider range of Pb source input gas flow rates under fixed Zr and Ti sources for pulse-MOCVD compared with that for continuous-MOCVD. Highly (111)-oriented films were obtained for pulse-MOCVD regardless of their thickness, while the (111)-orientation decreased with film thickness for continuous-MOCVD. This suggests that the orientation homogeneity along the film thickness is higher for pulse-MOCVD films than for continuous-MOCVD films. The surface roughness of the pulse-MOCVD films was smaller than that of the continuous-MOCVD films and this result corresponds to the decrease of the leakage current density of the film. Well-saturated hysteresis loops with good square shapes were obtained, and the remanent polarization (P
r) and the coercive field (E
c) values of 100-nm-thick films prepared by pulse-MOCVD were 37 µC/cm2 and 82 kV/cm, respectively.
Protonic Conduction in the Single Crystals of SrZr0.95M0.05O3 (M=Y, Sc, Yb, Er)
Authors: Higuchi Tohru , Tsukamoto Takeyo , Sata Noriko , Hiramoto Kiyohisa , Ishigame Mareo , Shin Shik
Published: October 2002

The protonic conductivities of SrZr0.95M0.05O3 doped with four acceptor ions (M3+=Y3+, Sc3+, Yb3+, Er3+) have been studied in the single crystal form. The protonic conductivity is found in four acceptor ions, indicating that protons migrate by hopping from site to site. The Yb-doped crystal has the lowest activation energy and the highest conductivity amongst the four acceptor ions. This is considered to be due to the difference in strength of the O–H bond with different acceptor doping.
4-(Dimethylamino)-1-ethylpyridinium Iodide: A New Colorless Organic Ionic Crystal for Second-Order Nonlinear Optics
Authors: Kosuge Anwar , Okada Shuji , Oikawa Hidetoshi , Nakanishi Hachiro
Published: October 2002

A new organic ionic crystal of 4-(dimethylamino)-1-ethylpyridinium iodide (DMAEPI) was synthesized for use in second-order nonlinear optics, and its crystal structure was found to belong to the orthorhombic space group Pmn21. This crystal is considered to be a promising candidate for frequency conversion of diode lasers, since it has an estimated off-diagonal component of second-harmonic coefficient (d) which is about three-fourths that of the yellowish (4-nitrophenyl)-L-prolinol (NPP) irrespective of the cutoff wavelength at approximately 390 nm.
Construction of a Sample Cell of Poisonous Organic Solvents in Supercritical State for Small-Angle X-Ray Scattering Measurements
Authors: Ayusawa Asako , Morita Takeshi , Kusano Kouhei , Miyagi Hiroshi , Shimokawa Yuji , Matsuo Hitoshi , Nishikawa Keiko
Published: October 2002

A sample cell with a small internal volume was constructed to perform small-angle X-ray scattering (SAXS) measurements for poisonous samples such as benzene in the supercritical state. The cell was specially designed to keep temperature and pressure of the samples constant. Use of the cell makes it possible to prepare samples easily and quickly for SAXS measurements.
Structural Transformations During Sb Adsorption on Si(111)–In(4×1) Reconstruction
Authors: Bommisetty V. Rao Bommisetty V. Rao , Dimitry V. Gruznev Dimitry V. Gruznev , Toyokazu Tambo Toyokazu Tambo , Chiei Tatsuyama Chiei Tatsuyama
Published: October 2002

Understanding of initial stages of compound semiconductor growth on Si substrates is important for achieving atomically flat heterointerfaces, which are necessary for the fabrication of many advanced devices. Present report details the formation of InSb(2×2) reconstruction on the Si(111) substrate by Sb adsorption on Si(111)–In(4×1) surface phase and illustrates the structural transformations caused by the reordering of excess In. Higher Sb adsorption destroys the InSb phase with the coalescence of most of the In into 3D islands. This coalescence is accompanied by the formation of well-ordered Si(111)–Sb(2×1) phase between 260 and 350°C. Possible atomistic mechanisms responsible for the structural transformations are detailed.
In-Situ Electrical Study of a Reversible Surface Modification and a Nanomachining of Gold Microstrips by the Voltage-Biased Atomic Force Microscope Tip in Air
Authors: Kim Byong Man , Min Yo-Sep , Lee Nae Sung , Sok Jung Hyun , Kim Moon Kyung , Chae Soo Doo , Ryu Won Il , Chae Hee Soon
Published: October 2002

We report on a reversible polymerization of ambient carbonaceous deposits on the surface of gold microstrips by means of a voltage-biased atomic force microscope tip in air. This approach is found capable of controlled writing, erasing, and rewriting of carbon-rich deposits with sizes in nanometer regime. Physical mechanism for this reversible patterning is proposed to be the current-induced electrochemical process. In addition, we introduce a novel nanomachining technique based on an electric field enhanced cutting process.
Higher Order Nonlinear Dielectric Imaging Using Scanning Nonlinear Dielectric Microscopy
Authors: Yasuo Cho Yasuo Cho , Koya Ohara Koya Ohara
Published: October 2002

The higher order nonlinear dielectric imaging technique using scanning nonlinear dielectric microscopy (SNDM) is investigated. The resolution of the higher order nonlinear dielectric imaging is much higher than that of the conventional nonlinear dielectric imaging which detects the lowest order of the nonlinear dielectric constant. It is demonstrated that this higher order imaging is very useful for observing a surface layer with a unit cell scale thickness formed on ferroelectric material.
Phase Transition of Silicon-Nitride Monolayer on Si(111) Surface Observed by Scanning Tunneling Microscopy
Authors: Morita Yukinori , Tokumoto Hiroshi
Published: October 2002

Phase transition of a silicon-nitride (SiN) monolayer on a Si(111) surface was observed by ultrahigh vacuum scanning tunneling microscopy (UHV-STM). The STM image showed an 8/3×8/3 regular array of dots on the Si(111)-8×8 surface. After annealing at 1030°C, the image changed to a 3/4×3/4 regular array of dots, which corresponds to the quadruplet surface. The rotation angle of one of the four quadruplet domains was directly measured and found to be about 10° with respect to the crystallographic structure of the Si(111) surface. Further annealing at 1050°C changed the 3/4×3/4 structure to the 7×7 structure, which means that the SiN monolayer decomposed and was removed from the surface completely. Overall annealing behavior observed in our STM experiments was consistent with low-energy electron diffraction (LEED) and electron energy loss spectroscopy (EELS) data reported previously.
Fabrication of a Nanogap on a Metal Nanowire Using Scanning Probe Lithography
Authors: Takashi Miyazaki Takashi Miyazaki , Kei Kobayashi Kei Kobayashi , Toshihisa Horiuchi Toshihisa Horiuchi , Hirofumi Yamada Hirofumi Yamada , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

A molecular electronics device (MED), which makes use of the functionality of one or several molecules, is a very attractive nanotechnology. However, it is necessary to both fabricate conductive metal nanowire circuits and insert the desired functional molecule at any position on the circuits in order to realize superintegrated circuits using molecular electronics. Therefore, a technique for fabricating nanogaps at any position on a metal nanowire is very important. We patterned an electron-beam negative resist SAL601 using the scanning probe lithography (SPL) technique and the resist patterns were transferred to the underlying titanium film by wet etching. We fabricated a continuous 20-µm-long Ti nanowire, thus this method can be combined with conventional photolithography. Using this combination, we fabricated a Ti nanowire connected to a large Pt pad electrode, and measured its current–voltage property with an atomic force microscopy (AFM) conductive tip. Moreover, we fabricated nanogaps on this line pattern by switching off the voltage bias between the AFM tip and the sample for a short time. Using these techniques, we fabricated nanogap electrodes with both nanometer-scale width and gap. It is expected that the electrodes can also be applied for electric measurement of one or several molecules.
Surface Potential Measurement of Oligothiophene Ultrathin Films by Kelvin Probe Force Microscopy
Authors: Keiichi Umeda Keiichi Umeda , Kei Kobayashi Kei Kobayashi , Kenji Ishida Kenji Ishida , Shu Hotta Shu Hotta , Hirofumi Yamada Hirofumi Yamada , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

Surface structures and local surface potential of oligothiophene single molecular films deposited on metal substrates were investigated by Kelvin probe force microscopy using the frequency modulation detection method. Two-dimensional growth of the dimethylquinquethiophene (DM5T) films with the molecular axes perpendicular to the metal substrates was observed. Furthermore, the obtained surface potential of the DM5T film was 170 mV higher than that of Pt substrate and 200 mV lower than that of Ta substrate.
Effect of Hydrogen Termination on Ba Reaction on the Si(100) Surface
Authors: Ojima Kaoru , Yoshimura Masamichi , Ueda Kazuyuki
Published: October 2002

The effect of hydrogen termination on Ba reaction on the Si(100) surface at the initial stage of Ba adsorption was investigated by means of scanning tunneling microscopy (STM). On the bare Si(100) surface, Ba atoms form chain-shaped structures of Ba coverage up to 1/3 monolayer (ML), which extend perpendicular to the Si dimer row. The chain-shaped structure can change its shape because of the movement of Ba atom along the dimer row. On the other hand, in the case of Ba adsorption on a monohydrogenated Si(100)2×1 surface, Ba atoms make clusters, particularly at defect sites. In addition, Ba clusters can move across the dimer row.
Elastic Scattering by a Metal Sphere with an Adsorbed Molecule as a Model for the Detection of Single Molecules by Scanning Probe Enhanced Elastic Resonant Scattering (SPEERS)
Authors: C. Fischer Ulrich , Jörg Heimel Jörg Heimel
Published: October 2002

It was shown previously that by scanning near-field optical microscopy (SNOM) using the tetrahedral tip (T-tip) as a probe it was possible to obtain images of metal nanoparticles at a resolution below 10 nm. Therefore we started to investigate whether it is possible to obtain images of single dye molecules at a resolution below 10 nm. A model is proposed for the detection of single molecules by SNOM by a probe enhanced elastic resonant scattering process. Local plasmon excitation of the T-tip is suggested to lead to a large enhancement of the elastic resonant scattering signal of a dye molecule.
Fully Quantum-Mechanical Modeling of Tunneling Current in Ultrathin Gate Oxide Metal-Oxide-Semiconductor Devices
Authors: Iwata Hideyuki
Published: October 2002

Quantum-mechanical modeling of tunneling current from the quantized layer in ultrathin gate oxide metal-oxide-semiconductor field-effect transistors (MOSFETs) has been described. The coupled Schrödinger and Poisson equations, taking into account the wave-function penetration into the gate oxide and gate electrode, have been solved self-consistently. In order to formulate the discretized Schrödinger equation and the tunneling current density, a first-order perturbation approach has been employed, along with a new boundary condition on the wave function at the gate electrode-oxide interface. By introducing this boundary condition, the Schrödinger equation can be solved without using mesh points inside the gate electrode. The experimental verification of this tunneling current model has also been presented for the inversion layer of ultrathin gate oxide (1.5–2.0 nm) MOSFETs. Moreover, the effects of the wave-function penetration on quantization in the substrate have also been investigated in detail.
Study on Behavior of Electron Irradiation Defects and Impurities of Czochralski Silicon with Annealing by Positron Annihilation
Authors: Tamano Takuya , Hori Fuminobu , Oshima Ryuichiro , Hisamatsu Tadashi
Published: October 2002

Positron annihilation lifetime experiments have been performed for B-doped p-type Czochralski silicon (CZ-Si) wafers irradiated at 300 K with 1 MeV electrons with fluences between 1014 and 1017 e/cm2. In order to examine the thermal behavior of defects having shorter lifetime than that of the bulk, isochronal annealing experiments were carried out from 300 K to 900 K. The measurements were performed at 100 K to improve the positron trapping rates for defects. It is found that components having longer lifetime than that of the bulk behave differently, and they comprise by thermal donors (TD) and divacancies (V2). The short-lifetime component observed in the present experiments is responsible for a complex defect with impure interstitial oxygen atoms, doped B atoms and vacancies. The short-lifetime defects change into vacancy-type defects and thermal donors in certain ranges of annealing temperatures.
Intraband Relaxation Time in Wurtzite GaN/AlGaN Quantum-Well Structures with Spontaneous Polarization Effects
Authors: Seoung-Hwan Park Seoung-Hwan Park
Published: October 2002

Spontaneous (SP) and piezoelectric (PZ) polarization effects on the intraband relaxation time for wurtzite (WZ) GaN/AlGaN quantum wells (QWs) are investigated theoretically as functions of structural parameters. These are also compared with the data for the flat-band (FB) model without an internal field. The linewidths for the carrier-carrier and carrier-phonon scatterings of the FB model are almost constant irrespective of the Al composition, while those of the self-consistent (SC) model decrease with the increase of the Al composition except for the h-ph scattering. Also, it is observed that the linewidths of the SC model are significantly reduced compared with those for the FB model, except for the h-ph scattering. The h-ph scattering for the SC model below \hbarωLO has linewidths larger than the FB model due to the increase of the term related to the Fermi functions. The linewidths of both FB and SC models are almost constant irrespective of the well width, except for the e-h and h-e scatterings of the SC model. In the case of the e-h and h-e scatterings, the linewidths greatly decrease with the well width because of the increase of the spatial separation of wave functions. It is shown that the linewidths of both FB and SC models are a weak function of the barrier width.
Analysis of Potential Distribution and Current–Voltage Characteristic in Polyimide Langmuir–Blodgett Films
Authors: Li Cheng-Quan , Noguchi Yutaka , Wu Hong-Cai , Iwamoto Mitsumasa
Published: October 2002

The current–voltage (I–V) characteristics of Au electrode (M)–polyimide (PI) Langmuir–Blodgett (LB) film (I)–Al electrode (M)-MIM element are analyzed, taking into account the interfacial electrostatic phenomena and the presence of the interfacial electronic states. On the basis of the Richardson–Schottky model, the attractive force and potential energy created by a series of mirror image charges against both electrodes are calculated. A positive bias (V
ex>0) applied to an Au–PI LB film–Al element gives rise to the injection of electrons from the Au electrode into the lowest unoccupied molecular orbitals (LUMO) of PI LB film, whereas a negative bias (V
ex<0) causes the injection from Al electrode. The potential distributions across the PI LB film and the potential barrier height under the condition of various externally applied voltages (V
ex) are calculated, assuming the presence of surface states at the metal/film interface. It is determined that the calculation results of the I–V characteristics can predict the experimental results.
The Characterization of Surface Acoustic Wave Modes on Rotated Y-Cut Quartz (ST-X Quartz) with Different AlN Film Thickness
Authors: Lee Maw-Shung , Chang Feng-Chih , Wu Sean , Wu Long
Published: October 2002

The Y-rotated, X-propagating (ST-X) cut of quartz is used extensively for the development of surface acoustic wave (SAW) devices. Besides the commonly used generalized SAW (GSAW) mode, this crystal cut also supports a pseudo-SAW (PSAW) mode and a high velocity pseudo-SAW (HVPSAW) mode. AlN thin films are an attractive material that have some excellent characteristics, such as high surface acoustic wave (SAW) velocity, piezoelectricity, high-temperature stability, and stable chemical properties. In this paper, the AlN films with different thickness were successfully sputtered on ST-X quartz to study the SAW modes. The X-ray diffraction (XRD) pattern exhibited the AlN films were c-axis-oriented hexagonal structures. The result exhibited that the added AlN layer can effectively enhance the acoustic velocities. As the ratio (film-thickness/acoustic-wavelength) increased, the velocities of GSAW and PSAW were all increased but the HPSAW velocity maintained the same value.
Influence of the Microstructures on the Dielectric Properties of ZrTiO4Thin Films at Microwave-Frequency Range
Authors: Kim Yongjo , Oh Jeongmin , Kim Tae-Gon , Park Byungwoo
Published: October 2002

The dielectric properties of paraelectric ZrTiO4thin films were investigated in the microwave-frequency range. The dielectric losses (tan δ) and dielectric constants (ε) were successfully measured up to ∼ 5 GHz using a circular-patch capacitor geometry. The effects of the microstructures on the dielectric properties were also investigated. The ZrTiO4films were deposited at different temperatures and RF power densities to vary the film microstructures. As the deposition temperature and RF power density were increased, the film crystallinity was enhanced and dielectric losses decreased. The microwave dielectric losses correlated very well with the level of local strain and unit-cell dilation, while the dielectric constants did not alter significantly.
Two Figures of Merit for Field Emitters Deduced from Fowler–Nordheim Plots
Authors: Kai Junjiro , Kanai Masaki , Tama Masayoshi , Ijima Kenji , Tawa Yasuhiro
Published: October 2002

Two factors are deduced from Fowler–Nordheim plots of field emitters, one from their slopes and the other from their slopes and intercepts. The former factor concerns the work function and local field conversion factor, and the latter concerns the emitting area. These two factors are shown to be useful as figures of merit for field emitters both theoretically and experimentally. The derivation of these two factors and an expression of onset voltage using them are presented. It is illustrated that the onset voltage gives the overall figure of merit for field emitters, whereas the two factors proposed here as figures of merit are useful for further detailed discussions for evaluating field emitters and processes to fabricate them.
Laser-Triggered Spark Gap for High-Energy KrF Laser Amplifiers
Authors: Okuda Isao , Owadano Yoshiro
Published: October 2002

The design and experimental results of laser-triggered spark gaps for switching pulse forming lines in a 3 kJ class KrF laser amplifier is reported. Through the electric-field optimization in the spark-gap vessel, electrical stress on the insulator surface is alleviated and the gap inductance is reduced. With the use of this spark gap, fast rise-time (10 ns) high-voltage pulses (600 kV/270 ns) are obtained with a small jitter (5 ns/1σ).
Suppression of Corrugated Boundaries in Multilayer Fresnel Zone Plate for Hard X-Ray Synchrotron Radiation Using Cylindrical Slit
Authors: Yasumoto Masato , Tamura Shigeharu , Kamijo Nagao , Suzuki Yoshio , Awaji Mitsuhiro , Takeuchi Akihisa , Takano Hidekazu , Kohmura Yoshiki , Handa Katsumi
Published: October 2002

Corrugated zone roughness of a circular Cu/Al multilayer Fresnel zone plate (FZP) was successfully suppressed. Such a zone corrugation was often observed in the concentric multilayers prepared using a conventional sputtering apparatus. The zone corrugation is a consequence of the oblique component of the deposition flux (i.e. shadowing effect). We therefore set a cylindrical slit (a linear slit on the surface of a stainless steel cylindrical shield) between the target and the substrate in order to eliminate the oblique flux. As a result, the zone corrugation was not observed using a scanning ion microscope (SIM).
Comparison of a 10 V Josephson Junction Array System and a Conventional 10 V Measuring System by Measuring Zener Reference Standard
Authors: Murayama Yasushi , Nishinaka Hidefumi , Sakamoto Yasuhiko , Endo Tadashi
Published: October 2002

A 10 V Josephson junction array system and a conventional 10 V measuring system composed of a 1 V Josephson junction array voltage standard system and a 10:1 voltage divider were compared by measuring the Zener reference standard's 10 V and 1.018 V outputs. The average difference on comparison with 10 V output was -0.024 µV with 0.120 µV dispersion that corresponds to an experimental standard deviation of all measurement data. The average difference on comparison with 1.018 V output was -0.005 µV with 0.017 µV dispersion. Results show that there is no discrepancy between the two systems.
Wiring of Bumpless, Three-dimensional Integrated Si Wafers Block Using Through-hole Interconnections
Authors: Satoh Akinobu
Published: October 2002

Through-holes having an aspect ratio of 52.5 were formed with a hole density of 11.6 holes/mm2 on N-type Si wafers (Miller index: 100), using the optical excitation electropolishing method (OEEM). These Si wafers were bonded together in the three-dimensional direction by water glass bonding to form a five-layer integrated block. All wiring of this integrated block was performed in one operation by refilling the through-holes of the block with metal (indium) from the holes in its bottom surface by the closed type molten metal suction method. At the same time, the wiring trenches which require low resistance were also filled with metal. This is a new method of wiring the wafer-level, three-dimensional integrated block without the need for inner bumps. In addition, we have found a method of controlling the contact angle of metal with respect to SiO2 by the field effect utilizing a metal oxide semiconductor (MOS) structure to prevent the metal put in deep capillaries from dropping due to its own weight. This technology is a break-through in packaging wafer-level, ultra-high-density three-dimensional integrated blocks which will be needed in the first half of the 21st century.
Defect Properties of CuInS2 Single Crystals Grown by Horizontal Bridgman Method with Controlling S Vapor Pressure
Authors: Hiroaki Matsushita Hiroaki Matsushita , Tomohiro Mihira Tomohiro Mihira , Takeo Takizawa Takeo Takizawa
Published: October 2002

We have analyzed the lattice defects of CuInS2 bulk single crystals prepared by the horizontal Bridgman method with controlling S vapor pressure. The grown crystals have p-type conduction and electrical resistivities of more than 103 Ω·cm at room temperature. From measurements of the Hall effect, photoluminescence, optical absorption and photoconductivity, the activation energies of acceptors in CuInS2 crystals are shown to be of 85 meV, 115 meV and 360 meV, which are respectively ascribed to Cu-vacancies, In-vacancies and extrinsic impurities; whereas donors of 35 meV activation energy are ascribed to S-vacancies.
Numerical Analysis to Improve the Stabilized-Efficiency of Amorphous Silicon Solar Cells with New Device Structure
Authors: Dairiki Koji , Yamada Akira , Konagai Makoto
Published: October 2002

Numerical analysis using a Scharfetter and Gummel solution of Poisson's equation is carried out to find new device structures in order to increase the stabilized-efficiency of amorphous silicon (a-Si) solar cells. The relationship between density of acceptor states in absorber-layer (N
A) and the characteristics of a-Si solar cells are calculated. It is found that stabilized-efficiency is increased when the distribution of electrons, holes and electric field inside the absorber-layer were controlled. In this study, carrier concentration of i-layer, p/i interface and i/n interface are investigated by calculation. As a result, stabilized-efficiency of 8.1% of a conventional a-Si solar cell could establish a high stabilized-efficiency of 9.3% by increasing the N
A as same as the density of defect states in i-layer and also by applying partially doping near p-side of i-layer.
Thermal-Treatment Induced Deep Electron Traps in AlInP
Authors: Sung Wei-Jer , Huang Kai-Feng , Lin Wen-Jen , Tseng Tseung-Yuen
Published: October 2002

The effects of thermal treatment on the quality of AlInP film, grown by metal-organic chemical vapor deposition (MOCVD), have been carefully investigated using deep level transient spectroscopy (DLTS). Two thermal-treatment-induced deep levels were observed in the samples thermal-treated above 500°C and shall be attributed to the generation of phosphorus vacancies (Vp) by evaporation of phosphorus from AlInP surface. Examination of these deep levels provided a relatively simple means of understanding the thermal-treatment-induced behavior, thus allowing us to determine an appropriate process for manufacturing AlInP-based products.
Optical Detection by a La0.67Ca0.33MnO3-y Thin-Film Microbridge
Authors: Hong Meng-Tsong , Chen Ying-Chung , Hsu Ching-Chung , Wu Wei-Chuang , Chow Timothy-Chi , Chou Hsiung
Published: October 2002

A La0.67Ca0.33MnO3-y
(LCMO) thin film has been grown by laser ablation and was fabricated into a microbridge by conventional photolithography and dry etching for optical detection. The measured photoresponse, ΔV, of this LCMO thin-film microbridge reveals that it is bolometric in nature. The photoresponse is linearly proportional to the bias current I
b and the power density of irradiation W
D, which strongly suggests the applicability of an LCMO thin-film microbridge to a linear optical detector. The ratio of the photoresponse to the irradiated power density, ΔV/W
D, is independent of the incident-light wavelength λ from 0.633 to 3.5 µm. The dependence of the photoresponse on modulated frequency f, follows the ΔV∝f
-0.21 relation. Under I
b=100 µA and f=5 Hz at an operating temperature T
op=223 K, the responsivity S and noise voltage V
n are 685 V/W and 20 nV·Hz-0.5, respectively, for this LCMO thin-film microbridge. From the measured S and V
n, the noise equivalent power (NEP) and detectivity D
* were be calculated to be 2.92×10-11 W·Hz-0.5 and 2.76×109 cm·Hz0.5·W-1, respectively, for this LCMO thin-film microbridge. The experimental results from this LCMO thin-film microbridge show the practical applicability of this new detector system compared to other established detectors.
Realization of GaAs/AlGaAs Lasers on Si Substrates Using Epitaxial Lateral Overgrowth by Metalorganic Chemical Vapor Deposition
Authors: Kazi Zaman Iqbal , Thilakan Periyasamy , Egawa Takashi , Umeno Masayoshi , Jimbo Takashi
Published: October 2002

In this paper, we report on the fabrication and characterizations of a GaAs-based laser using the epitaxial lateral overgrowth (ELO) technique. ELO is an epitaxial growth technique capable of yielding low-dislocation-density III-V films on Si. To realize the effectivity of this procedure, two types of lasers were fabricated by changing the positions of the top p+-GaAs and metal contact in-line with the ELO layer and in-line with the line seed region. The longer lifetime for the lasers with the top p+-GaAs and metal contact in-line with the ELO layer proves the suitability of the ELO technique.
Time-Resolved Study of Intense Terahertz Pulses Generated by a Large-Aperture Photoconductive Antenna
Authors: Toshiaki Hattori Toshiaki Hattori , Keiji Tukamoto Keiji Tukamoto , Hiroki Nakatsuka Hiroki Nakatsuka
Published: October 2002

Saturation behavior of intense terahertz radiation pulses emitted by a large-aperture photoconductive antenna was studied by observing the waveforms of the generated terahertz pulse using the electrooptic sampling method. A peak terahertz field up to 5.7 kV/cm was observed. By increasing the pump pulse fluence, saturation of the peak terahertz field, shift of the peak appearance time and narrowing of the terahertz pulse were observed. These experimental results were found to be qualitatively consistent with the results of simulation based on the current surge model.
Design and Fabrication Process of Optically Pumped GaInAsP/InP Stripe Laser with Resonant Pumping for High-Power Operation
Authors: Onishi Yutaka , Koyama Fumio , Iga Kenichi
Published: October 2002

A high-power GaInAsP/InP semiconductor laser optically pumped by a 0.98 µm high-power broad area laser has been proposed. A vertical resonant pumping scheme is introduced to increase the absorption efficiency of the pump light. It is shown that the fraction of absorbed pump light can be increased up to 99% by inserting a highly reflective mirror with a reflectivity of 99%. In addition, a vertical resonant cavity using a GaAs/AlAs distributed Bragg reflector (DBR) was formed by a low-temperature wafer bonding technique.
Synthesis of Microcrystals from Frozen Acetone Irradiated by a Femtosecond Laser
Authors: Okoshi Masayuki , Higuchi Satoshi , Hanabusa Mitsugu
Published: October 2002

We synthesized microcrystals from frozen acetone irradiated by a 130-fs, 790-nm ultrashort pulse laser. They were shaped into an elongated hexagonal pillar form. The measurements of X-ray diffraction peaks supported the fact that crystals were formed, and one of the observed peaks matched the d-value of one of the carbyne allotropes (C IX). The density of 2.58±0.04 g/cm3 was close to that of α-carbyne. In addition, the microcrystals were stable in acetone solution.
A Novel Driving Mechanism for the Linear Piezo-Motors
Authors: Lin Wu , Ann Ngoi Kok , Ng Lim Enk
Published: October 2002

The friction-type motor is the overwhelming type in the field of piezoelectric motors. The limitations of the friction-type motors are their inability to achieve high output push force or torque. In this paper, a novel mechanism based on the theory of self-lock is proposed for the linear piezoelectric motors and a basic model is built to test the feasibility of the new mechanism. The new motor, which transmits the push force and displacement generated by a piezoelectric actuator to the output directly, can provide much higher push force than all existing piezoelectric motors. In addition, the achieved positioning accuracy is within 10 nm with the help of a hybrid-positioning strategy. The new motor can be applied in cases where both high positioning precision and heavy load are essential. Based on the new mechanism, three prototype models are proposed.
Effects of Annealing on Tantalum Pentoxide Films in N2 and N2O Gas Environments
Authors: Houng Mau-Phon , Wang Yeong-Her , Horng Jui-Hong , Huang Rui-Chang
Published: October 2002

The effects of annealing in N2 and N2O gas environments on the thin tantalum pentoxide (Ta2O5) films have been comparatively studied in this research. Annealing in N2O favored the stoichiometric Ta2O5 film formation because the most significant decrease in the intensity signal of transmittance detected at 612 cm-1 was obtained by Fourier transform infrared spectroscopy. Using X-ray photoelectron spectroscopy, the Ta 4f spectrum had a 1.9 eV spin-orbit splitting between the peak signal of Ta 4f7/2 at 26.2 eV and that of Ta 4f5/2 at 28.1 eV. Moreover, enhancement of the intensity signal corresponding to stoichiometric Ta2O5 at 530.7 eV was also clearly shown in O 1s spectrum. This implied that oxygen species released by N2O reduce the amount of oxygen vacancies and interfacial defects to form a thermodynamically stable interface. Low leakage current density, nearly no hysteresis and low flat-band voltage in capacitance–voltage measurements also supported the above results. However, the deficiencies induced by annealing were out-diffusion of Si atoms into the Ta2O5 films and an increase in the interfacial thickness of silicon oxide that directly decreased the effective dielectric constant of Ta2O5.
Structure of Vacuum-Deposited Tetramethyltetraselenofulvalene–Tetracyanoquinodimethane Complex Film
Authors: Chen Jin , Ueda Yasukiyo
Published: October 2002

Tetramethyltetraselenofulvalene–tetracyanoquinodimethane (TMTSF–TCNQ) complex film was prepared and vacuum-deposited on the cleaved (001) surface of KCl and KBr substrates. The unit cell parameters of the red form crystal reported previously, were revised as a=1.3768 nm, b=1.2671 nm, c=0.6998 nm, α=103.78°, β=98.49° and γ=75.4°. The TMTSF–TCNQ complex film was composed of red form crystals regardless of the source material and grew epitaxially on the KBr and KCl substrates with the following relationship: [100](0-12)TMTSF–TCNQ∥<100>(001)KBr, [100](0-12)TMTSF–TCNQ∥<100>(001)KCl or [100](0-12)TMTSF–TCNQ∥<110>(001)KCl. The change in epitaxy depending on the type of substrate and the transformation from the black form crystal to the red form one during the evaporation process are discussed.
Epitaxial Growth of γ-In2Se3 Films by Molecular Beam Epitaxy
Authors: Tomohiko Ohtsuka Tomohiko Ohtsuka , Kazuyuki Nakanishi Kazuyuki Nakanishi , Tamotsu Okamoto Tamotsu Okamoto , Akira Yamada Akira Yamada , Makoto Konagai Makoto Konagai , Uwe Jahn Uwe Jahn
Published: October 2002

Epitaxial growth of γ-In2Se3 film was investigated by molecular beam epitaxy (MBE). γ-In2Se3 epiataxial films with a defect wurtzite structure were successfully grown on GaAs(111)B substrates for the first time. The crystal structure of the γ-In2Se3 epitaxial film was determined by X-ray diffraction (XRD) and atomic force microscopy (AFM). It was found that γ-In2Se3 epitaxial films exhibit a vacancy-ordered crystal structure and that sharrow hexagonal cone structures were formed on the film surface. Furthermore, optical properties of the γ-In2Se3 epitaxial films were investigated by spatially resolved cathodoluminescence (CL).
Submicron Via-Hole Filling using Al Low-Pressure Seed Process
Authors: Yun Jong-Ho , Kim Ku-Young , Jin Sung-Gon , Yoon Kyoung-Ryul , Lee Sang-Hwa , Ryu In-Cheol , Park Sung-Ki
Published: October 2002

The submicron via-hole filling using a two-step Al sputtering process which consists of an Al low-pressure seed (ALPS) process and physical vapor deposition (PVD) Al, is described in this paper. The effect of the type of intermetal dielectric (IMD) material used, such as hydrogen silsesquioxane (HSQ), high-density plasma (HDP) oxide, and siloxane silicon-on-glass (SOG), on the via esistance and via-hole filling capability was evaluated and discussed. The Al film behavior after ALPS deposition, preheating, and PVD Al were investigated and it was determined that the out-gassing of moisture from siloxane SOG IMD significantly affects the via resistance and the key-hole formation in the via. A comparison of the via resistances of the Al-plug and W-plug was made. On the basis of the results, Al plugging with IMD materials such as HSQ or HDP oxide is considered to be superior to W plugging because of the lower via resistance and cost.
Nonlocal Hot-Electron Transport and Capture Model for Multiple Quantum Well Structures Excited by Infrared Radiation
Authors: Victor Ryzhii Victor Ryzhii , Robert Suris Robert Suris
Published: October 2002

In this paper, a model for hot-electron transport and capture phenomena in semiconductor heterostructures with multiple uncoupled quantum wells (QW) excited by infrared radiation is presented. The model takes into account the nonlocal character of the electron transport and capture of mobile electrons propagating over the barriers. It includes the Poisson equation and balance equations for electrons and their energy. The model is used for the calculation of steady-state spatial distributions of the electric-field and the average electron energy in multiple QW structures. The conditions of the formation of periodic electric-field domains revealed recently in ensemble Monte Carlo particle simulations are found. The obtained results are compared with the previous analytical calculations based on a simplified model. The relationships between phenomenological parameters of the latter and QW structure parameters are obtained. The developed analytical model highlights the origin of periodic electric-field domains in multiple QW structures and explains some features of such domain behavior.
Enhancement of Ar8+ Current Extracted from RIKEN 18 GHz Electron Cyclotron Resonance Ion Source by Moving the Plasma Electrode toward the Resonance Zone
Authors: Higurashi Yoshihide , Nakagawa Takahide , Kidera Masanori , Aihara Toshimitsu , Kase Masayuki , Yano Yasushige
Published: October 2002

We have successfully increased the beam intensity of Ar8+ ions by moving the plasma electrode of RIKEN 18 GHz electron cyclotron resonance ion source 1.0 cm toward the resonance zone. At this electrode position, 1.25 mA of Ar8+ was obtained at an extraction voltage of 13.5 kV an microwave power of 650 W. We observed that the beam intensity increased approximately 50% by moving the plasma electrode at the same extraction voltage. We also found that the beam intensity of the lower charged states, such as 9+, 8+, is strongly enhanced, while the beam intensity of the higher charged states of Ar ions (11+, 12+) is markedly decreased.
Molecular Orientation of Alkyldicyanoquinonediimine and Alkyldicyanoquinonediimine–Cu Langmuir–Blodgett Films: Rod-Lozenge Model
Authors: Ikegami Keiichi
Published: October 2002

A simple rod-lozenge model was proposed as the first step for discussing the relationship between the orientation of the alkyl-chain part and that of the N,N
′-dicyanoquinonediimine (DCNQI) part of Langmuir–Blodgett (LB) films of alkylDCNQI and alkylDCNQI–Cu, which had recently been fabricated and characterized by polarized IR spectroscopy. Taking into account the reported out-of-plane order parameters of individual molecular axes, this model could depict the structures of those LB films.
Flexible Inductive Transducer with Magnetic Resistance Influenced by Variable Overlap Area
Authors: Choi Dong-June , Kim Soo Hyun
Published: October 2002

Inductive transducers for measuring displacement are divided into two groups according to their measurement range. A variable air-gap type transducer is widely used for a measurement small range. A conventional variable air-gap type transducer has high sensitivity but lacks a linear measurement range. The air gap is also increased to maintain linearity as the measurement range increases, which induces a loss of sensitivity. The proposed variable overlap-area type transducer retains the original sensitivity and its linearity does not deteriorate in spite of variations of the measurement range. The proposed transducer is a flexible system that can increase its measurement range as well as maintain high sensitivity and linearity. The experimental results obtained using the prototype indicate that the sensitivity is higher than 2200 mV·V-1 mm-1 and the linearity error is below ±0.075% in the range of ±200 µm.
Precise Control of Gas Concentration Ratio in Process Chamber
Authors: Nagase Masaaki , Kitano Masafumi , Shirai Yasuyuki , Ohmi Tadahiro
Published: October 2002

A new system for controlling gas concentration in a process chamber was developed using a combination of a new flow controller and a gas pumping system. The new flow controller does not exhibit overshooting; thus, a stable gas flow rate can be realized in a process chamber after valve operation. Furthermore, very rapid gas displacement in the chamber can be realized by combined gas flow system and pumping system. As a result, it took only 2 s to stabilize chamber pressure and gas composition from purge gas to process gases using Fourier transform infrared spectroscopy (FT-IR) method. It is possible to control process parameters such as gas concentration and working pressure during the entire process using this system.
Range-Modulated Pencil Beam Algorithm for Proton Dose Calculations
Authors: Ryosuke Kohno Ryosuke Kohno , Yoshihisa Takada Yoshihisa Takada , Takeji Sakae Takeji Sakae , Akihiro Nohtomi Akihiro Nohtomi , Toshiyuki Terunuma Toshiyuki Terunuma , Keiji Matsumoto Keiji Matsumoto , Hiroyuki Matsuda Hiroyuki Matsuda
Published: October 2002

The range-modulated pencil beam algorithm (RMPBA) has been developed for proton treatment planning on the basis of the pencil beam algorithm (PBA) to reduce the calculation time yet realize sufficient accuracy. It uses the depth-dose distribution of the range-modulated beam as a central-axis term of pencil beams. The spread of the range-modulated pencil beam is derived by assuming that the protons pass through the average thickness of the ridge-filter. The accuracy of dose calculations by the RMPBA is verified by comparison with dose measurements in water performed using a silicon semiconductor detector. The results of the measured dose distributions agree well with those of the calculations using the RMPBA. Furthermore, the calculation time required by the RMPBA is one-sixth of that required by the PBA in the case of the six-step ridge-filter. Therefore, the dose-calculation method by the RMPBA will be useful and applicable to actual treatment planning of proton therapy.
A New Method for Evaluating the Radiographic Imaging Quality using the Beam Stopper
Authors: Hideteru Yoshida Hideteru Yoshida , Shigehiro Fukushima Shigehiro Fukushima , Hitoshi Kanamori Hitoshi Kanamori , Masamichi Shimamura Masamichi Shimamura
Published: October 2002

A new method was developed for evaluating radiographic imaging quality by introducing a beam stopper. The sharpness is estimated by this method for a radiographic screen-film system by taking a radiograph of the beam stopper instead of the conventional X-ray slit. Because the contrast difference relates directly to the visibility of the radiographs, the beam stopper estimation relates directly to the visual rating of blurring systems.
Fabrication of Bi–La–Sr–Mn–O Uncooled Microbolometer
Authors: Hayashi Ken-ichi , Ohta Eiji , Wada Hideo , Higuma Hiroko , Miyashita Shoji
Published: October 2002

Since perovskite manganese oxide Bi–La–Sr–Mn–O (BLSMO) has a large temperature coefficient of resistance (TCR: defined as 1/R dR/dT) of above 3%/K, it has been considered to be a suitable candidate for use as an uncooled IR bolometer material. We fabricated a single pixel device of the BLSMO microbolometer and evaluated it. The BLSMO film was deposited by RF magnetron sputtering at ambient temperature in an oxygen atmosphere. The film showed the TCR of 3.1%/K at room temperature. The size of the single pixel device is 38×38 µm2. To achieve high infrared absorption, the detector contains an infrared absorbing membrane with a high fill factor of 90%. In a vacuum, the detector showed a thermal conductance of 1.3×10-7 W/K and a responsivity of 4.8×105 V/W. According to these numerical values, a noise equivalent temperature difference (NETD) of the BLSMO microbolometer was estimated as being about 0.1 K with f/1.0 optics.
Influence of the Amorphous Silicon Thickness on Top Gate Thin-Film Transistor Electrical Performances
Authors: Martin Sandrine , Chiang Chun-Sung , Nahm Jeong-Yeop , Li Tong , Kanicki Jerzy , Ugai Yasuhiro
Published: October 2002

We have analyzed the influence of the hydrogenated amorphous silicon (a-Si:H) thickness on the electrical performances of top gate thin-film transistors (TFTs). We have observed that, when the a-Si:H thickness increases, the threshold voltage and the subthreshold slope decrease. The modification of the TFT apparent field-effect mobility has also been investigated: we have shown that it first increases with the a-Si:H thickness, and then decreases for thicker a-Si:H films. This change of electrical performances is most likely associated with both the variation of a-Si:H microstructure during the film depositions and the effect of parasitic source and drain series resistances. We have demonstrated that for a given TFT geometry, it is therefore possible to define an optimum a-Si:H thickness ensuring maximum TFT electrical performances, and that this optimum thickness increases significantly with the TFT channel length.
Comparative Study of Degenerate Four-Wave Mixing and Laser-Induced Fluorescence Techniques as Diagnostic Methods for Laser Ablation Plume
Authors: Morishita Kouki , Kawaguchi Norihito , Okada Tatsuo
Published: October 2002

The degenerate four-wave mixing (DFWM) technique has been applied for the first time to the diagnostics of the laser ablation plume in order to overcome some difficulties encountered in the laser-induced fluorescence (LIF) diagnostic method, such as the interference with the intense plasma background light from the plume, the self-absorption and the collisional quenching in LIF signals due to the high density of the plume. A comparative study between the LIF and DFWM techniques is presented.
Reflective Display Associated with In-Plane Rotation of Nematic Liquid Crystal
Authors: Lee Seung Hee , Hong Seung Ho , Kim Hyang Yul , Seo Dae-Shik , Lee Gi-Dong , Yoon Tae-Hoon
Published: October 2002

We have fabricated a novel reflective nematic liquid-crystal cell driven by a fringe field. In the absence of an electric field, the liquid-crystal molecule is homogeneously aligned and when a fringe field induced by interdigital electrodes is applied, liquid-crystal molecules rotate in plane in the entire whole area. A conventional in-plane switching (IPS) cell was impossible for application to a reflective system due to its low aperture ratio. However, a newly designed fringe-field switching (FFS) cell is possible due to its high transmittance. Furthermore it exhibits a wide viewing angle intrinsically owing to the in-plane rotation of the liquid-crystal director. Several reflective systems with either two polarizers or one polarizer with a quarter-wave retardation film are possible. In this study, we investigate the switching principle of each system and compare their electrooptic characteristics by simulation and experiment.
Thermal, Mechanical and Electrical Properties of Pd-Based Thin-Film Metallic Glass
Authors: Liu Yongdong , Hata Seiichi , Wada Kouichi , Shimokohbe Akira
Published: October 2002

As a kind of amorphous alloy, metallic glasses are suitable materials for micromachines because their size effect is considered to be absent. However, neither the fabrication process nor the physical properties of thin-film metallic glasses (TFMGs) have yet been examined. In this paper, Pd-based (Pd76Cu7Si17, atomic composition) TFMG was first fabricated by an RF-magnetron sputtering method. The existence of a supercooled liquid region (SCLR) and the thermal stability with respect to crystallization were measured by a differential scanning calorimeter (DSC). The existence of the SCLR was reconfirmed by a thermomechanical analyzer (TMA). The hardness of Pd-TFMG was measured by a mechanical testing machine for micro-sized specimens (MMT2000), while the Young's modulus was measured by a MMT2000 in the bending mode as well as by a TMA in the tensile mode. The resistivity of Pd-TFMG was tested by the four-point probe method. Finally, the influences of deposition conditions were discussed and the physical properties of TFMG were compared with those of Pd-based bulk metallic glass.
Internal Photoemission from Ag Nanoparticles Embedded in Al2O3 Film
Authors: Osamu Mamezaki Osamu Mamezaki , Minoru Fujii Minoru Fujii , Shinji Hayashi Shinji Hayashi
Published: October 2002

Photocurrent properties of Al2O3 films containing Ag particles a few nanometers in diameter were studied. In the dark, the films exhibit T
-1/2 dependence of ln
(σ), where σ and T are the conductivity and temperature, respectively. This dependence indicates that the electron transport is carried out by thermally activated electron tunneling between Ag nanoparticles. Under UV-light irradiation, the photocurrent produced in the films was observed. The photocurrent could be well explained by the internal photoemission from Ag nanoparticles and/or electrodes.