bluuebunny/crossref_metadata_2025 huggingface dataset:
Lamellar Structure in Melted-Slowly Cooled Vinylidene Fluoride/Trifluoroethylene (86/14) mol% Copolymer
Authors: Sunao Sasaki Sunao Sasaki , Kohji Kubo Kohji Kubo , Akira Funato Akira Funato , Akio Chiba Akio Chiba
Published: October 2002

Lamellar structure, and its thermally induced changes in melted-slowly cooled vinylidene fluoride/trifluoroethylene (86/14) mol% copolymer were studied by scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS). SAXS intensity data observed at room temperature showed peaks at arounds≃7.5 ×10-3Å-1ands≃1.35 ×10-3Å-1, the latter of which is caused by thick lamellar stacks such as those observed by SEM (sis the magnitude of the scattering vector). During the heating process, the higher-angle peak disappeared at 147–155°C, while the lower-angle peak disappeared at around 170°C (the melting point of the sample). These SAXS data were analyzed by fitting to lamellar stack models. For the data in the range 25–147°C, a model in which thin and thick lamellar stacks coexist was used. For the data in the range 155–165°C, a model in which only thick lamellar stacks exist was used. The calculated intensities were in good agreement with the observed intensities, which demonstrates that in the range 25–147°C the copolymer is composed of stacks of lamellae about 85 Å thick and stacks of lamellae about 570 Å thick, and that in the range 155–165°C it is composed of only the thick lamellar stacks. The mean crystallinity of the thin lamellar stacks was found to decrease markedly with increasing temperature, which indicates that thin lamellar stacks disappear in the range 147–155°C due to the melting of the crystals within them.
Silicon Microactuators for Computer Disk Drives
Authors: Weilong Tang Weilong Tang , Viktoria Temesvary Viktoria Temesvary , J. Jason Yao J. Jason Yao , Yu-Chong Tai Yu-Chong Tai , Denny K. Miu Denny K. Miu
Published: October 2002

Silicon micromachining will be an important manufacturing technology for future-generation, high-performance optical and magnetic storage products. In this paper, we shall present recent results related to the design and fabrication of silicon micromachined electromagnetic piggyback microactuators for significantly increasing the track density of magnetic (and potentially optical) rigid disk drives.
On the Thermal Conductivity of Magnetic Fluid
Authors: D. K. Wagh D. K. Wagh , Ashima Avashia Ashima Avashia
Published: October 2002

The formula for the thermal conductivity of magnetic fluid is derived considering thermal conductivity as transport of thermal energy. It is found that the thermal conductivity of a magnetic fluid depends on magnetic field gradient and certain microscopic parameters which characterize the magnetic fluid.
Thermal Expansion Coefficients of Alkali Halides and Alkaline-Earth Fluorides
Authors: Hideaki Inaba Hideaki Inaba
Published: October 2002

The thermal expansion coefficients of alkali halides and alkaline-earth fluorides have been estimated and analyzed using Ruffa's method by reevaluating the parameter used. The Morse potential has been used to evaluate the thermal expansion coefficient assuming the Debye model for the frequency distribution of the Morse oscillator. The parameter of the Morse potential has been determined by fitting the thermal expansion coefficients of alkali halides at 293 K to the experimental values. Using the parameter the thermal expansion coefficients of alkali halides and alkaline-earth fluorides in a wide range of temperatures have been calculated. The calculated thermal expansion coefficients thus obtained are in excellent agreement with the experimental ones except for the excess contribution due to vacancy formation at high temperatures. The excess term has been analyzed and the enthalpies of vacancy formation due to Schottky defects have been obtained. The enthalpies of vacancy formation are shown to be linearly dependent on Debye temperature and cohesion energy for alkali halides and alkaline-earth fluorides separately.
Diffraction and Polarization Properties of a Liquid Crystal Grating
Authors: Zhan He Zhan He , Toshiaki Nose Toshiaki Nose , Susumu Sato Susumu Sato
Published: October 2002

Diffraction properties of an amplitude liquid crystal grating with a periodic electrode structure are studied under different polarizer configurations. Based on these experimental results, polarization characteristics of light diffracted from this grating are discussed. Both diffraction light intensities and polarization states of this liquid crystal grating can be controlled electrically. Symmetrical diffraction light intensities but antisymmetrical polarization states in corresponding negative and positive diffraction orders are demonstrated.
A Study of High Pretilt Angle Generation in Nematic Liquid Crystal (5CB) on Rubbed Polythiophene Surfaces with Alkyl Chain Lengths
Authors: Seo Dae-Shik , Kobayashi Shunsuke , Nishikawa Michinori , Yabe Yoshikazu
Published: October 2002

High pretilt angles in nematic liquid crystals (NLC) have been generated on rubbed polythiophene (PTP) surfaces with different alkyl chain lengths. The pretilt angle of the NLC, 4-n-pentyl-4′-cyanobiphenyl (5CB), was observed on unidirectionally rubbed PTP surfaces with alkyl chains with more than 9 carbon atoms. We obtained pretilt angle of 15–40° on rubbed PTP surfaces with 10 carbon atoms in the alkyl chain. Also, the pretilt angles of 65–80° of 5CB were obtained on rubbed PTP surfaces with 11 and 12 carbon atoms in the alkyl chain. We suggest that this high pretilt angle generation in 5CB is due to the surface-excluded volume effect by the alkyl chain lengths between the LCs and the PTP surfaces. Finally, we conclude the odd-even effect on rubbed PTP surfaces is clearly contributed to the pretilt angle generation.
MgO(200) Highly Oriented Films on Si(100) Synthesized by Ambient-Controlled Pulsed KrF Excimer Laser Deposition Method
Authors: Ishiguro Takashi , Hiroshima Yasushi , Tsuyoshi Inoue Tsuyoshi Inoue
Published: October 2002

MgO film growth on Si(100) using the ambient-controlled pulsed KrF excimer laser deposition method has been performed under a wide range of synthesis conditions: oxygen pressure (P
O2
) of 10-6–10-3 Torr, substrate temperature (T
sub) of 100–300° C, and laser irradiation energy density on Mg metal target of 0.6–2.0 J/cm2. MgO(200) pole figures of MgO films are measured by the X-ray ( CuKα) diffraction method using Schulz's reflection attachment. Almost all MgO films have strong (200)-preferred orientation and rather weak (220)-preferred orientation. The crystallographic relation of the former case is MgO(200)//Si(100) and MgO[01*BAR*1*BAR*]//Si[01*BAR*1*BAR*]. MgO film with the highest degree of (200)-preferred orientation was fabricated under the optimized conditions of T
sub=300° C, energy density= 1.5 J/cm2, and P
O2
=1×10-4 Torr.
Formation of Self-Assembled Organic Ultrathin film by Chemisorption on Silicon Crystal Surface
Authors: Takahagi Takayuki , Nagasawa Yoshikatu , Ishitani Akira
Published: October 2002

A highly oriented ultrathin organic film was successfully prepared on a silicon single-crystal surface by chemisorption of a silane coupling molecule to a silanol group on the substrate surface. The extended molecular chains of the film were found to align approximately perpendicular to the substrate surface due to the close packing of organic molecular chains. We successfully assembled an organic multimolecular-layer film on a silicon surface with the repeated reaction of a bifunctional silane coupling molecule.
The Application of a Carbon Protective Layer to Metal Evaporated Tape
Authors: Endo Katsumi , Ishikawa Junko , Osamu Yoshida Osamu Yoshida , Noriyuki Kitaori Noriyuki Kitaori
Published: October 2002

Carbon protective layers for metal evaporated (ME) tapes were prepared using electron cyclotron resonance chemical vapor deposition (ECR-CVD). Raman spectroscopy was used to evaluate the carbon protective layers. It was found that the quantity of luminescent substances in the carbon film affected the overall durability of the protective layer. Raman spectroscopy was very useful in this analysis. Our results imply that not only hardness but also flexibility is required for the application of carbon films. The quantity of luminescent substances in the films was measured using a new parameter I
b/I
p, obtained from the Raman spectra. Protective layers with a particular range of I
b/I
p were found to be optimum durability. It is significant for the investigation of carbon protective layers that their durability can be easily determined by Raman spectroscopy.
Application of a Polarizing Holographic Optical Element to a Recordable Optical Head
Authors: Nishino Seiji , Yamamoto Hiroaki , Kasazumi Kenichi , Wada Hidenori , Saimi Kousei Sano
Published: October 2002

A polarizing holographic optical element (HOE) with compensating grooves on the surface of a LiNbO3 substrate has good polarizing beam-splitter characteristics. This polarizing HOE was applied to a recordable optical head with an integrated laser and photodetector unit. In the optical head, a correct far-field tracking method is constructed by setting the polarizing HOE and a quarter-wave plate right under the objective lens, which can be moved with the objective lens. A holographic pattern of the polarizing HOE is divided into 20 portions along a disc track direction for spot size focus error detection and far field tracking detection. Wth this optical head, conventional CD play-back and recording signals on phase change discs were performed. Then the tracking offset caused by objective lens shift was measured and determined to be markedly decreased. Signal degradation by the ±1 st light diffracted by a polarizing HOE was not observed. Good characteristics of recording and play-back for phase change discs were also obtained. This recordable optical head was found to have desirable characteristics and high productivity.
Effects of He Gas Addition on the Production of Active Particles in rf Magnetron Sputtering
Authors: Harada Kanji , Kishida Satoru , Matsuoka Takeru , Maruyama Takafumi , Tokutaka Heizo , Fujimura Kikuo , Koyanagi Tsuyoshi , Fujii Takamichi
Published: October 2002

We measured optical emission spectra during the deposition of Bi2Sr2Ca

n
-1Cu

n

O

x

(BSCCO) films by an rf magnetron sputtering method with a BSCCO powder target. It was shown that the active particles produced are ionized oxygen molecules and CuO radicals when He+O2 is used as a sputtering gas. The results of X-ray photoelectron spectroscopy indicated that the BSCCO films prepared using He gas have the same metal composition as the target. In addition, we confirmed that the use of He as a sputtering gas enhances the oxidation in the preparation of CuO films.
Time Behavior of Heat Diffusivity during L-H-L Transitions in JT-60U
Authors: V. Neudatchin Sergei , Tomonori Takizuka Tomonori Takizuka , Hiroshi Shirai Hiroshi Shirai , Nobuaki Isei Nobuaki Isei , Yutaka Kamada Yutaka Kamada , Yoshihiko Koide Yoshihiko Koide , Masayasu Sato Masayasu Sato , Masafumi Azumi Masafumi Azumi
Published: October 2002

The L-H-L transitions have been analyzed mainly for high-field pulses (B

t
≈4 T) in JT-60U. The simultaneous response of electron temperature T
e has been clearly observed during L-H-L transitions over a wide plasma region. This T
e evolution is described as the result of the fast jump of electron heat diffusivity, δχ e, over the wide plasma region. Values of δχ e were obtained as 0.5 m2/s < | δχ e | < 1 m2/s, which usually increase with radius. The simultaneous response of ion temperature T
i was also observed to be that of similar to the T
e response. The jump of ion heat diffusivity, δχ i, is similar to that of δχ e and usually increases with radius, as does δχ e. In a low-field pulse (B
t ≈2.5 T), | δχ i | is as large as 2 m2/s. Values of δχ are consistent with the change of the energy confinement time during transitions.
Transient Photoinduced Voltage Due to Electron Transfer in Porphyrin Polyimide Langmuir-Blodgett Films
Authors: Xiaobin Xu Xiaobin Xu , Tohru Kubota Tohru Kubota , Mitsumasa Iwamoto Mitsumasa Iwamoto
Published: October 2002

Photoinduced electron transfer in porphyrin polyimide (PORPI) Langmuir-Blodgett (LB) films incorporated in ITO/PI/PORPI/C20/Al devices was investigated using a fast transient voltage measuring system. The presence of traps in PORPI LB films was indicated by the initial rise of the photoinduced voltage. Based on the biasing voltage, temperature, and electrode dependencies of the photoinduced transient voltage, the generation of electrons in PORPI films was explained in terms of the Onsager model.
Estimation of Surface Absorptivity and Surface Temperature in Laser Surface Hardening Process
Authors: Sun Yann-Shouh , Weng Cheng-I , Tei-Chen Chen Tei-Chen Chen , Wang-Long Li Wang-Long Li
Published: October 2002

A two-dimensional, quasi-static, inverse heat conduction problem (IHCP) is implemented to investigate the absorption efficiency of surface coatings in laser surface hardening process. The analysis of IHCP includes the utilization of the method of direct sensitivity coefficient and the measurement of interior temperatures nearby the laser heating surface. The results shows that the estimation of surface absorptivity generally agrees with that observed by experimental works. It is realized that the different kinds of coating make influences on the surface absorptivity as well as surface temperature significantly. Furthermore, the power density and scanning speed of laser beam to control the quality of surface hardening may be determined based on the informations of heat flow in the workpiece.
Fabrication and Characterization of the Pd-Silicided Emitters for Field-Emission Devices
Authors: Wang Chih-Chong , Ku Tzu-Kun , Hsieh Iing-Jar , Huang-Chung Cheng Huang-Chung Cheng
Published: October 2002

The structure of Pd-silicided field emitters based on the silicon micromachining technology has been demonstrated. The uniform and extremely sharp silicided emitters are formed using wet chemical etching, low-temperature oxidation sharpening (LTOS), metal coating, and furnace annealing. The silicided emitters are firstly identified by the bright-field, dark-field images, and diffraction patterns of transmission electron microscope (TEM). Under the applied voltage of 1100 V, the anode currents of the Pd-coated and silicided emitters are 16 µ A and 26 µ A, respectively. The values of threshold voltage V
T for Pd-coated and silicided emitters are about 745 V and 785 V, respectively. The lower threshold voltage of the Pd-coated emitters is duo to the smaller emission work function of palladium. The emission work function of the Pd-silicided emitters is calculated to be 8.31 eV. Furthermore, the long and short-term current stabilities of silicided emitters is also better than that of Pd-coated ones. These results show that these silicided emitters have potential applications in vacuum microelectronics to obtain superior lifetime, reliability, and stability.
Theoretical Study of Current and Barrier Height between Aluminum Tip and Silicon Surface in Scanning Tunneling Microscopy
Authors: Nobuhiko Kobayashi Nobuhiko Kobayashi , Kenji Hirose Kenji Hirose , Masaru Tsukada Masaru Tsukada
Published: October 2002

The first-principles calculations for the electronic structure of the aluminum
tip and the silicon surface in scanning tunneling microscopy are performed
using the recursion-transfer matrix method, which is an effective method for
exploring the microscopic electronic states of a bielectrode system under
electric field and current.
The atomic-scale current distribution and the potential
barrier between the tip and the surface are presented. It is revealed that
the opening of a hole in the potential barrier occurs when the tip-sample
distance is 10 a.u. at a surface bias of +2.0 V.
Cu Film Growth on a Si(111) Surface Studied by Scanning Tunneling Microscopy
Authors: Tomimatsu Satoshi , Hasegawa Tsuyoshi , Makiko Kohno Makiko Kohno , Shigeyuki Hosoki Shigeyuki Hosoki
Published: October 2002

We observed a change in growth mode of Cu, while dynamically observing Cu film growth on a Si(111)-7×7 surface during Cu deposition at room temperature by scanning tunneling microscopy (STM). Initially, Cu atoms were adsorbed mostly on the faulted halves of the 7×7 structure. Then, up to about 2 ML coverage, small Cu islands appeared. As the coverage increased from 2 to 3 ML, the growth mode changed into quasi-layer-by-layer growth. With further deposition, 3-D islands having hexagonal terraces grew.
Multibeam Optical System Incorporating a Microlens Array
Authors: Tokumaru Haruki , Kiyotaka Arai Kiyotaka Arai , Norikazu Kawamura Norikazu Kawamura
Published: October 2002

Parallel recording using a multibeam laser diode array is effective for recording at a high data transfer rate. Focused spot interval equal to the track pitch is realized effectively in an optical disk drive by tilting the spots away from the track direction. However, this method is not applicable in an optical tape recording system using a rotating optical head. We studied theoretically and experimentally a new multibeam optical system incorporating a microlens array to realize a narrow spot interval. The beams that pass through the microlens can be treated as Gaussian beams. The introduction of the microlens array realized a small spot interval of 4 µm at a transmittance of 40%. This value is larger than that without the microlens array by a factor of about 20.
Differentiation of Chemically Functional Groups in Stearoyl Amide and Anilide with Scanning Tunneling Microscopy
Authors: Hideto Takeuchi Hideto Takeuchi , Susumu Kawauchi Susumu Kawauchi , Atsushi Ikai Atsushi Ikai
Published: October 2002

Scanning tunneling microscopy (STM) was applied to distinguish chemically functional groups in stearoyl amide and anilide molecules adsorbed on the liquid-solid interface of phenyloctane and graphite. In contrast to previously reported carboxyl and hydroxyl groups, amide and anilide groups were imaged as more readily tunneling parts than the hydrocarbon part. Stearoyl amide molecules were in a head-to-head alignment suggesting hydrogen bonding between the amide groups, while stearoyl anilide molecules were in a head-to-tail arrangement. The STM images were compared with the shape of the molecular orbitals calculated for isolated molecules to confirm the intuitive assignment of the functional groups.
Scanning Tunneling Microscopy of UV-Induced Gasification Reaction on Highly Oriented Pyrolytic Graphite
Authors: Shun-ei Ozeki Shun-ei Ozeki , Takeshi Ito Takeshi Ito , Kiyohiko Uozumi Kiyohiko Uozumi , Izumi Nishio Izumi Nishio
Published: October 2002

Real-space observations of gasification reaction of graphite surface caused by UV irradiation were made using scanning tunneling microscopy (STM). The formation of etch pits on highly oriented pyrolytic graphite (HOPG) surface during gasification reaction was investigated. At the beginning of gasification reaction, domelike structures were formed. Further irradiation produced randomly distributed deep etch pits. When UV-irradiated samples were kept for 3 weeks at 50°C, the irregularly shaped deep etch pits stabilized and formed shallow etch pits one or two monolayers deep.
Instrumentation of the High-Vacuum Atomic Force Microscope
Authors: Yasutake Masatoshi , Takehiro Yamaoka Takehiro Yamaoka , Yasunori Nagatani Yasunori Nagatani
Published: October 2002

The high-vacuum atomic force microscope (HV-AFM) is a useful tool that is used in various sample environments and achieve good Z axis sensitivity in a noncontact mode operation because the cantilever is free from hydrodynamic damping. The instrument is designed with the aims of minimizing the measuring time, simplifying the operation and achieving high performance. A pumping pressure of about 10-4 Pa is obtainable within 15 min. To achieve easy operation, the optical lever deflection detection head is placed outside the vacuum chamber. The vibration isolation is achieved using an elastic damper and a magnetic-floating-type turbomolecular pump. This vibration isolation method works well enough to obtain the atomic-resolution image of a highly oriented pyrolytic graphite (HOPG) sample. We checked the sensitivity of the instrument using the noncontact mode of operation of a magnetic force microscope (MFM). The Z axis sensitivity in vacuum operation was compared with that in ambient operation. The quality factor increased by more than 25 times and the Z axis sensitivity increased by more than 10 times in vacuum operation (10-4 Pa).
Ultrasonic Atomic Force Microscope with Overtone Excitation of Cantilever
Authors: Kazushi Yamanaka Kazushi Yamanaka , Shizuka Nakano Shizuka Nakano
Published: October 2002

We propose a novel atomic force microscope (AFM) combined with ultrasonic frequency vibration of a cantilever excited at its support. This method enables both topography and elasticity imaging of stiff samples such as metals and ceramics, without a need for bonding a transducer to the sample. When the sample surface is contacted with a tip attached to the cantilever, the cantilever vibration mode is changed according to the sample properties. It is theoretically predicted that the amplitude and resonant frequency of vibration at higher-order modes are useful parameters for elasticity evaluation of stiff samples. A preliminary experimental verification of this principle is presented using a glass-fiber-reinforced plastic sample. Clear elastic contrast was successfully obtained using a soft cantilever only when it was vibrated at MHz frequency higher-order modes.
The Analysis of Bending Stress and Mechanical Property of Ultralarge Diameter Silicon Wafers at High Temperatures
Authors: Tetsuo Fukuda Tetsuo Fukuda
Published: October 2002

In this paper, we investigate the bending stress during thermal annealing of 300 mm diameter wafers on various support structures. We calculate the bending stress generated in the wafers using linear elastic theory and investigate the relationship between the stress and the mechanical strength of silicon crystals. We discuss the temperature range and support structure which can avoid crystallographic slippage in these ultra-large diameter wafers.
Focusing Characteristics of an Optical Head with Superresolution Using a High-Aspect-Ratio Red Laser Diode
Authors: Masahisa Shinoda Masahisa Shinoda , Kenjiro Kime Kenjiro Kime
Published: October 2002

The focusing characteristics, when using a superresolution technique, for a high-aspect-ratio laser beam were investigated theoretically. The spot size, sidelobe intensity, and laser beam transmission efficiency were calculated against the shading mask width, fill factor, and optical disc tilt. It was revealed that, for a given transmittance, performing superresolution in the region of fill factors greater than 1 is effective both for reducing the spot size and for increasing the laser beam transmission efficiency. However, since superresolution sharply increases the sidelobe, it must be carried out in a practical range.
Improved Characteristics of p+-n Junctions formed by Excimer Laser Annealing with Low Temperature Pre-Annealing
Authors: Tsukamoto Hironori , Yamamoto Hiroshi , Noguchi Takashi , Haruko Masuya Haruko Masuya , Toshiharu Suzuki Toshiharu Suzuki
Published: October 2002

P+-n diodes with shallow junctions less than 50 nm deep were formed utilizing single pulse excimer laser annealing. The diode characteristics and the crystallinity near the junctions was investigated and it was found that the characteristics were improved by annealing the sample at 600° C for 1 h prior to excimer laser annealing. A low leakage current density of ≤10 nA/cm2 under reverse bias and ideal I–V curves of 60 mV/dec. over 7 decades under forward bias were obtained. The average leakage current and the device to device leakage current fluctuation were both reduced when the pre-annealing was used. The crystallinity near the junction was investigated by cross sectional transmission electron microscopy (TEM).
Influence of Oxygen and Nitrogen in the Intrinsic Layer of a-Si:H Solar Cells
Authors: Kinoshita Toshihiro , Isomura Masao , Yoshihiro Hishikawa Yoshihiro Hishikawa , Shinya Tsuda Shinya Tsuda
Published: October 2002

The effects of oxygen and nitrogen on hydrogenated amorphous silicon (a-Si:H) films and solar cells are systematically studied in the initial and light-soaked states. The oxygen and nitrogen concentrations were varied from 1018 to 1021 cm-3 and 1016 to 1019 cm-3, respectively. In the initial state, dark conductivity and photoconductivity increase, and the activation energy of dark conductivity decreases with increase in the oxygen and nitrogen concentrations, because of the creation of donorlike states. These film properties after light-soaking, however, are independent of the oxygen and nitrogen concentrations, probably because they are dominated by light-induced states. On the other hand, the conversion efficiency of solar cells in both the initial and light-soaked states drops as the oxygen and nitrogen concentrations increase. Collection efficiency measurements show that the electric field distribution in the i-layer is affected by the donorlike states even after light-soaking. The photovoltaic properties of solar cells more sensitively reflect the effect of oxygen and nitrogen incorporation than the film properties.
Thermal Analysis of Chemical Reaction Forming the CuGaSe2 Single Phase
Authors: Hiroaki Matsushita Hiroaki Matsushita , Hiroyuki Jitsukawa Hiroyuki Jitsukawa , Takeo Takizawa Takeo Takizawa
Published: October 2002

The chemical reaction which forms the CuGaSe2 phase has been investigated by differential thermal analysis and powder X-ray diffraction. The two mixtures of CuGa+2Se and Cu+Ga+2Se are used as starting materials. In the former mixture, the CuGaSe2 phase has been formed incompletely below the melting point of CuGaSe2. In the latter mixture, the CuGaSe2 phase has been formed by the exothermic reaction between CuSe2 and Ga phases at about 900°C, after the formation of the CuSe2 phase below 380°C. In contrast to the case of CuInSe2, the selenization of CuGa alloy is not necessarily required for growing the CuGaSe2 single phase. The chemical reaction between Cu selenides and Ga at temperatures higher than 900°C works to remove heterogeneous products and form a CuGaSe2 single phase.
A Comprehensive Study of High-Level Free-Carrier Injection in Bipolar Junction Transistors
Authors: Yue Y. , Liou J. J. , Ortiz-Conde A. , Garcia Sanchez F.
Published: October 2002

This paper presents a comprehensive study on the effects of high-level free-carrier injection on the current transport of bipolar junction transistors (BJTs). Detailed information for the free-carrier concentration, electric field, and drift and diffusion current components in the quasi-neutral base (QNB) under high-level injection are calculated using the modified ambipolar transport equation and using several different approximations for the majority-carrier current in the QNB. It is shown that high-level injection can create a large retarding field which is in the opposite direction of the built-in field associated with the nonuniform doping concentration. High-level injection also enhances recombination in the QNB, thus resulting in a position-dependent minority-carrier current in the region even if the base is thin. Our results further suggest that the widely used zero majority current approximation gives rise to a larger error compared to other lesser known approximations.
Angle Resolved X-Ray Photoelectron Spectroscopic Analysis on the Surface of Wet-etched Copper
Authors: Kang Min-Gu , Jo Moon-Ho , Kim Hyung-Ho Park
Published: October 2002

Thermally evaporated copper was chemically etched with 3.5M CuCl2+0.5M HCl+0.5M KCl solution at room temperature. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface chemical bonding states. The result shows that chemically etched copper surface is composed of carbon, oxygen, chlorine, and copper. The bonding state of the surface has been known to be indistinguishable due to their small chemical shift in the photoelectron spectra. However, using the nondestructive angle resolved XPS technique the distribution of bonding states was revealed. They could be completely distinguished through the qualitative and quantitative comparison of related bonding states in the observed elements. After air exposure of wet etched Cu for 2 days, the bonding state of the surface was also analyzed quantitatively through photoelectron and Auger electron spectroscopic works.
Determination of Thickness of Thin Thermal Oxide Layers on Czochralski-Grown Silicon Wafers from their Longitudinal Optical Vibrational Mode
Authors: Hiroshi Shirai Hiroshi Shirai , Ryuji Takeda Ryuji Takeda
Published: October 2002

Infrared transmission spectra of the longitudinal optical (LO) mode (1250 cm-1) of thin thermal oxide layers (10–100 Å, formed at 800–950° C in O2 or O2 diluted with N2) on silicon wafers were measured at p-polarized 73.7° incidence, based on the Berreman effect. An excellent linear correlation was found between the LO absorbance and the oxide thickness, which exhibits no dependence upon the oxygen content in silicon.
Incoherence Effect of Single-Mode Pump on Second-Harmonic Generation
Authors: Zhou Wang-Long , Mori Yusuke , Takatomo Sasaki Takatomo Sasaki , Sadao Nakai Sadao Nakai
Published: October 2002

A single-mode laser beam has a partially incoherent nature. By expressing such a single-mode beam as an array of square-root damping waves, we have derived a factor that describes the influence of the incoherence of a single-mode pump on second-harmonic generation. This factor is analytically formulated as a function of the ratio of crystal length to laser coherence length. When this ratio is smaller than 1.1, the value of the factor is above unity with a maximum of 1.253, indicating that a single-mode pump leads to enhanced second-harmonic intensity.
Compensation for Birefringence of Oriented Polymers by Random Copolymerization Method
Authors: Iwata Shuichi , Tsukahara Hisashi , Eisuke Nihei Eisuke Nihei , Yasuhiro Koike Yasuhiro Koike
Published: October 2002

Birefringence is caused by orientation of polymer chains during injection molding or extrusion, and is a large obstacle to optical applications. Transparent zero-birefringence copolymers were successfully synthesized by randomly copolymerizing two monomers having positive and negative birefringence, respectively. Since the anisotropic polarization of the negative birefringent monomer units is compensated by the positive birefringent monomer units on the same polymer chain, the birefringence is compensated on the length scale of only several monomer units and becomes zero for any degree of orientation. Methyl methacrylate (MMA) was used as the negative birefringent monomer, and 2,2,2-trifluoroethyl methacrylate (3FMA) as the positive birefringent monomer. Poly(MMA-co-3FMA) copolymer synthesized with a composition of MMA/3FMA=45/55 (wt./wt.) showed no birefringence for any draw ratio when a sample film was uniaxially heat-drawn to 3.5 times its original length. The total scattering loss of the zero-birefringence copolymer was 65.9 dB/km, which is comparable to those of homopolymers.
Pt/PZT/n-SrTiO3 Ferroelectric Memory Diode
Authors: Gotoh Kohtaroh , Tamura Hirotaka , Takauchi Hideki , Yoshida Akira
Published: October 2002

We fabricated a new nonvolatile ferroelectric memory, which consists of vertical metal-ferroelectric- semiconductor diodes. Our diode has a simpler structure than an Ferroelectric Random Access Memory (FRAM) cell, and operates at a lower voltage than Metal Ferroelectric Semiconductor Field Effect Transistors (MFS-FETs) or conventional flash memories. We demonstrated the memory operation using a Pt/PZT/n- SrTiO3 diode in this work. We deposited (001)-oriented PZT on (100) 0.5 wt% Nb doped n-type SrTiO3 substrate using a laser ablation technique. The diodes had a hysteresis loop in their capacitance-voltage characteristics due to ferroelectric polarization in the PZT layer. Their current-voltage curves were Schottky-diode-like and also had a hysteresis loop due to the ferroelectric remanent polarization. We confirmed correct nonvolatile and nondestructive memory readout operation. The write voltages were -5 V to write a logic “0” and above 2.5 V to write a logic “1”. The read voltage was 0.8 V.
Optical Properties of Er-Doped CuAlS 2
Authors: Yasukazu Kimura Yasukazu Kimura , Tsuyoshi Ohgoh Tsuyoshi Ohgoh , Igor Aksenov Igor Aksenov , Katsuaki Sato Katsuaki Sato
Published: October 2002

Photoluminescence (PL) spectra of Er-doped CuAlS2 single crystals grown by the chemical vapor transport technique were studied for the first time. Two kinds of crystals were prepared under different doping conditions, i.e., one was doped with Er alone (type I crystals) and the other were doped with Er and a very small amount of Fe (type II crystals). PL spectra of both type I and type II crystals showed three sharp emissions, at 2.34 eV (A-emission), 2.26 eV (B-emission) and 1.85 eV (C-emission), which were attributed to 2H11/2 →4I15/2, 4S3/2 →4I15/2 and 4F9/2 →4I15/2 f-f transitions of Er3+ ions, respectively. The intensity of f-f emisions in type II crystals was substantially larger than that in type I crystals. The emission peak at 2.34 eV (A-emission) has an excitation band at 3.24 eV, which is assigned to 4I15/2 →4G11/2 transitions of Er3+ ions on the Dieke diagram. In addition to the Er-related f-f emissions, a broad yellow-orange emission band was observed in both crystals at low temperatures. The yellow-orange emission dominated the room-temperature (RT) emission spectra of type I crystals, whereas the emission was almost quenched at RT in the case of type II crystals. The enhancement of Er-related emission and the quenching of the yellow-orange emission due to the presence of Fe impurity are discussed in terms of the site preference and the charge neutrality requirement.
Transient Measurements of the Excitation Efficiency in ZnS-based Thin Film Electroluminescent Devices
Authors: Zeinert Andreas , Barthou Charles , Benoit Paul Benalloul
Published: October 2002

A series of electric pulses is applied to virgin alternating-current thin film electroluminescent ZnS-based samples in order to investigate the behaviour of the excitation efficiency within the first drive periods. One observes a decrease of the excitation efficiency from the first pulse on. The steady state values of the transferred charge and the excitation efficiency are attained after about ten drive periods. These transient measurements permit one to investigate the establishment of the bulk space charge in the ZnS layer in this kind of devices.
Analysis of Radiation Damage to Si Solar Cells under High-Fluence Electron Irradiation
Authors: Yamaguchi Masafumi , Taylor Stephen J. , Yang Ming-Ju , Matsuda Sumio , Kawasaki Osamu , Hisamatsu Tadashi
Published: October 2002

Radiation testing of Si n+–p–p+ space solar cells has revealed an anomalous increase in short-circuit current I
sc, followed by an abrupt decrease and cell failure, induced by high-fluence (>1016 cm-2) electron irradiation. A model which can be used to explain these phenomena by expressing the change in majority-carrier concentration p of the base region as a function of the electron fluence has been proposed in addition to the well-known model in which I
sc is decreased due to minority-carrier lifetime reduction with irradiation. The reduction in p due to majority-carrier trapping by radiation-induced defects has two effects; one is broadening of the depletion layer which contributes to the increase in the generated photocurrent and that in the recombination-generation current in the depletion layer, and the second is an increase in the resistivity of the base layer resulting in an abrupt decrease of I
sc and failure of the solar cells.
Hydrogen Passivation of Donors and Hydrogen States in Heavily Doped n-Type Silicon
Authors: Fukata Naoki , Sasaki Shinichi , Fujimura Shuzo , Haneda Hajime , Kouichi Murakami Kouichi Murakami
Published: October 2002

We have studied hydrogen passivation of phosphorus (P) donors and hydrogen states in heavily doped n-type silicon by electron spin resonance (ESR) of P donors and conduction electrons. A remote-treatment method of atomic hydrogen was used for the introduction of H atoms. The hydrogen passivation fraction measured in the P-doped Si samples shows strong dependence on donor concentration. The most effective substrate temperature for hydrogen passivation is between 100 and 120° C. It is found, from the reactivation of hydrogen-passivated P donors by isochronal annealing, that the recovery stage of P donors shifts to higher temperatures with decreasing donor concentration. These results suggest that the binding of the P–Si–H complex due partially to the Coulomb interaction decreases with increasing P concentration. Hydrogen-induced platelets are also discussed.
Binary Crystallizable Glass Composite for Low-Dielectric Multilayer Ceramic Substrate
Authors: Jau-Ho Jean Jau-Ho Jean , J.-I. Shen J.-I. Shen
Published: October 2002

A binary crystallizable glass composite containing cordierite glass and anorthite glass for applications in the area of low-dielectric multilayer ceramic packaging has been investigated. The initially amorphous glass composite forms crystalline phases of anorthite and cordierite during firing, and can be densified up to a relative sintered density greater than 97% at 875° C for 15–60 min. The resultant composites have a dielectric constant in the range of 4.7–5.3 at 1 MHz and a linear thermal expansion coefficient of 3.7–5.1×10-6 K-1 in the temperature range of 20–200° C.
Microstructural Characteristics of Ba(Mg1/3Ta2/3)O3 Ceramics and Its Related Microwave Dielectric Properties
Authors: Youn Hyuk-Joon , Kim Kyung-Yong , Hwan Kim Hwan Kim
Published: October 2002

Microstructural characteristics such as second phases, defect types and order structure were investigated in Ba(Mg1/3Ta2/3)O3 [BMT] ceramics using X-ray powder diffraction, scanning electron microscopy, wavelength-dispersive spectroscopy, and transmission electron microscopy. Two types of second phases having higher and lower Ba/Ta ratio compared to stoichiometric BMT, maybe exist in calcined powder of BMT. While one of them was consumed during sintering for 2 h, the other was remained after sintering. These results were discussed in terms of probable defect types in matrix of BMT. The presence and change of specific defect types can be correlated with the contribution of specific defect types to sintering behavior. Theoretical intensity of (100) superlattice reflection and saturated order parameter was also discussed. The microwave dielectric properties of sintered samples was discussed in terms of the presence of second phase and thus related defects types.
A New Write Compensation Pulse for High-Density Recording on Magnetically Induced Super Resolution (MSR) Media
Authors: Kanno Masayoshi , Okumura Mariko , Nakaoki Ariyoshi , Masahiko Kaneko Masahiko Kaneko , Hideo Owa Hideo Owa
Published: October 2002

We have studied the write power margin for an magnetically induced super resolution (MSR) by front aperture detection (FAD) disk system and investigated a method for evaluating jitter which uses XY-mapping visualization. Using this method, we evaluated the effect of conventional write compensation on the shifts of the leading and trailing edges and developed a new write compensation pulse that is optimized for a high density system such as the ISO 8X. We confirmed the advantages of using the new write compensation pulse for MSR.
The Role of Processing Variables in the Flux Growth of Lead Zinc Niobate-Lead Titanate Relaxor Ferroelectric Single Crystals
Authors: Mulvihill Maureen L. , Park Seung Eek , Risch George , Li Zhuang , Kenji Uchino Kenji Uchino , Thomas R. Shrout Thomas R. Shrout
Published: October 2002

Relaxor ferroelectric single crystals of Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZN-PT) are of interest as high performance transducers due to their very large piezoelectric coupling and dielectric properties. A high temperature flux solution method was used to grow (1- x)PZN-( x)PT, where x= 0.0, 0.1 and 0.15 single crystals. Processing conditions were optimized to increase the size and yield of the perovskite crystals, including variation of the flux to composition ratio, cooling rate, soak time and soak temperature. The crystals varied in size from 0.01 cm to 1.5 cm on an edge, and in color from opaque to brown due to the changes in processing conditions. The crystals were characterized by XRD, dielectric constant and dielectric loss measurements. As the content of PT increased the transition from the paraelectric to the ferroelectric phase approached first order behavior and the crystal structure transformed from rhombohedral to tetragonal. This structure transition caused the lattice constant along the c-axis to elongate as the c/a ratio increased. At room temperature, the dielectric constants for the PZN-PT compositions along the [111] or [001] axes were as great as 5000 and the dielectric losses were as low as 0.01.
Sequential Deposition of NbN/MgO Film on Si(100) Using Pulsed KrF Excimer Laser Deposition Method with Different Ambiences
Authors: Hiroshima Yasushi , Ishiguro Takashi , Kobayashi Takashi
Published: October 2002

Sequential formation of NbN/MgO bilayers on Si(100) using pulsed KrF excimer laser deposition with different ambiences of oxygen and nitrogen has been performed. The effects of nitrogen ambience on the NbN formation in this sequential process are examined. The deposited films are characterized by X-ray ( Cu-Kα) diffraction, X-ray photoelectron spectroscopy and measurement of the critical temperature of superconducting transition. The concentration of nitrogen in the NbN film increases with the ambient pressure up to 9×10-2 Torr and superconducting transition is observed at ∼12.7 K. However, the plume distribution became broader with increasing N2 gas pressure and non- negligible oxidation of the NbN films occurred. The reasons for the oxidation problem are related to the enhancement due to the multiple collisions between the ablated particles and oxygen impurity, which is mainly generated by resputtering from the surfaces of both the previously deposited MgO film substrate and its holder.
Solid-Phase Reactions of Diffusion Barriers of Ti and TiN to Copper Layers on SiO2
Authors: Takeyama Mayumi , Noya Atsushi , Sakanishi Kouichirou , Sasaki Hikaru Seki
Published: October 2002

Thin films of Ti and TiN interposed between the Cu layer and SiO2 are examined as a diffusion barrier as well as an adhesion-promoting layer for Cu metallization technology. Solid-phase reactions and/or interdiffusion taking place in the Cu/Ti/ SiO2/Si and Cu/TiN/ SiO2/Si systems are examined by X-ray diffraction and the depth profiling method using Auger electron spectroscopy and X-ray photoelectron spectroscopy. The reduction of SiO2 through the formation of Ti-oxides occurs at the Ti/ SiO2 interface even in the as-deposited Cu/Ti/ SiO2/Si system. In addition to this, the formation of Ti5Si3 and interdiffusion which result in the formation of Cu–Ti intermetallic compounds due to annealing at 450° C are evident, and lead to intermixing of the whole system. The use of TiN instead of Ti drastically suppresses the reaction and interdiffusion, and the Cu/TiN/ SiO2/Si system is stable even after annealing at 850° C, though the incorporation of a small amount of Ti into the Cu layer is observed.
Surface Smoothness and Step Bunching on GaAs (111)B Facets Formed by Molecular Beam Epitaxy
Authors: Nakamura Yusui , Tanaka Ichiro , Takeuchi Norishige , Koshiba Shyun , Noge Hiroshi , Sakaki Hiroyuki
Published: October 2002

GaAs trapezoidal structures grown by molecular beam epitaxy on mesa-patterned (001) substrates have been studied by atomic force microscopy to clarify the morphology of (111)B facet planes. It is found that multi-atomic steps of 1–4 nm in height Δ appear on the facets with typical periods Λ of 30–60 nm. When the mis-orientation angle Δθ of mesa-stripes with respect to [110] increases from 2° to 7°, the corrugation height Δ is found to increase monotonically. Thus the mis-orientation angle Δθ must be minimized to form smooth facet structures.
Surface Structure of Zr–O/W(100) System at 1700 K
Authors: Irokawa Yoshihiro , Mitsuhashi Riichirou , Lee Suchan , Min Kyung-youl , Inoue Masahiko , Yoshihide Kimura Yoshihide Kimura , Ryuichi Shimizu Ryuichi Shimizu
Published: October 2002

The surface structure of Zr–O/W(100) at 1700 K was studied by reflection high-energy electron diffraction and ion scattering spectroscopy. It has been revealed that Zr atoms align themselves to form p(1×1) structure in the topmost atomic layer of the Zr–O/W(100) surface at 1700 K.
Resonant Directional Excitation of Helicon Waves by a Helical Antenna
Authors: Keiji Suzuki Keiji Suzuki , Keiji Nakamura Keiji Nakamura , Hideo Sugai Hideo Sugai
Published: October 2002

High-density plasmas are produced by 13.56 MHz, 1–2 kW discharges in a magnetic field B
0 of 0.02 T, using a helical antenna of length d=12–24 cm and azimuthal rotation of π. When the direction of B
0 is reversed, the positions of the highest electron density and the highest wave amplitude move from one side of the antenna to the other side. In order to understand such behavior, a small-amplitude wave is excited in the helicon plasma using three types of antennas: right-hand (M=+1), left-hand (M=-1) and linear (M=±1) polarization antennas. Only right-hand polarized waves are observed irrespective of antenna type. In the case of the M=+1 antenna, large-amplitude helicon waves are resonantly launched toward one side of the antenna when the axial wavelength λ//∼d or 2d. Such antenna action is explained in terms of wave interference.
Energy Transfer to Gas-Puff Z-Pinch and X-Ray Radiation
Authors: Keiichi Takasugi Keiichi Takasugi , Hideaki Suzuki Hideaki Suzuki , Kinya Moriyama Kinya Moriyama , Tetsu Miyamoto Tetsu Miyamoto
Published: October 2002

Gas-puff z-pinch plasmas were generated using rare gases (Ne, Ar and Kr). The intensities of XUV and X-ray radiations increased with atomic number Z of the gas. The net energy transferred to the plasma also increased with Z of the gas, which is a direct result of strong radial compression of the plasma column. Multiple ionization plays an important role in the strong compression of the high Z z-pinch plasma.
Creeping Discharge Characteristics under Rectangular Pulse Voltage in SF6 Gas
Authors: Nakayama Hiroshi , Onoda Mitsuyoshi , Nishida Tsuyoshi , Kubota Takehumi , Humihiro Kamatani Humihiro Kamatani , Katunori Watabe Katunori Watabe
Published: October 2002

The effect of a barrier set up between a needle and a plate in SF6 gas was investigated under pulse voltage. It was found that inserting a barrier resulted in unusual bending of the creeping discharge path and extension of the equivalent length between electrodes. Consequently, a long time lag of breakdown and high breakdown voltage were obtained.
Positive Ions in RF Discharge Plasma of CF 4 Gas in a Planar Diode
Authors: Itsuo Ishikawa Itsuo Ishikawa , Shinya Sasaki Shinya Sasaki , Kazuya Nagaseki Kazuya Nagaseki , Yukinori Saito Yukinori Saito , Shinji Suganomata Shinji Suganomata
Published: October 2002

Positive ions were measured in situ by direct sampling from CF4 discharge space at 13.56 MHz using a quadrupole mass spectrometer. CF3
+ is observed predominantly with smaller amounts of CF2
+ and CF+. With increasing RF power, both CF2
+ and CF+ shift to the lower energy side of CF3
+, and their intensities tend to increase. Such a phenomenon is also observed as controlling the potential of a sampling tip externally. These seem to suggest that CF2
+ and CF+ are produced mainly in the sheath region.