bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Investigation on Silicon-Nitride Film Growth: Statistical Approach
Authors: Ishitani Shiro Koseki , Fujimura Yuichi
Published: October 2002

The dependence of SiN

x

film growth on the initial energy was investigated theoretically using a statistical model based on nonempirical molecular orbital results. Our theoretical calculations successfully explain the experimental finding that it is easier to control the ratio of Si–N and Si–Si bond yields when a mixture of SiH2Cl2 and NH3 rather than that of SiH4 and NH3 is used as the source gas.
Gettering Characteristics of Heavy Metal Impurities in Silicon Wafers with Polysilicon Back Seal and Internal Gettering
Authors: Ogushi Satoshi , Sadamitsu Shinsuke , Marsden Kieran , Yasuo Koike Yasuo Koike , Masakazu Sano Masakazu Sano
Published: October 2002

The gettering behavior of polysilicon back seal (PBS) and internal gettering (IG) with isothermal annealing (600–1000° C) was systematically investigated for Fe contamination by deep level transient spectroscopy (DLTS). There was a clear dependence of the PBS gettering efficiency on the PBS deposition temperature and on annealing temperatures used in the gettering processes. The use of lower deposition temperatures and lower gettering temperatures resulted in a higher gettering efficiency. IG efficiency has a clear dependence on size and density of the oxygen precipitate. In the case of a bulk micro defect (BMD) density of 105 cm-2, it was necessary for the platelet oxygen precipitate size to be larger than 200 nm, while a polyhedral oxygen precipitate size of 100 nm was sufficient in obtaining IG effects for an Fe contamination level of 1012 atoms/cm3. The gettering efficiency has a clear correlation with the volume of the oxygen precipitates per unit volume of the silicon wafers. These results suggest that Fe atoms are gettered within the oxygen precipitates and not in the area surrounding them.
As Surface Segregation during the Growth of GaInP on GaAs
Authors: Dehaese Olivier , Wallart Xavier , Olivier Schuler Olivier Schuler , Francis Mollot Francis Mollot
Published: October 2002

We have studied the interface between GaInP and GaAs grown by gas source molecular beam epitaxy using X-ray photoelectron spectroscopy. The presence of As atoms at the phosphide surface is detected, even for an epilayer thickness as large as 5000 Å. We show that this can be explained by the segregation of a small amount of As (∼1%) incorporated during GaInP growth. On the other hand, a large (∼6 monolayers) interface broadening is observed and results mainly from the incorporation of a large amount of As at the interface due to gas mixing during the commutation. Although a large difference in chemical bond strength exists between anions and cations at the interface which could lead to important interdiffusion processes, the reaction between GaAs and GaInP is impeded at 500° C. This implies that, at this temperature, kinetic factors are dominant. Hence, with an optimized gas commutation sequence, it should be possible to grow nearly abrupt interfaces between GaInP and GaAs at 500° C.
Atomically Flat 3C-SiC Epilayers by Low Pressure Chemical Vapor Deposition
Authors: Yuuki Ishida Yuuki Ishida , Tetsuo Takahashi Tetsuo Takahashi , Hajime Okumura Hajime Okumura , Sadafumi Yoshida Sadafumi Yoshida , Toshihiro Sekigawa Toshihiro Sekigawa
Published: October 2002

We have investigated the heteroepitaxial growth of 3C-SiC on Si by low pressure chemical vapor deposition (LPCVD) using a silane-propane-hydrogen reaction gas system. By the growth at low pressure below 10 Torr, several problems arising from atmospheric pressure CVD (APCVD) were solved, namely the growth of protrusions was suppressed and thickness uniformity was improved. Moreover, atomically flat surfaces were obtained. Although the growth temperatures in the case of LPCVD were lower than those in the case of APCVD, LPCVD epilayers showed excellent crystallinity and luminescence properties, comparable with those of APCVD epilayers.
Growth and Characterization of CuInS2 Films grown by Rf Ion-Plating
Authors: Kondo Ken-ichi , Nakamura Susumu , Sano Hiroyuki , Sato Hiroshi Hirasawa
Published: October 2002

Films of the chalcopyrite semiconductor C
u
I
n
S
2 were grown by rf ion-plating at a relatively low substrate temperature of 400° C, which allows us to use a large size inexpensive glass substrate, for various levels of substrate bias, ranging from +50 V to -50 V. The Cu and In compositions were controlled by varying the electron beam power of the Cu2S and In2S3 sources. There were significant differences in the surface morphology and crystallinity between films prepared under either negatively biased or floating conditions and films prepared under either positively biased or grounded conditions. Single phase CuInS2 films of good quality were obtained when the substrate was subjected to the floating conditions. Cu ions seem to play a very important role in the growth of Cu

x

S

y

which acts as an accelerator for growing good crystalline CuInS2 at a relatively low temperature.
A Generalized Expression for Collector Transit Time of Heterojunction Bipolar Transistors Taking Account of Electron Velocity Modulation
Authors: Hiroki Nakajima Hiroki Nakajima
Published: October 2002

A generalized expression for the collector transit time of heterojunction bipolar transistors is derived taking account of the electron velocity modulation effect. The derivation requires no assumption for the electron velocity profile and the obtained simple expression includes all the previous analytic models. The validity of the generalized expression is confirmed by the fact that the expression can be derived independently from both the induced-current-phase-delay and the charge-control perspectives.
P-type AlAs Growth on a GaAs (311)B Substrate Using Carbon Auto-Doping for Low Resistance GaAs/AlAs Distributed Bragg Reflectors
Authors: Akimasa Mizutani Akimasa Mizutani , Nobuaki Hatori Nobuaki Hatori , Noriyuki Ohnoki Noriyuki Ohnoki , Nobuhiko Nishiyama Nobuhiko Nishiyama , Nobuyuki Ohtake Nobuyuki Ohtake , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: October 2002

A high p -type hole-concentration AlAs layer has been successfully grown on a GaAs (311)B substrate by metalorganic chemical vapor deposition with using a Carbon auto-doping technique. The doping concentration was well controlled by changing only V/III ratios. The hole concentration was as high as 2 ×1019 cm-3 at a V/III ratio of 6. A very low resistance of p -type distributed Bragg reflector was obtained with a δ-doping technique to GaAs/AlAs interfaces.
Large Inductance Superconducting Quantum Interference Device Magnetometer for Magnetoencephalography Measurement
Authors: Ahmad Rashdi Shah , Kubo Masateru , Hirata Yoshihiro , Kuriki Shinya , Nakayama Satoshi
Published: October 2002

The characteristics of the low T
c dc superconducting quantum interference devices (SQUIDs) having a large inductance of 1 nH were investigated. The degradation of the modulation voltage due to the large inductance parameter β L was recovered by damping the SQUID inductance with a resistor having twice the junction resistance. The modulation voltage of 20 µ V was close to the value given by the computer simulation. The value of the measured flux noise, using a dc bias flux-locked-loop with a cooled tank circuit, of 21 µΦ0/√ Hz was about 8 times larger than the theoretical value. The flux noise at the white region increased to 39 µΦ0/√ Hz after removing the tank circuit, but because of the improved flux transfer efficiency from the input coil to the SQUID a white field noise of about 10 fT/√ Hz was obtained using a second order axial gradiometer. A clear auditory evoked field was observed using the large β L SQUID magnetometer which was directly coupled to the amplifier.
Optimum Thickness of Magnetic Layer for Short-Wavelength Magnetic Recording
Authors: Kitaori Noriyuki , Osamu Yoshida Osamu Yoshida , Hirohide Mizunoya Hirohide Mizunoya
Published: October 2002

Metal-evaporated (ME) tape contains no resin therefore, it has a high magnetic flux density that is superior to that of a conventional metal-powder (MP) tape. Thus, the ME tape has potential for use in high-density magnetic recording and in other new types of media. We prepared tapes whose magnetic layer thickness varied between 540 Å and 3190 Å. The tapes were produced continuously using Co oblique evaporation onto a base film. The fixed coercive force was maintained at about 1400 Oe. Using these tapes, we determined the optimum magnetic layer thickness needed to obtain a high video performance at short recording wavelengths. We also determined that the magnetic tape must have a certain minimum thickness for recording within a given system, and that the optimum thickness increases at a rate of 6% compared to the increase in the recording wavelengths. The difference from the theoretical ratio of 25% is thought to be due to the actual head gap length (0.22 µ m).
High Stability Resonator for Pulsed Solid State Lasers
Authors: Chu Hong , Jhon Young Min , Plotnikov Sang Sam Choi
Published: October 2002

We propose a new resonator configuration which has high stability against mirror misalignment and also has high damage threshold suitable for pulsed laser operation. It was experimentally shown that in our new resonator scheme with appropriate parameters, the output energy was practically stable for mirror misalignment tilting angle up to ±30 mrad, which is 20 times larger than that with ordinary resonator configurations.
Femtosecond Optical Pulse Compressor Using CS 2 Liquid-Core Fiber with Negative Delayed Nonlinear Response
Authors: Yasuhiro Sato Yasuhiro Sato , Ryuji Morita Ryuji Morita , Mikio Yamashita Mikio Yamashita
Published: October 2002

We propose a new femtosecond optical pulse compressor using a CS2 liquid-core fiber with negative delayed nonlinear response through induced-phase modulation in a normal-dispersion region. We numerically confirm that, with a 23 kW, 100 fs pump pulse, a 100 fs hyperbolic-secant pulse is compressed to ∼30 fs by this compressor without any additional external phase compensation. From the comparison of effective nonlinear refractive index between CS2 and silica fibers, it is shown that the efficiency of this compressor is almost the same as that of the conventional silica fiber-grating compressor.
Selected-area Deposition of Diamond Films on Silicon Nitride-coated Silicon Substrates Using Negatively Biased Microwave Plasma Enhanced Chemical Vapor Deposition Technique
Authors: Chen Yung-Hsin , Lin Chen-Ti Hu
Published: October 2002

Selected-area deposition (SAD) of diamond films has been successfully grown on silicon substrates, using silicon-rich nitride (SiN) precoatings and a negatively biased microwave plasma enhanced chemical vapor deposition technique. However, diamond growth is limited on stoichiometric nitride ( Si3N4) precoatings, which are ascribed to the insulation of these layers. The application of a negative bias voltage is thus blocked. Lowering the total pressure in the CH4/H2 mixture from 75 Torr to 60 Torr significantly suppresses the nucleation of diamonds on the Si-substrate, without modifying it on the SiN-substrate, so that a high selectivity (>200) SAD diamond film is obtained. Optical emission spectroscopy (OES) indicates that the large etching rate on the Si-surface, due to the reduction in the carbonaceous-to-hydrogen ratio, is the main factor of nucleation suppression. Scanning electron microscopy (SEM) and Raman spectroscopy indicate that the SAD and the quality of diamonds is optimized under deposition conditions such as 60 Torr total pressure, 2500 W microwave power, CH4-to-H2=15:300 sccm and 120 VDC bias.
A Chemical Dry Etching of Si and SiO2 Substrates by F atoms in a Discharge Flow
Authors: Masaharu Tsuji Masaharu Tsuji , Yukio Nishimura Yukio Nishimura
Published: October 2002

F atoms were generated by a low power microwave discharge of various Ar/CF4 mixtures in a fast discharge flow. They were used for Si and SiO2 etching at room temperature. The variations of the relative concentration of F as functions of various etching parameters were monitored by observing CH( A2Δ– X2Π r) emission resulting from the Ar(3P0,2)/CH3 reaction. The emission spectra of Ar/CF4 mixtures in the microwave discharge indicated that CF4 was decomposed into C and F atoms in the discharge region because of the lack of emissions from CF*, CF2
*, and CF3
*. The etching rates of Si and SiO2 were about 700 and 70 Å/min, respectively, at a microwave power of 100 W, an Ar flow rate of 3000 sccm, a CF4 flow rate of 250 sccm, a total pressure of 0.23 Torr and a distance between the center of discharge and the substrate of 12 cm.
Atomic Scale Indium Distribution in a GaN/In0.43Ga0.57N/Al0.1Ga0.9N Quantum Well Structure
Authors: Kisielowski Christian , Liliental-Weber Zuzanna , Nakamura Shuji
Published: October 2002

Quantitative high resolution electron microscopy (HRTEM) is used to map the indium distribution in a GaN/In0.43Ga0.57N/Al0.1Ga0.9N quantum well at the atomic scale. Samples with atomically flat surfaces were prepared for microscopy by anisotropic chemical etching. The developed preparation procedure minimizes a possible confusion of thickness variations with local compositional fluctuations in the lattice images. An irregular distribution of indium is observed that is attributed to the formation of clusters with estimated diameters of 1–2 nm. The indium concentration gradient across GaN/In0.43Ga0.57N interfaces is measured to extend typically over a distance of 1nm. It is more than twice as large across the In0.43Ga0.57N/Al0.1Ga0.9N interface. Indium segregation into the Al0.1Ga0.9N layer during crystal growth is likely to cause this unusual large width of the In0.43Ga0.57N/Al0.1Ga0.9N interfaces. This introduces an asymmetric In distribution across the quantum well with respect to the growth direction.
Ferromagnetic Resonance in Cobalt-Modified Iron-Oxide Particulate Tapes
Authors: Osamu Kohmoto Osamu Kohmoto
Published: October 2002

The magnetic anisotropy field (H
a) of Co-modified- Fe3O4 acicular particles in particulate tapes was studied using ferromagnetic resonance. The value of H
a of the particles has been determined to be 3.50 kOe, assuming a saturation magnetization (M) of 0.398 kG. Since the anisotropy field due to the acicular shape anisotropy is calculated to be 2.34 kOe for the particles with an axial ratio of 10, the contribution to H
a of the Co modification on the particle surface is estimated to be 1.16 kOe.
Evaluation of Electrical Properties of Evaporated Thin Films of Metal-Free, Copper and Lead Phthalocyanines by In-Situ Field Effect Measurements
Authors: Kudo Kazuhiro , Sumimoto Tsutomu , Hiraga Kouji , Shigekazu Kuniyoshi Shigekazu Kuniyoshi , Kuniaki Tanaka Kuniaki Tanaka
Published: October 2002

We have fabricated thin-film transistors consisting of evaporated thin films of metal-free, copper and lead phthalocyanines, and estimated the electrical parameters of carrier mobility, carrier concentration and electrical conductivity by in-situ field effect measurements. We have also investigated the effect of introducing of oxygen gas into the vacuum chamber and of thermal annealing on the electrical parameters of the films. We found that the carrier concentration and carrier mobility are strongly influenced by the metals in the phthalocyanine molecules and by oxygen gas exposure.
The Analysis of Trace Impurities in Nitrogen Gas by High Pressure Ionization Mass Spectrometry
Authors: Ishihara Yoshio , Umehara Hitomi , Akira Nishina Akira Nishina , Tetsuya Kimijima Tetsuya Kimijima
Published: October 2002

We developed high pressure ionization mass spectrometry (HPIMS) to monitor trace impurities in nitrogen ( N2) gas in order to establish an ultra-high purity (UHP) N2 supplying technology for ULSI fabrication. We also demonstrated that the oxygen ( O2), carbon dioxide ( CO2) and moisture ( H2O) in N2 can be measured with a high sensitivity and accuracy using HPIMS. The ion intensities of O2, CO2 and H2O in N2 with HPIMS was increased about one order of magnitude more than that with atmospheric pressure ionization mass spectrometry (APIMS). The excellent linearity between the ion intensity and O2 concentration was obtained with a correlation coefficient over 0.9999 in the range from 5 ppb to 50 ppb. The reproducibility and accuracy of measurement could be improved since the pressure of the ionization chamber was controlled precisely by using HPIMS.
New Data on the Nonlinear Optical Constant, Phase-Matching, and Optical Damage of AgGaS 2
Authors: Akiko Harasaki Akiko Harasaki , Kiyoshi Kato Kiyoshi Kato
Published: October 2002

The nonlinear optical constant of AgGaS2 was determined to be d
36 (AgGaS2)=(0.84 ±0.1) ×d
36 (AgGaSe2) =(34.8 ±4) pm/V from the direct comparison of the second-harmonic generation conversion (SHG) efficiencies of a CO2 laser at 9.2714 µm observed in AgGaSe2 under the identical experimental conditions. The phase-matching conditions for type-1 SHG in both AgGaS2 and AgGaSe2 are presented together with the damage thresholds at 9.2714 µm and 2.097 µm.
Influence of Gas Flow Conditions on Cluster Size Distribution in the Gas Evaporation Method
Authors: Koga Kenji , Ikeda Takuji , Ohshima Ken-ichi , Harutoshi Takeo Harutoshi Takeo
Published: October 2002

Cluster size distribution was found to be largely varied by altering the gas flow conditions in the gas evaporation method, where clusters are generated in one chamber and carried into the other chamber through a nozzle with a helium gas stream. Mean and mode diameters of clusters were found to be inversely proportional to the pressure difference between the two chambers, indicating that the gas flow condition influences the coalescence growth of the clusters in free space.
Stability, Bifurcation and Chaos of a Pendulum on a Rotating Arm
Authors: Zheng-Ming Ge Zheng-Ming Ge , Fu-Neng Ku Fu-Neng Ku
Published: October 2002

This paper presents an analytical and numerical study of the dynamical behavior of a pendulum on a rotating arm. There are four control parameters, which influences the behaviors of mechanical system, namely: the length ratio of the arm to pendulum, the damping, the frequency and the gravity force. The sufficient conditions for the stability are obtained using damped Mathieu equation theory and the Lyapunov direct method. It is found that stable equilibrium positions depend on four control parameters, the gravity force that appears as as an oscillating exciting torque and the length ratio in system causes the existence of a chaotic attractor or regular, several different types of transitions to chaos are studied. The Melnikov method is used to show the existence of chaotic motion. The treatment of the Melnikov integral is different for different length ratio. The magnitude effects of the length ratio parameter is important to acknowledge the existence of a chaotic attractor or regular motion. Moreover, numerical simulations including bifurcation diagrams are constructed to investigate dynamical behavior of the system. The transitions to chaos are confirmed by calculation of Lyapunov exponents. More detailed numerical investigations appear in phase trajectories and Poincaré maps.
Frequency Conversion of Magnetostatic Waves through Nonlinear Magnetization
Authors: Wang Qi , Li Chun-fang , Bao Jia-shan , Awai Ikuo , Boardman A. D.
Published: October 2002

The possibilities of the generation of the second-order dc and second-harmonic magnetic fields excited by the magnetostatic surface wave (MSSW) and backward volume wave (MSBVW) in ferromagnetic films have been analyzed and discussed through the calculations of the source terms in the equations satisfying the magnetostatic potentials. The results show that the nonlinear magnetization responses of the film to the MSSW can generate neither dc nor the second-harmonic magnetic fields, and the responses to the MSBVW will not induce the dc field, but could excite second-harmonics in the conditions of phase-matching andH0/M0≤cos2(θ/3). The general expressions of the third-order nonlinear magnetization induced by electromagnetic waves are also derived, and the contributions of the second-order magnetization are analyzed.
The Influence of the Buried Oxide Defects on the Gate Oxide Reliability and Drain Leakage Currents of the Silicon-on-Insulator Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: Iwamatsu Toshiaki , Ipposhi Takashi , Yamaguchi Yasuo , Imai Yukari , Maegawa Shigeto , Natsuro Tsubouchi Natsuro Tsubouchi , Tadashi Nishimura Tadashi Nishimura
Published: October 2002

The relation between gate oxide and buried oxide (BOX) reliabilities was investigated for several silicon on insulator (SOI) materials. The yield values of the gate oxide breakdown depend on the BOX leakage currents. The gate leakage currents and BOX leakage currents were observed at the same position by optical luminescence. By scanning electron microscope (SEM) observation at the luminescence region in the low-dose separation by implanted oxygen (SIMOX) substrate, it was found that the SOI layer had disappeared, and voids appeared in the BOX layer. In addition, Q
bd of the gate oxide was low in the capacitor where the BOX leakage currents were observed. It is thought that the crystalline quality of the SOI layer on the imperfect BOX layer was degraded, causing the gate leakage currents. Moreover, it was observed that the yield value of the drain leakage currents of the SOI metal-oxide-semiconductor field-effect transistors (MOSFET's) also depended on the BOX leakage currents.
Growth Mechanism in the Metalorganic Vapor Phase Epitaxy of Metastable GaP1-xNx Alloys: A Growth Interruption Study
Authors: Miyoshi Seiro , Yaguchi Hiroyuki , Onabe Kentaro , Shiraki Yasuhiro , Ryoichi Ito Ryoichi Ito
Published: October 2002

The metalorganic vapor phase epitaxy (MOVPE) of metastable GaP1-
x

N

x

alloys applying a growth interruption technique is performed. In the growth procedure, different from conventional MOVPE, a cycle of 1 ML growth and growth interruption (Ga precursor supply is turned off) is repeated. The nitrogen content (x) decreases with the increasing growth interruption time due to the desorption of nitrogen during the interruption. This means that the solid composition of the alloy is determined by the competition between the supply and the desorption of nitrogen at the film surface. The nitrogen adsorption/desorption model is presented. The time constant of the nitrogen desorption is obtained to be 0.47 s at 670° C. It is clarified that in the conventional (without growth interruption) MOVPE of the alloys, low growth temperature and high growth rate decrease the nitrogen desorption from the film surface and thus result in a large nitrogen content. We succeeded in growing the alloys with x as large as 6.3% by using a low growth temperature (650° C) and a high growth rate (5 MLs/s).
The Effect of Oxidation Source Gas on Epitaxial Al 2O 3 Films on Si
Authors: Takayuki Kimura Takayuki Kimura , Atsuhiro Sengoku Atsuhiro Sengoku , Hideki Yaginuma Hideki Yaginuma , Yoshitaka Moriyasu Yoshitaka Moriyasu , Makoto Ishida Makoto Ishida
Published: October 2002

Epitaxial growth of Al2O3 on Si has been investigated by using ultrahigh-vacuum chemical vapor deposition (UHV-CVD). Film thickness uniformity in a wafer was progressed by UHV-CVD method with a hot wall heating system, but the film surface morphology of grown films was worse than that grown by low-pressure chemical vapor deposition (LP-CVD) with a cold wall heating system. Reaction between Si surface and N2O was carried out by LP-CVD and UHV-CVD, and it is supposed that N2O gas etches the Si surface rather than O2 gas at the initial growth stage in UHV-CVD. High crystalline quality of Al2O3 films was obtained at 1000°C by changing the oxidation source gas from N2O to O2. Al2O3 film crystalline quality and electrical property were improved by using O2 gas.
Moisture Sensitivity of Holographic Gratings Recorded in Photosensitive Polyimide
Authors: Joudi El M. El , Dress P. , R. P. Podgorsek R. P. Podgorsek , H. Franke H. Franke
Published: October 2002

For the ultraviolet (UV) photosensitive polyimide Probimide\circR 412 the dynamic behavior of induced refractive index changes due to indiffusion of water molecules is investigated by two different methods. On the one hand the optical waveguide anisotropy of thin films ( 2.41 µm) is determined in a transient experiment. On the other hand volume phase gratings in thick films ( 50–60 µm) are produced using holographic technique and the time dependence of the diffraction efficiency is monitored upon exposure to moisture. A crosslinking of the photosensitive polyimide can be achieved by UV illumination. Different sensitivities to moisture of exposed (crosslinked) and unexposed waveguide films are observed. This results in a change of the diffraction efficiency of a phase grating where exposed and unexposed regions alternate with each other. A simple model for the time dependence of the diffraction efficiency is presented and discussed.
Room-Temperature Photoreflectance of CuAlxGa 1-xSe 2 Alloys
Authors: Sho Shirakata Sho Shirakata , Shigefusa Chichibu Shigefusa Chichibu , Shigehiro Isomura Shigehiro Isomura
Published: October 2002

Photoreflectance (PR) spectra have been measured at room temperature for single crystals of CuAlxGa1-x
Se2 alloys grown by the chemical vapor transport method. Exciton transition energies related to valence-to-conduction bands at room temperature (E

A
, E

B
and E

C
in eV) have been determined as a function of composition as E

A
=2.654x + 1.674(1-x)-0.22x(1-x), E

B
=2.767 x + 1.749(1-x)-0.17x(1-x) and E

C
=2.923x+1.972(1-x)-0.32x(1-x). The PR results are discussed in terms of PL spectra.
Growth of YBa2Cu3O7-x Superconducting Thin Films on [111] Oriented Ag Films
Authors: Otake Naoto , Matsumoto Hiroyuki , Tohru Asai Tohru Asai , Kazunori Kato Kazunori Kato
Published: October 2002

YBa2Cu3O7-
x

(YBCO) superconducting thin film was prepared on a [111] oriented Ag film using off-axis rf magnetron-sputtering. The [111] oriented Ag film was prepared on the (001) single-crystal natural mica substrate at a substrate temperature of 200° C under argon atmosphere. The YBCO film grew with, not only a strong orientation for the c-axis, but also with the three-symmetrical orientation for a and b axes on the mica/Ag substrate without post-annealing. The full-width at half maximum (FWHM) intensity of the 003 ω-rocking curve of the YBCO film was 1.52°. The optimal substrate temperature was 620° C, when the partial pressure of oxygen was 1.0×10-2 Torr. T
c (onset) and T
c (zero) of the films were 84 K and 77 K, respectively, according to the AC magnetic susceptibility measurements. The J
c of the film was measured by the conventional four-probe method, and the J
c (J//a
b) value was 1.4×104 A/cm2 at 77 K in a liquid nitrogen bath. The YBCO film showed the thickness dependence of T
c to be due to the large lattice mismatch of Ag(111) to YBCO (001).
Temperature Dependence of Interface Wall Energy in Exchange-Coupled Triple-Layered Films
Authors: Tabata Masahiro , Kobayashi Tadashi , Shiomi Shigeru , Masuda Morio
Published: October 2002

Simulations and experiments were carried out on the temperature dependence of the interface wall energy in exchange-coupled triple-layered (ECTL) films of Tb–Fe/Gd–Fe(–Co, Bi)/Dy–Fe–Co. In this simulation, the mean field theory and the noncontinuum model were applied in calculating their magnetization and the interface wall energy, respectively. The temperature dependence of the interface wall energy was found to depend mostly on that of the magnetization in the intermediate layer. It was concluded that one of the ways to improve the temperature dependence of the interface wall energy in the ECTL films for applications is to substantially reduce the exchange energy between Gd and Fe pair atoms, for example, by adding a small amount of Bi to the Gd–Fe–Co layer or by substituting a heavier rare-earth element for Gd in the Gd–Fe–Co intermediate layer.
Thermal Birefringence Effect on the Performance of a Laser-Diode Pumped Solid-State Laser
Authors: Kiriyama Hiromitsu , Yoshida Takuji , Srinivasan Narayanan , Matsui Hiroki , Nishida Kanji , Yamanaka Masanobu , Izawa Yasukazu , Tatsuhiko Yamanaka Tatsuhiko Yamanaka , Sadao Nakai Sadao Nakai
Published: October 2002

We report the high-sensitivity measurements of two-dimensional (2D) thermal birefringence distribution in a laser-diode (LD) pumped Nd:glass (HAP4) laser under lasing (at 1054 nm) and under no lasing conditions. The thermal birefringence was reduced under the lasing condition owing to the depletion of stored energy by stimulated emission. By inserting a 90° quartz rotator between two identical LD pumped Nd:glass rods, almost perfect birefringence compensation was achieved. The power loss due to thermal birefringence was evaluated quantitatively using the Jones matrix method. A considerable reduction of power loss, from over 12% before compensation to less than 0.4% after compensation, was observed. The output performance of this laser was in fairly good agreement with the estimation after taking into account the power loss due to thermal birefringence.
Influence of Bi2O3 Impurities in Ceramic ZnO on Photoacoustic Spectra
Authors: Taro Toyoda Taro Toyoda , Satoshi Shimamoto Satoshi Shimamoto
Published: October 2002

Photoacoustic (PA) spectroscopy is applied to study the optical absorption of ceramic ZnO doped with 1 mol% Bi2O3 sintered at different temperatures (700–1100° C). PA signal intensities plotted semilogarithmically reveal two individual regions below 3.0 eV (A: 3.0–2.7 eV; B: 2.6–2.4 eV). The steepness factor (slope of exponential optical absorption) obtained at region A decreases with increasing sintering temperature, indicating an increase of Bi2O3 segregation at particle surfaces and grain boundaries. The steepness factor at region B increases rapidly with increasing sintering temperature, indicating an occurrence of structure ordering (decrease of defect states) by the Bi2O3 liquid phase sintering effect.
Ferroelectricity of Bi2SrTa2O9 Single Crystals Grown by the Self-Flux Method
Authors: Machida Akio , Nagasawa Naomi , Takaaki Ami Takaaki Ami , Masayuki Suzuki Masayuki Suzuki
Published: October 2002

Ferroelectric hysteresis of a Bi2SrTa2O9 single crystal, a promising candidate for ferroelectric random access memories (FeRAM), was observed at 200° C. This single crystal, grown by the self-flux method, has a composition characterized as Bi

x

Sr

y

Ta2O9 (x=1.91±0.05, y=1.27±0.08). Observing the optical anisotropy of the c-plane, it was found that this material has a Curie temperature (T
c) higher than 250° C. Measuring the electrical properties on the c -axis and in the c -plane, it was confirmed that this material has electrical anisotropy. Furthermore, the domain motion of the crystal was observed under an electric field using a high-resolution charge-coupled-device (CCD) microscope system.
Phase Diagram in La-modified Pb(Sc 1/2Nb 1/2)O 3–PbTiO 3 Binary Ceramics System
Authors: Kazunari Maruyama Kazunari Maruyama , Zhiming Chen Zhiming Chen , Masatoshi Adachi Masatoshi Adachi
Published: October 2002

The phase boundaries in La-modified Pb(Sc1/2Nb1/2)O3–PbTiO3 system (La-PSN/PT), expressed as Pb(1-x)Lax[(Sc1/2Nb1/2)yTi(1-y)](1-x/4)O3, were determined. The phase diagram was found to consist of three phases: paraelectric cubic, ferroelectric tetragonal and ferroelectric rhombohedral at room temperature. The Curie temperature of the solid-solution ceramics decreases with increasing La content. The plot of the Curie temperatures of the samples with different La-PSN/PT compositions obtained at about 25°C, presents a curve from the composition of La-PSN/PT 2.5/100/0 to 25.5/0/100. Above room temperature, the morphotropic phase boundary (MPB) plots a straight line from composition 0/57.5/42.5 to 12.2/60.9/39.1. The electrical properties of the binary ceramics materials near the MPB were investigated.
Analysis of Fatigue Characteristics in Fe-doped Pb(Zr 0.52Ti 0.48)O 3 Thin Films by Switching Currents
Authors: Gyu Chae Byung , Jae Lee Su , Suk Yang Yong , Seong Hyun Kim Seong Hyun Kim , Min Su Jang Min Su Jang
Published: October 2002

The polarization fatigue for ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) thin films has a known relation with oxygen vacancies occurring in the films during fabrication processes. Fe-doped PZT thin films were intentionally deposited with consideration for the effects of oxygen vacancies regarding fatigue using rf-magnetron sputtering. The remanent polarization is suppressed to half its initial value after 109 bipolar switching cycles. From the observance of the switching currents with consideration to applied voltages, switching characteristics in the films were studied by fitting using the Kolmogorov-Avrami (K-A) theory. It was revealed from the switching currents as a function of fatigue cycles that the quantity of switched charges decreased with increasing switching cycles, but the dimensionality with respect to domain growth was unchanged as compared to its initial value. The velocities of domain wall motions before and after fatigue were also unchanged, indicating that the motion of the domain walls by applied pulse voltages was not an additional obstacle concerning fatigue processes. Therefore, in the case of polarization fatigue by subjecting to electric cycles, the domain states in these films may not be affected by the fatigue.
Conditions for Self-Organization of 45° Vortex and Phase Lag in Electric Polarization
Authors: Kiriyama Takahiro , Ozawa Takeshi , Akimoto Takuo , Hideyuki Yoshimura Hideyuki Yoshimura , Toshio Mitsui Toshio Mitsui
Published: October 2002

When an alternating electric field of 10 kHz is applied to a suspension of micron-size polystyrene particles in an aqueous NaCl or KCl solution, four states appear: (a) homogeneous suspension, (b) pearl chains, (c) vortexlike turbulence and (d) 45° vortexes, i.e., clusters elongated at an inclination of ±45° to the electric field in which the particles are circulating. Conditions for the occurrence of the four states are determined by changing the salt concentration and the amplitude and frequency of the electric field. Experimental results confirm the hypothesis that the phase lag of particle polarization against the electric field plays an important role in producing the vortex states (c) and (d). The vortexlike turbulence (c) seems to be triggered by asymmetric boundary conditions existing in the experimental apparatus. Self-organization of the 45° vortexes (d) seems to be initiated by the formation of clusters due to particle density fluctuation.
Output Characteristics of a Dye Laser Amplifier with Pump Direction and Polarization
Authors: Jang Won Kweon , Kim Sung Ho , Ko Do Kyeong , Cha Byung Heon , Lee Jong Min
Published: October 2002

We investigated the output characteristics of a dye laser amplifier in which optical pump direction changes the amplifier performance. The extraction efficiency was 60% for double-side pumping, and 25.5% for longitudinal pumping. The output energy was maximum when the polarization of the input beam and the pump beam were parallel. All experimental data were obtained using an optimum wavelength of 575 nm.
Amorphous Titanium Silicide Phase Formation by Surface Microroughness on Si(100)
Authors: Lee Sukjae , Lee Hwackjoo , Jeon Hyeongtag
Published: October 2002

The formation of amorphous Ti-silicide phase on two different kinds of Si(100) substrates was investigated. Two different substrates, the off-axis Si(100) which was cut with 4° to the (100) plane and the on-axis Si(100) which was cut with less than 0.5° were prepared. The Si(100) substrates were examined with atomic force microscope (AFM) to verify the atomic scale microroughnesses of the initial Si substrates after HF clean removing the native oxide. The on-axis Si(100) substrate exhibited much rougher surface morphology than that of the off-axis Si(100). The atomic scale microroughness of two different Si(100) substrates such as atomic steps and pits were investegated by high resolution transmission electron microscopy (HRTEM). Ti thin films were deposited in an e-beam evaporator after HF clean and the amorphous Ti-silicide layers were formed by annealing. The amorphous layer thicknesses on the on axis Si(100) exhbited thicker than those of the off-axis Si(100) and this difference of amorphous Ti-silicide layer thicknesses was considered to be related with atomic scale microroughnesses of Si surface.
Production of Multicharged Os Ion Beams from Organic Metal Compounds Using a RIKEN 18 GHz Electron Cyclotron Resonance Ion Source
Authors: Nakagawa Takahide , Kidera Masanori , Miyazawa Yoshitoshi , Hemmi Masatake , Chiba Toshiya , Inabe Naohito , Kase Masayuki , Kageyama Tadashi , Kamigaito Osamu , Akira Goto Akira Goto , Yasushige Yano Yasushige Yano
Published: October 2002

We successfully produced the multicharged osmium (Os) ions using metal ions from voatile compounds (MIVOC) method from a RIKEN 18 GHz electron cyclotron resonance ion source (ECRIS). Beam intensities of Os28+,33+ ions were 10 and 2.5 eµA at the RF power of 250 W, respectively.
Effect of Substrate Temperature on Molecular Orientation in Evaporated Thin Films of Vinylidene Fluoride Oligomer
Authors: Yoshida Yuji , Ishida Kenji , Ishizaki Katsunori , Horiuchi Toshihisa , Matsushige Kazumi
Published: October 2002

A newly synthesized vinylidene fluoride oligomer (OVDF), for which ferroelectric properties are expected when the electric dipoles with the molecules are all aligned, was employed as a prospective evaporation material. Particularly, the crystal structure and molecular orientation in evaporated thin films were examined by a total reflection X-ray diffractometer and reflection absorption infrared spectroscopy. Consequently, it was revealed that the crystal structure of the evaporated films was similar to the form II crystals of poly(vinylidene fluoride) which is a polymeric sample of OVDF, and that the molecular orientations are perpendicular to the substrate. Moreover, it was observed that the molecular orientation changed from perpendicular to parallel to the substrate at the substrate temperature between -30 and -50° C and the stable crystal structure was form II.
Radiation Dosimetry Measurements with Real Time Radiation Monitoring Device (RRMD)-II in Space Shuttle STS-79
Authors: Takao Sakaguchi Takao Sakaguchi , Tadayoshi Doke Tadayoshi Doke , Takayoshi Hayashi Takayoshi Hayashi , Jun Kikuchi Jun Kikuchi , Nobuyuki Hasebe Nobuyuki Hasebe , Toshisuke Kashiwagi Toshisuke Kashiwagi , Takeshi Takashima Takeshi Takashima , Kenichi Takahashi Kenichi Takahashi , Tamotsu Nakano Tamotsu Nakano , Shunji Nagaoka Shunji Nagaoka , Shimpei Takahashi Shimpei Takahashi , Hisashi Yamanaka Hisashi Yamanaka , Katsumi Yamaguchi Katsumi Yamaguchi , Gautam D. Badhwar Gautam D. Badhwar
Published: October 2002

The real-time measurement of radiation environment was made with an improved real-time radiation monitoring device (RRMD)-II onboard Space Shuttle STS-79 (S/MM#4: 4th Shuttle MIR Mission, at an inclination angle of 51.6° and an altitude of 250–400 km) for 199 h during 17–25 September, 1996. The observation of the detector covered the linear energy transfer (LET) range of 3.5–6000 keV/µm. The Shuttle orbital profile in this mission was equivalent to that of the currently planned Space Station, and provided an opportunity to investigate variations in count rate and dose equivalent rate depending on altitude, longitude, and latitude in detail. Particle count rate and dose equivalent rate were mapped geographically during the mission. Based on the map of count rate, an analysis was made by dividing whole region into three regions: South Atlantic Anomaly (SAA) region, high latitude region and other regions. The averaged absorbed dose rate during the mission was 39.3 µGy/day for a LET range of 3.5–6000 keV/µm. The corresponding average dose equivalent rates during the mission are estimated to be 293 µSv/day with quality factors from International Commission on Radiological Protection (ICRP)-Pub. 60 and 270 µSv/day with quality factors from ICRP-Pub. 26. The effective quality factors for ICRP-Pub. 60 and 26 are 7.45 and 6.88, respectively. From the present data for particles of LET > 3.5 keV/µm, we conclude that the average dose equivalent rate is dominated by the contribution of galactic cosmic ray (GCR) particles. The dose-detector depth dependence was also investigated.
Cooperative European Programs for the Development of Semiconductor Patterning Equipment
Authors: Steve Wittekoek Steve Wittekoek
Published: October 2002

This paper gives an update on the cooperative programs for semiconductor equipment development in Europe. The background and founding structure of the ESPRIT, and MEDEA programs are explained. Recent projects in the field of micro lithography equipment such as the step and scan programs, the 193 nm technology program “ELLIPSE and programs to develop 300 mm wafer equipment are described briefly. In these joint projects Semiconductor Manufacturers, Equipment and Material Suppliers and Technical Institutes are participating. In some cases cooperations with non-European companies have been successfully implemented. This global cooperation is expected to increase in view of the increased costs of technology developments.
Fabrication of 0.13-µm Device Patterns by Argon Fluoride Excimer Laser Lithography with Practical Resolution Enhancement Techniques
Authors: Ogawa Tohru , Uematsu Masaya , Onodera Toshio , Nakazawa Keisuke , Takahashi Makoto , Ohfuji Takeshi , Ohtsuka Hiroshi , Sasago Masaru
Published: October 2002

This paper presents the formation results of 0.13-µ m device patterns using argon fluoride (ArF) excimer laser lithography that does not incorporate strong resolution enhancement techniques such as levenson type phase-shifting mask or quadrupole illumination. Device patterns of 0.13-µ m can be fabricated by ArF excimer laser lithography when a high performance single-layer photoresist, an anti-reflective layer, an attenuated phase-shifting mask with an off-axis illumination are used. A 0.5-µ m depth-of-focus with a 10.8% exposure latitude can be obtained. Furthermore, 0.12-µ m-rule gate patterns of memory and logic devices can be fabricated. A 1.0-µ m depth-of-focus for a 0.13-µ m pattern will be achieved.
Ferroelectricity and Electric Conduction Characteristics of Sr-Modified Lead Zirconate Titanate Thin Film Capacitors
Authors: Yang Yong Suk , Lee Su Jae , Kim Seong Hyun , Byung Gyu Chae Byung Gyu Chae , Min Su Jang Min Su Jang
Published: October 2002

Ferroelectric (Pb0.9Sr0.1)(Zr0.53Ti0.47)O3 (PSZT) thin film capacitors were prepared on Si substrates with a platinum-electrode coated on the underside by a sol–gel method. X-ray diffraction patterns showed that PSZT thin films were polycrystalline and the peaks of perovskite structure appeared uniquely in films annealed above 650°C. Ferroelectricity and electric conduction characteristics were observed by measuring the frequency dependent dielectric constant (ε
′–f), the capacitance versus voltage (C–V), the ferroelectric hysteresis (D–E) loops, and the leakage current density versus field (J–E). The remanent polarization and the coercive field using a sinusoidal voltage of 1 kHz and 10 V were approximately 21 µC/cm2 and 67 kV/cm, respectively. The ohmic conduction and space-charge-limited current conduction were the dominant charge transport mechanisms in sol–gel deposited PSZT films. The resistivity of PSZT films in ohmic conduction region was 4×108 Ωcm and the density of traps was about 6.5×1019 cm-3. The drift mobility at room temperature was about 86 cm2/Vs for a 240-nm-thick film and 42 cm2/Vs for a 400-nm-thick film.
0.15 µm Electron Beam Direct Writing for Gbit Dynamic Random Access Memory Fabrication
Authors: Nakajima Ken , Yamashita Hiroshi , Kojima Yoshikatsu , Hirasawa Satomi , Tamura Takao , Yamada Yasuhisa , Tokunaga Kenichi , Ema Takahiro , Kondoh Kenji , Naka Onoda Naka Onoda , Hiroshi Nozue Hiroshi Nozue
Published: October 2002

This paper describes 0.15 µ m electron beam (EB) direct writing techniques for Gbit dynamic random access memory (DRAM) fabrication. In order to use EB direct writing for reliable fine pattern fabrication on the 0.15 µ m level, an EB direct writing system technique, a resist process technique, a cell projection (CP) mask preparation technique, which is indispensable for improving the writing throughput, and a data preparation technique with proximity effect correction must be improved respectively and combined successfully. The proximity effect correction for all fine patterns in a full-scale DRAM chip is especially important for achieving a CD accuracy of less than 0.02 µ m, which is required for device fabrication and margin. For obtaining the reliable shot stitching accuracy between CP and variably shaped (VS) EB writings, we adopted the cross-correlation method, which was used to decide the size and center position of the CP shot. A single-layer resist system without an over-coated conducting layer was used for reliable device fabrication. In addition, for improving the CD accuracy for all 0.15 µ m designed patterns in a full-scale chip, we developed a data partition process suitable for CP mask pattern data and an improved 1-dimenshinal(1-D) calculation method for proximity effect correction. Utilizing these techniques, the full-scale 4Gbit DRAM, which was designed with 0.15 µ m minimum feature size, was fabricated successfully with 0.05 µ m (| mean|+3σ) overlay accuracy, 0.02 µ m (| mean+3σ) stitching accuracy, and less than 0.02 µ m (3σ) CD accuracy, all of which were sufficient for the required device fabrication.
Investigation of Charge Injection in Gas-Impregnated Polyethylene by Measurement of Electroluminescence under AC Voltage
Authors: Takehiko Mizuno Takehiko Mizuno , Yuan-Shing Liu Yuan-Shing Liu , Wataru Shionoya Wataru Shionoya , Kouiti Yasuoka Kouiti Yasuoka , Shozo Ishii Shozo Ishii
Published: October 2002

Electroluminescence (EL) in polyethylene (PE) impregnated with N2, O2 or SF6 gas has been measured under ac voltages to investigate the effect of impregnation gas on charge injection. EL is strongly dependent on the processes of electron injection and transport in the surface region of PE. The results of our measurements of EL indicate that the process of electron injection is greatly affected by the type of impregnation gas in PE. In particular, O2 gas which is electronegative and chemically reactive markedly affects the charge injection process, causing a reduction in EL inception voltage and barrier height at the electrode-polymer interface. The surface states induced by the presence of O2 gas or by oxidation of PE enhance the electron injection. However, electrons injected into such surface states likely contribute little to EL. N2 gas also causes a reduction in the EL intensity but does not induce a change in the EL inception voltage and the barrier height in comparison with those in the degassed case. N2 gas probably affects an electron transport process such as intermolecular conduction in the surface region of PE rather than the electron injection process.
Improved Alignment Accuracy Using Lens-Distortion Correction for Electron-Beam Lithography in Mix-and-Match with an Optical Stepper
Authors: Gotoh Yasuko , Nakayama Yoshinori , Matsuzaka Takashi , Saitou Norio , Hojyo Yutaka , Kawahara Toshikazu , Tawa Tsutomu
Published: October 2002

The mix-and-match use of an electron-beam (EB) lithography system and an optical stepper is an effective approach to achieving higher resolution while maintaining high throughput in the fabrication of Gbit DRAMs and advanced ASIC devices. In this approach, the highly accurate alignment of patterns exposed by different lithography methods is essential. In this paper, the lens distortion of the optical stepper is examined and distorted patterns are aligned with an EB lithography system. The overlay accuracy in this mix-and-match application was 51.4 nm (3σ) which corresponds to Gbit DRAMs fabrication.