bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Material Systems on the Polarization Behavior of Holographic Polymer Dispersed Liquid Crystal Gratings
Authors: Takeshi Karasawa Takeshi Karasawa , Yoshinao Taketomi Yoshinao Taketomi
Published: October 2002

This study has investigated the effects of the material systems involved in the fabrication processes on the polarization behavior of a volume holographic grating. The diffraction efficiency of the gratings fabricated using prepolymer/liquid crystal mixtures shows strong dependence on the polarization of incoming light. Depending on the materials used in the formation of a grating, the diffraction properties are such that either p- or s-polarized light is strongly diffracted while the light with the other polarization is very weakly diffracted. The magnitude of the dependence on the polarization is greatly affected by the type of monomers, liquid crystals and substrates. The comparison of various types of monomers added to the base prepolymer mixtures, two distinctly different types of liquid crystals and glass slides and indium-tin oxide (ITO) coated glass as substrates was carried out using polyester-based and urethane-based oligomers.
Epitaxial Growth of TiSi2 (C49) on (001)Si by Rapid Thermal Annealing
Authors: Li-Ming Wang Li-Ming Wang , Shinn-Tyan Wu Shinn-Tyan Wu
Published: October 2002

A rapid thermal annealing at 670° C is performed for 20 s on a titanium film (35 nm) on <0 0 1> silicon. Epitaxial growth of TiSi2 of a C49 structure is induced by the annealing, when the substrate is heated to 400° C before titanium sputtering. In contrast, a fibre texture is obtained if the substrate is not heated. The in-plane orientations determined by X-ray and electron diffraction are in good agreement with those theoretically calculated using the method of the maximum number of coincidence sites at the epitaxial interface.
Impulse Response of Metal-Semiconductor-Metal Photodetectors Using a Conformal Mapping Technique and Extracted Circuit Parameters
Authors: Wohlmuth Walter , Arafa Mohamed , Fay Patrick , Seo Jong-Wook , Adesida Ilesanmi
Published: October 2002

The impulse response of interdigitated InGaAs metal-semiconductor-metal photodetectors (MSMPDs) is modeled using a two dimensional transit-time calculation coupled with an equivalent circuit model of the intrinsic and parasitic elements of the MSMPDs. The simulated and experimental bandwidths of InGaAs MSMPDs with resistive transparent indium-tin-oxide and low-resistivity opaque titanium/gold electrodes are in excellent agreement and were found to be 6 and 11 GHz, respectively. The electrode width and spacing of these devices are 3 µm and the active area is 2500 µm2. This model aids in the design of MSMPDs with various electrode geometries, electrode materials, semiconductor materials, and methods of illumination.
Estimation of Dislocation Concentration in Plastically Deformed Al–Li Based Alloy by Positron Annihilation
Authors: Mamdouh Abdelrahman Mamdouh Abdelrahman
Published: October 2002

Measurements of positron annihilation mean lifetime τ have been performed on eight different specimens of Al–Li based alloy plastically deformed at room temperature up to 40% thickness reduction. This measurement shows clearly positron trapping by dislocations. The positron lifetime τ exhibits a saturation for deformations larger than (15%) thickness reduction. The fitted lifetime varies from (183 ±2 ps) for annealed sample to (205 ±2 ps) for the dislocation saturated value. Using a trapping model, the data yield the values of µ= 3.83×10-8 cm3 s-1 for the specific trapping rate and σ= 3.58×10-15 cm2 for the trapping cross section, some what lower than those for plastically deformed Al single crystals. The value obtained for Δτ, the increase in lifetime of positrons trapped at dislocations in plastically deformed Al–Li based alloy sample over annihilation in the annealed sample, is 22 ps. This is about 40% of the lifetime increase for the case of positrons trapped at dislocations in plastically deformed Al single crystals. Dislocation densities at different thickness reduction have been estimated.
Self-Interstitials in Silicon
Authors: Okino Takahisa , Shimosaki Toshitada , Takaue Ryoichi
Published: October 2002

Self-interstitial concentration I normalized to the thermal equilibrium concentration C
I
0 was previously derived as a function of diffusion time t, the absolute temperature T, the diffusivity D
I and the specimen thickness w from the well-known diffusion equation for self-interstitials in silicon. Antoniadis also demonstrated that the time-averaged and normalized self-interstitial concentration  is obtained as a function of t and T from the oxidation stacking faults data. By fitting the former I to the latter  and using Stolwijk et al..'s relation between D
I and C
I
0 derived from the diffusion data of Au in silicon, D
I and C
I
0 were determined as a function of T. Furthermore, the fractional component of the interstitialcy mechanism for silicon self-diffusion was investigated, assuming a local equilibrium between self-interstitials and vacancies in silicon. It was found that self-diffusion occurs mainly via vacancies.
Annealing Properties of Sputtered CoSi2 and Sputtered and Reactive Sputtered TiN Contacts on n-Si
Authors: Ghader Eftekhari Ghader Eftekhari
Published: October 2002

Thermal stability of sputtered CoSi2 and TiN and reactive sputtered TiN contacts on n-Si were examined. It was determined that reactively sputtered contacts with 70% Ar and 30% N2 have better properties than the other two contacts. CoSi2 contacts were found stable except a sharp increase in their reverse current was observed when annealed at temperature higher than 850°C.
The Γc–Γv Transition Energies of AlxIn1-xP Alloys
Authors: Ishitani Yoshihiro , Hamada Hiroshi , Minagawa Shigekazu , Yaguchi Hiroyuki , Shiraki Yasuhiro
Published: October 2002

The transition energies at 20 K for the Γ 6c–Γ 7v (electron-heavy hole) (E
s
hh(x)) and for the Γ 6c–Γ 6v(1) (electron-light hole) (E
s
lh(x)) of strained and disordered Al

x

In1-
x

P (0.43≤x≤0.62) on GaAs substrates were measured using a photoreflectance method. They are expressed as E
s
hh(x)=1.488(±0.020)+2.30(±0.04)·x, and E
s
lh(x)=1.738(±0.030)+1.81(±0.06)·x( eV). The Γ 6c–Γ 8v transition energies for unstrained layers (E
u(x)) were also measured at 20 K as E
u(x)=1.418(±0.007)+2.42(±0.01)·x ( eV). The unstrained samples were InP, Al0.53In0.47P on a GaAs substrate and Al0.73In0.27P on a GaAs0.61P0.39 substrate. The shift of the transition energies due to stress was obtained from these transition energies. The hydrostatic and shear deformation potentials for Al

x

In1-
x

P alloys were calculated to be -5.23(±0.60) eV and -1.67(±0.26) eV by comparing the experimental results and the theoretical formulae.
Evidence that N2O is a Stronger Oxidizing Agent than O2 for the Post-Deposition Annealing of Ta2O5 on Si Capacitors
Authors: Lau Wai Shing , Qian Peng Wei , Sandler Nathan P. , McKinley Kevin A. , Chu Paul K.
Published: October 2002

Cross-sectional transmission electron microscopy (XTEM), secondary ion mass spectrometry (SIMS) and capacitance measurements were used to study the effect of post-deposition annealing on Ta2O5/Si structures. A significantly thicker SiO

x

interfacial layer was formed at the Ta2O5/Si interface, if N2O was used instead of O2 for post-deposition annealing. This indicates that N2O is a stronger oxidizing agent than O2. It is known that the leakage current of Ta2O5 capacitors is greatly reduced if N2O is used instead of O2 for post-deposition annealing. This may also be partially explained by postulating that N2O annealing is more effective in the suppression of oxygen vacancies. Furthermore, the suppression of Si diffusion from the Si substrate into Ta2O5 due to the thicker SiO

x

interfacial layer can be another factor. The basic reason for the superiority of N2O is that the energy required to produce free O atoms is lower than that for O2. From this point of view, we can also predict that the use of NO will be worse than that of O2 because the energy required to produce free O atoms is higher than that of O2.
The Microstructure of As Precipitates in Si Delta-Doped GaAs Grown by Low-Temperature Molecular Beam Epitaxy
Authors: Hsieh Li Zen , Huang Jin Hua , Su Zi Ang , Guo Xing Jian , Shih Han Chang , Meng Chyi Wu Meng Chyi Wu
Published: October 2002

The structure relationship of the As precipitates found in post-annealed Si δ-doped GaAs layers grown by low-temperature molecular beam epitaxy is elucidated by transmission electron microscopy (TEM). There are six extra spots around the diffraction pattern of GaAs for a sample annealed at 700° C. The As precipitates and GaAs matrix are found to be semicoherent with the hexagonal [-1-21] As parallel to the cubic [110] GaAs. Because of the different lattice constants and Bravias lattices between GaAs and As precipitates, these extra spots are formed by double-diffraction effects. The high-resolution TEM images show two types of Moiré fringes. One is the parallel Moiré pattern and the other is the rotation Moiré pattern. The relative positions of the extra spots in the diffraction pattern correspond to the orientation and spacing of Moiré fringes.
Annealing Properties of Defects in Ion-Implanted 3C-SiC Studied Using Monoenergetic Positron Beams
Authors: Uedono Akira , Itoh Hisayoshi , Ohshima Takeshi , Suzuki Ryoichi , Ohdaira Toshiyuki , Tanigawa Shoichiro , Aoki Yasushi , Yoshikawa Masahito , Nashiyama Isamu , Mikado Tomohisa , Okumura Hajime , Yoshida Sadafumi
Published: October 2002

Annealing properties of defects in N2
+- or Al+-implanted 3C-SiC were studied using monoenergetic positron beams. For as-implanted specimens, the mean size of the open volume of defects was estimated to be close to that of divacancies. Based on the annealing behavior of the characteristic value of the S parameter corresponding to the annihilation of positrons trapped by vacancy-type defects, the temperature range for the annealing of defects was divided into five stages, and they were arbitrarily designated as I–V. Annealing behavior in stages I (20–500° C), II (500–800° C) and III (800–1000° C) was identified as the agglomeration of vacancy-type defects due to migrations of carbon vacancies, Si vacancies and vacancy complexes such as divacancies, respectively. Stages IV (1000–1200° C) and V (1200–1400° C) were assigned to be the formation of extended defects and their recovery processes, respectively. Effects of the species of the implanted ions and the substrate temperature during ion implantation on annealing properties of defects are also discussed.
Influence of Near-Surface Defects in Si Induced by Reactive Ion Etching on the Electrical Properties of the Pt/n-Si Interface
Authors: Koyama Masato , Cheong Chon-wa , Yokoyama Koji , Ohdomari Iwao
Published: October 2002

We investigated the influence of near-surface defects induced by reactive ion etching on the electrical properties of the Pt/n-Si interface. By analyzing the temperature dependence of the I-V characteristics of the damaged interface, we confirmed that the dominant current transport in the interface was the thermionic emission process under our experimental conditions. The Schottky barrier height was lowered due to the change in the Fermi-level position at the interface. The positively charged donor-like defects are responsible for the change in the Fermi-level at the damaged interface.
The Most Essential Factor for High-Speed, Low-Power 0.35 µm Complementary Metal-Oxide-Semiconductor Circuits Fabricated on Separation-by-Implanted-Oxygen (SIMOX) Substrates
Authors: Yoshino Akira , Kumagai Kouichi , Hamatake Nobuhisa , Susumu Kurosawa Susumu Kurosawa , Koichiro Okumura Koichiro Okumura
Published: October 2002

We present experimental data concerning the propagation delay time and the power consumption of 0.35 µ m complementary metal-oxide-semiconductor (CMOS) gates (inverter, NAND, NOR) fabricated on the commercial standard high dose separation-by-implanted-oxygen (SIMOX) substrates. Each CMOS gate was composed of the fully depleted (FD) mode N- and P-type metal-oxide-semiconductor (NMOS and PMOS) transistors or the partially depleted (PD) mode ones with no body-contact. On the basis of the experimental data, together with SPICE simulation results, we show that the FD-mode is not the primary factor for high-speed, low-power performances of the CMOS/SIMOX circuits, but the reduced drain parasitic capacitance (both the bottom and the peripheral components) with the thin film silicon-on-insulator (SOI) structure is. Furthermore, we show the significance of the design and control of the transistor threshold voltage and/or the off-state leakage current for high-speed, low-power CMOS/SIMOX circuits.
Experimentally Proven Equation for the Collector-Depletion-Layer Transit Time of npn Bipolar Transistors
Authors: Mochizuki Kazuhiro , Takashi Uchino Takashi Uchino , Tohru Nakamura Tohru Nakamura
Published: October 2002

The dependence of the collector-depletion-layer transit time of npn bipolar transistors, τ C, on the effective depletion-layer width, W
C, was found to be well fitted by τ C=W
C/v
s, where v
s is the electron saturation velocity, while it was not fitted by the well-known equation τ C=W
C/2v
s, indicating that the effect of inductive current is negligible.
Excitation of Phonon-Polaritons with Asymmetric Transient Grating
Authors: Kawashima Hitoshi , Sasaki Fumio , Shunsuke Kobayashi Shunsuke Kobayashi , Toshiro Tani Toshiro Tani
Published: October 2002

In this study, we investigate asymmetric grating as a scheme for mapping the amplitude profile of an optical pulse onto a terahertz phonon-polariton in electrooptic crystals. The grating configuration is theoretically evaluated paying particular attention to the effect of spectral narrowing due to the spatial periodicity of the interference fringes. Its impacts and implications are fully analyzed. For an input optical pulse with a tailored profile, an important result is that the linear chirp of the optical pulse can reveal itself in the duration of the polariton and in directionally asymmetric responses. Experimental results show a temporal shift between the counter propagating wavepackets. This is one of the directional asymmetries and is sound evidence that the polariton responds to the amplitude profile of the optical pulse.
Quantitative Analysis of Cell Gap Margin for Uniform Optical Properties Using In-Plane Switching of Liquid Crystals
Authors: Masahito Oh-e Masahito Oh-e , Katsumi Kondo Katsumi Kondo
Published: October 2002

The allowable range of marginal variation of the cell gap to ensure uniform optical properties when using in-plane switching (IPS) of liquid crystals was evaluated quantitatively. The analysis yielded relationships of transmittance into the cell gap in bright, selected bright and selected intermediate states. The selected state was defined as the state in which a particular constant voltage was applied to the liquid crystals to obtain the desired state in a series of evaluations for different cell gaps. The relationships were used to evaluate normalized variations of transmittance (|ΔT/T|) corresponding to the difference in the cell gap from the optimal value (Δd), and the variations were compared with those in the twisted and supertwisted nematic modes. As a result, the marginal variation for a uniform display using the IPS of liquid crystals was quantitatively confirmed to be much narrower than that in the twisted nematic mode. In the selected bright state, the variation was between those of the twisted and supertwisted nematic modes, while it was comparable to the cell gap margin of the supertwisted nematic mode in the intermediate state; i.e., the variation of ±0.1 µ m in the twisted nematic mode corresponded to that in a range of ±0.02 to ±0.04 µ m in the IPS mode.
Structure and Dielectric Properties of (Ca1-xNd2x/3)TiO3
Authors: Yoshida Masashi , Hara Naoki , Takahiro Takada Takahiro Takada , Akira Seki Akira Seki
Published: October 2002

(Ca1-
x

Nd2
x
/3)TiO3 sintered samples are fabricated with 0≦x≦1 and the crystal structure and dielectric properties are investigated. It is shown that (Ca1-
x

Nd2
x
/3)TiO3 has an orthorhombic GdFeO3-type structure for 0≦x≦0.69 and an La2/3TiO3-type double-layered perovskite structure for 0.78≦x≦0.93. High ε and high f
Q values are obtained for the GdFeO3 phase of (Ca1-
x

Nd2
x
/3)TiO3, e.g., ε=108 and f
Q=17200 GHz for x=0.39. On the other hand, for the La2/3TiO3 phase, ε is between 80 and 100 and f
Q is below 1000 GHz.
Improvements of the Properties of Chemical-Vapor-Deposited (Ba,Sr)TiO 3 Films through Use of a Seed Layer
Authors: Choi Young-Chul , Lee Joon , Lee Byung-Soo
Published: October 2002

(Ba,Sr)TiO3 (BST) thin films were deposited on seed-layer/Pt/SiO2/Si substrates by chemical vapor deposition and the properties of the films were investigated. The effect of rapid thermal annealing (RTA) was also examined. The seed layer used in this experiment was the 10-nm-thick BST film fabricated by RF magnetron sputtering. Both the application of the seed layer and RTA increased the crystallinity of the BST films, which resulted in improved dielectric properties of the films. The seed layer suppressed the formation of an oxygen-deficient layer at the interface between BST and the bottom electrode, which resulted in a decrease of the current density of the Pt/BST/Pt capacitor. Furthermore, the current density was further decreased by RTA. With increasing deposition temperature, both the dielectric constant and the current density of the BST films deposited on the seed layers increased.
Characterization of Cleaved GaAs Tips for Scanning Tunneling Microscopy
Authors: Masahiro Yoshita Masahiro Yoshita , Takuji Takahashi Takuji Takahashi
Published: October 2002

We have studied tunneling spectroscopy using cleaved n-type GaAs tips in a scanning tunneling microscope (STM) to characterize the electronic properties of the cleaved tips. The tunneling spectra were measured for a set of GaAs tips and metal surfaces and GaAs flat surfaces and metal tips. The spectra obtained for a GaAs tip and a metal surface are symmetrical for a bias voltage with narrower energy gaps, which are different from those with a GaAs flat surface and a metal tip. This result indicates a stronger pinning of the surface Fermi level at midgap in the cleaved GaAs tips than that in the GaAs flat surface. This characteristic is also confirmed by photoresponse measurements in the STM.
Employing Two Unique Schemes to Investigate the Beam Lifetime in Storage Rings
Authors: Ian C. Hsu Ian C. Hsu
Published: October 2002

To investigate the relative beam lifetime contributions from the Touschek effect and the gas scattering effects, the two unequal bunches method is conventionally used. However, in a multibunch operation, the lifetimes can significantly differ from that measured by the few bunches mode. In this study, we present a method, that we fill every bucket and then measure the beam lifetimes before and after enlarging the transverse beam sizes. This measurement allows us to estimate the Touschek lifetime and the gas scattering lifetime, including the ion effects. According to the measurement results, the Touschek lifetime is longer by 8% when measured by the multibunch method than when estimated by the two unequal bunches method. Also, there is a 54% discrepancy of the gas scattering lifetime. The possible error sources for the two methods are also discussed, and it is obtained that the multibunch method is the superior one.
Hysteresis Phenomena at the Bunch Lengthening Process in the Accumulation Ring
Authors: Takao Ieiri Takao Ieiri
Published: October 2002

The bunch length was measured using a real-time bunch-length monitor based on the beam spectrum in the accumulation ring. Hysteresis phenomena were observed in the bunch lengthening. That is, two bunch lengths existed depending on changing the direction of the beam current. A longitudinal instability of a bunch was calculated using calculated wake potential by a computer code based on a linearized Vlasov equation. The growth rate was calculated as a function of the energy spread at a fixed beam intensity. It was found that the growth rate did not decay monotonously, but had an unstable peak after decaying to a stable minimum value as the energy spread increased. There are two stable regions of the energy spread on both sides of the peak, suggesting the hysteresis.
Axial Structures of the Alfvén Ion Cyclotron Mode in the GAMMA10 Tandem Mirror
Authors: Kumagai Akira , Ichimura Makoto , Nakamura Motoyuki , Tanaka Satoru , Kanazawa Seikou , Takayama Seiichi , Ishikawa Eiji , Satake Chikako , Inutake Masaaki , Hojo Hitoshi , Teruo Tamano Teruo Tamano , Kiyoshi Yatsu Kiyoshi Yatsu
Published: October 2002

Axial structures of the Alfvén ion cyclotron (AIC) mode have been investigated in the GAMMA10 tandem mirror. The AIC mode is a microinstability driven by an anisotropy in the velocity space, and is excited as an axial eigenmode in the GAMMA10. There are several discrete peaks in the frequency range of ω/Ω ci∼0.8–0.9, where Ω ci is the ion cyclotron frequency at the midplane of the central cell. A driving term of the AIC mode is theoretically given by β⊥(T
⊥/T
//)2. Here, β⊥ is a perpendicular beta value and T
⊥/T
// is a temperature anisotropy (an ion temperature ratio between perpendicular and parallel to the magnetic field line). In GAMMA10, the AIC mode is observed in the range of β⊥(T
⊥/T
//)2≥0.3 (which is much smaller than the theoretical prediction of β⊥(T
⊥/T
//)2≥3.52). This is thought to be related to the wave structure in the axial direction. The frequency ω and axial wave number k
// of each mode changed with β⊥ and T
⊥/T
//. As β⊥ and T
⊥/T
// increased, the AIC frequency range became wide and the AIC wave changed from a propagating wave to a standing wave.
Studies of a Magnetic Neutral Loop Discharge Based on Laser Diagnostics of Electron Behavior and Atomic Processes
Authors: Sakoda Tatsuya , Miyao Takayuki , Kiichiro Uchino Kiichiro Uchino , Katsunori Muraoka Katsunori Muraoka
Published: October 2002

In order to understand plasma formation processes in a neutral loop discharge, measurements of population densities of excited levels of helium atoms were performed using laser induced fluorescence (LIF) spectroscopy. At the same time, profiles of electron density n
e and electron temperature T
e were measured using Thomson scattering. The results of these measurements were analyzed using a collisional-radiative model of helium atoms in the plasma. It was found that population densities of excited levels of the helium atoms were consistent with the values of n
e and T
e. This indicates that it is not necessary to consider an existence of a high energy electron component which may be supposed to theoretically exist in addition to the Maxwellian energy distribution function for the bulk of electrons at the measured temperature T
e. Also, it was shown that the energy deposition to electrons in the vicinity of the neutral loop plays a essential role in the formation of the neutral loop discharge plasma.
Interferometer Measurements in Pulsed Plasma Experiments
Authors: Lisitsyn Igor V. , Kohno Susumu , Kawauchi Toshinori , Sueda Tsuyoshi , Sunao Katsuki Sunao Katsuki , Hidenori Akiyama Hidenori Akiyama
Published: October 2002

The interferometer measurements are extremely informative in plasma experiments allowing direct evaluations of the electron density. The primary goal of the work presented, is to build a laser interferometer which meets the requirements of the highest possible simplicity, economy, convenience and ease of construction. These requirements are successfully satisfied while maintaining high sensitivity (±0.5°–of phase shift) and a wide density range (1014 and 1019 cm-2–line-integrated) of the interferometer. In our experiments we used a low average power (5 mW) He–Ne laser without complicated and costly stabilization or detection environments. The He–Ne laser interferometer with the Michelson arrangement was used to measure the line-integrated plasma densities in various plasma experiments. Time- and spatially-resolved density measurements were performed for a plasma opening switch, a laser produced plasma, an electrothermal launcher and railgun plasmas.
Micromachined Traveling Wave Motors: Three Dimensional Mechanical Optimization and Miniaturization Limits Evaluation
Authors: Minotti Patrice , Cusin Pierre , Le Moal Patrice , Ferreira Antoine
Published: October 2002

This paper concerns a physical limits evaluation with respect to the miniaturization of traveling wave type ultrasonic motors (TWUM) down to the millimeter scale. According to present knowledge in research dedicated to centimeter scale TWUM, two different prototypes, whose external diameters are φ 5 mm and φ 2 mm, have previously been designed through numerical calculations, and fabricated using watch making technologies. An experimental characterization has been carried out in order to identify the main physical and technological limitations specific to millimeter scale traveling wave motors. The very first numerical results presented in this paper show important outcomes related to the miniaturization of TWUM. In particular, the limits of current mechanical assumptions such as those related to the two-dimensional mechanical behavior of the stator/rotor interface and also to the rotor's rigidity are clearly shown by a three dimensional finite element calculation. New design rules are thus given in order to allow the mechanical architecture of TWUM to be optimized. The corresponding results indicate that powerful torque/speed characteristics can be expected, and therefore show the adequacy of traveling wave ultrasonic motors for direct-drive actuation down to the millimeter scale.
Modal Precession of a Hemispherical Shell Gyro Excited by Electrostatic Field
Authors: Chan-Shin Chou Chan-Shin Chou , Chia-Ou Chang Chia-Ou Chang
Published: October 2002

In this paper the precessional phenomenon of the modal pattern of a rotating hemispherical shell gyro excited parametrically by electrostatic forces is investigated. Niordson's thin shell theory, which included the extensional deformation of the middle surface and was derived in an invariant form, is employed and the rotary inertia is added. The modal equations of motion are coupled by the Coriolis force and the applied electric field. The method of multiple scales is used to determine quantitatively the vibrational displacement of the shell from which the precessional rate of the modal vibration pattern can be extracted. It is also shown that the modal precessional rate for the parametrically excited vibration case is found to be the same as that of the freely vibrating one. Experiments are performed on a rotating quartz hemispherical shell excited electrostatically to verify the theoretical results.
Anisotropic Transport Properties in Twin-Free Bi2Sr2CaCu2Ox Thin Films on Tilted LaAlO3 (001) Substrates
Authors: Takayuki Ishibashi Takayuki Ishibashi , Toshihiro Kawahara Toshihiro Kawahara , Katsuaki Sato Katsuaki Sato , Kiejin Lee Kiejin Lee , Ienari Iguchi Ienari Iguchi , Mitsuo Kawabe Mitsuo Kawabe
Published: October 2002

Anisotropic transport properties of twin-free Bi2Sr2CaCu2O
x
(BSCCO) thin films were studied. Twin-free BSCCO thin films were prepared by molecular beam epitaxy (MBE) on LaAlO3 (001) substrates tilted 6° toward the [110] direction. By postannealing in high vacuum (HV) of 10-8 Torr at a temperature of 300–400°C, the carrier density per CuO2 plane was reduced from 0.5 to 0.3. The anisotropy parameter (γ) was determined to be 38 in the HV-annealed sample.
Deflection of a Velocity Compressed Yb Atomic Beam by a Multi-Mode Spectral Laser
Authors: Watanabe Masayoshi , Ohmukai Ryuzo , Tanaka Utako , Hayasaka Kazuhiro , Hidetsuka Imajo Hidetsuka Imajo , Shinji Urabe Shinji Urabe
Published: October 2002

We have generated a continuous, monovelocity Yb atomic beam based on a technique combining velocity compression and beam deflection. Two single-mode lasers were used to compress the thermally broadened velocity distribution, and a multi-mode spectrum of a mode-locked laser was used to extract the compressed part as a deflected beam. The observed deflection angles were compared with the calculations. Deflection angles up to 12° were obtained.
Wideband Tuning of a High-Pressure CO2 Laser by means of Intracavity Active Frequency Shift
Authors: Shinozaki Tatsuya , Suda Akira , Nagasaka Keigo , Hideo Tashiro Hideo Tashiro
Published: October 2002

Intracavity active frequency shift, a unique method of shifting the frequency of pulsed lasers, was applied to a high-pressure CO2 laser which has a continuous gain profile over a wide range of the spectrum. In order to extend the amount of frequency shift, the dependence of the maximum frequency shift on the laser gas pressure was investigated. As a result, it was found that the maximum frequency shift was limited by the gain duration time rather than by the gain bandwidth at a pressure of 8–10 atm. By shortening the cavity length, the maximum frequency shift of 9 GHz was obtained at a pressure of 8 atm. Then, the grating-mirror cavity was applied to demonstrate the frequency shift starting from each lasing line of the CO2 laser. According to numerical calculations, the maximum frequency shifts starting from most lasing lines of a multi-isotope cw CO2 laser can exceed 10 GHz, resulting in coverage of almost the entire gain spectrum in the high-pressure CO2 laser.
Relaxation Oscillations in Fiber-Grating-Tuned Erbium-Doped Fiber Lasers
Authors: Shinya Toru Mizunami , Sanjay Gupta Sanjay Gupta , Teruo Shimomura Teruo Shimomura
Published: October 2002

Relaxation oscillations were studied experimentally and theoretically in a fiber-grating-tuned erbium-doped fiber laser with a doped fiber length of 7 to 9 m. Two regions of amplitudes in the relaxation oscillations were observed. For small-amplitude oscillations, the measured relaxation oscillation frequency agreed with that given by an approximate equation. For large-amplitude oscillations, chirping in the relaxation oscillation frequency was observed. A numerical analysis based on rate and propagation equations was performed to analyze this chirping. The results qualitatively agreed with those of the experiment. Wavelength tuning was also performed using a Peltier device. The tuning range was 2.1 nm for a grating in the 1.53–1.55 µ m region.
Thermal Decomposition and Deformation of Dye and Polycarbonate in Compact Disc-Recordables
Authors: Huh Y. J. , Kim S. H. Kim
Published: October 2002

Thermal decomposition and deformation of a compact disc-recordable were simulated and observed. From the calculations, the writing power for the dye melting, dye decomposition and the polycarbonate (PC) deformation was predicted, and was experimentally confirmed by atomic force microscope (AFM) observation of the dye layer and PC surfaces. The deformation effects of each layer were evaluated according to the recording characteristic, the carrier to noise ratio (CNR). In the wrting power range of 4.0–6.0 mW, the deformation of the PC substrate contributes to the CNR increase and the PC plays an important role in efficiently improving the CNR.
Photographic Observation System for DC Prebreakdown Phenomena in Dielectrics Using the Long Image Guide Scope
Authors: Kazunori Kadowaki Kazunori Kadowaki , Shinichi Arikawa Shinichi Arikawa , Sakae Nishimoto Sakae Nishimoto , Isamu Kitani Isamu Kitani
Published: October 2002

The observation technique for dc prebreakdown in dielectrics was established by the use of a long image guide scope which was set in front of an image intensifier with a high speed gate. The passage time of a prebreakdown image through the scope was longer than the response delay time of the gate. Therefore the gate could be closed as soon as the prebreakdown image arrived at the image intensifier.
Saturation Effect on the Lineshape of Faraday Rotation Spectrum in Krypton
Authors: Miyakoshi Daisuke , Aoyama Makoto , Tohei Takehisa , Minoh Arimichi , Motowo Tsukakoshi Motowo Tsukakoshi
Published: October 2002

The Faraday rotation spectra were observed at 810.4 nm of the 5s
12–5p
22 transition in atomic krypton using a single mode diode laser. The lineshapes at the resonance were changed largely with laser intensity. At a low laser intensity the lineshape is a normal form of the differential of a dispersion curve. As the laser intensity increases, a Gaussian curve appears, overlapping the normal curve. At a sufficiently high laser intensity, the Gaussian component dominates the latter. The spectral change is ascribed to the development of optical and Zeeman coherence.
Production of Carbon Clusters Using Plasma Chemical Vapor Deposition in He/CH4 Glow Discharge
Authors: Sasaki Suguru , Kitagawa Nobuhiko , Noriharu Takada Noriharu Takada , Masaaki Nagatsu Masaaki Nagatsu
Published: October 2002

The production of carbon clusters using the chemical vapor deposition process in He/CH4 glow discharge plasma has been carried out. A relation between the soot content and plasma discharge conditions has been examined by changing the gas-mixture ratio of helium and methane gas pressures. Optical emission spectra were measured to determine the existence of carbon atoms, hydrogen atoms and C2 components, which are the by-products during the synthesis of carbon clusters. The soot deposited on the substrate or on an inner chamber wall was analyzed using a laser desorption reflectron time-of-flight mass spectrometer (TOF-MS). Results showed that carbon clusters of C
n
with n=10–50 were produced in the He/CH4 glow discharge plasma. Furthermore, C60 fullerene was also observed in addition to the lower C
n
carbon clusters.
Dynamic Aperture for High-Brilliance Optics of the Photon Factory Storage Ring
Authors: Kim Eun-San , Yukinori Kobayashi Yukinori Kobayashi , Masahiro Katoh Masahiro Katoh
Published: October 2002

The dynamic apertures in several lattices for the low emittance of the Photon Factory storage ring (PF ring) have been investigated by a simulation method using the code Strategic Accelerator Design (SAD). The dynamic apertures in each lattice without and with machine errors were obtained by a tune survey in the simulation. It was also shown how large are the dynamic apertures compensated after corrections of a closed orbit distortions. The operating tunes in low-emittance lattices can be obtained based on the view point of dynamic apertures obtained from a tune survey. It is shown that a low-emittance 90° cell lattice provides sufficient dynamic aperture after a correction of the closed orbit distortion in the PF ring.
Phase Retrieval from Defocused Images and Its Applications in Lithography
Authors: von Bunau Rudolf M. , Hiroshi Fukuda Hiroshi Fukuda , Tsuneo Terasawa Tsuneo Terasawa
Published: October 2002

This paper discusses the application of iterative phase retrieval method to phase measurement in optical lithography. A simple algorithm was developed for reconstructing phase information from image intensity distributions measured under different defocus conditions. The phase distribution in the image plane and in the pupil plane are reconstructed from the images obtained using the micro-lithography simulation microscope, MSM100 (Zeiss). Two applications of this method in optical lithography meteorology were investigated. First, the phase transmission of phase-shifting masks was successfully measured both for alternating and for attenuating type masks. The reconstructed phase showed that the uniform background of light leaking from the opaque regions on the mask can affect the phase in the image plane. Second, the possibility of using this method in measuring aberrations of projection optics was examined.
A Fast Eliminating System of Narrow Electron-Beam Exposure-Figures for Improving Pattern Accuracy
Authors: Moriizumi Koichi , Nakao Hiroomi , Kamiyama Kinya , Kitada Osamu , Taoka Hironobu , Masayuki Terai Masayuki Terai , Hisaharu Miwa Hisaharu Miwa
Published: October 2002

We have developed a system for fast elimination of narrow electron-beam (EB) exposure-figures, which degrade pattern accuracy when using a variable shaped writing scheme. In order to reduce the processing time, a hierarchical and a distributed processing method have been developed. In addition, two kinds of narrow-figure elimination methods have been evaluated for further reduction of the processing time: a whole figure-merge method and a pinpoint figure-merge method. It was found that both methods must be selectively used because the best method strongly depends on the total amount of initial narrow figures in input data. The developed system has been applied to EB exposure data for 5× reticles of a 256 Mbit dynamic random access memory (DRAM). The pinpoint figure-merge method was used because its processing speed was 1.5 times higher than the other method for this case. The narrow-figure elimination has been completed successfully in a practical time; it was 2.8 hours for 4 critical layers of a 256 Mbit DRAM.
Mechanical Modeling of Projection Electron-Beam Lithography Masks
Authors: Dicks Gerald A. , Engelstad Roxann L. , Liddle Edward G. Lovell
Published: October 2002

The production of microchips with circuit features in the sub-0.13 µm regime will require an advanced lithography technique such as SCattering with Angular Limitation Projection Electron Lithography (SCALPEL). The mask used in this technique is subject to intrinsic and extrinsic loads during fabrication, mounting, and exposure, giving rise to mechanical distortions which lead to pattern placement errors. In order to develop a low distortion mask, finite element models have been created to identify sources of distortion and quantify the resulting errors. The models are then used as predictive tools to optimize the design of the mask so that distortions do not exceed the error budget. The focus of this study was to investigate the mask membrane distortions induced during the fabrication process and pattern transfer for a preliminary test case of a SCALPEL mask. More specifically, out-of-plane and in-plane distortions were calculated and the sensitivity of this response to variations in mask design parameters was determined.
Pitch Dependence of Linewidth in the 0.25 µm Patterns Fabricated Using Positive Chemically Amplified Resist
Authors: Usujima Akihiro , Wada Hajime , Oikawa Akira , Kaimoto Yuko , Kenji Nakagawa Kenji Nakagawa
Published: October 2002

We investigated the proximity bias characteristic of 0.25 µ m patterns used with three types of positive chemically amplified resists of differing material and properties. To determine the proximity bias characteristics, we examined how the relationship between the pitch and the linewidth varies with post-exposure-bake (PEB) temperature and time. Our experiment revealed that each resist exhibits its own unique proximity bias characteristics. We also found that the proximity bias characteristics of the three resists depended to a large extent on the PEB temperature: the lower the PEB temperature, the greater the resemblance of the proximity bias characteristics to the optical characteristic. Considering this and using the pitch vs. linewidth curve with PEB time as a parameter, we concluded that the proximity bias characteristic of resists largely depends on the diffusion of acids and other thermal effects in the resists. These characteristics resemble optical characteristics as the PEB temperature decreases, the acids diffuse to a lesser extent, and the thermal effects decrease.
High-Aspect-Ratio Nanometer-Pattern Fabrication Using Fullerene-Incorporated Nanocomposite Resists for Dry-Etching Application
Authors: Shibata Tomohiro , Ishii Tetsuyoshi , Hiroshi Nozawa Hiroshi Nozawa , Toshiaki Tamamura Toshiaki Tamamura
Published: October 2002

This paper presents the improved performance of a nanocomposite resist system that incorporates an unseparated mixture of fullerenes C60 and C70 into ZEP520, a positive electron-beam resist, particularly focusing on the enhancement of mechanical strength and dry-etching resistance. This system exhibits similar improvements to that of a pure C60-incorporated system; 90-nm-pitch high-aspect-ratio (>5) resist patterns without pattern collapse and a 10-% enhancement of dry-etching resistance are obtained in a 10-wt% fullerene mixture-incorporated system due to the reinforcement effect induced by the fullerene incorporation. In addition, 80-nm-pitch resist patterns are successfully transferred to SiN film by C2F6-reactive ion etching without any harmful effects. The use of an unseparated mixture of C60 and C70, which is commercially available at a much lower price than pure C60, will greatly facilitate the practical application of the nanocomposite resist system from the economic point of view.
Low-Temperature Dry Etching of GaAs and AlGaAs Using 92-MHz Anode-Coupled Chlorine Reactive Ion Etching
Authors: Saitoh Tadashi , Tetsuomi Sogawa Tetsuomi Sogawa , Hiroshi Kanbe Hiroshi Kanbe
Published: October 2002

The etching characteristics and the damage induced by low-temperature etching have been studied using 92-MHz anode-coupled reactive ion etching. Due to the suppression of sidewall etching, vertical profiles of GaAs and AlGaAs have been obtained by lowering the substrate temperature during etching. The etching rates of GaAs and AlGaAs become identical at low temperatures. The exciton peak intensity in the photoluminescence spectrum decreased with a decrease in etching temperature, suggesting a slight increase in damage in low-temperature etching. It is also found that pronounced stoichiometry change in the subsurface region takes place in low-temperature etching.
Electron Beam Doping by Superdiffusion in Unirradiated Regions (X<300 Å) of Semiconductors at Room Temperature
Authors: Wada Takao , Fujimoto Hiroshi , Toyota Daisuke , Masuda Haruho , Yamada Yoshiyasu , Mizusawa Kenichi
Published: October 2002

Electron beam doping processes in the damageless region and at room temperature were investigated before annealing. In the three-layer system of layer 3/layer 2/layer 1, the impurity sheet (layer 2) was sandwiched between two semiconductor wafers. The surface of layer 3 was irradiated with electron beams of 750 keV and 7 MeV. Interstitials of displaced atoms in the overlayer, which were introduced by irradiation, migrated to the surface of the semiconductors. These interstitials diffused rapidly at the surface with a very large surface diffusivity of ∼10-5 cm2· s-1. The diffusion process was observed using an atomic force microscope (AFM). Impurity concentrations in the surface layer during irradiation were found to be on the order of matrix atom concentration. Electron irradiation produced a number of self-interstitials that migrated with large surface diffusivities at the surface. Diffusion was enhanced due to the kick-out mechanism at the interface of the system and in the depth direction of the semiconductors.
50 nm Pattern Etching of Si Wafer by Synchrotron Radiation Excited CF 4 Plasma
Authors: Ryoichi Inanami Ryoichi Inanami , Tomoya Yamada Tomoya Yamada , Shintaro Ohsaki Shintaro Ohsaki , Shinji Ogawa Shinji Ogawa , Shinzo Morita Shinzo Morita
Published: October 2002

50 nm lines and spaces pattern etching on a Si wafer in a synchrotron radiation (SR) excited CF4 gas atmosphere was performed under a negative bias voltage in which the SR light beam was irradiated perpendicularly to the Si wafer. As etching species, positive ions are expected to be predominant. The SR excited plasma and the excited species are discussed.
Fabrication of Two-Dimensional InP Photonic Band-Gap Crystals by Reactive Ion Etching with Inductively Coupled Plasma
Authors: Fujiwara Yasufumi , Kikuchi Koji , Hashimoto Masayuki , Hatate Hitoshi , Imai Toshiaki , Takeda Yoshikazu , Nakano Hirohiko , Honda Masahiro , Tatsuta Toshiaki , Tsuji Osamu
Published: October 2002

We fabricated two-dimensional (2D) InP photonic band-gap crystals by reactive ion etching (RIE) with a SiCl4/Ar inductively coupled plasma (ICP) chemistry, and characterized their reflective characteristics in the optical wavelength region by Fourier-transformed infrared reflection absorption spectrometry (FTIR-RAS). The photonic band-gap crystals consisted of a periodic array of parallel air rods of circular cross section whose intersections with a perpendicular plane form a triangular lattice in InP substrates. Prior to the fabrication of the periodic array of air rods, the photonic band structure for electromagnetic waves was calculated theoretically in the sample structure and was predicted to appear in the optical wavelength region. In RIE with the SiCl4/Ar ICP chemistry, we systematically investigated the InP etch rate and the etch selectivity of InP over SiO2 as functions of various etching parameters, to fabricate deep air rods with a vertical profile. The effect of the N2O addition to the SiCl4/Ar ICP chemistry was investigated and it was revealed that the addition of a small amount of N2O results in an improvement in the vertical profile with a slight increase in the InP etch rate. The InP etch rate and the etch selectivity of InP over SiO2 depended strongly on the SiCl4 flow rate. In FTIR-RAS measurements, characteristic features were observed in the optical wavelength region, depending on the diameter of the air rods. Behaviors of the features were discussed in relation to theoretically calculated densities of states.
Ordered Two-Dimensional Nanowire Array Formation Using Self-Organized Nanoholes of Anodically Oxidized Aluminum
Authors: Shingubara Shoso , Okino Osamu , Sayama Yasuyuki , Hiroyuki Sakaue Hiroyuki Sakaue , Takayuki Takahagi Takayuki Takahagi
Published: October 2002

Self-organization of a two-dimensional array of nanoholes which were formed by anodic oxidation of aluminum was investigated quantitatively using fast Fourier transformation (FFT) analysis of scanning electron microscopy (SEM) images. The highly ordered array of nanoholes with diameters of 26 nm was obtained by two-step anodization at anodic voltage around 40 V, and oxalic acid concentration of 0.5 M. A two-dimensional ordered array of Au free standing nanowires was successfully fabricated by the deposition of Au using DC electroplating in nanoholes of aluminum oxide, by removal of the aluminum oxide barrier layer using wet chemical etching. The present method has a high efficiency to fabricate ordered nanowire array of a variety of conductive materials in a large area, and wide applications for fabricating quantum effect devices and materials would be expected.
Theory on High-Vacuum Planar Magnetron Discharge
Authors: Tsutomu Miura Tsutomu Miura , Tatsuo Asakaki Tatsuo Asakaki
Published: October 2002

A theory on high-vacuum planar magnetron discharge for the wide range of E
a/B
A>2.0×106/n V/(m·T) has been developed (E
a: magnitude of the average electric field strength; B
A: magnetic flux density at the anode; n: power index of the potential distribution). The relevant parameters on the ionizing collisions and the geometrical factors from the cross section of erosion are incorporated in the theory. The discharge current I becomes a function of E
a/B
A with the parameter of B
A. With E
a/B
A fixed, I∝B
A is shown. The optimum E
a/B
A ratio gives the local maximum of I. This ratio depends on n and the power index of magnetic flux density distribution N. In the range of E
a/B
A≧2.3×107/n V/(m·T), function I becomes the simple form I∝E
a

M

B
A
1-M
, where M=N/(n-1+N). Experimental work has also been carried out.