bluuebunny/crossref_metadata_2025 huggingface dataset:
Fraction of Interstitialcy Component of Phosphorus and Antimony Diffusion in Silicon
Authors: Takashi Shimizu Takashi Shimizu , Toshio Takagi Toshio Takagi , Satoru Matsumoto Satoru Matsumoto , Yoshiyuki Sato Yoshiyuki Sato , Eisuke Arai Eisuke Arai , Takao Abe Takao Abe
Published: October 2002

The effect of nitride films on the diffusion of phosphorus and antimony in silicon has been investigated, in order to extract the fractional interstitialcy component of these dopant diffusion. Nitride film deposited on silicon substrate is used as an extrinsic source of vacancies. The phosphorus diffusion is retarded and the antimony diffusion is enhanced in silicon under nitride films. By observing the variation of the retardation in phosphorus diffusion and the enhancement in antimony diffusion, it is determined that the fraction of interstitialcy component in phosphorus and antimony diffusion is approximately 0.96 and 0, respectively.
Control of the Exchange-Coupling Force in Magnetic Super Resolution Magnetooptical Recording Media with In-Plane Magnetization Layers
Authors: Nishimura Naoki , Tsunashima Shigeru
Published: October 2002

The exchange-coupling force between GdFeCo readout layers and TbFeCo memory layers has been investigated for magnetically induced super resolution (MSR) magnetooptical recording media with in-plane magnetization layers. The exchange-coupling force can be suppressed in the mask area while mediated in the aperture area by introducing GdFe intermediate layers with large negative perpendicular magnetic anisotropy at room temperature and with relatively low Curie temperatures. As a result, the masking effect is substantially improved, and the recorded information of the memory layer can be copied more completely onto the readout layer at readout temperatures, resulting in a higher performance of MSR media.
Reduction of the Floating Body Effect in SOI MOSFETs by Using Schottky Source/Drain Contacts
Authors: Mika Nishisaka Mika Nishisaka , Tanemasa Asano Tanemasa Asano
Published: October 2002

A new silicon-on-insulator metal-oxide-semiconductor field-effect transistor (SOI MOSFET) structure, which employs the Schottky contacts at the source/drain, is proposed to suppress the floating-body effect. Using a Schottky contact, excess holes in the channel region are smoothly absorbed into the source and the impact ionization near the drain is reduced due to the built-in field. Analysis with two-dimensional simulation verifies these effects. As a result, the early drain breakdown of the SOI MOSFET is suppressed. A test device fabricated using Er silicide self-aligned technology proves the technical feasibility of the proposed device.
Formation of an Atomically Abrupt Si/Ge Hetero-Interface
Authors: Keiji Ikeda Keiji Ikeda , Satoshi Sugahara Satoshi Sugahara , Yasutaka Uchida Yasutaka Uchida , Tomonori Nagai Tomonori Nagai , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

A novel method has been proposed for forming an abrupt interface in the Si/Ge heterostructures. Solid Si network of two monolayers in thickness was successfully grown on a Ge(100) surface. The Si/Ge transition layer, fablicated by the proposed method and a successive gas-source moleculer beam epitaxy was found to be atomically narrow, since it was less than 1 nm in width which is the resolution limit of the evaluation system.
Mechanisms of X-Ray Radiation-Induced Damage in (Ba, Sr)TiO3 Capacitors
Authors: Tarutani Masayoshi , Suita Muneyoshi , Horikawa Tsuyoshi , Tanimura Junji , Kawahara Takaaki , Yamamura Mikio , Sumitani Hiroaki , Ono Kouichi
Published: October 2002

X-ray radiation-induced damage has been investigated for (Ba, Sr)TiO3 [BST] capacitors prepared by chemical vapor deposition (CVD). Synchrotron radiation (SR) X-ray irradiation with ∼1.65 keV photons was conducted directly on the Pt/BST/Pt and Ru/BST/Ru capacitors at different dose levels of 10, 50 and 130 mJ/cm2. Measurements of the leakage current versus applied voltage showed an increase in the leakage current caused by X-ray irradiation. The degree of degradation in the current leakage tended to depend both on the X-ray dose and on the initial film properties. However, upon a subsequent annealing at 400°C in an O2 ambient, the degradation was seen to be completely removed and the initial properties were recovered. The degradation and its observed recovery are ascribed to the creation and annihilation of trapped positive charges in BST films, induced by charge damage.
Ultrahigh-Speed Integrated Circuits Using InP-Based HEMTs
Authors: Enoki Takatomo , Yokoyama Haruki , Umeda Yohtaro , Otsuji Taiichi
Published: October 2002

The device technologies for 0.1-µm-gate InP-based high electron mobility transistors (HEMTs), which consist of an InAlAs/InGaAs modulation-doped structure on an InP substrate, are described. They yielded a current gain cutoff frequency (f
T) of over 180 GHz and a transconductance (g
m) of over 1 S/mm in circuits. An InP recess-etch stopper improved the uniformity of threshold voltage and enabled us to apply HEMTs in digital ICs. A diode consisting of an InAlAs Schottky junction is monolithically integrated with a HEMT and used as a level shifter in digital ICs. By combining novel circuit technologies and the HEMT-IC technologies, the maximum operation speed of IC has been pushed up to over 40 Gbit/s. As a benchmark for future large-capacity networks, electrically multiplexed and demultiplexed 40 Gbit/s, 300 km transmission was successfully demonstrated using the device technologies described here.
Wafer Bonding of InP to Si and its Application to Optical Devices
Authors: Wada Hiroshi , Kamijoh Takeshi
Published: October 2002

Wafer bonding technology has been investigated to integrate InP lasers on Si wafers for optoelectronic integrated circuits. Room temperature continuous-wave (CW) operation of edge-emitting lasers and photo-pumped operation of surface-emitting lasers have been achieved. A novel bonding process which allows an integration of the optical devices on structured wafers, such as Si LSI wafers, has also been proposed. The wafer bonding is thought to be a promising technique to implement optical interconnections between Si LSI chips.
Improved Response of Uni-Traveling-Carrier Photodiodes by Carrier Injection
Authors: Shimizu Naofumi , Watanabe Noriyuki , Furuta Tomofumi , Ishibashi Tadao
Published: October 2002

We have studied the ultrafast response of uni-traveling-carrier photodiodes with photo-absorption layer doping levels from 2.5 ×1017 to 2.5 ×1018 cm-3. It is found that 3-dB band width increases with the output voltage in the low output region. This enhancement is more prominent for a lower doping level in the photo-absorption layer. From the analysis of the carrier transport in the photo-absorption layer, we attribute the observed enhanced bandwidth as a result of the self-induced electric field associated with carrier injection.
Highly Reliable Operation of InGaAlAs Waveguide Photodiodes for Optical Access Network Systems
Authors: Nakamura Hitoshi , Shishikura Masato , Tanaka Shigehisa , Matsuoka Yasunobu , Ono Tsunao , Tsuji Shinji
Published: October 2002

Reliability of InGaAlAs mesa waveguide photodiodes suitable for low-cost modules applied to access network systems is investigated. Stable operation for 9600 hours has been confirmed so far in the bias-temperature accelerated aging test. Median lifetime at a field service temperature of 85°C is estimated to be over 100 years by using the measured activation energy of 0.48 eV. Change in dark current during aging is explained by the hole accumulation at the interface between a crystal surface and a passivation film. The waveguide photodiode is confirmed to be highly reliable for access network applications.
Interface Effects on the Photoluminescence of GaAs/GaInP Quantum Wells
Authors: Vanelle Eric , Mesrine Magali , Grandjean Nicolas , Christiane Deparis Christiane Deparis , Jean Massies Jean Massies
Published: October 2002

The influence of indium surface segregation, As–P exchange at the interfaces and residual incorporation of As and P on the photoluminescence properties of GaAs/GaInP quantum wells, is investigated both theoretically and experimentally. It is shown that these effects may lead to an important energy shift or compensate each other depending on growth conditions. As a consequence the exploitation of photoluminescence spectra in such heterostructures have to be carefully carried out. Four samples have been especially designed to study, in addition to indium segregation, the As–P exchange at the GaAs on GaInP interface. Their low temperature photoluminescence study illustrates the complex behaviours observed in this material system. Photoluminescence spectra are shown to be very sensitive to the interface chemistry, in particular As–P exchange.
Hall Effect in Fe–Cr–Co Alloy Thin Films
Authors: Chang Hui-Chen , Yen-Hwei Chang Yen-Hwei Chang , Shyue-Yen Yao Shyue-Yen Yao
Published: October 2002

This paper presents the Hall effect and microstructure of Fe–XCr–10Co, Fe–XCr–Co (weight ratio W

F
e/W

C
o=1), and Fe–60Cr–XCo alloy films. After deposition by ion beam sputtering (IBS), the Hall voltage (V

H) and Hall coefficient (R

H) values of the as-deposited films were found to be small. After heat treatment, phase separation into α1 (ferromagnetic phase) and α2 (paramagnetic phase) was observed and verified by high resolution transmission electron microscope (HRTEM). By aging the Fe–60Cr–15Co films at 550° C for 80 min, we found the maximum Hall resistivity (ρ
H) and Hall voltage (V

H) values which are 30 µ Ω· cm and 1.2 mV, respectively (measured at 77 K and 14 kOe). The extraordinary Hall coefficient (R

S) is about 0.408 cm3/C. The Hall coefficient is positive for both as-deposited and annealed films. The alloy composition and heat treatment condition which influence film's microstructure obviously affect the Hall property.
Effective Medium Approximation in Voronoi Network Systems
Authors: Tomoyuki Nagaya Tomoyuki Nagaya , Yoshihiro Ishibashi Yoshihiro Ishibashi
Published: October 2002

The validity of the effective medium approximation in the two-dimensional Voronoi network is investigated. Two different Voronoi network models are introduced as the electric models of the polycrystalline materials. One is a random resistor model in which the Voronoi polygon and the boundary between the polygons are regarded as an insulator and a resistor, respectively. The other is a random capacitor model in which the Voronoi polygon and the boundary are regarded as a pure conductor and a capacitor, respectively. It is found that the accuracy of the effective medium approximation for the Voronoi network models is sufficient to estimate the average resistance or capacitance of the network.
Tunable, Strongly Non parabolic Confinement in a Quasi-One-Dimensional Electron Gas Formed by Epitaxial Regrowth
Authors: Ciná Salvatore , Arnone Donald D. , Burroughes Jeremy H. , Norman Carl E. , Burke Theresa , Hughes Howard P. , Pepper Michael , Ritchie David A.
Published: October 2002

A new type of quasi-one-dimensional electron gas (Q1DEG) characterised by a tunable, strongly non parabolic confining potential in the lateral direction has been produced, using molecular beam epitaxy to grow a high-mobility heterostructure on a (311)A GaAs substrate selectively etched to expose (100) facets. The electron gas on the (100) facets is confined in one dimension by the two-dimensional hole gases on the (311)A facets, forming a p-n-p structure. Infrared cyclotron resonance (CR), magneto resistance and electron-beam-induced current (EBIC) measurements have been made on these Q1DEGs for various biases (V
h) between the hole and electron gases to investigate its effects on the confinement potential. Two different regimes are present. For V
h>-1.9 V, a strong peak attributable to a confined magnetoplasmon (CPM), together with its higher-frequency harmonics, are observed in the CR spectra. For V
h<-1.9 V, a new mode appears and the CPM no longer fits the experimental data. The anomalous dependence of the resonance frequency on carrier density, together with the EBIC images, provides some understanding of the tunable, non parabolic nature of the confining potential.
Room Temperature Nb-Based Single-Electron Transistors
Authors: Shirakashi Jun-ichi , Matsumoto Kazuhiko , Miura Naruhisa , Konagai Makoto
Published: October 2002

Room temperature operation of Nb/Nb oxide-based single-electron transistors (SETs) was successfully achieved and was reported in detail. First, the SETs were fabricated using a scanning probe microscope (SPM)-based anodic oxidation technique and then the junction area was further reduced by thermal oxidation. Ultra-small tunnel junctions were easily obtained by utilizing these two types of oxidation processes, and clear single-electron charging effects were observed through the Nb/Nb oxide-based SETs at room temperature.
Electric Field Induced Recombination Centers in GaAs
Authors: Atsushi Kawaharazuka Atsushi Kawaharazuka , Kenji Shiraishi Kenji Shiraishi , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

We investigated the lateral electric field effect in a GaAs/AlGaAs single quantum well and in AlGaAs and GaAs single layers. We observed the quenching of photoluminescence spectra at low temperatures even when the electric field was much lower than that required for the dissociation of the excitons. To explain this phenomenon we propose a model of new recombination center formation by considering the displacement of charged atoms. We also performed theoretical calculations. By ab initio calculations, we found that a meta-stable state exists when negatively charged Ga atoms are displaced to the interstitial sites. The calculated potential barrier height from the stable state to the meta-stable state was as high as 0.5 eV. However, the meta-stable to stable transition barrier height was only 0.05 eV. These results are consistent with the experimental results.
In-Situ Contactless Characterization of Microscopic and Macroscopic Properties of Si-doped MBE-Grown (2×4) GaAs Surfaces
Authors: Hashizume Tamotsu , Ishikawa Yasuhiko , Yoshida Toshiyuki , Hasegawa Hideki
Published: October 2002

Correlation between macroscopic electronic properties of the molecular beam epitaxy (MBE)-grown Si-doped GaAs (001) (2×4) surfaces with microscopic atomic structures was in situ investigated using ultrahigh vacuum scanning tunneling microscope (UHV STM), UHV contactless capacitance-voltage (C-V), UHV photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) techniques. Surface defects including kinks, steps, holes, islands and missing As atoms in As dimer rows were observed at the Si-doped (2×4) GaAs surfaces. Contactless C-V results directly showed the surface Fermi level pinning. The observed macroscopic C-V and PL behavior cannot be explained by the previous kink-acceptor model, assuming that each kink forms a discrete acceptor level, but it indicates Fermi level pinning by U-shaped continuous surface states.
Low Temperature Near-Field Photoluminescence Spectroscopy of InGaAs Single Quantum Dots
Authors: Saiki Toshiharu , Nishi Kenichi , Ohtsu Motoichi
Published: October 2002

We investigate InGaAs single-dot photoluminescence spectra and images using a low-temperature near-field optical microscope. By modifying the commonly used near-field technique, a high spatial resolution and high detection efficiency are achieved simultaneously. Local collection of the emission signal through a 500 nm (λ/2) aperture contributes to the single-dot imaging with a λ/6 resolution, which is a significant improvement over the conventional spatially resolved spectroscopy. Tailoring the tapered structure of the near-field probe enables us to obtain the emission spectra of single dots in the weak excitation region, where the carrier injection rate is ∼107 excitons/s per dot. By employing such a technique, we examine the evolution of single-dot emission spectra with excitation intensity. In addition to the ground-state emission, excited-state and biexciton emissions are observed for higher excitation intensities. By a precise investigation of the excitation power dependences of individual dots, two-dimensional identification of their emission origins is obtained for the first time.
Maskless Selective Epitaxial Growth on Patterned GaAs Substrates by Metalorganic Chemical Vapor Deposition
Authors: K. Park Chang-Sik Son , Kyu Kim Seong-Il Kim , Suk-Ki Min Suk-Ki Min , In-Hoon Choi In-Hoon Choi
Published: October 2002

Maskless one-step selective CCl4-doped GaAs epilayers have been grown on patterned GaAs substrates by atmospheric pressure metalorganic chemical vapor deposition. The growth technique has potential for realizing a well-defined quantum confinement structure and lateral structure device. Round shaped CCl4-doped GaAs epilayer was selectively grown inside a U-groove and on the sidewalls of a mesa with a significant lateral growth rate enhancement, whereas no growth was observed outside U-groove and on top of the mesa.
Growth of Luminescent GaAsP on Si Substrate by Metalorganic Molecular Beam Epitaxy Using GaP Buffer Layer
Authors: Masahiro Yoshimoto Masahiro Yoshimoto , Yasuhiro Watanabe Yasuhiro Watanabe , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

GaAs1-x
P
x
(0.2<x<0.7) was grown on a Si substrate with a GaP buffer layer by metalorganic molecular beam epitaxy. The surface smoothness was taken to be an indicator for the improvement of GaAsP crystallinity. The optimal growth temperature and thickness of the buffer layer for obtaining a smooth surface were determined based on results of atomic force microscopy and reflection high-energy electron diffraction. While GaAsP epilayers grown directly on Si showed no photoluminescence (PL), GaAsP grown on Si with a thin GaP buffer layer (∼100 Å) at 300°C showed PL. GaAsP epilayers of n-type were obtained with Sn-doping during growth. The electron conduction in n-type GaAsP was explained by carrier conduction in both the Γ valley and the X valley.
Medium-Range Structure in Chalcogenide Glasses
Authors: Tanaka Keiji
Published: October 2002

The first sharp diffraction peak which signifies medium-range structural order in chalcogenide glasses has been studied based on some observations and the construction of ball-and-stick models. The crystalline model originally proposed by Vaipolin and Porai-Koshits provides straighforward explanations for most features.
Reactive Ion Etching of ZnS Films using a Gas Mixture of Methane/Hydrogen/Argon
Authors: Su Shui Hsiang , Yokoyama Meiso , Su Yan Kuin
Published: October 2002

ZnS epitaxial layers grown using metalorganic vapor phase epitaxy were etched by reactive ion etching (RIE) employing a gas mixture of CH4, H2 and Ar. The etching rates were investigated as functions of the plasma parameters: rf power density, the relative composition and the total flow rate of reactive gases. It was determined that the amount of CH4 in CH4/H2 gas discharge decides whether a polymer will be produced. The optimum composition of the mixed gas was 1CH4/7H2/4Ar, when the pressure, rf power density and total flow rate were 30 mTorr, 0.4 W/cm2 and 30 sccm, respectively. The quality of the etched surfaces under these conditions was examined using X-ray photoelectron spectroscopy and photoluminescence. It was determined that the etching process does not damage the ZnS film based upon the results of photoluminescence spectra.
Effect of Foreign Gas on Peak Power and Rotational Relaxation for Optically Pumped CO2 4.3 µm Laser
Authors: Shimizu Fumiko O. , Homma Takahiro , Nakao Masaya , Takahashi Hiroki , Hirata Tadashi , Minoh Arimichi
Published: October 2002

From the peak output power measurement for the optically pumped CO2 4.3 µm pulse laser, the effect of foreign gas and the molecular dynamics are examined. For the CO2 4.3 µm and 10.6 µm pump sequence laser pulses occurring in the same discharge tube, the optimization of the peak output power is discussed. The J-profile of delay time from the start of the pump sequence pulse to the peak of the 4.3 µm laser pulse indicates that rotational relaxation due to CO2–CO2 collision via |ΔJ|=2 transition occurs, and also suggests the inclusion of the |ΔJ|>2 transition process.
PdGeSbTe Alloy for Phase Change Optical Recording
Authors: Hirota Kusato , Ohbayashi Gentaro
Published: October 2002

Phase change optical recording disks using a Pd–Ge–Sb–Te quaternary alloy demonstrated high crystallization speed and long-term thermal stability of the amorphous recording marks. This alloy film can be crystallized by a short duration laser pulse of less than 100 ns. It is applicable to a single beam overwrite optical recording system. The crystallized portion of this recording layer on the disk is assigned to single phase and polycrystalline face-centered-cubic (fcc) crystals by transmission electron diffraction. A small amount of Pd atoms (typically 0.2 to 3 at.%) in this alloy improve the thermal stability of amorphous marks.
Characterization of n-CdSe0.7Te0.3/(aq) Polyiodide Energetic Interface and Photoelectrochemical Studies
Authors: Das V. Damodara , Damodare Laxmikant
Published: October 2002

The vacuum deposited thin films of n-CdSe0.7Te0.3 of 5000 Å thickness have been characterized by X-ray diffraction (XRD) for structural analysis, by energy despersive analysis of X-rays (EDAX) for compositional analysis and the scanning electron microscopy (SEM) for surface studies. Similar films have been deposited on Indium Oxide precoated microslide glass plates and the photoelectrochemical properties of n-CdSe0.7Te0.3/polyiodide junction are investigated for suitability for solar energy conversion by I–V measurements in the dark. Also, the carrier concentration and flat band potential have been calculated from the space charge capacitance vs voltage measurements. The minority carrier diffusion length, L
p has been determined using Gärtner's model. Using the Mott-Schottky plots, the energy band diagram at flat band condition has been constructed. The occurrence of high quantum efficiency and high power conversion efficiency have been explained.
Development of Piezoelectric Accelerometer of Charge-Shear Type Having Temperature-Independent Sensitivity
Authors: Ochiai Tsutomu
Published: October 2002

A piezoelectric accelerometer based on detecting piezoelectric charge Q
1 caused by shear strain S
5 has been developed, which consists of two piezoelectric elements made from a ferroelectric ceramic and one condenser element also made from a ferroelectric ceramic. Positive temperature dependence of dielectric constant of the former piezoelectric element (PbZr0.51Ti0.49O3 modified with 0.7 mol% Nb2O5) is compensated by negative dependence of the latter condenser element [Pb0.8La0.2(Zr0.4Ti0.6)0.95O3 or Pb0.7Sr0.2La0.1(Zr0.5Ti0.5)0.975O3] over a range of -50 to 300°C, with the result that sensitivity and its deviation are obtained to be 42×10-12 C/G and within 5%, respectively.
Dynamical Properties of Solid CO2 under Shock Compression
Authors: Koichi Tanaka Koichi Tanaka , Yasushi Ido Yasushi Ido
Published: October 2002

In this study, particle velocities and stresses in solid phase carbon dioxide were measured for pressures up to 500 MPa, using the split Hopkinson pressure bar method and the plate impact method. The particle velocities were measured using the electromagnetic induction method, while the stresses were measured using Polyvinylidene fluoride gauges. The shock Hugoniot is obtained mainly by employing the impedance match method. Also, some macroscopic change of the granular structure under shock loading was observed. The experimental results indicate that a transition from the shock compression curve to the isothermal compression curve occurs at around 110 MPa.
Compositional Inhomogeneity of InGaN Grown on Sapphire and Bulk GaN Substrates by Metalorganic Chemical Vapor Deposition
Authors: Sato Hisao , Sugahara Tomoya , Naoi Yoshiki , Sakai Shiro
Published: October 2002

The compositional inhomogeneity of the InGaN layers in GaN/InGaN/GaN double-hetero (DH) and InGaN/GaN single-hetero (SH) structures grown by metalorganic chemical vapor deposition (MOCVD) on sapphire (0001) and bulk GaN was investigated by means of cathodoluminescence (CL) and energy dispersive X-ray (EDX) spectroscopy. Dotlike CL image of the band edge emission from InGaN was observed. The bright spots were found to have higher indium content compared to that on the outside of the spots. The compositional inhomogeneity increased and the density of the spot decreased with increasing film thickness. Hexagonal hillocks, which had higher indium content and emitted stronger CL, were observed on the surface of the SH structure. Compositional inhomogeneity of homoepitaxial InGaN on bulk GaN substrate was much less compared to that of InGaN on sapphire revealing that dislocation plays a key role in producing an inhomogeneity. A possible mechanism that explains these phenomena is proposed.
Surface of Bi2Sr2CaCu2O y Single Crystals Heated in Air
Authors: Akito Tanaka Akito Tanaka , Satoru Kishida Satoru Kishida , Yasuhiro Yamauchi Yasuhiro Yamauchi , Heizo Tokutaka Heizo Tokutaka
Published: October 2002

We treated Bi2Sr2CaCu2Oy (BSCCO) superconducting single crystals at various temperatures in air and investigated their surfaces with X-ray photoelectron spectroscopy. From the results, we determined that the carbon and oxygen impurities on the surfaces of BSCCO single crystals were removed by heating them in air at 400°C for 1 h. This was also confirmed by an Auger electron spectroscopy. In addition, the results of the half-width of the Cu-2p main peak and the intensity ratio of satellite to main peaks indicated that the optimum heat treatment temperature for obtaining a clean surface of BSCCO single crystal was approximately 400°C. The method is thought to be effective for cleaning the surfaces of superconducting oxides with various formations.
Variation of Radial Plasma Density Profile with the Excitation Frequency in a Magnetron-Type Plasma
Authors: Wickramanayaka Sunil , Li Yunlong , Iizuka Satoru , Takagi Ken-ichi , Nakagawa Yukito , Tsukada Tsutomu , Sato Noriyoshi
Published: October 2002

The variation of the radial profile of plasma density with the excitation frequency was investigated using a magnetron-type plasma source. The plasma source is comprised of a cylindrical shaped rf electrode and two annular magnets attached to the outer surface of the rf electrode. As the excitation frequency of the plasma, 13.56 MHz, 40 MHz and 60 MHz were used. The radial profile of plasma density was observed in the downstream at 12 cm below the axial center of the rf electrode. Measurements were carried out for Ar plasma for pressures < 10 mTorr. The applied rf power varied from 200 W to 1500 W. The radial profile of the plasma density at a given distance from the axial center of the rf electrode changes with the change of excitation frequency. When the excitation frequency is 40 MHz, a radially uniform plasma could be obtained 12 cm below the axial center of the rf electrode. The nonuniformity of this plasma over an area of 300 mm diameter is <±5% regardless of the applied rf power. A change of pressure slightly affects the radial uniformity of the plasma. Plasmas produced by two other frequencies show a higher nonuniformity at the same distance from the axial center.
Fabrication of Sub-Micron Gap Structures using Directly-Deposited Amorphous Carbon Wires
Authors: Miura Naruhisa , Yamada Akira , Konagai Makoto
Published: October 2002

An amorphous carbon (a-C) wire was directly deposited using scanning electron microscopy to determine a sub-micron gap in coplanar-type metal electrodes. The wire was employed to a lift-off mask for defining the gap between source and drain electrodes. By newly employing a ZnO buffer layer for removing the a-C wire, a gap size of 60 nm was successfully achieved. Moreover, this process was applied to fabricate a superconducting weak link device using a heavily phosphorous-doped Si thin film as a channel material.
Quantitative Analysis of Domain Walls in Magneto-Optic Thin Films By Magnetic Force Microscopy
Authors: Phillips Gavin N. , Ito Yusuke , Suzuki Takao
Published: October 2002

A study of domain walls in amorphous TbFeCo alloy and Co/Pt multilayer thin
films suitable for magneto-optic recording has been made using magnetic force
microscopy. The quantitative analysis of magnetic force microscope (MFM) data
in order to obtain domain wall widths is outlined and a methodology for the
measurement of the dimensions of features in MFM images independent of
imaging conditions introduced. It was found that the size of features
corresponding to domain walls are approximately an order of magnitude larger
than expected.
Upper-bound Frequency for Measuring mm-Wave-Band Dielectric Characteristics of Thin Films on Semiconductor Substrates
Authors: Ikuta Kenji , Umeda Yohtaro , Ishii Yasunobu
Published: October 2002

The upper-bound frequency is estimated to be approximately 60 GHz, from the measurement on thin film capacitors of SrTiO3 (STO) deposited by the electron-cyclotron-resonance (ECR) sputtering. The upper-bound frequency is found to be defined by the parallel stray element located between the capacitor and the series stray element in the lead electrode. This parallel stray element was not included in our previous study. By changing stray circuit configuration from parallel-series to parallel-series-parallel, the upper-bound can be successfully extended from 60 GHz to 110 GHz. The measurable capacitance range is approximately two orders of magnitude (from 0.01 pF to 1 pF) for a 50-GHz upper-bound. And it is one order of magnitude for a 110-GHz upper-bound. It is also demonstrated that the ECR sputtered STO thin films can be used in a wide frequency range up to 110 GHz.
Effects of Microstructure on Optical Properties of Ge2Sb2Te5 Thin Films
Authors: Kim Jin-Hong , Kim Myong R.
Published: October 2002

The effects of thin film microstructure on the optical properties of Ge2Sb2Te5 recording
medium and their wavelength dependence were investigated. The microstructure of thin films
was modified by changing sputtering Ar gas pressure during sample preparation. The
variations in microstructure and film density were examined for samples prepared at various
Ar gas pressures. The optical properties were dependent on the sputtering gas pressure and
could be correlated with the film microstructure.
High Density Mastering Using Electron Beam
Authors: Kojima Yoshiaki , Kitahara Hiroaki , Kasono Osamu , Katsumura Masahiro , Wada Yasumitsu
Published: October 2002

A mastering system for the next-generation digital versatile disk (DVD) is
required to have a higher resolution compared with the conventional mastering
systems. We have developed an electron beam mastering machine which features
a thermal field emitter and a vacuum sealed air spindle motor. Beam
displacement caused by magnetic fluctuation with spindle rotation was about 60 nm(p-p)
in both the radial and tangential directions. Considering the servo gain of
a read-out system, it has little influence on the read-out signal in terms of
tracking errors and jitters. The disk performance was evaluated by recording
either the 8/16 modulation signal or a groove on the disk. The electron beam
recording showed better jitter values from the disk playback than those from a
laser beam recorder. The deviation of track pitch was 44 nm(p-p). We also
confirmed the high density recording with a capacity reaching 30 GB.
The Path from a Digital Versatile Disc (DVD) using a Red Laser to a DVD using a Blue Laser
Authors: Yokogawa Fumihiko , Ohsawa Seiichi , Iida Tetsuya , Araki Yoshitsugu , Yamamoto Kaoru , Moriyama Yoshiaki
Published: October 2002

The next generation digital versatile disc(DVD) using a blue laser
is required to have 15 Gbytes capacity so that it can reproduce motion
picture expert group 2(MPEG2) video stream with a main profile at a high
level format for a maximum of 133 min.
To achieve this goal, further improvements are necessary
in both the recording and the reproducing systems.
For the recording system the authors developed a super resolution
recording material and an electron beam recording system.
For the reproducing system the authors devised four technologies:
a Viterbi decoder, a liquid crystal tilt servo system, a cross
talk cancel system and a tangential adaptive equalizer.
By combining these with a pick up head of 430 nm vavelength/0.6 NA lens
and a 0.6-mm-thick substrate, the authors confirmed sufficient
tilt margins in the case of 12.7 Gbytes (radial tilt margin:
±1.61°, tangential tilt margin: ±0.48°).
Our next target is to work on the 15 Gbytes capacity.
A Compact Disc-Recordable Compatible Digital Versatile Disc Pickup with a Lens for 780 nm and 650 nm Wavelengths
Authors: Lee Chul Woo , Chung Chong Sam , Yoo Jang Hoon , Lee Yong Hoon , Kim Tae Kyung , Son Yong Ki , Kim Seok Jung , Kim Pyong Yong Seong and Kyung Sik
Published: October 2002

Two types of compact disc-recordable(CD-R) compatible digital versatile
disc (DVD) pickups have been developed.
One has separate conjugate points for DVD and compact disc(CD) readouts.
The other has a common conjugate point for DVD and CD readouts.
Optical and signal properties are considered for both types.
Both types have been shown to exhibit good qualities for practical use.
Coupling-Enhanced Control for Optical Disk Drives
Authors: Yang Jian-Dong , Pan Long-Fa , Pei Xian-Deng , Xu Duan-Yi
Published: October 2002

The positioning system of optical disk drives is becoming more and more important with the increase in the track density and rotation speed. Dual-stage actuators are used in the positioning servo system of optical disk drives. A coupling-enhanced design is intrudued for the tracking servo systems without a position sensor to detect the relative displacement between the two stages. By enhancing the coupling between the two stages, the first stage can obtain equivalent feedback information from the second stage. The tracking servo system can be designed as one servo loop, and only one controller is needed to control a dual-stage actuator. The multivariable problem can be treated as a single-variable problem and the design is simpler.
A Partial Response Maximum Likelihood Simulator to Evaluate the Effects of Various Deterioration Factors in Optical Disks
Authors: Yutaka Kashihara Yutaka Kashihara , Yuji Sakai Yuji Sakai , Yutaka Okamoto Yutaka Okamoto , Hiromichi Kobori Hiromichi Kobori
Published: October 2002

For higher density optical disks,
it has been examined whether
the partial response maximum likelihood (PRML) method can be used
for signal detection.
There have been, however, few theoretical studies about
this method under the condition that the readout signal is
deteriorated by various kinds of factors.
We have developed a PRML simulator for optical disks
to evaluate the PRML method theoretically
taking, for example, crosstalk and disk tilt into account.
We report the configuration of this PRML simulator and
some results the simulator has yielded.
Three-Dimensional Optical Memory Using Glasses as a Recording Medium through a Multi-Photon Absorption Process
Authors: Qiu Jianrong , Miura Kiyotaka , Hirao Kazuyuki
Published: October 2002

The feasibility of multilayered optical data storage was examined in SiO2 and Ge–SiO2
glasses by using a focused 800 nm, 120 fs, 200 kHz pulsed laser. The glasses are transparent
in the wavelengths ranging from 300 to 1000 nm. After the irradiation with the 800 nm
tightly focused femtosecond laser, a refractive-index bit was formed in the glasses. The
relationships between the size of refractive-index bit versus average power and irradiation
duration of the laser pulse have been examined. ESR spectra showed a significant increase in
the concentration of SiE' and GeE' color centers in the laser irradiated glasses. Writing 3-dimensional
refractive-index bit inside the transparent glasses based on a multi-photon
absorption process is expected to become a useful method used to fabricate optical memory
with both an ultra-high storage density and an ultra-high recording speed.
Proposal of Ultrahigh Density Optical Disk System Using a Vertical Cavity Surface Emitting Laser Array
Authors: Goto Kenya
Published: October 2002

An ultrahigh density optical disk system of Tera bit/inch2 is described. This system utilizes a
vertical cavity surface emitting laser (VCSEL) diode array as a parallel optical beam source which can
make the disk system more useful at a high data transfer rate and bit density using evanescent waves
from each laser cavity. In order to avoid the diffraction limited restriction to the optical beam the
near-field optics is adopted to the parallel beam optical head. 1 bit size on the surface of the disk is
10–20 nm in diameter. A polished glass disk substrate is deposited by either phase change medium or
photon mode optical medium. The medium thickness of the disk is approximately 10–20 nm. The optical
gap size between the surface of the medium and laser output windows of a VCSEL array head is
controlled within 20 nm using contact head technology.
Influence of Pulsed Electron Cyclotron Resonance Plasma on Gate Electrode Etching
Authors: Fujiwara Nobuo , Maruyama Takahiro , Miyatake Hiroshi
Published: October 2002

The etching characteristics and the plasma parameters in
pulsed electron cyclotron resonance (ECR) plasma were investigated
using different control methods of microwave power. The
relationships between pulse control condition and etch properties
were discussed. Practical etching process which requires higher
etch rate can be realized using fixed average power control. This
result can be explained by means of the relationship between etch
rate and ion current density.
The fixed average power control is also effective for notch
reduction. This result is achieved by supplying a large amount of
high energy electrons at the beginning of microwave on-time. This
mechanism is confirmed by means of time-resolved optical emission
spectroscopy.
Enhancement of Reactivity in Au Etching by Pulse-Time-Modulated Cl2 Plasma
Authors: Ohtake Hiroto , Samukawa Seiji , Oikawa Hirokazu , Nashimoto Yasunobu
Published: October 2002

In Al, Au and Pt metal etching processes, low etching rate and low etching
selectivity are serious problems. To achieve a breakthrough in these problems, metal
etching by pulse-time-modulated plasma was investigated. In particular, the Au etching
rate was increased significantly in the pulsed plasma even when the ion energy decreases.
However, an increase in the etching rate cannot be observed in Al etching. As a result, it is
speculated that the increase in the Au etching rate is caused by the increase in the
evaporation rate of Au etching products, which results from the injection of negative ions.
A Study of the O2-SO2 Plasma Etch Chemistry for Top Surface Imaging Photoresist Dry Development
Authors: Huang Z. S. , Melaku Yosias , Nguyen Wendy
Published: October 2002

We have investigated O2–SO2 plasma chemistry and studied the impact of relevant aspects of the plasma
chemistry on top surface imaging (TSI) silylated photoresist dry etch development processes. The studies
focused on aspects of plasma chemistry relating to the formation of a polymer deposit postulated to be
responsible for profile sidewall passivation. A nonvolatile deposit produced by the etching plasma was
observed and analyzed. Mass spectrometry analysis suggested that the deposit exists in the form of a
nonvolatile sulfur oxide. X-ray photoelectron spectroscopy (XPS) analysis of the wafer surface indicated
that it is a hydrated sulfur trioxide polymer resulting from chemical reactions of O2 and SO2 plasma. Our
studies also indicated that chamber conditioning produced by sulfur trioxide polymer deposition causes no
observable variation in critical dimension (CD) and profile results when evaluated on a Lam TCP 9400SE
plasma etcher, nor does our in situ dry cleaning method used to prevent excessive build-up of the deposit.
Subsequent pattern transfer to underlying polysilicon layers from the TSI silylated photoresist was found to
be little affected by this aspect of O2–SO2 plasma chemistry. Based on these observations, we postulated
that the observed sulfur trioxide polymer deposit may be responsible for profile sidewall passivation and
etch anisotropy enhancement associated with SO2 addition to the O2 plasma for photoresist dry
development.
Microdefects in an As-Grown Czochralski Silicon Crystal Studied by Synchrotron Radiation Section Topography with Aid of Computer Simulation
Authors: Satoshi Iida Satoshi Iida , Yoshirou Aoki Yoshirou Aoki , Kouhei Okitsu Kouhei Okitsu , Yoshimitsu Sugita Yoshimitsu Sugita , Hiroshi Kawata Hiroshi Kawata , Takao Abe Takao Abe
Published: October 2002

Grown-in microdefects of a Czochralski (CZ) silicon crystal grown at a slow growth rate were studied by section topography using high energy synchrotron radiation. Images of the microdefects in the section topographs were analyzed quantitatively using computer simulation based on the Takagi-Taupin type dynamical diffraction theory of X-rays, and reproduced successfully by the simulation when the microdefects were assumed to be spherical strain centers. Sizes and positions of the microdefects were able to be determined by detailed comparison between the experiments and the computer simulations. The validity of the computer simulation in an analysis of the section topographs is discussed.
Interfacial Reaction between Aluminum Metal and Boron-Doped Polysilicon in a Planar Type Antifuse Device
Authors: Baek Jong Tae , Park Hyung-Ho , Ahn Byung Tae , Jun Chi Hoon , Kim Youn Tae , Song Yoon Ho , Kim Jongdae
Published: October 2002

The interfacial reaction between Al metal and boron-doped polysilicon was
investigated to understand the mechanism of link formation in the planar type antifuse
with a polysilicon pad and two Al electrodes. In the antifuse, the Si–Al alloy filament
with a low resistance was formed only on the boron-doped polysilicon pad, not on the
phosphorus-doped or undoped polysilicon pads. After annealing Al/boron-doped
polysilicon at 400°C for 20 min, an Al-B compound (AlB2) was found by the reaction
between Al metal and solute borons at the grain boundaries of polysilicon using Auger
electron spectroscopy, X-ray diffractometer, and X-ray photoelectron spectroscopy. In
the planar type antifuse device, the formation of AlB2 at the grain boundaries might act
as a seed for the conductive filament formation by supplying Al from the positive
electrode. After forming a low resistance Si–Al alloy filament, it grows toward the
negative electrode by the reaction between supplied Al and highly reactive solute
borons segregated at the grain boundaries.
Ti3+:sapphire Thin Films Fabricated by Pulsed-Laser Deposition
Authors: Hiroshi Uetsuhara Hiroshi Uetsuhara , Toru Nasu Toru Nasu , Yoshiki Nakata Yoshiki Nakata , Nilesh Vasa Nilesh Vasa , Tatsuo Okada Tatsuo Okada , Mitsuo Maeda Mitsuo Maeda
Published: October 2002

Ti3+:sapphire thin films were deposited on sapphire substrates by pulsed-laser deposition (PLD) process. A smoother surface was obtained at lower pressure in a chamber. Their fluorescence characteristics were confirmed and the emission characteristics comparable with the bulk Ti3+:sapphire crystal were obtained.
Structure of Amorphous Selenium
Authors: Yukitaka Kobashi Yukitaka Kobashi , Shiro Kodera Shiro Kodera
Published: October 2002

The structure of amorphous selenium prepared by quenching from molten selenium at 620 K to room temperature has been studied by X-ray diffraction. The diffraction intensity of monochromatized Ag Kα radiation was determined to be s=22.0 Å-1. The mean coordination numbers of neighbouring atoms with an interval of 0.1 Å at the distances of the crystalline forms were calculated and compared with the observed radial distribution curves. Theoretical diffraction intensities were also calculated for these structures. By comparison with the observed data, the mesh parameters could be estimated on the assumption that the strain distributions in the sample are Gaussian and the standard deviations of interatomic distances are linearly proportional to their mean distances and are larger for interchain (or -ring) atoms than for intrachain (or -ring) atoms. The β-monoclinic structure best fitted the obtained data.
The Effect of Multiply Charged Ions on the Vickers Hardness of (Ti,Al)N Films
Authors: Suzuki Akira
Published: October 2002

Films deposited by the cathode arc ion plating method contain many droplets, and thus the films are of inferior quality. However, recent investigations show that the number of droplets is reduced by a magnetic field formed on the surface of the target. (Ti,Al)N films deposited by a magnetic field of 200 G have few droplets and good crystallization properties. Under conditions with and without a magnetic field, (Ti,Al)N films are deposited by the conventional method and by the high-discharge voltage method which generates multiply charged ions. Comparison between the Vickers hardness of these films is carried out. In both cases, films deposited by the high-discharge voltage method are harder than those obtained by the conventional method.
Afterglow Characteristics of an X-Ray Irradiated Imaging Plate
Authors: Taku Kimura Taku Kimura , Katsuyuki Inabe Katsuyuki Inabe
Published: October 2002

The effect of time and temperature dependence of the afterglow intensity are measured for several kinds of commercial imaging plates composed of BaFBr0.85I0.15:Eu2+ and BaFBr:Eu2+.
Emission spectra of the afterglow reveal a single band with a maximum around 400 nm. It is found that the afterglow intensity is usually increased with increasing temperature. The time dependence of the afterglow is analysed using a recombination model particularly in relation to the temperature and the distance between electrons and holes. It is shown that theoretical curves with three reasonable parameters are in good agreement with the experimental data.
A relation between afterglow and fading is also discussed using the proposed recombination model.
Plasma Characterization in Chlorine-Based Reactive Ion Beam Etching and Chemically Assisted Ion Beam Etching
Authors: Matsutani Akihiro , Koyama Fumio , Iga Kenichi
Published: October 2002

We measured the chlorine plasma characteristics in reactive ion beam etching (RIBE)
and chemically assisted ion beam etching (CAIBE) process. In the CAIBE process, the
energy peak of Cl+ ionized by Ar+ appears in the energy range of 50–70 eV and this Cl+ energy
peak increases with an increase of Ar+ energy. We observed that the excited state Cl2 density
in CAIBE is lower than that in RIBE as measured by appearance mass spectrometry (AMS).
New Piezoelectric Polymers
Authors: Fukada Eiichi
Published: October 2002

Four kinds of piezoelectric polymers are introduced. Submicron thin films
of polyurea are prepared by vapor deposition polymerization. Poled films of
aromatic polyurea exhibit the piezoelectric constant d
31=20 pC/N, which is
almost independent of temperature in the range of 100 to 200°C. Aliphatic
polyureas show a ferroelectric hysteresis with a coercive field of about
100 MV/m. Single crystalline films of a copolymer of vinylidene fluoride and
trifluoroethylene were prepared by annealing elongated films at a paraelectric
temperature range avoiding the side surface contacts. No lamella structures
were present and the crystallinity was near 100%. The large electromechanical
coupling factors k
33=0.3 and k
31=0.1 were observed. A large electrostrictive
constant R=2.6×10-17 m2/V2 was observed for polyurethane. With a dc bias
field of 15 MV/m, a piezoelectric constant of d
33=600 pC/N was obtained,
which was larger than that of PZT. A shear piezoelectric constant
d
14=-10 pC/N was obtained for oriented films of poly-L-lactic acid, which were
optically active and biodegradable. After poling, this polymer showed the
tensile piezoelectricity and pyroelectricity.