bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and Electrical Properties of Ferroelectric Pb(Zr1-xTix)O3–SiO2 Glass–Ceramic Thin Films Derived by the Sol–Gel Method
Authors: Wang Xusheng , Ishiwara Hiroshi
Published: October 2002

Ferroelectric PbZr1-x
Ti
x
O3–SiO2 (SiO2=0–30 mol%) glass–ceramic thin films were fabricated by sol–gel and rapid thermal annealing (RTA) techniques on Pt/Ti/SiO2/Si(100) substrates. The perovskite-phase PbZr1-x
Ti
x
O3 crystallites were grown in the films, preferentially along the (111) direction for lower SiO2 concentration (≤20 mol%) and along the (100) direction for higher SiO2 concentration (≥30 mol%). It was found that the Zr/Ti ratio in the films decreased with increasing SiO2 content. It was also found in the samples with SiO2 concentration up to 20 mol% that the hysteresis shape in the polarization vs voltage (P–V) characteristics was not seriously degraded, while such quantities as remnant polarization, dielectric constant, and loss became lower than those of a pure PZT thin film. Furthermore, the PZT+5 mol%SiO2 thin film was found to show a saturated hysteresis loop and good retention property. These results indicate that the ferroelectric glass–ceramic thin film is one of the promising candidate gate material for FET-type ferroelectric memory applications.
RF Potential Formation in Electronegative Plasma Column under a Magnetic Field
Authors: Peter Cicman Peter Cicman , Hiroharu Fujita Hiroharu Fujita
Published: October 2002

The experimental results on the radial RF potential formation in electronegative plasma with an applied axial magnetic field are reported by comparing the results of the electropositive plasma. The successful control of plasma potential has been established in a wide range of potential values even lower than the potential of the grounded chamber wall by biasing both the separation grid and the end plate.
Radical Density Measurement at Low-Pressure Discharge Denitrification by Appearance Mass Spectrometry
Authors: Ito Kohei , Hagiwara Katsuyuki , Nakaura Hiroyuki , Tanaka Hidekazu , Onda Kazuo
Published: October 2002

In discharge denitrification, radical production by electron collision with combustion gas is a key process which determines the denitrification process and its performance. In this study N, O, OH and H radical densities have been measured by appearance mass spectrometry in a low-pressure discharge field with parallel electrodes (2 cm gap) under simulated combustion gas flow. Also, electric field, electron number density and electron temperature at the radical sampling position have been measured by the Langmuir probe method. Under constant discharge pressure the radical density (cm-3) was about 1011–1012 cm-3, and the density increased with increasing the discharge current. Under constant discharge current, both the radical concentration [-] and electron temperature increased with decreasing pressure. The radical concentration in the cathode fall region was greater than that for the outer region. Additionally, we measured the concentration change of NO mixed in the simulated combustion gas and observed a little change of the NO concentration.
A Multi-Functional Sensor for Liquid Characterization and Identification
Authors: Preethichandra Daluwathu Mulla Gamage , Shida Katsunori
Published: October 2002

Liquid identification according to their physical properties is a well known technique and different types of stand alone sensors are used to measure each of these parameters. However, in this paper we propose a single multi-functional sensor for the measurement of four parameters namely, temperature, viscosity, clarity and permittivity of a liquid. The operation of the proposed sensor is theoretically described and its performances are experimentally tested. This multi-functional sensor can be used to identify an unknown liquid for its maximum likelihood into a characterized zone of liquids maintained in a previously built database.
Mass Effect of Etching Gases in Vertical and Smooth Dry Etching of InP
Authors: Matsutani Akihiro , Ohtsuki Hideo , Muta Seiichi , Koyama Fumio , Iga Kenichi
Published: October 2002

We compared several kinds of etching gases in inductively coupled plasma (ICP) and electron cyclotron resonance (ECR) plasma etching processes for investigating the etching performance. It was found that a heavy etching gas such as SiCl4 plays an important role for smooth etching of InP, which is independent of ICP and ECR plasma sources.
Polarization Dependence Analysis of Optical Loss in Small-Aperture Metal Waveguides for Near-Field Optics
Authors: Gen-ichi Hatakoshi Gen-ichi Hatakoshi , Hideto Furuyama Hideto Furuyama
Published: October 2002

Optical intensity profile and optical loss in small-aperture metal waveguides were analyzed by a one-dimensional waveguide model and the beam propagation method. Guided mode profile and optical loss have a great dependence on the polarization direction of the guided lightwave. The loss for the TM0 mode is two orders of magnitude smaller than that for the TE0 mode for a slit width of less than half-wavelength. A very small spot is available at high efficiency by using a metal waveguide and an incident light with TM polarization.
Consideration of Jitter on Mark-Edge Recording
Authors: Maeda Takeshi , Minemura Hiroyuki , Tsuchinaga Hiroyuki , Shimano Takeshi
Published: October 2002

Almost all optical disks have adopted a mark edge recording standard to increase the data capacity. The interchangeability of drives and media is important because an optical disk is exchangeable media. This paper focuses on a jitter characteristic that is important for estimating this interchangeability. The deviation factors of jitter are analyzed and an analysis equation of jitter regarding the probability of generating a mark and space is deduced. In addition, a method to measure the remaining-edge shift in these factors is reported.
Thermal Cross-Erase Issues in High-Data-Density Phase-Change Recording
Authors: R. Meinders Erwin , H. R. Lankhorst Martijn , J. Borg Herman , J. Dekker Martijn
Published: October 2002

We report on the numerical simulations of high-data-density phase-change recording (DVR-blue and DVR-red) in order to analyse the phenomenon of thermal cross-erase in land/groove recording. In particular, if a maximum data capacity is pursued, which involves a small radial track pitch, thermal cross interference may become an important issue. The question of whether or not the temperature distributions and the related thermal cross-erase probability scale with the optical spot size is addressed. Two different thermal models (a planar model and a land/groove model) were used in which laser heating was simulated. Reliable temperature predictions and related trend analyses require a proper model and accurate input parameters. The thermal conductivity of the different layers in the stack was obtained from measurements performed with a time-resolved static tester setup in combination with a novel melt-threshold method. Since thermal cross-erase is dependent on the temporal temperature distribution in the stack, we analysed the most important parameters that possibly contribute to a reduction of the temperature, and thus the cross-erase probability, in the adjacent track.
Polymer Thin Films Containing Azo Dye for Rewritable Media
Authors: Kim Jin-Hong , Hong Ki-Myung , Na Hai-Sub , Han Yang-Kyoo
Published: October 2002

The writing and erasing properties of azo-dye-doped polymer thin films at a blue wavelength were investigated. The optically induced birefringence in the polymer film due to a linearly polarized light can be utilized for digital optical data storage. The dependence of the contrast of a stored pattern on temperature was examined to estimate the thermal stability of the polymer films. Bits could be written and erased by irradiation of the linearly and circularly polarized laser beam, respectively.
Analysis of Probe Signal Power Dependence of All-Optical Wavelength Converter Using Semiconductor Optical Amplifiers
Authors: Shin Si-mon , Lee Min-ho , Han Sang-Kook
Published: October 2002

We analyzed the influence of the probe signal power on the wavelength conversion in an interferometric all optical wavelength converter using semiconductor optical amplifiers (SOAs). The carrier density variation inside an SOA due to longitudinal signal amplification and nonradiative recombination is investigated and the following variation of amplified spontaneous emission (ASE) is considered. In case of using a high probe signal power, the frequency response of the wavelength converter and bit error rate (BER) of the converted signal are improved as a result of the reductions of ASE noise and carrier lifetime.
Rewritable Dual-Layer Phase-Change Optical Disk Utilizing a Blue-Violet Laser
Authors: Akiyama Tetsuya , Uno Mayumi , Kitaura Hideki , Narumi Kenji , Kojima Rie , Nishiuchi Kenichi , Yamada Noboru
Published: October 2002

We have demonstrated for the first time the feasibility of using a rewritable dual-layer phase-change optical disk utilizing a blue-violet laser. For the first medium, we adopted a very thin recording layer with a new phase-change material Ge–Sn–Sb–Te, and a 10-nm-thick silver-alloy reflective layer to obtain a large transmittance and high-quality signals. For the second medium, we optimized the thickness of each layer to obtain both a large optical absorption of the recording layer and a small heat capacity. Carrier-to-noise ratios of more than 50 dB, erasability of more than 30 dB and recording powers of 8 mW for the first medium and 11 mW for the second medium were obtained under typical recording conditions corresponding to a capacity of 27 GB per one side of a 120 mm disk and a user data transfer rate of 33 Mbps.
The Effects of Metal-Doped GeSbTe Films on Light Scattering-Mode Super-Resolution Near-Field Structure (Super-RENS)
Authors: Men Liqiu , Tominaga Junji , Fuji Hiroshi , Kikukawa Takashi , Atoda Nobufumi
Published: October 2002

The optical, thermal kinetics and dynamic characteristics of disks comprising iron (Fe), zinc (Zn) or bismuth (Bi) doped GeSbTe recording films were investigated. The optical constants n and k were decreased when using Fe and Zn doped recording films, while Bi doped GeSbTe recording films yielded a reduced n value and enhanced k value. Crystallization temperature T

c
and crystallization activation energy E

a
of metal-doped GeSbTe films depended on specimen structures and doping metals. It was found that the readout durability in light scattering-mode super-resolution structure (LSC super-RENS) could be improved greatly by using Fe, Zn doped recording films.
Experimental Results of Space Layer Thickness for Blue-Wavelength Dual-Layered Disc
Authors: Lee Kyung-Geun , Park Chang-Min , Yoon Du-Seop , Ro Myung-Do , Kim Yoon-Gi , Park In-Sik , Shin Dong-Ho
Published: October 2002

To determine the effects of spherical aberration due to defocus and interference of layer 0(L0) and layer 1(L1) in high-density dual layered-discs, 17 sets of discs structures are measured while maintaining thickness uniformity of the space layer within ±1.5 µm for one revolution. After measuring the discs, an optimum thickness of 30 µm of the space layer is obtained.
High-Density Recording Using an Electron Beam Recorder
Authors: Wada Yasumitsu , Katsumura Masahiro , Kojima Yoshiaki , Kitahara Hiroaki , Iida Tetsuya
Published: October 2002

A high-density optical disk fabricated using electron beam mastering exhibited excellent performance. Read-only disks with the recording capacity of 25 to 30 GB were fabricated by electron beam mastering and their jitter values were evaluated by a blue laser read out system. As a result, very low jitter values of 5.4, 6.2 and 7.7% were obtained for the disks whose capacity was 25, 27.5 and 30 GB, respectively. Characteristics of the disks such as track pitch variation, track roundness and recording stability are also shown. The electron beam recorder used in the experiments is described. In particular, details of the electron beam column, properties of the beam, how to adjust and evaluate the beam and a beam blanker are presented. Finally, several problems are addressed.
Radial and Tangential Tilt Detection for Rewritable Optical Disks
Authors: Katayama Ryuichi , Meguro Shunichi , Komatsu Yuichi , Yamanaka Yutaka
Published: October 2002

In an optical disk system which uses a short wavelength laser diode and a high numerical aperture objective lens, it is necessary to detect and compensate for the disk tilt, because the coma aberration deteriorates the read/write characteristics and the tilt margin becomes narrower. This paper presents a new radial and tangential tilt detection method for rewritable optical disks, which is based on the intensity distribution of the reflected light from the disk. This method features high sensitivity (about 0.37/° for radial direction and about 0.51/° for tangential direction) and is suitable for high-frequency servo operation. Moreover, it can be combined with the differential push-pull detection method and the land/groove detection method by using three beams. Experimental results have demonstrated the validity of this method.
New Method of Calibrating Adaptive Writing Pulses for Digital Versatile Disc Random Access Memory (DVD-RAM) 4.7 GB Drive
Authors: Furumiya Shigeru , Fukushima Toshiyuki , Yamazaki Yukihiro
Published: October 2002

In this paper, a new method of calibrating adaptive writing pulses suitable for installing into the digital versatile disc random access memory (DVD-RAM) 4.7 GB drive is described. To obtain a wider margin of write/read operation, it is desirable to optimize all adaptive parameters for every disk inserted into the drive. We propose the jitter minimizing (JM) method, which is characterized by using selected test patterns, detecting only jitter in the drive and applying a search algorithm to obtain bottom jitter. As a result of optimizing all parameters by JM, the total calibration time is 4.8 s with the accuracy of ≤1 ns, and overwrite jitter of random data is 8.6% at the drive. It is proved that JM offers the same results as the measurement by the time interval analyzer (TIA), uses small-sized hardware and exhibits satisfactory performance for application in commercial drives.
Performance of Run-Length-Limited (3, 11) Code for Optical Storage
Authors: Jun Lee Jun Lee , Jaehyung Kim Jaehyung Kim , Sehyung Yong Sehyung Yong , Jaejin Lee Jaejin Lee
Published: October 2002

This paper introduces a run-length-limited (RLL) (3, 11) code and compares its performance with that of the EFMPlus code using four different detection methods including partial response maximum likelihood (PRML), fixed delay tree search with decision feedback (FDTS/DF), partial response with decision feedback equalizer (PR-DFE) and decision feedback equalizer (DFE). The advantages of the proposed code are: (1) the larger density ratio and (2) the simple encoder/decoder.
Equalization for Digital Holographic Data Storage
Authors: Choi An Sik , Baek Woon Sik
Published: October 2002

In this study, a finite-impulse-response (FIR) equalizer was employed in a holographic memory system to mitigate intersymbol interference (ISI) generated during storage and retrieval of two-dimensional data in holographic data storage. We showed experimental results with improved bit-error rate (BER) performance.
A Flexible, Programmable, High-Speed Laser Driver IC for Optical Recording
Authors: Immink Andre. H. J. , Homberg John. A. T. M. van den , Cormack Jamie. J. A. Mc , Slenter Andre. G. J. , Noot Jan , Tryzna Mischa , Verhoeven Henri
Published: October 2002

Transport of high frequency write strategy signals from the main board to the optical pickup unit (OPU) becomes more and more difficult due to the rapidly increasing data rate in optical recording. Furthermore, power dissipation on the OPU increases, leading to large variations in ambient temperature. As laser efficiency strongly depends on operating temperature it is important to have accurate laser power control algorithms to obtain a constant writing performance. For this purpose a high-speed laser driver integrated circuit in standard Complementary Metal Oxide Semiconductor (CMOS) technology has been designed which is flexible for optical recording formats like Compact Disc-recordable/rewritable (CD-R/RW), Digital Versatile Disc (DVD-R/RW) and the new Digital Video Recorder (DVR). It features a differential, low voltage swing interface and digital laser power control based on a single parameter algorithm. The IC, with a silicon area of 13.7 mm2 is intended for mounting on the OPU. Multi-track overwrite jitter of 8.5% was measured on DVR discs at 48 Mbit/s using a blue Nichia laser diode.
New Readout Method Using an Optical System with Differential Numerical Aperture Between Forward and Return Optical Paths
Authors: Kayama Hiroshi , Asada Jun'ich , Nishiwaki Seiji , Momoo Kazuo , Saitoh Youichi
Published: October 2002

We have developed a new readout method using an optical system with a differential numerical aperture between forward and return optical paths (i.e., a differential numerical aperture (NA) method). This method realizes jitter merits for larger NA and wide tolerance for smaller NA. We will show calculated and measured results of jitter and tolerance for a 4.7 GB-digital versatile disk-random access memory (DVD-RAM) disk system due to the differential NA method.
Super-Resolution by Combination of a Solid Immersion Lens and an Aperture
Authors: D. Milster Tom , Kevin Erwin Farhad Akhavan , M. Felix David , Kusato Hirota Kusato Hirota , Steven Koester Steven Koester , Kei Shimura Kei Shimura , Yan Zhang Yan Zhang
Published: October 2002

A solid immersion lens is combined with various aperture shapes in order to improve resolution. Both metallic and dielectric apertures are investigated, and optimum shapes for each are determined. Fabrication techniques for each type of combination probe are discussed and implemented, and a simple experiment with a dielectric combination probe scanning a reflective grating demonstrates improved resolution compared to a solid immersion lens alone.
Physical Characteristics and the Format of Digital Versatile Disc-Recordable
Authors: Muramatsu Eiji , Shirota Akira , Horikawa Kunihiko , Kato Masahiro , Taniguchi Shoji , Inoue Akiyoshi
Published: October 2002

The 4.7 GB digital versatile disc-recordable (DVD-R) disc format has been developed to introduce very useful recordable feature in the digital versatile disc (DVD) family. We developed disc media and the write pulse control method. In our examination, recorded signal qualities of the DVD-R disc are equivalent to those of the DVD-Read-Only disc (ROM). We realized a jitter value of less than 6% using write pulse strategy with the adaptive edge shift control technology. The physical characteristics of the recorded signals satisfy all the requirements of single-layered DVD-ROM disc.
Digital Data Storage and Computing by a Vector Holographic Memory System
Authors: Kawano Katsunori , Minabe Jiro , Ishii Tsutomu
Published: October 2002

We have applied polarization multiplexing to digital data storage and logic operation. Two digital data pages with mutually orthogonal polarization directions were recorded with a reference beam within the same volume of polyester containing cyanoazobenzene units in the side chain. Illuminating the polyester with the reference beam simultaneously yielded the two data pages. The polarization states of the two retrieved images were mutually orthogonal, because the polyester film is capable of recording arbitrary polarization states. Thus, there was no significant cross talk between the two reconstructed data pages. The bit error rates of the two retrieved pages were estimated to be 10-9 and 10-6. Furthermore, by detecting an appropriate polarization component of the diffracted beams, we have successfully obtained subtraction and addition signals between the two multiplexed pages. Since this system is also applicable to logic operation, it would take advantage of the high-density storage, fast transfer rates, and fast processing speeds.
Multilevel Recording in Erasable Phase-Change Media by Light Intensity Modulation
Authors: Shieh Han-Ping D. , Chen Yen-Lin , Wu Cheng-Heng
Published: October 2002

Multilevel recording has an advantage of increasing the recording density without extensively altering the current optical configuration. Four-level recording schemes in phase-change disks using either two or three recording layers were demonstrated. By modulating the intensity of the laser pulse, marks were recorded in any of the recording layers, forming four recording regions. Utilizing the large difference in refractive indices between the amorphous and crystalline states, each recording region corresponds to a different reflectance. For the four-level recording disk, if each recording region represents two-bit data, then the recording density of the four-level disk can be higher by a factor of two than that of a conventional disk recorded by pulse position modulation (PPM).
Concentration of Electric Field near Si Dot/Thermally-Grown SiO2 Interface
Authors: Ishikawa Yasuhiko , Kosugi Masaaki , Tsuchiya Toshiaki , Tabe Michiharu
Published: October 2002

The dot-induced concentration of electric field was studied by current-voltage (I–V) measurements of metal-oxide-semiconductor (MOS) diodes containing a high density of Si dots embedded in the gate SiO2. Using a nanometer-scale local oxidation process developed by the authors, single-crystalline Si dots covered with a thermally grown SiO2 were formed on a tunnel SiO2/n
+-Si substrate. I–V measurements through the gate SiO2 (∼20 nm thick) showed enhancement of the Fowler-Nordheim (FN) tunneling current in comparison with the conventional MOS diode. This phenomenon was ascribed to a strong electric field generated locally near the gate SiO2/Si dot interface, which reflects the ultrasmall curvature of the Si dot. In fact, simulation of the potential distribution provided evidence of the concentration of the electric field.
Effects of Annealing on Electrical Coupling in a Multilayer InAs/GaAs Quantum Dots System
Authors: J. Chiquito Adenilson , A. Pusep Yuri , C. Galzerani Sérgio Mergulhão , T. Moshegov Nicolai
Published: October 2002

We present a systematic investigation of the capacitance–voltage measurements and Raman scattering on a multilayer InAs/GaAs self-assembled quantum dots system annealed at different temperatures. We observed a decrease of the electrical coupling of the electrons trapped in the dots located in the different layers. Raman scattering revealed the modifications of the dots morphology which influenced on the observed increase of the localization of electrons in the dots after the annealing process. We also observed that the annealing at 600°C altered the plane of the dots into layers of an In
x
Ga1-x
As alloy.
Single-Electron Tunneling Effects in Nylon 11 Thin Films Containing Nanoparticles
Authors: Minoru Fujii Minoru Fujii , Yoku Inoue Yoku Inoue , Shinji Hayashi Shinji Hayashi , Kensuke Akamatsu Kensuke Akamatsu , Shigehito Deki Shigehito Deki
Published: October 2002

Very thin Nylon 11 films (≤20 nm in thickness) containing Au or Ge nanoparticles (Au/Nylon 11 or Ge/Nylon 11) were prepared by a thermal relaxation technique, and current–voltage (I–V) characteristics in the vertical direction of the films were studied. In the case of Au/Nylon 11, the plan and cross-sectional transmission electron microscopic (TEM) images revealed that Au nanocrystals are spontaneously aligned in the middle of the upper and lower electrodes and Nylon 11 tunneling barriers are formed between Au nanocrystals and electrodes. In the case of Ge/Nylon 11, lattice fringes corresponding to Ge crystals with the diamond structure were not observed in TEM images, suggesting that amorphous Ge particles are dispersed in Nylon 11 films. Clear Coulomb staircases were observed in the I–V characteristics in both cases.
Quantum Dot Formation in Single-Wall Carbon Nanotubes
Authors: Suzuki Masaki , Ishibashi Koji , Ida Tetsuya , Aoyagi Yoshinobu
Published: October 2002

We report on the low-temperature electrical transport measurements of individual single-wall carbon nanotubes (SWNTs), and provide evidence of the single and multi-quantum dot formations in the measured Coulomb blockade characteristics. The multi-quantum dot formation is supported by a strong temperature dependence of the number of Coulomb blockade oscillation peaks, the so-called “stochastic Coulomb blockade”. Experimental observations are discussed by considering a possible barrier formation due to damage or defects as well as deposited-metal contacts.
Analysis of Nanostructure Formation Using Photon/Electron Spectroscopies: Cu on SiC Substrates
Authors: An Zhenlian , Hirai Masaaki , Kusaka Masahiko , Saitoh Taeko , Iwami Motohiro
Published: October 2002

Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED) studies of Cu deposition on a 6H-SiC(0001) surface have shown fine-particle formation with an average size of approximately 2 nm for a 6H-SiC(0001) C-face at a nominal Cu coverage of approximately 2 ML, where its size depends on the nominal Cu film thickness. Soft-X-ray emission spectroscopy (SXES) of an annealed Cu(60 nm)/3C-SiC(001) specimen clarified that little reaction occurred at the Cu/SiC interface. The heated specimen is considered to have Cu islands on top.
Electronic States and Transport Phenomena in Quantum Dot Systems
Authors: Mikio Eto Mikio Eto
Published: October 2002

Electronic states and transport phenomena in semiconductor quantum dots are studied theoretically. Taking account of the electron-electron Coulomb interaction by the exact diagonalization method, the ground state and low-lying excited states are calculated as functions of magnetic field. Using the obtained many-body states, we discuss the temperature dependence of the conductance peaks in the Coulomb oscillation. In the Coulomb blockade region, elastic and inelastic cotunneling currents are evaluated under finite bias voltages. The cotunneling conductance is markedly enhanced by the Kondo effect. In coupled quantum dots, molecular orbitals and electronic correlation influence the transport properties.
Theory of Tunneling Processes in Quantum Structures
Authors: Isawa Yoshimasa , Horii Hideto
Published: October 2002

A theoretical framework to build a concrete analysis method for tunneling processes through quantum structures (QSs) is proposed based on Keldysh Green's function. As a result of three steps of transformations, we deduce the general expression for the current flowing through QSs which corresponds to the nonequilibrium and the nonlinear version of the Kubo formula. It is revealed how we can achieve the general formula successfully. It is shown that, in tunneling processes through QSs, both the elastic scattering and the inelastic scattering play an essential role. Our framework is expected to be applicable to various QSs fabricated by metals, semiconductors, superconductors and magnetic materials, since our procedure is not sensitive to details of the Hamiltonian.
Sideband Quenching in a Driven Double-Barrier System –Scaling Behavior for Inhomogeneous Potentials–
Authors: Jun-ichiro Ohe Jun-ichiro Ohe , Kousuke Yakubo Kousuke Yakubo
Published: October 2002

Using a transfer matrix method, we have studied the relationship between the conductance of a harmonically driven quantum dot system and the strength V
ac of the time-varying potential in both cases of \hbarω≠Δε and \hbarω= Δε, where ω is the frequency of the time-varying potential and Δε is the energy distance between adjacent resonant levels of the system. In the off-resonance condition (\hbarω≠Δε), it is found that conductance dips appear in the V
ac dependence of the sideband conductance instead of the perfect sideband quenching predicted by previous works. Our results show that conductance dips corresponding to the quenching scale with ω-1, while previous theories have suggested that the spectral weight of sideband components is scaled by ω-2 for inhomogeneous time-varying potentials. Under the resonance condition (\hbarω=Δε), our calculation shows the Rabi-type level splitting. The quenching effect of the Rabi-type splitting is also discussed.
Absorption Spectrum and Optical Parameters of Nd-Doped Barium Sodium Niobate Crystals
Authors: Xia Hai-Rui , Guo Ming , Meng Xian-Lin , Zhu Li , Wang Ji-Yang
Published: October 2002

Nd-doped barium sodium niobate, (Ba2Na)1-x
Nd
x
Nb5O15 (Nd:BNN), crystallizes with x=0.025 in a tetragonal system with a filled tungsten bronze structure and the point group 4 mm, conforming to the space group P4b
m and z=2. The Curie temperature was 537±2°C. The lattice constants were a=b=1.2446(1) and c=0.3991(1) nm at room temperature. The measured absorption of Nd:BNN was compared to the Judd-Ofelt (JO) theory. When applied, the JO theory of parity-forbidden electric-dipole transitions of rare-earth ions on non-centrosymmetric sites demonstrates good agreement. An absorption band around 808 nm to match laser diode pumping is about three times broader than that of Nd-doped yttrium aluminum garnet crystal. The three intensity parameters Ω
t
were fitted as 5.677×10-20, 2.231×10-20, and 4.106×10-20 cm2 at t=2, 4 and 6, respectively. The fluorescence branch ratio at 1060 nm is 52.38%. The largest integrated emission cross section ∑(4
F
3/2→4
I
11/2) is 10.36×10-18 cm. These results indicate the crystal's potential applications as a practical laser material.
Effect of Blending on Electrical Conduction and Breakdown of Low-Density Polyethylene Films with Different Densities
Authors: Cho Don-Chan , Mori Tatsuo , Mizutani Teruyoshi , Ishioka Mitsugu
Published: October 2002

In this study, the effect of blending on physical and electrical properties of low-density polyethylene (LDPE) was investigated. Two kinds of LDPEs whose densities are evaluated to be 0.9179 g/cm3 and 0.9192 g/cm3, respectively, were used and blended according to different blend ratios. The LDPE with a blend ratio of 50 wt% had the lowest impulse breakdown strength, F
BImp, at 30°C. However, the LDPE with a blend ratio of 50 wt% also had the highest F
BImp at 90°C among all specimens. The DC breakdown strength, F
BDC, decreased with the increase of the blend ratio at 30°C but increased at 60°C and 90°C. However, the F
BDC did not depend on the blend. The current densities for all specimens were almost the same at 30°C, but decreased with a blend ratio up to 75 wt% at 90°C. By analyzing X-ray diffraction (XRD) patterns, we found that the crystal size in the (020) plane increased with a blend ratio up to 50 wt%, and the LDPE with a blend ratio of 50 wt% had the largest crystal size in the (020) plane among all specimens. It was found that the F
BImp was strongly related to the crystal size in the (020) plane.
Quantum Size Effects of InAs- and InGaAs-Quantum Dots Studied by Scanning Tunneling Microscopy/Spectroscopy
Authors: Takeshi Yamauchi Takeshi Yamauchi , Yasushi Matsuba Yasushi Matsuba , Yasuaki Ohyama Yasuaki Ohyama , Masao Tabuchi Masao Tabuchi , Arao Nakamura Arao Nakamura
Published: October 2002

Scanning tunneling spectroscopy has been used to study quantum size effects on the electronic structure of InAs and In0.46Ga0.54As quantum dots (QDs) in correlation with their morphologies. It is found that for both samples, the measured band gap increases with decreasing dot height. The observed height dependence of the gap energy has been well reproduced by the calculation based on a one-dimensional quantum well model. For the In0.46Ga0.54As QD, however, enrichment of In-composition in the dot compared to the nominal composition has been observed.
Detection of Edge-Conducting Channels in Quantum Hall Systems Using a Single-Electron Transistor
Authors: Hiroyuki Fujioka Hiroyuki Fujioka , Shingo Katsumoto Shingo Katsumoto , Yasuhiro Iye Yasuhiro Iye
Published: October 2002

We report detection of the edge channel of a two-dimensional electron gas (2DEG) in quantum Hall regime, through the measurement of the chemical potential variation and the compressibility of a 2DEG using a single-electron transistor (SET) on top of the 2DEG. The measurements at higher frequencies enabled us to detect the incompressible electronic states of the fractional quantum Hall effect (FQHE), the results of which indicate a method for resolving the edge channel of FQHE spatially.
Optical Properties and Laser Applications of (InGa)As/(AlGa)As Self-Assembled Quantum Dots
Authors: Henini Mohamed , Patanè Amalia , Polimeni Antonio , Eaves Laurence , Main Peter , Levin Alexander , Hill Geoffrey
Published: October 2002

We study the photoluminescence and laser properties of (InGa)As/(AlGa)As self-assembled quantum dots (QDs). By varying the Al content in the (AlGa)As matrix and/or stacking several QD layers, the room temperature dot luminescence is tuned over a wavelength range from 0.8 µm to 1.3 µm. In particular, by embedding the (InGa)As QD layer in a GaAs/AlGaAs quantum well, an high temperature light emission from the dots can be obtained (up to 500 K). We also study the properties of QD lasers and show that both cavity effects and thermal coupling between dots play an important role in determining the QD laser emission.
Higher Picosecond Photoresponsivity Realized by Introducing Hole-Capturing Levels of Iron in GaAs
Authors: Ohsawa Jun , Ozaki Yasutaka
Published: October 2002

Control of transient carrier populations has been achieved by the use of carrier-capturing properties of relevant individual deep levels. Slow contribution from holes to transient photocurrents has been successfully suppressed so that the fast component of electron current becomes dominant. This has been realized by introducing deep acceptor levels of iron into undoped semi-insulating GaAs bulk material. Photoresponses to picosecond light pulses with and without iron doping were compared. A sharp peak at the leading edge, whose width is less than 100 ps, is increased for the iron-doped one. An additional cause of this could be reduced electron capture due to a concomitant decrease of deep donors such as electron levels No. 2 (EL2) and No. 6 (EL6). Iron-diffused epitaxial material, which has much lower concentrations of grown-in deep levels, showed the same electron-dominated characteristics, confirming the effectiveness of the hole-capturing nature of the iron level.
Monolithic Integration of Resonant Tunneling Diodes, Schottky Barrier Diodes and 0.1-µm-gate High Electron Mobility Transistors for High-Speed ICs
Authors: Matsuzaki Hideaki , Osaka Jiro , Itoh Toshihiro , Sano Kimikazu , Murata Koichi
Published: October 2002

Monolithic integration technology for resonant tunneling diodes (RTDs), Schottky barrier diodes (SBDs), and 0.1-µm-gate high electron mobility transistors (HEMTs) was developed. The integration process was investigated to overcome the difficulty in fabricating both RTDs with a mesa height of 530 nm and HEMTs with a gate length of 0.1 µm. The HEMT and SBD structures were grown by metalorganic chemical vapor deposition (MOCVD) on a 2-inch InP substrate. The RTD structure was regrown by molecular beam epitaxy (MBE) on the top layer grown by MOCVD. The characteristics of the fabricated devices showed good uniformity. An analog-to-digital converter and a selector circuit fabricated with these devices operated properly. The presented integration technology is a promising way to provide novel circuits with RTDs, SBDs and 0.1-µm-gate HEMTs.
Carbon Diffusion through SiO2 from a Hydrogenated Amorphous Carbon Layer and Accumulation at the SiO2/Si Interface
Authors: Krafcsik Olga H. , Vida György , Pócsik István , Josepovits Katalin V. , Deák Péter
Published: October 2002

Carbon diffusion in a SiO2/Si system was investigated. The source was provided by chemical vapor deposition of a hydrogenated amorphous carbon layer onto the oxide at low temperature. From layers with low oxygen content, no carbon outdiffusion was detected up to 1190°C. If the O content was high, the diffusion would start suddenly at 1140°C, and carbon accumulation would be found on the Si side of the SiO2/Si interface in the form of SiC precipitates. These results are interpreted by assuming oxygen-assisted dissociation of carbon atoms from the carbon layer in form of CO molecules, fast CO diffusion through SiO2 and an exothermic reaction of CO with Si. No carbon segregation was found in SiO2. Consequences of carbon island formation during SiC oxidation are pointed out.
A Comparative Study on the Attributes of Ions in Nematic and Isotropic Phases
Authors: Sawada Atsushi , Manabe Atsutaka , Naemura Shohei
Published: October 2002

The complex dielectric constant of 4-n-pentyl-4′-cyanobiphenyl (5CB) was measured between 0.0001 Hz and 1 kHz in nematic and isotropic phases. Dielectric relaxation due to space-charge polarization was observed for both phases. In the nematic phase, the diffusion coefficient D
⊥ and the mobility µ⊥ of ions in 5CB were determined by theoretical analysis for the frequency dependence of the complex dielectric constant. The mobility µ∥ was estimated by an extrapolation procedure utilizing a magnetic field. The activation energies for µ⊥ and µ∥ were calculated in accordance with the Arrhenius plots; furthermore, the relationship between the mobility and the viscosity coefficients of 5CB was investigated. The Miesowicz viscosity coefficients η1, η2 and η3 were considered in the nematic phase, and it was found that the product value of µ⊥ and η3 is almost the same as that of µ∥ and η2 but smaller than the value obtained in the isotropic phase.
The Subbands and Resonant Tunneling of a Two-Dimensional Electron Gas in a HgCdTe Metal-Insulator-Semiconductor Structure
Authors: Ki Hong Jin , Young Sung Sangsig Kim , Chul Chung Yun , Ung Kim Sun , Jang Park Mann
Published: October 2002

Electron tunneling spectroscopy was performed at 77 and 4.2 K for the measurement of the tunneling current as a function of the bias voltage, which provided the information on the subbands and resonant tunneling of a two-dimensional electron gas confined in an n-type HgCdTe accumulation layer in the Hg1-x
Cd
x
Te–ZnS–In junction structure. Our analysis of the tunneling current versus applied bias measured at 77 K indicates that the subband energy level in a Hg0.79Cd0.21Te accumulation layer of a HgCdTe metal-insulator-semiconductor (MIS) structure is located at -59 meV for the ground state and -13 meV for the first excited state relative to the Fermi level. In addition, negative differential resistance was observed for the Hg0.79Cd0.21Te at 4.2 K when the applied bias was larger than the difference between the work function of Indium and the electron affinity of ZnS. Our calculation based on transfer matrix method suggests that this negative conductance be attributed to Fowler-Nordheim tunneling induced by adjusting the transmission width of a ZnS barrier.
Reconstructions of 6H-SiC(0001) Surfaces Studied by Scanning Tunneling Microscopy and Reflection High-Energy Electron Diffraction
Authors: Hisada Yoshiyuki , Hayashi Kazuhiko , Kato Kiyoshige , Aoyama Tomohiro , Mukainakano Shinichi , Ichimiya Ayahiko
Published: October 2002

Surface reconstructions and surface decomposition of 6H-SiC(0001) covered with Si were observed using scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEED). The 3×3 structure terminated with Si atoms was obtained by annealing at 1050°C; this changed to a mixture of the graphite 1×1 and SiC 6×6 by annealing at 1300°C. The graphite 1×1 consisted of two types of graphite lattices, rotated 30° with respect to the SiC lattice and along the SiC lattice. The SiC 6×6 was terminated with C atoms. The RHEED spots due to the double diffraction between the SiC (02) spot and the graphite spot rotated by 30° with respect to the SiC lattice were observed. The thickness of the graphite layer and the area of the graphite region increased by successive annealing. String-shaped structures were formed along the steps at 1450°C. Further annealing up to 1800°C resulted in the formation of a thick graphite layer and amorphous carbon.
Processing and Properties of Low-Fire Ni–Cu–Zn Ferrite with V2O5
Authors: Jean Jau-Ho , Lee Cheng-Horng
Published: October 2002

Vanadium oxide has been found to be an effective sintering aid for preparation of dense Ni–Cu–Zn ferrite. The addition of a small amount of V2O5 (1–2 wt%) in the Ni–Cu–Zn ferrite enhances the densification greatly, but reduces the activation energy of densification significantly. Moreover, the grain growth becomes more evident when V2O5 is present. A chemical reaction taking place at the interface of V2O5/Ni–Cu–Zn ferrite, which results in reactive liquid phase sintering, is attributed to the above results. However, the above interfacial reaction also causes segregation of NiO onto grain boundaries and dissolution of V2O5 into the ferrite, yielding reduction in initial magnetic permeability.
Effects of Shape Anisotropy in CoO/Co/Cu/NiFe/Cu/Co Wires
Authors: Kimura Takashi , Mozumi Gon , Wakaya Fujio , Gamo Kenji
Published: October 2002

Magnetic wires consisting of the CoO/Co/Cu/NiFe/Cu/Co structures with a variable width in the range from 0.3 µm to 10 µm were fabricated by using electron-beam lithography and Ar ion milling. The width dependencies of the coercive forces in each magnetic layer and the width dependence of the exchange bias in the CoO/Co layer were investigated by using the giant magnetoresistance effect. In the Co and NiFe layers, the coercivities varied almost in proportion to the inverse wire width, and can be explained by considering the width dependencies of the demagnetic fields. In the CoO/Co layer, the coercivity enhancement of the Co layer, which may be caused by the random exchange interaction, was observed. The width dependencies of the coercive force and exchange bias in the CoO/Co layer were explained by the suppression of the fluctuation of the exchange bias. This suggests that the easy axes in the CoO layer are regulated by the shape anisotropy in the Co layer.
Diffraction from Polymer-Stabilized Cholesteric Texture Films
Authors: Ko Tsung-Chih , Fan Yun-Hsing , Shieh Ming-Feng , Fuh Andy Ying-Guey , Huang Chi-Yen , Tsai Ming-Shann , Jiang I-Min
Published: October 2002

We have performed diffraction experiments on polymer-stabilized cholesteric texture (PSCT) films made from E48-BAB6 mixtures cured at various UV intensities. The diffraction observed in these samples is the Qu'etelet-type ring pattern, which is generated from the scattering of light by the clusters of the polymer networks and the focal conic domains of cholesteric liquid crystals in a PSCT cell. We monitored the dynamic change of the intensity of the first ring of a sample during polymerization. After polymerization, both the electro-optical characteristics and the diffracted ring intensities of various orders were measured. The results showed that both the applied voltage and the UV curing intensity affected the diffraction intensity significantly. Furthermore, the results obtained from diffraction measurements correlate with the electro-optical ones. Thus, the diffraction measurements could provide us with another qualitative, nondestructive method to analyze PSCT devices.
Spherical Aberration Detection in the Optical Pickups for High-Density Digital Versatile Discs
Authors: Shimano Takeshi , Umeda Mariko , Ariyoshi Tetsuo
Published: October 2002

A new method of detecting the spherical aberration of a ray is described. In a high-density digital-versatile disc system achieved by means of a high-numerical-aperture objective lens system or a multilayer disc system, it is important to reduce the aberrations caused by substrate thickness error and layer distance, respectively. When rays with spherical aberration converge, the focus of the far-axis ray deviates from that of the near-axis ray, and gradually moves towards the optical axis. Based on this phenomenon, we demonstrated that spherical aberration can be detected by subtracting the focus-error signal of the far-axis ray from that of the near-axis ray. The resulting spherical aberration signal can be used in a phase-control device, such as an expander lens actuator or a liquid-crystal phase shifter, to produce a dynamic servo controller that can compensate for spherical aberration.
High-Track-Density Optical Disc by Radial Direction Partial Response
Authors: Kobayashi Seiji , Horigome Toshihiro , Yamatsu Hisayuki
Published: October 2002

We propose a new recording method, the radial direction partial response (RPR), with which we are able to use a narrow track pitch. This method can be used only for optical read-only-memory discs. We present experimental results of this method combined with the multilevel recording technique called “single carrier independent pit edge recording” (SCIPER). (The combined method is called SCIPER-RPR). When a track pitch of 0.45 µm and 0.28 µm/bit in linear recording density is read out by a digital versatile disc (DVD) equivalent optical pickup, we confirmed a bit error rate of 1.5×10-4.
Spin Accumulation in a Quantum Cluster Resolved in Tunnel Junctions
Authors: Brataas Arne , Hirano Masaki , Inoue Junichiro , Nazarov Yuli V. , Bauer Gerrit E. W.
Published: October 2002

Transport through a small metal island attached to two ferromagnetic reservoirs by tunnel junctions is considered. The discrete energy levels due to size quantization, the Coulomb charging energy and the non-equilibrium spin accumulation due to the spin-dependent tunneling rates are taken into account. Analytical results for the zero-bias conductance and magnetoresistance are found. In the nonlinear current–voltage regime, numerical calculations reveal discrete jumps in the tunnel magnetoresistance when the applied voltage is in resonance with the energy difference associated with tunneling of an electron into the ground or excited states of the quantum cluster. Effects of spin-dependent discrete energy levels in magnetic quantum clusters on the tunnel magnetoresistance are studied in detail.
Bistable States of Ferroelectric Hysteresis Loops in a Heteroepitaxial BaTiO3 Thin Film Capacitor
Authors: Kazuhide Abe Kazuhide Abe , Naoko Yanase Naoko Yanase , Takashi Kawakubo Takashi Kawakubo
Published: October 2002

Polarization vs voltage (P–V) hysteresis loops were investigated for a heteroepitaxial BaTiO3 thin film capacitor. Depending on amplitude of DC bias voltage which was superposed on alternative triangular waves, two types of P–V hysteresis loops were observed. They were characterized by the magnitude of the voltage shift from 0 V and named “on” and “off” states after their position. The transition between the two states exhibited hysteresis when the DC bias voltage was gradually increased and decreased. When intermediate amplitude of the DC bias voltage was applied, a “mixed” state appeared in the hysteresis loop, in which polarization reversal took place in two steps. Owing to the “on” state stabilized in the hysteresis loop, ferroelectric polarization of the heteroepitaxial capacitor was confirmed to be retained for longer than 4 h at 0 V.
Preparation of RhO2 Thin Films by Reactive Sputtering and Their Characterizations
Authors: Kato Kiyohiko , Abe Yoshio , Kawamura Midori , Sasaki Katsutaka
Published: October 2002

Thin films of RhO2, which belongs to the family of conducting platinum group metal oxides, were prepared by reactive sputtering. Influences of sputtering parameters, such as rf power and substrate temperature, and postdeposition annealing on crystallinity, chemical bonding state and resistivity of the deposited films were studied, in order to obtain low-resistivity RhO2 thin films. The resistivity of the deposited films decreased with decreasing rf power. Plasma emission measurement suggested that oxidation of Rh proceeded under the low rf power condition. Poorly-crystallized conducting RhO2 thin films with resistivity of 300–500 µΩcm were prepared at substrate temperatures below 150°C; the resistivity of the films increased with increasing substrate temperature above 150°C due to the formation of semiconducting Rh2O3. After postdeposition annealing in oxygen atmosphere at up to 700°C, well-crystallized RhO2 films were formed, and the minimum resistivity of 80 µΩcm was obtained.