bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanofabrication for Quantum Devices
Authors: Kern D. P. , Lee K. Y. , S. A. Rishton S. A. Rishton , S. J. Wind S. J. Wind
Published: February 2005

Fabrication of structures for investigation of quantum effects frequently involves the use of MBE/CVD type growth processes to achieve control on an atomic scale in vertical direction and a wide range of combinations of lithography and pattern transfer techniques for control in lateral directions. The challenges ahead lie in the degree of lateral control with which the lithography can be performed, i.e. resolution and placement accuracy, but also in the throughput of the lithography equipment once technological applications are considered. Electron beam resolution can certainly extend to the 1 nm regime, in the case of the STM even to 0.1 nm, appropriate resist materials have to be found, however. Parallelism may be introduced into nanolithography through contact printing with X-rays, electron, ion, or X-ray projection, or arrays of miniaturized scanning electron or ion columns. Pattern transfer relies on a broad spectrum of subtractive and additive processes ranging from wet and dry etching to selective growth techniques. Pattern fidelity and damage to the material are the key issues.
Fabrication of Atomic-Scale Structures on Si(111)-7×7 Using a Scanning Tunneling Microscope (STM)
Authors: Huang Dehuan , Uchida Hironaga , Aono Masakazu
Published: February 2005

A single Si atom or a group of a few Si atoms can be extracted from a predetermined position of the Si(111)-7×7 surface through field evaporation with a scanning tunneling microscope (STM). A method of tip preparation which makes Si atom extraction reliable is presented. The results of many individual Si atom extraction experiments are discussed on the basis of the statistics of extraction with the Si(111)-7×7 unit cell.
Recent Developments for Sub-Quarter Micrometer Fabrication
Authors: Rousseaux F. , Haghiri-Gosnet A. M. , CHEN Y. , M. F. Ravets M. F. Ravets , H. Launois H. Launois
Published: February 2005

Resolution capability of synchrotron radiation based proximity lithography has been investigated in the sub-quarter micrometer range using an advanced X-ray stepper and high resolution SiC/W X-ray masks. High resolution tungsten gratings and single lines as small as 60 nm are now currently available. Such masks were tested by contact printing in the L2M lithography station implemented at Super-ACO synchrotron facility in Orsay-France. Also, the influence of diffraction on feature sizes was studied with 30-40 µm proximity gap using various positive and negative resists: PMMA, RAY-PF, SAL 601. It was found that 0.10 to 0.12 µm linewidths can be achieved for gratings and 0.15 to 0.20 µm for isolated lines. This resolution limit can be overpassed by a double exposure technique associated with a lateral mask-stage translation. Examples of feature size down to 80 nm were readily achieved at 40 µm gap.
Theoretical Evaluation of Compositional Contrast of Scanning Electron Microscope Images
Authors: Kotera Masatoshi , Yamaguchi Satoru , Takafumi Fujiwara Takafumi Fujiwara , Hiroshi Suga Hiroshi Suga
Published: February 2005

The compositional contrast in the scanning electron microscope image is calculated for Al-Cu, Si-Cu and Al-Si contacts. An electron scattering phenomenon in the specimen is simulated in a direct manner. Electron refraction at the boundary, because of the agreement of each Fermi energy at the boundary, is precisely taken into account. The backscattered electron image shows better resolution than the secondary electron image in terms of the boundary contrast when the primary electron energy is 1 keV. The signal intensity varies depending on materials adjacent to the location observed. The ultimate resolution of the compositional contrast of the scanning electron microscope can be below 1 nm.
Drastic Enlargement of Grain Size of Excimer-Laser-Crystallized Polysilicon Films
Authors: Choi Do-Hyun , Shimizu Kazuhiro , Osamu Sugiura Osamu Sugiura , Masakiyo Matsumura Masakiyo Matsumura
Published: February 2005

Polysilicon thin films with extremely large grains (grain size more than 50 µm, i.e., three orders of magnitude more than the typical value) have been formed using an excimer-laser crystallization method for the first time. This drastic enlargement was achieved by the reduction of the solidification rate of molten silicon by the small heat capacitance effect of the thin silicon-dioxide membrane used as a substrate. Crystallinity and film properties have been evaluated from Raman spectroscopy, resistivity, Hall effect and transistor characteristics. The Hall mobility of electrons was as high as 610 cm2/Vs.
Characteristics of Plasma-Enhanced-Chemical-Vapor-Deposition Tetraethylorthosilicate Oxide and Thin-Film-Transistor Application
Authors: Nishi Yutaka , Funai Takashi , Izawa Hideo , Fujimoto Takeo , Morimoto Hiroshi , Ishii Mitsuo
Published: February 2005

In order to make application to the low-temperature thin-film-transistor (TFT) process possible, the deposition of SiO2 films by plasma-enhanced-chemical-vapor-deposition (PECVD) using tetraethylorthosilicate (TEOS) was investigated. It was shown that the oxide films with low Si-OH content had good electrical properties: for example, low interface state density of 5×1010 cm-2 eV-1 and high breakdown strength of 8 MV/cm. In addition, polycrystalline-silicon (poly-Si) TFT's employing TEOS-SiO2 films as gate insulators were fabricated and examined. It was confirmed that the TEOS-PECVD method was a promising method for forming gate insulators. This paper reports on TEOS-SiO2 films and poly-Si TFT's.
Process Techniques of 15-inch Full-Color High-Resolution Liquid Crystal Displays Addressed by a-Si Thin Film Transistors
Authors: Fujii Kenichi , Tanaka Yasuo , Honda Kouichi , Tsutsu Hiroshi , Hideo Koseki Hideo Koseki , Sadayoshi Hotta Sadayoshi Hotta
Published: February 2005

A 15 inch-diagonal-size full-color liquid crystal display (LCD) with 1152(×3)×900 pixels has been fabricated which enables a portable workstation with improved display performances. The process techniques used for this development are described, with special reference to metallization and dry etching. In multilevel metallization, Cr/Al interconnection is metallurgically undesirable. By contrast, the Cr/Ti/Al metal system provides excellent properties of contact resistivity and thermodynamical stability. Dry etching processes are developed for multilayered insulating films and metallization-related bilayers, namely SiO2/TaO
x
/SiN
x
/(i/n+)a-Si and a-Si/Ti, respectively. Fine patterning and easier stepcoverage of subsequently deposited layers are achieved.
Completely Erasable Phase Change Optical Disk
Authors: Iwasaki Hiroko , Ide Yukio , Harigaya Makoto , Yoshiyuki Kageyama Yoshiyuki Kageyama , Itaru Fujimura Itaru Fujimura
Published: February 2005

A phase change optical disk using a new quaternary system of Ag-In-Sb-Te as the active layer will be reported. With this disk, “complete erasure” of the recorded signal has been achieved. A carrier-to-noise ratio of 47 dB and an erase ratio of -47 dB were obtained in the two-pass writing-erasing mode with a linear velocity of 7 m/s and a writing power of 11 mW. In the one-pass overwriting mode, a carrier-to-noise ratio greater than 40 dB was obtained and this recorded signal was also completely erased. The peak power and the bias power for the overwriting were 10 mW and 5 mW, respectively. The facts that the widths of the written marks are narrow and that no large crystalline grains are observed in the periphery of the written marks are considered to be the major causes for the high erasability. We also found that the existence of fine crystalline particles in the initialized active layer can be considered to be of great advantage to high sensitivity.
Synthesis of Bi-Sr-Ca-Cu-O High-Tc Phase from a Parent Compound of Ca(Sr)CuO2
Authors: Hontsu Shigeki , Nishibuchi Osamu , Horiuchi Takeshi , Ogura Kiyoshi , Ishii Junya , Kawai Tomoji , Kawai Shichio
Published: February 2005

The synthesis of bulk Bi-Sr-Ca-Cu-O superconductors has been performed from Ca(Sr)CuO2 as a parent structure reacting with Bi and Sr as other containing compounds. It is proven that the high-T
c phase with three Cu-O2 sheets, Bi2Sr2Ca2Cu3O10, is readily obtained from the above special starting materials. Using the carbonates of each metal ion as starting materials, however, the low-T
c phase is mainly obtained.
Pattern Recognition with Circular Harmonic Filtering and Phase-Only Circular Harmonic Filtering Using a Vander Lugt Filter
Authors: Yau Hon-Fai , Tong Yuh-Ping , Lee Cheng-Min , Chang Chi-Ching , Ming-Wen Chang Ming-Wen Chang
Published: February 2005

A simple method of synthesizing a Vander Lugt circular harmonic (CH) filter is introduced. This method involves only one optical Fourier transformation instead of two. An optical pattern recognition experiment with this type of CH filter has shown that it is superior to a computer-generated binary CH filter.
Master Recording Using Kr Ion Laser
Authors: Makoto Itonaga Makoto Itonaga , Tetsuya Kondo Tetsuya Kondo
Published: February 2005

Resolution of a master recorder using Kr ion laser was investigated by means of computer simulation and experimentation. Limitary pit length P
L
min was indicated by the k factor: P
L
min=k×(wavelength)/(numerical aperture). When the duty of the write pulse D
T was 0.5, k was 0.56 in simulation. For D
T=0.36, k was 0.57. In the experiment pit widths were measured from scanning electron micrographs. Experimental results showed the same tendency as the simulated results. K factors in the experiment were 15.8 percent (D
T=0.5) or 20.7 percent (D
T=0.36) worse than those in the simulation. The optical system of the recorder is tested using the Twyman-Green interferometer and the knife-edge method. An interferogram shows a good performance. Measured half-width of the spot was 0.24 µm. It was close to the ideal diameter of 0.23 µm.
Development of Actuators for Small-Size Magneto-Optical Disk Drives
Authors: Ichihara Junichi , Koichi Tezuka Koichi Tezuka , Koichi Ogawa Koichi Ogawa
Published: February 2005

This paper describes the development of focusing and tracking actuators for compact low profile magneto-optical disk drives. We clarify a structural optimization mechanism that raises the upper mechanical resonant frequencies of the actuators to 30 kHz. Optimized drive motors reduce power consumption.
Improvement in Lasing Properties of an Integrated Flying Optical Head with a Diamond-Film-Coated Slider
Authors: Ukita Hiroo , Hiroshi Nakada Hiroshi Nakada , Tetuo Abe Tetuo Abe
Published: February 2005

The heat dissipation in a junction-up mounted 1.3-µm-wavelength InGaAsP laser diode/photodiode on a flying optical head slider is analyzed by infrared microscopy. The temperature rise is reduced by about 50% for a slider with a diamond film. This reduction corresponds to a 27-fold increase (31°C temperature drop) in the lifetime of the laser diode and confirms the possibility of head operability in multilaser diodes on a slider.
New Structure Disk for a Magneto-Optical Composite Head System
Authors: Koda Tomohiro , Kawashima Tetsuji , Goro Fujita Goro Fujita , Tetsu Watanabe Tetsu Watanabe
Published: February 2005

A new structure disk was developed for a magneto-optical (MO) composite head system. The new disk has a thin readout substrate under and a high magnetic permeability layer over the MO layer. The effect of the high magnetic permeability layer was confirmed experimentally and agreed well with theoretical results. The normal component of the magnetic field at the MO layer is enhanced 1.6 times by the high magnetic permeability layer.
Analysis of Leading Edge/Trailing Edge Independent Detection Method in Optical Disk
Authors: Sugiyama Hisataka , Maeda Takeshi , Saitoo Atsushi , Nishida Tetsuya , Horigome Shinkichi , Arai Shinichi , Shigematsu Kazuo , Watanabe Hitoshi , Gotoh Akira
Published: February 2005

The effects of independent detection of leading edge / trailing edge on edge-shift and jitter are investigated for typical heat-mode recording processes using read-out pulse width, recording timing measurements and thermal simulation. In addition, in order to investigate the edge-shift reduction limit for this new method, a method is proposed to analyze what causes the edge-shifts; it statistically evaluates the relative edge intervals between adjacent edges of a particular worst-case recording pattern. Our results clarify that the new method is effective for reducing edge-shifts and jitter.
The Characteristics of a SrS:CeCl3 Thin-Film Electroluminescent Device Prepared by Multi-Source Deposition Method
Authors: Yoshiki Chubachi Yoshiki Chubachi , Kazushi Aoyama Kazushi Aoyama
Published: February 2005

A blue-emitting SrS:Ce EL device was developed by multi-source deposition method with strontium metal, sulfur and cerium chloride. The formation of SrSO4 in deposited films was confirmed by X-ray diffraction and a quadrupole mass spectrometer (QMS) analysis. The luminance-voltage (L-V) curve became steeper with increasing Ce concentration. In the light output waveform the first peak and the third peak at high Ce concentration were weaker than those at low Ce concentration. The light output when the aluminum electrode was biased positively was weaker than that when it was biased negatively. These optical characteristics are discussed on the basis of the proposed model.
High Speed Recording Characteristics of 3-Beam Drive
Authors: Yamamoto Manabu , Saito Minoru , Katoh Kikuji , Akinori Watabe Akinori Watabe , Ichiro Yamada Ichiro Yamada
Published: February 2005

A 3-beam magneto-optical (MO) disk drive with overwriting and read-verifying functions achieves a high data transfer rate of 2.1 MB/s at a disk rotation of 5400 rpm. The 3-beam drive has sufficient focusing, tracking servo performance and a read/write phase margin of more than 35% to allow for the use of ISO standard 130-mm MO disks. Read/write compatibility with a wide write power margin is obtained between the 3-beam drive and conventional MO drives.
Robust Servo System of Optical Disk Drive
Authors: Masaharu Ogawa Masaharu Ogawa , Teruo Furukawa Teruo Furukawa
Published: February 2005

The requirement for an optical disk drive to operate properly under the existence of violent external vibration has been growing because portability of the drive increases as it becomes miniaturized. In order to improve a servo system's resistance to external vibration, an objective lens velocity feedback method in a two-stage tracking servo system and two-degree-of-freedom velocity control drive of a linear motor during the seeking operation are proposed. These methods are incorporated in 90 mm optical disk drives, and a vibration test is performed to investigate improvements in the servo performance. When the vibration is 0.5 g at 50 Hz, the average seeking time increases only 10% when compared with the condition of no external vibration.
Performance of Modulation Codes in Various Optical Recording Media
Authors: C. M. J. van Uijen C. M. J. van Uijen , J. H. M. Spruit J. H. M. Spruit
Published: February 2005

The performance of modulation codes has been measured in ablative and magneto-optic recording media as well as in mastered direct discs. The modulation codes studied include NRZ (i.e. the uncoded bit stream), runlength limited sequences, multi-level recording schemes, and differentially detectable codes. We also studied the performance of codes when the optical channel is equalised, particularly the case of partial response detection of NRZ.
The general conclusions are that: 1) differentially detectable codes require the full penalty in data density caused by the loss in code rate, 2) multi-level recording does not offer significant advantages, and step-constrained multi-level codes perform worse than their unconstrained counterparts, 3) runlength limited sequences are useful codes to enhance the density while offering additional practical advantages, and 4) partial response detection of uncoded bit streams transmitted through an equalised optical recording channel achieves the highest density.
Persistent Spectral Hole-Burning on a Subnanosecond Time Scale by Donor-Acceptor Electron Transfer in Zinc-Tetraphenylporphine/ p-Benzoquinone Systems
Authors: Hiroyuki Suzuki Hiroyuki Suzuki , Toshiyuki Shimada Toshiyuki Shimada
Published: February 2005

We report subnanosecond persistent spectral hole-burning in zinc-tetraphenylporphine/p-benzoquinone (ZnTPP/p-BQ) embedded in PMMA at liquid helium temperature. The hole formation mechanism is photoinduced one-photon electron transfer from photoexcited ZnTPP to ground state p-BQ. Spectral holes burnt in the present system are filled to half their initial depth when the temperature is increased to 25 K.
Effect of Aluminum on Ac Surface Photovoltages in Thermally Oxidized n-Type Silicon Wafers
Authors: Munakata Hirofumi Shimizu
Published: February 2005

Ac surface photovoltage (SPV) appears in thermally oxidized n-type silicon wafers which are pre-treated with an aluminum (Al)-contaminated RCA solution (the concentration of Al in the oxide: 1017 atom/m2), indicating that Al acts as a negative charge. The negative charge vanishes with removal of the surface layer (∼5 nm) of the oxide (∼61 nm) i.e., Al-induced charge resides in the surface layer of the thermally grown oxide.
Macrotrap Model for Charge-Carrier Transport in Low-Mobility Solids
Authors: Kalinowski Jan , Godlewski Jan , Piergiulio Di Marco Piergiulio Di Marco , Valeria Fattori Valeria Fattori
Published: February 2005

The neutral macrotrap model of charge carrier trapping has been developed to explain the electric field (F) and temperature (T) dependence of the effective charge carrier mobility (µeff) in low mobility solids. The potential barrier for the carriers localized in the neutral macrotraps (spatially extended trapping domains) can be effectively lowered by an external electric field accessible in the experiment, making the mobility and its thermal activation field dependent. The potential of a neutral macrotrap is approximated by Φ(r)=(3k
T/eσ) ln (r
0/r), where r is the distance from the center of the macrotrap, r
0 stands for its radius, e is elementary charge and σ is a characteristic parameter of the exponential energy distribution of point traps composing the macrotrap. The lowering of the barrier is proportional to F at low fields and to ln F at high fields. The field behavior of the effective mobility is governed by this lowering of the barrier and by its field-dependent position which, therefore, can be reached by the thermally activated carriers with a field-dependent probability in the process of carrier diffusion. The latter introduces a factor exp (-3k
T/σe
l
D
F) (l
D-diffusion length of the carriers) responsible for the self-consistency of the field dependence of the mobility and the Arrhenius temperature term exp [-E(F, T)/k
T]. This model provides a consistent description of representative experimental data reported for low-carrier mobility crystalline and disordered solids.
Pattern Formation in the Transient Periodic Splay Freedericksz Transition in a Nematic Liquid Crystal
Authors: Hiap Liew Ong Hiap Liew Ong
Published: February 2005

In the magnetic-field-induced Freedericksz transition in a parallel oriented nematic liquid crystal cell, the one-dimensional liquid crystal orientation profile can become a two-dimensional transient splay periodic profile by the backflow effects. The backflow effects result in a reduction of the effective viscosity and thus gives a faster response than that of the one-dimensional orientation profile. We introduce a vector potential description for the liquid crystal director and flow velocity, and obtain the general solution for the two-dimensional splay Freedericksz transition. The vector potential method gives solutions which inherently satisfy the fluid incompressibility condition and overcome the difficulties in the conventional `free boundary conditions'. The method enables us to express the flow velocities and the nematic director by a single variable, and simplifies the equations of motion to one equation of motion for the new variable. The general solution is obtained. The particular solution on the fastest growing mode is in agreement with that obtained by Hurd et al [J. de Physique 46 (1985) 905].
Anomalous Hg IN-Diffusion in MCT (x=0.2) During Low Temperature Hg Saturation Annealing
Authors: Sharma Rajesh K. , Vinod K. Singh Vinod K. Singh , Braj Bhushan Sharma Braj Bhushan Sharma
Published: February 2005

Anomalous Hg in-diffusion in bulk grown MCT (x=0.2) crystals at 260°C has been observed. The Hg in-diffusion has been found to become faster in presence of an Hg vapour source having a lower chemical potential of tellurium as compared to the crystals. The observed diffusion behavior has been discussed and explained in terms of Te precipitation and out-diffusion during annealing. The anomalous diffusion characteristics are typical of diffusion in a disordered medium.
Reversible Displacement Current Generation Due to Photochromism in a Spread Monolayer: Influence of Molecular Orientation
Authors: Majima Yutaka , Haruhiko Naruse Haruhiko Naruse , Mitsumasa Iwamoto Mitsumasa Iwamoto
Published: February 2005

Reversible displacement current generation due to the cis-trans photoisomerization of AZBAA monolayers containing azobenzene derivative was investigated by alternate irradiation with UV light and visible light. The direction of the displacement current generated by irradiation with visible light depended on the area per AZBAA molecule. The direction changed consecutively from negative to positive with compression of the AZBAA monolayer formed at the air-water interface. In contrast, the change in absorption spectra of the AZBAA monolayer at the air-water interface due to the cis-trans photoisomerization was observed in the entire range of the area per molecule. Finally, it was concluded from the displacement current measurement that the orientation of the AZBAA molecules distributed on a water surface was turned by the compression.
Diamond Synthesis by the Microwave Plasma Chemical Vapor Deposition Method Using the Pretreated Carbon Dioxide and Hydrogen Mixed-Gas System
Authors: Satoshi Katsumata Satoshi Katsumata
Published: February 2005

High-quality diamond was obtained by the microwave plasma-assisted chemical vapor deposition (plasma CVD) method using the pretreated carbon dioxide (CO2) and hydrogen (H2) mixed-gas system. The pretreatment method is as follows: at first, CO2and H2pass through the prereactor, where plasma is generated by microwave discharge, and then the reactant passes through the cold trap at around 185 K in order to remove water (H2O) produced in the plasma from CO2and H2. The residue of the pretreated CO2and H2mixed gas, which consists of CO, CO2and H2, is introduced into the main reactor where diamond is synthesized. Diamond can grow to a feed ratio of CO2/H2=25/100 sccm. Plasma diagnosis was performed using optical emission spectroscopy (OES) and gas chromatography (GC).
Molecular Orbitals and Third-Harmonic Generation for Symmetrically Substituted Benzylidene Aniline
Authors: Mori Yuhei , Kurihara Takashi , Toshikuni Kaino Toshikuni Kaino , Satoru Tomaru Satoru Tomaru
Published: February 2005

Molecular orbitals and third-order susceptibility are calculated for terephthal-bis-(4-N,N-diethylamino aniline). The main mechanism of third-harmonic generation is explained approximately by a three-level system. The effect of the orbital shape upon the susceptibility is analyzed. It is found that molecular orbital distortion, due to introduced nitrogen atoms, enhances the transition moment between excited states, 1Bu-2Ag, and this contributes to the third-order susceptibility.
Deuterated Impurities Monitored by Microwave Spectroscopy during Glow Discharge Cleaning
Authors: Mushiaki Motoi , Kubota Yusuke , Funato Yasuyuki , Miyahara Akira
Published: February 2005

Microwave spectroscopy was applied to monitoring of deuterated impurities produced by glow discharge cleaning (GDC). This method estimated the change in the quantity of the isotopic impurities by observing a rotational spectrum of water, HDO. For verifying the validity of the method, mass spectral behaviors of several light impurities (HDO, D2O, H2O, HD, D2 and H2) were studied simultaneously. The deuterated species decreased with time at their own diminishing rates, while normal water, H2O, showed no decrease during GDC. The rotational spectrum of HDO stood at the frequency of 22.3077 GHz. It was distant enough from the nearest neighbor (about 70 MHz) so that the observed line was identified definitely. The lowest partial pressure detected with a microwave spectrometer was 7×10-5 Pa.
In-Situ Counting of Process-Induced Particles
Authors: Kondo Kaoru , Ichijo Kazuo , Shinohara Keisuke , Hoshina Tamio , Tsubouchi Kazuo , Masu Kazuya
Published: February 2005

A flow-cell-type portable laser particle counter was developed for in-situ counting of process-induced particles. We measured process-induced particles when small amounts of moisture and oxygen were intentionally added to SiH4 diluted to 10% in argon gas. It was found that there existed a threshold concentration for particle generation caused by the reaction between SiH4 and moisture/oxygen; i.e., the number of particles was not linearly proportional to the moisture and oxygen concentrations. We also found that the size distribution of generated particles varied due to complex mechanisms such as coagulation of small particles.
Spray Selective Etch Process for Short-Cavity Fabrication of GaAs/GaAlAs Surface Emitting Laser
Authors: Tanobe Hiromasa , Tamanuki Takemasa , Uchida Toshikazu , Fumio Koyama Fumio Koyama , Kenichi Iga Kenichi Iga
Published: February 2005

We have improved the fabrication process forming the shortcavity structure for GaAs/GaAlAs vertical cavity surface emitting lasers. A complete flat epitaxial surface for the output side mirror was obtained by selectively removing the GaAs substrate using a spray wet etch. We present some results on surface characterization.
Characterization of Transmembrane Helices by a Probe Helix Method of Molecular Energy Calculation
Authors: Suwa Makiko , Mitaku Shigeki , Shimazaki Kazuko , Chuman Tatsuji
Published: February 2005

A theoretical method to characterize transmembrane helices by energy calculation was developed, in which interaction energy between a transmembrane helix and a probe helix was calculated. The applicability of this method was tested by using polyserine as a probe helix for the estimation of amphiphilicity of a given helix. The calculation for seven transmembrane helices of bacteriorhodopsin and halorhodopsin suggested that the angular profile of the interaction energy is closely related to the configuration of helices within the proteins and also to the two-dimensional crystalline array of bacteriorhodopsin.
Ionized Cluster Beam Deposition of Polycrystalline Thin Films of CuInSe2
Authors: Matsuda Seisuke , Kudo Yuki , Ushiki Takehito , Hiroki Inoue Hiroki Inoue , Katsuaki Sato Katsuaki Sato
Published: February 2005

Thin films of CuInSe2 were prepared by three-source ionized cluster beam (ICB) deposition on bare and Mo-coated glass substrates. Of the three elements composing CuInSe2, only In was ionized and accelerated. Single-phase chalcopyrite films were obtained in films prepared at acceleration voltages higher than 1 kV. The Cu/In ratio, as well as the electrical resistivity, was found to be controlled by changing the acceleration voltage. X-ray diffraction patterns, optical micrographs and scanning electron micrographs revealed that the crystallinity and the homogeneity of CuInSe2 grains were improved by application of acceleration voltages. The improvement was more obvious in the films grown on Mo-coated substrates.
Light Emission from Microcrystalline Si Confined in SiO2 Matrix through Partial Oxidation of Anodized Porous Silicon
Authors: Ito Toshimichi , Toshimichi Ohta Toshimichi Ohta , Akio Hiraki Akio Hiraki
Published: February 2005

Optical properties of microcrystalline Si embedded in a SiO2 matrix through a partial oxidation of anodized porous silicon using a wet process have been studied. Thick (∼30 µm) films thus obtained were dark red to light yellow in color, depending on the oxidation condition. The fundamental edge of the absorption spectra shifted to the higher energy side with increasing oxide fractions in the colored specimen. Visible light emissions from these specimens were observed at room temperature with photoexcitations using a He-Cd laser. All of the data, including the broadening effect in X-ray diffraction peaks, can be explained in terms of the size reduction effect of the Si islands confined in the SiO2 matrix.
Metastable States Observed by Optical Absorption of DX Centers in AlxGa1-xAs:Te
Authors: Mori Yuzo , Takashi Yokota Takashi Yokota , Hiroshi Ohkura Hiroshi Ohkura
Published: February 2005

With the use of thick n-type AlxGa1-xAs:Te crystals (x=0.29, 0.37 and 0.46) between 10 K and 300 K, optical absorption of deep levels, so called DX centers, has been measured in sequence under (a) thermal equilibrium and (b) non-equilibrium states induced by the photoionization of the deep DX center. Absorption found at the expense of the deep DX center absorption has a peak at 0.56 eV whenx=0.46: the band is related to the metastable persistent photoconductivity. The intensity correlation of the two absorptions indicates the presence of another metastable state which is optically inactive. This state is interpreted as a neutral donor state with reference to a negative U model of DX centers.
Luminescence and Multiphonon Raman Scattering Excited at Exciton-Forming Vibronic Absorption Subbands in Trans-Polyacetylene
Authors: Watanabe Toshio , Kubo Takaya , Hideo Takezoe Hideo Takezoe , Atsuo Fukuda Atsuo Fukuda
Published: February 2005

Resonance Raman scattering superimposed on near-infrared luminescence in trans-polyacetylene excited at 1.42 eV (876 nm) and 1.45 eV (854 nm) was observed using a Ti-sapphire laser. Cis- and trans-polyacetylenes were confirmed to behave quite similarly in optical and photocurrent responses, at least near their respective intrinsic absorption edges. Considerably clear vibronic triplet subbands appear in the reflection spectrum, and intense multiphonon Raman scattering occurs. The photocurrent excitation efficiency is practically zero at the absorption edge, and edge luminescence appears, although its yield is not high.
Strong Low-Frequency Noise in Polysilicon Emitter Bipolar Transistors with Interfacial Oxide due to Fluctuations in Tunneling Probabilities
Authors: Lau Wai Shing , Chor Eng Fong , Chee Seng Foo Chee Seng Foo , Wai Chee Khoong Wai Chee Khoong
Published: February 2005

Strong 1/f
α (2>α>1) noise was observed in polysilicon emitter bipolar transistors with an interfacial oxide layer sandwiched between the polysilicon and monocrystalline silicon emitter regions but not in similar transistors without interfacial oxide. The noise was explained as fluctuations in the carrier tunneling probabilities through the interfacial oxide. A simple equivalent circuit was proposed to model the strong 1/f
α noise.
Electron Irradiation Effects on the Transport Critical Current Density in a Bi1.5Pb0.5Sr2Ca2Cu3Ox Ceramic
Authors: Shiraishi Kensuke , Sakamoto Hiroshi , Yano Koichi , Otoguro Yasuo
Published: February 2005

A Bi1.5Pb0.5Sr2Ca2Cu3O
x
ceramic was sequentially irradiated with 3 MeV electrons at a dose rate of 2.5×1017 m-2·s-1 up to a dose of 2.0×1020 m-2 at ambient temperature, and the transport critical current density was measured as a function of temperature. The critical current density in zero field at temperatures below 65 K was increased by irradiation to 1.0×1020 m-2, and the radiation effect was more prominent at lower temperature. Upon further irradiation to 2.0×1020 m-2, the critical current density was reduced in the low temperature regime to a level less than the preirradiation value.
Fabrication of 300 Å Thick BiSrCaCuO Thin Films with Tc of 108 K by use of Ion Implantation
Authors: Kazuo Saito Kazuo Saito , Masatsugu Kaise Masatsugu Kaise
Published: February 2005

BiSrCaCuO thin films of 300 Å thickness were deposited on MgO(100) substrates by magnetron sputtering and were subsequently annealed at 875°C for 0.5 h. The annealed films exhibited markedly high T
c values in the range of 90 K. These films were irradiated with 100 keV Ar ions at 10 K and finally annealed at 730°C for 0.5 h. The T
c of these films increased to 108 K which is equivalent to the maximum value so far reported for this system. The role of 100 keV Ar ions in the film fabrication is described in terms of elastic nuclear collision events in the low-energy cascade region.
Large Saturation Field in Magnetoresistance for Epitaxial Co/Cu(111) Superlattices
Authors: Atsushi Kamijo Atsushi Kamijo , Hitoshi Igarashi Hitoshi Igarashi
Published: February 2005

(111)-oriented epitaxial Co/Cu superlattices have been grown onto Si(111) substrate by molecular beam epitaxy (MBE) technique. Large antiferromagnetic couplings (saturation fields H
s were as large as 30 kOe) were observed, which were quite large values, compared with those for sputtered [111]-textured multilayered films.
A New Kind of Electroluminescent Devices Containing Ultrathin Polyimide Langmuir-Blodgett Films as Insulators
Authors: Sekido Yoshihiro , Hayashi Tadashi , Fujii Sadao , Uekita Masakazu
Published: February 2005

By utilizing ultrathin (100 and 200 Å) polyimide Langmuir-Blodgett (PI LB) films as insulating layers and Ta2O5 as an electron injection layer, a new kind of multilayered thin film EL device having a low operating voltage of less than 100 V has been developed. Without Ta2O5, the threshold voltages were typically 50 V, but the slope of the luminance-voltage characteristic was not steep enough. By introducing two Ta2O5 layers, the luminance-voltage characteristics have been improved, and an operating voltage of 90 V has been achieved. This operating voltage is 50 V lower than that of a device which contains SiO2 instead of PI LB films.
Mechanism of Photoinduced Charge Transfer in Co(Li)-Doped ZnO Film
Authors: Kobayashi Kenkichiro , Maeda Tatsuro , Shigenori Matsushima Shigenori Matsushima , Genji Okada Genji Okada
Published: February 2005

A three-layer film consisting of In-doped ZnO, Co(Li)-doped ZnO and Li-doped NiO has been fabricated by means of a sputtering technique. The photocurrent spectrum of the Co(Li)-doped ZnO has been measured by applying a bias voltage between the In-doped ZnO and Li-doped NiO electrodes. A broad peak around 640 nm in the photocurrent spectrum is assigned to photothermal ionization of Co2+ ions. The time dependence of photocurrents indicates that the concentration of Co2+ ions is decreased by the irradiation of 500 nm and is recovered to the initial value by turning off the bias voltage.
Antiferroelectric Switching in Polymer-Dispersed Liquid Crystals
Authors: Molsen Henning , Heinz-Siegfried Kitzerow Heinz-Siegfried Kitzerow , Gerd Heppke Gerd Heppke
Published: February 2005

We investigated the switching behavior of the well-known antiferroelectric liquid crystal (R)-4-(1-methylheptyloxycarbonyl)phenyl-4'-octyloxybiphenyl-4-carboxylate (MHPOBC), embedded in a polymer matrix. The alignment of the liquid crystal in the UV-cured adhesive was controlled by mechanical shear during the polymerization-induced phase separation. Multistable switching with time constants down to 150 µs indicates that antiferroelectric PDLC devices are promissing for electrooptic application as flexible displays.
Three Types of Ternary Selenides with Layered Composite Crystal Structures Formed in the Pb-Nb-Se System
Authors: Oosawa Yoshinao , Gotoh Yoshito , Akimoto Junji , Tsunoda Tatsuo , Onoda Mitsugu Sohma
Published: February 2005

Three types of ternary selenides with layered composite crystal structures, (PbSe)1.14NbSe2[A], (PbSe)1.14(NbSe2)2[B] and (PbSe)1.14(NbSe2)3[C], have been prepared and characterized by powder X-ray diffraction, electron diffraction, intercalation and electric resistivity measurement. Results suggest that each selenide consists of PbSe layers(two-atoms-thick) and NbSe2 sandwiches(three-atoms-thick) stacked alternately with the ratios of 1:1 for A, 1:2 for B and 1:3 for C, respectively. Electric resistivity measurements suggest that B and C are superconductors whose transition temperatures are 3.4 K and 4.8 K, respectively.
Chemical Interactions between Arsenic and Boron Implanted in Silicon during Annealing
Authors: Yokota Katsuhiro , Sunagawa Yoshiyuki , Hirao Takashi , Ando Yasuo , Matsuda Kouji
Published: February 2005

Arsenic ions (As+) and boron ions (B+) were implanted into silicon (Si) at energies at which their respective projected ranges differed or coincided. Implanted As atoms reacted with implanted B atoms in a region where the population of implanted As atoms overlapped that of implanted B atoms. Such a complex as As2B was formed in the region.
Growth of Bi/Sb Superlattice
Authors: Takahashi Junzo , Miyagawa Tsugio , Araki Masatomi , Obata and Takeshi
Published: February 2005

The present work describes the growth at room temperature of Bi, Sb and Bi-12 at.%Sb films on glass substrates and a Bi/Sb 40-layer superlattice film on a single-crystal Si (111) substrate. Thin-film X-ray diffractometer measurements strongly show the (003) orientation of these films. Four peaks are observed in small-angle X-ray diffraction measurements of the Bi/Sb superlattice film and indicate good periodicity. Direct transmission electron microscopy (TEM) observations also clearly show the superlattice structure.
Epitaxial Growth of Bi/Sb Superlattice
Authors: Junzo Takahashi Junzo Takahashi , Tsugio Miyagawa Tsugio Miyagawa
Published: February 2005

The present work describes the heteroepitaxial growth at room temperature of a Bi/Sb superlattice film, for the first time, on a single-crystal cleaved BaF2(111) substrate. Four peaks were observed in small-angle X-ray diffraction of the Bi/Sb superlattice film, denoting good periodicity. In situ reflection high-energy electron diffraction (RHEED) observations show epitaxial growth after 60 layers of superlattice deposition. Cross-sectional transmission electron microscopy (TEM) observations also show the single-crystal image and diffraction pattern.
Adsorption of Na on the GaAs(110) Surface Studied by the Field-Ion-Scanning-Tunneling-Microscopy
Authors: Bai Chunli , Hashizume Tomihiro , Dong-Ryul Jeon Dong-Ryul Jeon , Toshio Sakurai Toshio Sakurai
Published: February 2005

The geometry and the coverage-dependent growth structures formed by Na deposition on the GaAs(110) surface at room temperature were studied using a field-ion scanning tunneling microscope. When the coverage is low, Na adatoms reside on the bridge site encompassing one Ga and two As surface atoms to form linear chains along the [11̄0] direction. The Na-Na nearest-neighbor distance in this low-density chain structure is 8 Å. At slightly increased coverage, the Na chains began to disorder. Some of them were packed closer to form domains showing a local 2×2 structure. None of high-density two dimensional ordered structures or low-density zigzag chains was observed, in contrast to the Cs/GaAs(110) system. Additional Na adsorption resulted in the formation of three-dimensional disordered clusters. The saturation coverage of Na was determined to be ∼0.1 ML (1 ML≡2 Na per substrate unit cell).
Fourier Analysis of Interference Structure in X-Ray Specular Reflection from Thin Films
Authors: Iida Kenji Sakurai
Published: February 2005

Interference oscillation observed in X-ray total external reflection from thin films was analyzed by the Fourier transform algorithm. The peak position in Fourier space was in good agreement with the layer thickness, and was determined independently from the surface/interface roughness. The principle of the present technique and its application to SiO2/Si thin films are shown. The advantages of the experiments using tunable synchrotron X-rays are also discussed.
Electron-Beam-Induced Structuring of Composite Oxides by means of Dipping Pyrolysis of Metal Naphthenate Films
Authors: Katsumi Mori Katsumi Mori , Soichiro Okamura Soichiro Okamura
Published: February 2005

We have found that metal naphthenate thin films reacted with an energized electron beam of 30 keV and that the structured metal naphthenate in the submicron range could be prepared through the development of electron-irradiated samples using the organic solvent, toluene. The electron beam sensitivity of the metal naphthenate films was about 2×10-3 C/cm2, which showed higher sensitivity than that of the electron beam induced chemical vapour deposition but lower than that of PMMA resist. After the heat treatment at 450°C for 20 minutes, submicron patterns of the composite oxide, consisting of a few kinds of oxides, were prepared.
First Demonstration of AlxGa1-xAs/Si Monolithic Tandem Solar Cells Grown by Metalorganic Chemical Vapor Deposition
Authors: Shimizu Hiroaki , Egawa Takashi , Soga Tetsuo , Takashi JIMBO Takashi JIMBO , Masayoshi Umeno Masayoshi Umeno
Published: February 2005

Al0.1Ga0.9As/Si and thin GaAs/Si monolithic two-terminal tandem cells, which are fabricated by thermal diffusion and metalorganic chemical vapor deposition (MOCVD), have exhibited the active area efficiencies of 16.3% and 15.6%, and the total area efficiencies of 13.8% and 13.1%, respectively. The key technologies required to fabricate the successful tandem cell are the formation of the p+-n junction in the Si substrate and the matching of the photocurrents between the top and the bottom cells.
Dependence of Hot-Carrier and Radiation Hardnesses of Metal-Oxide-Semiconductor Capacitors on Initial Oxide Resistance Determined by Charge-Then-Decay Method
Authors: Lin Jing-Jenn , Kuan-Chin Lin Kuan-Chin Lin , Jenn-Gwo Hwu Jenn-Gwo Hwu
Published: February 2005

Oxide resistances, R
ox's determined by the recently reported charge-then-decay method are used to predict the hot-carrier and radiation hardnesses of metal-oxide-semiconductor (MOS) capacitors. The measurement of R
ox is nondestructive to tested samples. It is found that a sample with a large R
ox sustains a high gate voltage during constant current stressing. After stressing, the generated interface trap state is large for this sample. Also, it is found that the radiation damage of an MOS capacitor is dependent on its R
ox. Samples with larger R
ox exhibit more radiation hardness than those with smaller R
ox after Co-60 irradiations. Strained-bond-induced micropores are possible origins for these observations.
Effect of Cooling Rate on Critical Current Density for Bi2Sr2CaCu2O8+δ/Ag Composite Tapes
Authors: Shimoyama Jun-ichi , Kase Jun-ichiro , Morimoto Takeshi , Kitaguchi Hitoshi , Kumakura Hiroaki , Togano Kazumasa , Maeda Hiroshi
Published: February 2005

Bi2Sr2CaCu2O8+δ(Bi-2212)/Ag composite tapes were prepared by melt-solidifying method and the relationship between cooling conditions after the melt-solidification and superconducting properties were investigated. A high cooling rate was found to be effective in suppressing the decomposition of Bi-2212 and in increasing J
c. A tape with high J
c of 2.4×105 A/cm2 at 4.2 K in 12 T was obtained by fast cooling. With annealing of this tape in N2 atmosphere, J
c of 3.1×104 A/cm2 at 77.3 K in 0 T was attained due to the enhancement of T
c.
Magnetic Properties of the (1223) Phase of Tl-Sr-Ca-Cu-O Superconductors with Strong Pinning in Liquid Nitrogen
Authors: Yuasa Toyotaka , Doi Toshiya J. , Soeta Atsuko , Inoue Naomi , Aihara Katsuzou , Tomoichi Kamo Tomoichi Kamo , Shin-Pei Matsuda Shin-Pei Matsuda
Published: February 2005

Pinning centers were successfully introduced into the Tl-(1223) phase of the Tl-Sr-Ca-Cu-O system using a partial melt method. The magnetization hysteresis and relaxation were studied between 10-100 K and 0-5.5 T by VSM (Vibrating Sample Magnetometer) and SQUID (Superconducting QUantum Interference Device) magnetometry. The magnetization hysteresis ΔM was 7-25 emu/cm3 at 77 K and 1 T in Tl-(1223) bulk samples. The intragrain J
c at 1 T calculated by Bean's model was 43000 and 230000 A/cm2 at 77 K and 40 K, respectively. From the zero-field-cooled and field-cooled measurements, the irreversible field at 77 K was 6.8 T. The thermal activation energy was estimated to be 250 meV at 77 K and 1 T from the measurement of the magnetization relaxation.
Proposal of an Optical Neurochip with Internal Analogue Memory and Its Fundamental Characteristics
Authors: Nitta Yoshikazu , Ohta Jun , Syuichi Tai Syuichi Tai , Kazuo Kyuma Kazuo Kyuma
Published: February 2005

An optical neurochip incorporating an analogue memory has been reported. The proposed neurochip is a three-dimensional optoelectronic integrated circuit consisting of a light-emitting diode array and a variable sensitivity photodetector array. In this letter, the preliminary experimental results are described. First, it is shown that the synaptic weights are stored in the variable sensitivity photodetector as the detection sensitivity with analogue values. Both the positive and the negative synaptic weights are memorized by changing the polarity of the electric signal which is applied in the write phase. Second, a novel type of matrix addressing method using the memory function is demonstrated for the realization of a large-scale optical neurochip.
Non-Contact, No Wafer Preparation Deep Level Transient Spectroscopy Based on Surface Photovoltage
Authors: Lagowski Jacek , Andrzej Morawski Andrzej Morawski , Piotr Edelman Piotr Edelman
Published: February 2005

We discuss a novel approach to Deep Level Transient Spectroscopy (DLTS) in which the emission of trapped minority carriers is analyzed employing the surface photovoltage (SPV) transient as measured in a non-contact manner on the native depletion barrier on semiconductor surfaces. Optical excitation is used as the trap-filling pulse. Experiments done on n-type GaAs demonstrate that the SPV-DLTS is suitable for wafer-scale, non-contact determination of deep level defects on semiconductor surfaces. The SPV approach can monitor emission rates up to 106s-1which is 102to 103above the limit of standard capacitance DLTS. The sensitivity of the method is comparable to that of the oplical capacitance DLTS.
Low Temperature Sintering of P2O5-Added Cordierite Glass with Lead Borosilicate Glass
Authors: Fu Lih-Shan Chen
Published: February 2005

Cordierite was prepared by the sintering of cordierite glass and lead borosilicate glass. With the addition of lead borosilicate glass, P2O5-added cordierite glass can be densified at lower sintering temperature. Owing to the flux effect of lead borosilicate glass, the coalescence of glass particles was aided by the viscous flow of the glass. Besides the advantage of lower temperature sintering, the addition of lead borosilicate glass enhances the formation of α-cordierite crystalline phase.
Effect of Hydrogen Plasma Treatment on Implantation Damage in Diamond Films Grown by Chemical Vapour Deposition
Authors: Mori Yusuke , Deguchi Masahiro , Eimori Nobuhiro , Ma Jing Shing , Nishimura Kazuhito , Kitabatake Makoto , Ito Toshimichi , Hirao Takashi , Akio Hiraki Akio Hiraki
Published: February 2005

Radiation damage in chemical vapour deposited (CVD) diamond produced by the implantation of 10-keV nitrogen ions has been studied using electron energy loss spectroscopy (EELS) and cathodoluminescence. Thermal annealing and a hydrogen plasma treatment have been employed to anneal out the implantation damage. Graphitization of ion implanted CVD diamond was observed after subsequent thermal annealing. On the other hand, similar EELS spectra to that of as-grown diamond have been obtained from ion-implanted CVD diamond after hydrogen plasma treatment.