bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Stability of Ni-C Multilayer Mirror for X-Rays
Authors: Nakajima Kunio , Aoki Sadao , Fujiwara Shuzo Sudo
Published: February 2005

The measurement of X-ray reflectivity has been performed with the lapse of annealing time for heat treatment up to 400°C in order to investigate the thermal stability of a nickel-carbon multilayer mirror for X-rays. The microstructural change of a multilayer film has been examined by means of X-ray diffraction, Auger electron spectroscopy and electron microscopy. The results show that the crystallization of nickel and the formation of nickel carbide occur for annealing above 300°C. As a consequence of microstructural changes, the surface and interfaces become rough, layer structure is destroyed, and the X-ray reflectivity shows a definite decrease.
Evaporation Source for Deposition of Protective Layers inside Tubes
Authors: Musa Geavit , Mustata Ion , Dinescu Gheorghe , George Bajeu George Bajeu , Elena Raiciu Elena Raiciu
Published: February 2005

A heated cathode arc can be ignited in vacuum in the vapours of the anode material due to the accelerated electron beam from the cathode. A small assembly, consisting of an electron gun as the cathode and a refractory metal crucible, containing the material to be evaporated, as the anode, can be moved along the axis of the tube whose inside wall is to be covered with a protective layer. The vacuum arc ignited between the electrodes in the vapours of the evaporating anode material ensures a high deposition rate with low thermal energy transport to the tube wall. This new method can be used for the deposition of various metal layers inside different kinds of tubes (metallic, glass, ceramics or plastics).
Band-Gap Energy Dependence of Emission Spectra in Rare Earth-Doped Zn(1-x)CdxS Thin Film Electroluminescent Devices
Authors: Miura Noboru , Sasaki Takashi , Hironaga Matsumoto Hironaga Matsumoto , Ryotaro Nakano Ryotaro Nakano
Published: February 2005

Electroluminescence has been measured for Zn(1-x)Cd
x
S thin films doped with rare earth ions. The ZnS thin film doped with the Pr ion shows the 495 and 658 nm emissions due to the transitions from the 3P0 to 3H4 and 3F2 levels, respectively. With increasing value of X, the emission from the 3P0 level vanished and 618 nm emission arose from the transition of 1D2→3H4. The reason for this change may be related to the band-gap energy of the host lattice. From these experimental results, it is concluded that the excitation process of the rare earth ions involves the energy transfer from the host lattice for the Zn(1-x)Cd
x
S electroluminescent devices. In addition, the transition around 800 nm emission for the Tm3+ ion is also discussed.
Preparation of Pb(Zr, Ti)O3 Films on Si Substrate by Laser Ablation
Authors: Kidoh Hideo , Ogawa Toshio , Yashima Hideyuki , Morimoto Akiharu , Shimizu Tatsuo
Published: February 2005

Lead-zirconate-titanate (PZT) thin films were prepared on oxidized Si(100)-substrate with a thin film electrode by laser ablation. Ferroelectric perovskite phase was obtained in the PZT films on Ni-alloy/SiO2/Si substrate with the substrate temperature above 500°C, but it was not obtained in the films on Pt/SiO2/Si. The switching voltage of remanent polarization (P
r) decreased with decreasing PZT film thickness. The 0.15-µm-thick film showed P
r of 15 µC/cm2 with a swing voltage of 5 V.
Preparation of Oxide Thin Films by Laser Ablation
Authors: Ogasawara Masaru , Shimizu Masaru , Shiosaki Tadashi
Published: February 2005

ZnO and PbZr0.9Ti0.1O3 (PZT) thin films were prepared by laser ablation using a KrF excimer laser. The c-axis-oriented ZnO thin films were successfully grown at substrate temperatures of 180-400°C in Ar and Ar+O2. The deposition rates of the films obtained ranged from 150 to 700 Å/min, and these values were larger than those of films grown by conventional magnetron sputtering. Perovskite-type PZT thin films with a rhombohedral structure were also successfully grown at 680°C. The deposition rates of the films obtained ranged from 40 to 240 Å/min, and these values were also larger than those of films grown by magnetron sputtering.
Dielectric Properties of RF-Magnetron-Sputtered (Ba, Pb)(Zr, Ti)O3 Thin Films
Authors: Torii Kazuyoshi , Toru Kaga Toru Kaga , Eiji Takeda Eiji Takeda
Published: February 2005

Barium lead zirconate titanate (or (Ba, Pb)(Zr, Ti)O3, BPZT) thin films have been successfully fabricated from a stoichiometric target by rf-magnetron sputtering. The dielectric properties of these films were investigated. They were found to have good properties for LSI capacitor applications, e.g., high dielectric constant (ε≈400), low temperature coefficient, low leakage current, and low crystallization temperature (550°C).
Metal Complexes for Preparing Ferroelectric Thin Films by Metalorganic Chemical Vapor Deposition
Authors: Nakai Tomoaki , Tabuchi Toshiya , Sawado Yoshinori , Ichizo Kobayashi Ichizo Kobayashi , Yoshiaki Sugimori Yoshiaki Sugimori
Published: February 2005

Recently, metal β-diketonato complexes have been used as a gas source for preparing ferroelectric thin films by metalorganic chemical vapor deposition (MOCVD). Since we have synthesized highly purified metal dipivaloylmethanato (DPM) complexes such as Pb(DPM)2, Sr(DPM)2 and Ba(DPM)2 for ferroelectric thin films, we have investigated several properties of these chelate compounds related to depositing thin films. Their volatility and toxicity have also been investigated. As a result, it has been found that these chelate compounds have low vapor pressure, but present the advantages of easy handling because of the low toxicity and the possibility of forming thin films at lower temperature.
Preparation of Pb(Zr, Ti)O3 Thin Films Using All Dipivaloylmethane Source Materials by Metalorganic Chemical Vapor Deposition
Authors: Yamazaki Hiroshi , Tsuyama Tomoko , Ichizo Kobayashi Ichizo Kobayashi , Yoshiaki Sugimori Yoshiaki Sugimori
Published: February 2005

Pb-bis-dipivaloylmethane [Pb(DPM)2], Zr(DPM)4 and Ti(DPM)2(i-OC3H7)2 are developed as the new chemical vapor deposition (CVD) sources for lead zirconate titanate (PZT) thin film. The growth rate of each of the single metal oxides PbO, ZrO2 and TiO2, was studied as a function of oxygen partial pressure. The growth rates of ZrO2 and TiO2 were independent of the input oxygen partial pressure, while the growth rate of PbO increased with increasing input oxygen partial pressure. PZT films were grown on (100) MgO substrates at 2.0 Torr by metalorganic chemical vapor deposition (MOCVD). The film grown at 500°C was amorphous. The film grown at 550°C was a mixed phase of a-axis- and c-axis-oriented perovskite. The film grown at 600°C was a single-phase c-axis-oriented perovskite.
Preparation and Evaluation of Pb(Zr·Ti)O3 Thin Films by Metalorganic Chemical Vapor Deposition
Authors: Tomonari Hajime , Ishiu Takehiko , Koichiro Sakata Koichiro Sakata , Tadashi Takenaka Tadashi Takenaka
Published: February 2005

Dipivaloylmethane (DPM) metalorganic precursors, Pb(DPM)2, Zr(DPM)4 and Ti(OPr
i
)2(DPM)2, are used as starting materials in the metalorganic chemical vapor deposition (MOCVD) method for the preparation of Pb(Zr
x
Ti1-x
)O3 (PZT) thin films. The films are deposited at the rate of 150 to 700 Å/min under atmospheric pressure and reduced pressure of 10∼30 Torr. The deposition rate is about ten times as high as that of the conventional sputtering method. The dielectric constant of the film (X=0.2) on a Pt/Si substrate is about 300 at room temperature. This value agrees with that of ceramic or sputtered films.
Influence of Energetic Particles on ZnO Films in the Preparation by Planar Magnetron Sputtering with Obliquely Facing Targets
Authors: Tominaga Kikuo , Sueyoshi Yasuhiko , Hiroshi Imai Hiroshi Imai , Masaki Shirai Masaki Shirai
Published: February 2005

Substrate temperature dependence of ZnO film properties such as c-axis orientation and optical transmittance was investigated. When the film bombardment became small at higher gas pressure such as 0.1 Torr, the degree of c-axis orientation of the film was improved at above 350°C, but the grain size of film was not dependent on the substrate temperature. When the film-was bombarded by energetic O- ions and O atoms at lower gas pressures, the film was degraded severely. The recovery of the film properties due to the elevated temperature was small. More defects were likely to be induced in the film at a high substrate temperature such as 350°C under film bombardment by the energetic particles.
Field-Excited Electron Emission from Ferroelectric Ceramic in Vacuum
Authors: Asano Jun-ichi , Imai Tadayuki , Masanori Okuyama Masanori Okuyama , Yoshihiro Hamakawa Yoshihiro Hamakawa
Published: February 2005

Electron emission into vacuum has been observed by applying pulse voltage to a thin plate of PZT ferroelectric ceramic. This electron emission has been obtained even in low vacuum of less than 10-1 Torr. The lowest pulse voltage for this emission is 75 V, and the largest emission current in a sample having a 7×0.3 mm2 electrode is 30 mA. The electrons are considered to be emitted from the surface of the ferroelectric plate near the electrode by very high field induced by polarization reversal. This electron emission can be applied as the electron emitter in vacuum electronic devices such as micro-triodes and flat panel displays.
Space Charge Effects on Ferroelectric Ceramic Particle Surfaces
Authors: Kiyoshi Okazaki Kiyoshi Okazaki , Hiroshi Maiwa Hiroshi Maiwa
Published: February 2005

The anomalous dielectric absorption current of BaTiO3 ceramics when an electric field is applied at above the Curie point was measured. The results cannot be explained by the famous Maxwell-Wagner double layer theory. The total charge of the charging and discharging absorption current was more than 1000 µC/cm2. The giant space charge produces “internal bias field” in the opposite direction to the first applied field. Another space charge is generated during the aging process after poling at below the Curie point. In this report, two types of space charge effects are described and discussed respect to “space charge stabilized effects” for electromechanical strength and the difficulties of polarization reversal applications due to “space charge asymmetric effects”.
Dielectric Properties of (PbCa)(MeNb)O3 at Microwave Frequencies
Authors: Kato Junichi , Hiroshi Kagata Hiroshi Kagata , Keiji Nishimoto Keiji Nishimoto
Published: February 2005

We have investigated the dielectric properties up to microwave frequencies of ceramics represented as (Pb1-x
Ca
x
)-(Me
m
Nb1-m
)O3 where Me is selected from Li, Na, Mg, Zn, Ni, Co, Fe, Y, Yb, Al and Cr. High Q values and small temperature coefficients of resonant frequency were obtained in (PbCa)(Mg1/3Nb2/3)O3, (PbCa)(Ni1/3Nb2/3)O3 and (PbCa)-(Fe1/2Nb1/2)O3 with perovskite structure. These dielectric constants and the Q values for a near-zero temperature coefficient are εr=73 with Q=1330, εr=59 with Q=1700 and εr=91 with Q=1650, respectively. The other ceramics with smaller amounts of perovskite phase had degraded characteristics, i.e., low Q values or large temperature coefficients. In lead- and calcium-based perovskite, it seems that the high dielectric constant occurs due to Pb content in A-sites and smaller average ion radius in B-sites.
Observation of Domain Structures in Tetragonal Pb(ZrxTi1-x)O3 Single Crystals by Chemical Etching Method
Authors: Tatsuya Hatanaka Tatsuya Hatanaka , Hideo Hasegawa Hideo Hasegawa
Published: February 2005

Domain structures in tetragonal Pb(Zr
x
Ti1-x
)O3 (PZT) single crystals etched by HF+HCl solution were observed by means of a scanning electron microscope. The relationship between the etch patterns of pseudocubic {100} faces and spontaneous polarization vectors was examined using micro-Raman spectroscopy and electron channeling patterns. Both the a-face and the positive c-face are quickly etched, but the former results in a rough surface while the latter results in a smooth one. The negative c-face is rather slowly etched. Another type of etch pattern with a wedge-shaped section was observed; this is usually observed in PZT ceramics but has not been reported in BaTiO3. This pattern can be explained by the difference in etch rates between various {100} faces and the peculiar domain structures which consist of a single domain region with narrow or wedge-shaped 90° domains. It is assumed that such a domain structure is, although unstable under electrical stress, stable under mechanical stress.
Desorption of Indium during the Growth of GaAs/InGaAs/GaAs Heterostructures by Molecular Beam Epitaxy
Authors: Teruo Mozume Teruo Mozume , Isao Ohbu Isao Ohbu
Published: February 2005

The desorption of indium during molecular beam epitaxy (MBE) growth of InGaAs and GaAs/InGaAs/GaAs quantum wells has been investigated by reflection high energy electron diffraction (RHEED). The indium desorption activation energy calculated from the temperature dependence of the InAs growth rate is shown to be almost same as the enthalpy of InAs decomposition. It was found that the RHEED pattern transition time, t1, from (4×2) of InGaAs to (2×4) of GaAs after GaAs heteroepitaxial growth on InGaAs began, was the desorption time of indium, which segregated to the growth front from the topmost layer of InGaAs. The activation energy determined from this process is close to the desorption enthalpy of indium from indium liquid.
TEM Moiré Pattern and Scanning Auger Electron Microscope Analysis of Anomalous Si Incorporation into MBE-grown Ge on Si(111)
Authors: Sugii Kiyomasa , Ishizawa Suzuko , Kobayashi Yoshihiro , Seki Hiroki Hibino
Published: February 2005

Ge islands are grown by molecular beam epitaxy (MBE) on Si(111) surfaces with an SPE-grown buffer layer, which was expected to prevent intermixing between the epitaxial Ge layer and the Si substrate. The epilayer composition analyzed from the spacing of the Moiré fringe indicates that the Ge islands should be a Si-Ge alloy rather than pure Ge and that the alloying of Ge with Si is greater near the edges of the island. The alloying phenomenon was verified by the compositional depth profile analysis using the scanning Auger electron microscope (SAM) technique. The Si incorporation into the Ge islands observed here cannot be explained by a bulk diffusion mechanism and is a seriously anomalous phenomenon since Si diffusion into Ge would be negligible at the growth temperature and time used ill this experiment.
High-Coercivity Nd-Fe-B-M Alloys with Low Level of Nd and B (M=Ti/V/Mo/Al)
Authors: Chin Tsung-Shune , Lin Cheng-Hao , Huang Sen-Huan , Yau Jiunn-Ming , Chu Tsung-Yao , Wu Cherng-Dean
Published: February 2005

The study by single-roller melt spinning and annealing on the [Nd(Fe, M)12]-(Nd2Fe14B) pseudobinary system has led to high-coercivity Nd-Fe-B-M alloys (M is Ti or V/Mo/Al) with both Nd and B contents less than the stoichiometric Nd2Fe14B compound. Optimum values of iHc=11.2 kOe, 4πMr=9 kG and (BH)m=12.5 MGOe were obtained from a Nd10.8Fe82.9B4.4Ti1.9 alloy melt-spun at a wheel velocity of 30 m/s, followed by annealing at 700°C for 1 h. The temperature dependence of coercivity fitted with the Gaunt model, and transmission electron microscopy (TEM) studies suggested that strong domain wall pinning at refined 2-14-1 grains might be the main reason for the high coercivity.
Third-Order Nonlinear Susceptibility of Cadmium for the Generation of Continuously Tunable Vacuum Ultraviolet Radiation
Authors: Hirofumi Sakai Hirofumi Sakai , Kenzo Miyazaki Kenzo Miyazaki
Published: February 2005

Third-order nonlinear susceptibility χ3for the two-photon resonant sum-frequency mixing in Cd vapor is calculated in the vacuum ultraviolet (VUV) spectral region from 110 nm to 138 nm, where the four levels, 61S0, 51D2, 71S0, 61D2, are used for the two-photon resonance. The results show that χ3for each resonance has a specific wavelength dependence, and the 51D2resonance is especially advantageous for the generation of broadly- and continuously-tunable VUV radiation in the spectral region concerned. The calculated results are compared with the wavelength dependences of the experimentally observed VUV power.
Reversible Optical Effects in Parylene-Coated Amorphous Ga-Se-S Films
Authors: Matsushita Tatsuhiko , Suzuki Akio , Arimoto Motohiko , Okuda Masahiro , Naito Hiroyoshi
Published: February 2005

Reversible optical changes mainly due to thermal effects in parylene-coated amorphous Ga-Se-S films (∼200 nm thick) are described. A distinctive feature is that there are large differences of transmittance ΔT
R between the `bleached' and the `darkened' states for λ=633 nm. A maximum value of ΔT
R was observed to be 72% for the composition S0.03(Ga0.05Se0.95)0.97.
Kinetics of Rapid Thermal Oxidation of Silicon
Authors: Fukuda Hisashi , Makoto Yasuda Makoto Yasuda , Toshiyuki Iwabuchi Toshiyuki Iwabuchi
Published: February 2005

We have proposed, for the first time, a practical model for ultrathin (<10 nm) SiO2 film growth in rapid thermal oxidation (RTO) kinetics. The results showed that the overall RTO growth can be well described by the linear-parabolic model proposed by Deal and Grove [J. Appl. Phys. 36 (1965) 3770]. Moreover, the model proposed indicates that in order to fit the experimental data, the oxide growth in a ramp-up process must be included in the linear-parabolic scheme. As a result, we have succeeded in explaining the RTO growth kinetics in the RTO temperature range from 950 to 1200°C and in a wide thickness range from 15 to 250 Å without making any special assumptions. The resultant activation energies for the linear rate constant (B/A) and for the parabolic rate constant (B) are 2.0 eV and 1.74 eV, respectively.
Dependence of the Saturation of Light-Induced Defect Density in a-Si:H on Temperature and Light Intensity
Authors: Isomura Masao , Nobuhiro Hata Nobuhiro Hata , Sigurd Wagner Sigurd Wagner
Published: February 2005

We studied the temperature and intensity dependence of the saturated density of light-induced defects (N
sat) in hydrogenated amorphous silicon (a-Si:H), established by high-intensity Kr+ laser illumination. The saturation value is insensitive to temperature below about 90°C. Above 90°C, N
sat drops with increasing temperature. This behavior can be explained within the defect pool model by a limited number of defect sites coupled with the concept of defect equilibrium. The experimental data suggest that the tail states do not direcily affect N
sat in device-quality a-Si:H.
Structural Characterization of Ge Microcrystals in GexC1-x Films
Authors: Carles Robert , Mlayah Adnen , Amjoud M'barek , Reynes Alain , Morancho Roland
Published: February 2005

Chemical and structural characteristics of Ge
x
C1-x
films grown by metalorganic chemical vapour deposition are examined. The effects of the precursor nature (tetravinyl- or tetraethylgermane), growth temperature (in the 500-580°C range) and carrier gas (He or H2) are analysed using electron microprobe, X-ray diffraction, X-ray photoelectron, infrared and Raman spectroscopies. The film structure is governed by the growth conditions. It evolves between two border-line cases: An amorphous-like Ge phase embedded in a graphitic matrix and a polycrystalline Ge phase. A comparative study of the average grain size deduced from X-ray diffraction and Raman scattering data is presented.
Optical Properties of ZnCdSe/ZnSSe Strained-Layer Quantum Wells
Authors: Wu Yi-hong , Ichino Kunio , Kawakami Yoichi , Shizuo Fujita Shizuo Fujita , Shigeo Fujita Shigeo Fujita
Published: February 2005

We have shown the optical properties of ZnCdSe/ZnSSe strained-layer single- and multiple-quantum wells (SQWs and MQWs) fabricated by metalorganic molecular beam expitaxy (MOMBE). Excitonic emission and absorption properties were investigated in detail by means of photoluminescence, photoluminescence excitation and absorption spectral measurements. A multiple longitudinal optical (LO)-phonon emission which is related to the relaxation of hot excitons has been observed in the photoluminescence excitation spectrum in a SQW. The temperature dependence of the emission intensity in the SQWs with three different well widths (10, 50, and 100 Å) shows the quenching of the exciton-emission intensity. For a 10 Å well the dependence shows Arrhenius thermally activated behavior, where the activation energy of about 70 meV is obtained. A theoretical analysis of the temperature dependence of an excitonic linewidth indicates that the exciton-LO phonon coupling constant is estimated to be 35 meV which is larger than that (5 meV) of GaAs/AlGaAs QW. As a result, this effect is the dominant cause of the exciton linewidth broadening.
Annealing Behavior of HF-Treated GaAs Capped with SiO2 Films Prepared by 50-Hz Plasma-Assisted Chemical Vapor Deposition
Authors: Hashizume Tamotsu , Hasegawa Hideki , Tochitani Gen , Shimozuma Mitsuo
Published: February 2005

Thermal stability of the SiO2/GaAs interface structures prepared by 50-Hz plasma-assisted chemical vapor deposition (PCVD) and the electrical activation of Si implanted into GaAs with SiO2 cap were investigated. X-ray photoelectron spectroscopy (XPS) analysis showed that the 50-Hz PCVD method at 200°C allowed the presence of an As-enriched layer, intentionally inserted by HF treatment before SiO2 deposition, at the SiO2/GaAs interface. After rapid thermal annealing (RTA) at 950°C for 20 s, in fact, the As-enriched layer still remained and it was effective in suppressing interfacial reactions which caused various shortcomings. In addition, carrier concentration profiles in excellent agreement with Lindhard-Scharff-Schiott (LSS) curves were reproducibly obtained by RTA in Si-implanted GaAs capped with both the As-enriched layer and the SiO2 film, demonstrating that this process is applicable to post-annealing of ion-implanted GaAs.
Direct Observation of the Growth Process of Ag Thin Film on a Hydrogen-Terminated Si(111) Surface
Authors: Naitoh Masamichi , Fumiya Shoji Fumiya Shoji , Kenjiro Oura Kenjiro Oura
Published: February 2005

Using a field emission scanning electron microscope (FE-SEM), we have observed the effects of the saturation of surface dangling bonds of Si(111) surfaces with atomic hydrogen upon Ag thin-film (∼10 monolayers) growth. In Ag deposition at high temperatures, we found that Ag islands grew to large sizes on a hydrogen-terminated surface compared with the results on the clean surface.
Slow Positron Production with a Modular Photon-Positron Converter Attached to a High-Current LINAC
Authors: Tanaka Hitoshi , Michishita Toshinori , Yuyama Tetsumori , Takami Kiyoshi , Kawase Yoichi , Akihiro Mohri Akihiro Mohri
Published: February 2005

A method of slow positron production was experimentally examined. X-rays radiating forward from a tantalum target upon the bombardment of linear accelerator (LINAC) electron beams (30 MeV, 0.4 A, 120 pps) penetrated fifty tungsten foil strips 25 µm thick, which were assembled into a heaped stack of five modules. Slow positrons emerging from the foil surfaces were extracted by applying stepwise electric potentials between neighbouring modules under the action of grid focussing. After the transport through a magnetic duct of 0.01 T and 9 m length, the obtained slow positron flow was 1.2×1011 [e+/s] during the LINAC beam pulse. This rate corresponds to the time-averaged production rate at 120 pps of 4.4×107 [e+/s] and the conversion efficiency of 4.9×10-8 [e+/e-]. The production rate found by a Monte-Carlo simulation using the EGS4 code is compared with the experimental one.
Effects of Oxygen Addition in the CCl4 Reactive Ion Etching of a-SiC:H Films
Authors: Tai-chin Lo Tai-chin Lo , Ho-chi Huang Ho-chi Huang
Published: February 2005

We have studied the effects of oxygen addition in the CCl4 reactive ion etching of hydrogenated amorphous silicon carbide (a-SiC:H) films. The effects of oxygen on the etching profile of a-SiC:H films, the etch rates of a-SiC:H and oxide, and the etching selectivity of a-SiC:H/oxide are examined. It is observed that the addition of oxygen into CCl4 plasma greatly increases the etch rate of a-SiC:H and the etching selectivity of a-SiC:H/oxide, while gradually changes the etching process from being anisotropic to isotropic. Experimental data are interpreted with the examining of the plasma phase chemistry and ion bombardment energy. An etch mechanism is proposed for explaining the observed effects.
Recent Advances in X-Ray Lithography
Authors: F. Cerrina F. Cerrina
Published: February 2005

We report some significant developments in the area of X-ray technology, in the area of the modeling of image formation, in distortion control and in mask replication. Early simple models have been replaced by complete optical calculations based on physical optics and including all relevant factors. These models provide good agreement with the available experimental results. In the area of mask distortions, the use of finite element analysis models has clarified the roles played by the various sources of stress and explained in greater detail the origin of temperature changes. These progresses have paved the way to the optimization of the exposure system and to the achievement of the large exposure latitude potential of X-ray lithography.
Overwrite on Sputtered Garnet Media Using Magnetic Field Modulation
Authors: Kuroda Sumio , Keiji Shono Keiji Shono , Seiya Ogawa Seiya Ogawa
Published: February 2005

Both a pregroove and aftergroove were formed in a garnet medium on a GGG substrate, and a reliable 785-nm laser diode tracking servo produced. Magnetic field modulation recording for the pregrooved media produced a carrier to noise ratio (CNR) of 48 dB, and overwriting gave complete erasure. Writing was impossible in the off-track zone of the aftergrooved media, which we believe will be useful in improving the overwrite power margin. There is a problem of deterioration of coercivity, caused by wet etching during fabrication of the aftergroove, which remains to be solved.
Kerr Enhancement by Layer Modulation in Co/Pt Multilayers
Authors: Yusu Keiichiro , Susumu Hashimoto Susumu Hashimoto , Koichiro Inomata Koichiro Inomata
Published: February 2005

Thus far, a good Kerr hysteresis loop has been obtained only for thickness ratios of Co to Pt lower than 0.6 in Co/Pt multilayers. It has been found in this study that perfect squareness can be obtained for ultrathin films even with a high thickness ratio of t
Co/t
Pt=1. This is caused by diminished magnetostatic energy. Furthermore, layer-modulated structures were investigated in order to increase the Kerr rotation angle. The Co/Pt multilayers were prepared by two-source rf-magnetron sputtering. Co/Pt multilayers with perfect squareness were deposited with a Pt interlayer, which resulted in excellent magneto-optical properties. In particular, the Kerr rotation angle measured from the glass-substrate side showed a very large value, 0.73 degrees. This Kerr enhancement is due to optical interference and multiple reflection. On the other hand, another interesting phenomenon was also obtained. Kerr hysteresis showed characteristic stepwise hysteresis loops when the interlayer Pt thickness was increased. Such layer-modulated multilayers have potentiality for high-density magneto-optical recording.
Device-Quality SiO2/Si(100) Interfaces Prepared by a Two-Step Remote Plasma-Assisted Oxidation-Depositon Process
Authors: Lucovsky G. , Ma Yi , Yasuda T. , Silvestre C. , Hauser J. R.
Published: February 2005

When using conventional high-temperature thermal oxidation processes to fabricate Si-based devices that include SiO2 dielectrics, the SiO2/Si interface and bulk-oxide layer are formed at the same time. We have developed a new low-temperature process that separates interface formation, by plasma-assisted oxidation, from bulk-oxide deposition, by plasma-assisted chemical-vapor deposition (CVD) and thereby separately controls, and optimizes the respective electrical properties of the SiO2/Si interface, and the SiO2 layer. This approach has been extended to multilayer oxide-nitride-oxide (ONO) dielectrics on Si substrates, and has also been successfully transferred to an integrated processing cluster tool that combines the new SiO2/Si oxidation/deposition process, with deposition of polycrystalline Si gate electrodes by a high-temperature, rapid thermal CVD process to form a stacked gate structure.
Surface Morphology and Line Fill Properties of Gold Grown by Organometallic Chemical Vapor Deposition
Authors: Hoshino Masataka , Kazumi Kasai Kazumi Kasai , Junji Komeno Junji Komeno
Published: February 2005

Dimethyl gold hexafluoroacetylacetonate, (DMAu(hfac)) was used to grow gold films by thermal decomposition. We found that surface morphology and line fill properties greatly depend on the substrate temperature and reactor pressure. Under optimum growth conditions, we have obtained gold films with flat surfaces and fine line fillings. We propose a growth model to explain the variation in surface morphology at various growth temperatures and reactor pressures.
Indium Arsenide Quantum Wires Fabricated by Electron Beam Lithography and Wet-Chemical Etching
Authors: Yoh Kanji , Kiyomi Kazumasa , Akira Nishida Akira Nishida , Masataka Inoue Masataka Inoue
Published: February 2005

We report the fabrication of deeply etched quantum wires on an InAs/AlGaSb heterostructure by utilizing electron beam lithography and wet-chemical etching. In order to avoid the inherent gate leakage current in heterostructures based on antimonides, deeply etched wire structures have been investigated. In two terminal devices of approximately 1000 Å wide quantum wires, quantized drain current through drain-induced-barrier-lowering has been observed at 77 K. Coulomb regulated SET characteristics were also observed at 77 K reflecting the small parasitic capacitance between terminals. Coulomb staircase characteristics and 1-D quantized current were seen to overlap in some devices. Various combinations of device parameter conditions have been discussed. Material, structural and temperature effects on the prospective device performances have been also discussed.
VLSI Fault Localization Using Electron Beam Voltage Contrast Image -Novel Image Acquisition and Localization Method-
Authors: Nikawa Kiyoshi , Nakamura Toyokazu , Hanagama Yasuko , Tsujide Tohru , Morohashi Kenji , Kanai Kenichi
Published: February 2005

Novel methods have been developed concerning voltage contrast image acquisition using the electron beam tester, and concerning fault searching on a VLSI chip, and have been applied to real faults of VLSI devices. The developed voltage contrast image acquisition method has been shown to have acquisition time about thousand times faster than that of the conventional stroboscopic method. The strategy used in searching is that of tracing back upstream of the fault by referring to the voltage-contrast-subtracted image. This strategy is more effective than the conventional dynamic fault imaging
(DFI) method where all the images on the entire chip area and all test vectors are acquired. The results showed that the location time was five times or more shorter than using conventional location methods such as electron beam waveform measurement with the aid of a computer aided design (CAD) database.
In-Situ Chemically Cleaning Poly-Si Growth at Low Temperature
Authors: Nagahara Tatsuro , Fujimoto Kenji , Kohno Naoki , Yusaku Kashiwagi Yusaku Kashiwagi , Hisashi Kakinoki Hisashi Kakinoki
Published: February 2005

We report a novel growth method of polysilicon thin films on glass substrates at a low temperature (450°C) by plasma chemical vapor deposition (PCVD) using SiH4/SiF4 mixture gases. In this method, the conventional low-cost glass substrates such as Corning 7059 may be used because of the low deposition temperature. Furthermore, the conventional vacuum chamber with its base pressure of ∼1×10-4 Pa, which is usually thought to be inadequate for high-quality Si growth because of its many impurities, can be used since the growing surface of polysilicon is in-situ chemically cleaned by SiF4 plasma. The polysilicon films obtained on glass show strong (100) preferred orientation. A grain size as large as 250 nm is obtained in a film with 700 nm thickness. The field-effect mobility of 44 cm2/V·s has been achieved in a thin-film transistor (TFT) using this polysilicon film.
Low-Temperature Polycrystalline Silicon Thin-Film Transistors for Large-Area Liquid Crystal Display
Authors: Miyata Yutaka , Furuta Mamoru , Tatsuo Yoshioka Tatsuo Yoshioka , Tetsuya Kawamura Tetsuya Kawamura
Published: February 2005

A low-temperature poly-Si thin-film transistor (TFT), having inverted-staggered structure, has been developed successfully using excimer laser annealing and ion doping. This TFT is suitable for pixel transistors of large-area and high-resolution LCDs. The maximum process temperature of the TFT fabrication steps is less than 450°C, so the same glass substrate on which amorphous Si TFT arrays are formed can be used in this poly-Si TFT process. Furthermore, most of the procedures, equipment and thin-film materials used to fabricate amorphous Si TFTs are compatible with fabrication of the poly-Si TFTs. On the other hand, some investigation of the CMOS driver circuit has been done, and it has been found that the threshold voltage of these poly-Si TFTs can be controlled easily by lightly doping of B ion into the channel region using the ion doping system.
Analysis Technique of Organic Contaminants on the Surface of the Polyimide Film of Liquid Crystal Displays
Authors: Kiichiro Mukai Kiichiro Mukai , Nobuaki Makino Nobuaki Makino
Published: February 2005

The presence of organic contaminants on the polyimide film surface causes picture nonuniformity in liquid crystal displays (LCDs). In order to determine the reason for this phenomenon, chemical identification of these contaminants is very important. We consider that the IR-Johnson method is useful for identifying unknown organic contaminants. This paper defines the surface sensitivity for this method. The spectrum for four-layer (about 100-Å-thick) Ba icosanoate LB film was observed by this method, and it was found that this spectrum has no polyimide peak. Analysis by the IR-Johnson method is effective for identification of unknown organic contaminants approximately 100 Å thick on polyimide films. The same samples were analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). It was shown that the mass spectra for TOF-SIMS were supplementary data for this identification.
Focusing-Error Detection Using a Mixed-Aberration-Generating Holographic Optical Element
Authors: Yoshinori Honguh Yoshinori Honguh , Isao Hoshino Isao Hoshino
Published: February 2005

A new focus error detecting method for an optical disk drive has been developed using a holographic optical element (HOE). The groove pattern on the HOE was designed using the ray-tracing and least-squares-fitting methods to attain a symmetric beam profile. It has been proven successfully that this method of focus error detection is insensitive to wavelength fluctuations, objective lens shifts, and tracking grooves.
Decay of Electrostatic Surface Potential on Insulators via Charge Injection, Transport and Trapping
Authors: Kasap Safa O. , Arun Bhattacharyya Arun Bhattacharyya , Zhilun Liang Zhilun Liang
Published: February 2005

Decay of the surface potential on an initially corona charged insulator via charge injection, transport and trapping is theoretically examined and a general partial differential equation is derived for the space and time dependence of the electric field E(x, t) in terms of the charge carrier mobility, µ, trapping time, τ′, and the trap capture coefficient C
t. The present formulation specifically takes into account that as deep trapping proceeds, the rate of trapping decreases due to trap filling. The numerical solution of this differential equation gives the instantaneous electric field, E(x, t), profiles in the sample which can be integrated to obtain the time evolution of the surface potential, V(t), rate of discharge, dV/dt, final residual potential, V
r, and also the fraction of traps filled as a function of µ, τ′ and C
t. Two experimental conditions are considered. (a) The time dependence of the electric field, E(0, t), at the surface is well defined by the charge injection process, which in the present case, corresponds to a weak step illumination. (b) The spatial dependence of the initial field, E(x, 0), is well defined by an appropriate short light pulse illumination at t=0.
Effect of Silver Dopant on Optical and Electrical Properties of Solution-Grown Cadmium Selenide Thin Films
Authors: Sharma Kailash Chand , Ramphal Sharma Ramphal Sharma , Jagadish Chand Garg Jagadish Chand Garg
Published: February 2005

In the present study, n-type thin films of CdSe have been grown onto glass substrates by using a solution growth technique. Different doping concentrations of Ag were doped in pure CdSe films, and the effects on the optoelectronic properties were observed. The optical band gaps (E
g) of these films were found to be dependent on doping concentration i.e., they decrease from 1.70±0.02 eV to 1.50±0.03 eV as doping concentration increases from 0.1 wt% to 25 wt%. Other optical parameters such as absorption coefficient, α, refractive index `n' and dielectric constant `ε' were also computed. The electrical conductivity of pure CdSe films was obtained as 10-7 Ω-1 cm-1 while doped films have 10-4 Ω-1 cm-1. Thermal activation energy of these films was estimated. Carrier concentration, mobility, thermoelectric power and photosensitivity were also studied at different dopant concentrations.
Flux Density Distribution in YBa2Cu3Ox Specimens with Fine Y2BaCuO5 Dispersions
Authors: Yokoyama Yuko , Jeong In Kwon , Park Yong Ki , Yoshikazu Nishihara Yoshikazu Nishihara
Published: February 2005

The flux density distribution in YBa2Cu3O
x
bulk superconductor with fine Y2BaCuO5 dispersion is observed from the change of domain patterns in iron garnet films. The flux density increases not only at the edge of the sample, but also at the inner part with increasing magnetic field. The region with large critical current was of a comparable size to the grain. It was concluded that the low critical current estimated from the transport method is due to the weak link of the grain boundary.
Effects of Dislocation and Stress on Characteristics of GaAs-Based Laser Grown on Si by Metalorganic Chemical Vapor Deposition
Authors: Egawa Takashi , Hasegawa Yoshiaki , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: February 2005

The thermally induced biaxial tensile stress in GaAs/Si is reduced by postgrowth patterning, and the reduction in stress is dependent on the pattern size and shape. For narrow stripe patterns the stress relief is obtained perpendicular to the stripe. For small square patterns the stress is relieved in both directions. Thermal cycle annealing is also effective in reducing the threading dislocations in GaAs/Si. A thermally cycle-annealed multi-quantum-well (MQW) laser on a Si substrate grown by metalorganic chemical vapor deposition has continuous threshold current as low as 24 mA at 300 K. Rapid degradation can be suppressed by postgrowth patterning for the thermally cycle-annealed laser with an 8-µm-wide stripe, which results from the reduction of the biaxial stress to the uniaxial stress.
Gas Temperatures in Impulse Discharge Channels at Low-Pressure Air
Authors: Otsubo Masahisa , Matsuo Hiroshi Nieda
Published: February 2005

Two types of glow-to-arc transition processes, following constricted and transitional glows, in a nonuniform field gap between a point anode and a protrusion on a plane cathode in low-pressure air under impulse voltage are investigated, observing the spatiotemporal variation of emission intensity of the discharges by means of an image converter camera. At the same time, the distribution of gas temperature along the gap axis is measured spectroscopically with high resolution in time. The results show that the gas temperature is raised to a considerably high, though not extreme level. Along the positive column, the gas temperature rise is higher in the constricted region, especially at two parts near the respective tips of the point anode and the cathode protrusion. The transition mechanisms from the glow to the arc are discussed.
A New Evaluation Method of Silicon Wafer Bonding Interfaces and Bonding Strength by KOH Etching
Authors: MITani Kiyoshi , Feijoo Diego , Giho Cha Giho Cha , Ulrich M. Gösele Ulrich M. Gösele
Published: February 2005

KOH anisotropic etching is used to study the interfaces of bonded silicon wafers. This method has been developed to detect the presence of bubbles or unbonded areas with a gap of less than 0.27 µm, which is the detection limit of an IR camera. Because of the anisotropic etching properties of KOH and the presence of interfacial oxide layers, the etching surface morphology is dependent on the crystallographic orientation of the cross section. Correlation of etching results to the bonding strength of silicon wafers with and without a thermally oxidized silicon layer is also discussed.
Band-Edge Luminescence of Strained SixGe1-x/Si Single Quantum Well Structures Grown on Si(111) by Si Molecular Beam Epitaxy
Authors: Fukatsu Susumu , Noritaka Usami Noritaka Usami , Yasuhiro Shiraki Yasuhiro Shiraki
Published: February 2005

Band-edge luminescence, no-phonon transitions due to symmetry-breaking alloy disordering in SiGe layers and transverse optical phonon replicas, were observed for the first time in Si0.8Ge0.2/Si single quantum well (SQW) structures grown on Si(111) substrates. SQWs were successfully grown by “solid source” Si molecular beam epitaxy at temperatures above 700°C strictly retaining well-ordered surface reconstruction as disclosed by intense Laue spots in in situ electron diffraction images. Low temperature growth was invariably associated with development of streaky features and was found to be detrimental to luminescence efficiency.
Superconducting Thin Films of “Infinite-Layer” Sr1-xNdxCuOy Synthesized by Pulsed-Laser Deposition
Authors: Sugii Nobuyuki , Kubo Koichi , Ichikawa Michiharu , Yamamoto Kiyoshi , H. Yamauchi H. Yamauchi , Shoji Tanaka Shoji Tanaka
Published: February 2005

Sr1-x
Nd
x
CuO
y
thin films were grown on SrTiO3 substrates by a pulsed-laser deposition technique. The laser-deposited films of Sr1-x
Nd
x
CuO
y
with x≦0.075 were single phase of the “infinite-layer” structure. The lattice parameter c decreased and the lattice parameter a increased, as the Nd content, x, increased. The largest value for the a-axis length did not exceed that reported for superconducting bulk samples. The expansion of the a-axis as x increased was apparently hindered by lattice dimensional mismatch between film and substrate. The films with x=0.10 and 0.125 had onset temperatures of superconducting transition around 26 K. Weak Meissner signals were observed at temperatures below 30 K.
Antiphase-Domain-Free InP on (100) Si
Authors: Tang Guang-Ping , Lubnow Andreas , Wehmann Hergo-Heinrich , Gregor Zwinge Gregor Zwinge , Andreas Schlachetzki Andreas Schlachetzki
Published: February 2005

We show that antiphase-domain-free InP can be grown by means of low-pressure metalorganic-vapor-phase epitaxy (LP-MOVPE) on exactly (100)-oriented Si by appropriate choice of growth parameters. A simple detection scheme for antiphase domains (APD) in InP is presented. The most likely reason for the absence of APDs on the InP surface is their annihilation during the growth.
Polymorphic Identification of Oxotitanium Phthalocyanines by Solid-State 13C-NMR Spectroscopy
Authors: Toshio Enokida Toshio Enokida
Published: February 2005

The polymorphic characteristics of five polymorphs of oxotitanium phthalocyanine (TiOPc; amorphous, α, β, γ and the m-form) have been investigated by means of solid-state cross-polarization magic-angle-spinning (CP/MAS) 13C-NMR spectroscopy. The solid-state CP/MAS 13C-NMR spectra have suggested magnetic differences in the TiOPcs. The well-separated chemical shifts mean superior regularity of the TiOPc molecules.
Characterization of Thin Surface Layers by an X-Ray Double-Crystal Method with a Sample Designated as the First Crystal
Authors: Nobuo Itoh Nobuo Itoh
Published: February 2005

It is shown that thin surface layers can be sensitively characterized by using an X-ray double-crystal method, in which a sample designated as the first crystal is irradiated with incident X-rays at a low glancing angle and the X-rays reflected from the surface layer are analyzed by a second crystal. The applicability is proved by observing GaAs crystals lapped with fine abrasives. Deviation of the full width at half-maximum (FWHM) of the rocking curve for lapped crystals from that of a perfect crystal is a few times larger than the value obtained by the conventional method in which the sample is the second crystal.
TEM Observation of a Piled Structure of Si/Ga/Si with Ga Monolayer
Authors: Wu Xiao-Jing , Horiuchi Shigeo , Izumi Koichi , Kikuta Seishi
Published: February 2005

A piled structure of Si/Ga(monolayer)/Si, grown by molecular beam epitaxy along Si (111) together with solid-phase epitaxy (SPE), is studied by transmission electron microscopy (TEM). It is found that some Ga concentrated islands are formed at the interface. The actual number of Ga atoms within these islands is much less than the expected one, suggesting that the diffusion of Ga atoms into Si occurs. A number of {111} microtwins form a defect layer near the surface. The formation of Ga concentrated islands must be related to Ga droplets formed in the initial doping state.
Undoped Silicon Layers Grown by Gas Source Molecular Beam Epitaxy Using Si2H6
Authors: Yoshinobu Tatsuo , Takashi Fuyuki Takashi Fuyuki , Hiroyuki Matsunami Hiroyuki Matsunami
Published: February 2005

Undoped Si layers were homoepitaxially grown on Si(001) substrates by gas source molecular beam epitaxy using pure disilane (Si2H6) at various substrate temperatures ranging from 533°C to 1000°C. Single-crystalline epilayers were obtained throughout the whole temperature range. Growth rates, crystallinity of the epilayers, and redistribution of impurities during crystal growth were investigated. Undoped layers grown at 700°C exhibited n-type conduction, with the carrier concentration in the 1014 cm-3 range and the electron mobility of 1500 cm2/V·s at room temperature.
P-N Conversion of Poly-Ge Films Fabricated by Plasma Assisted Deposition
Authors: Inoue Narumi , Hiroaki Kobayashi Hiroaki Kobayashi , Yoshizumi Yasuoka Yoshizumi Yasuoka
Published: February 2005

Polycrystalline Ge films have been fabricated on glass substrate by using a plasma-assisted deposition method. The polarity of Hall voltage of the films deposited at RF power of lower than 30 W corresponds to positive which indicates p-type conduction, but the polarity reverses in the films fabricated at RF power of higher than 50 W. This phenomenon is only seen for the films deposited in the hydrogen plasma, and no sign reversal occurs in the films deposited in the argon plasma.
Wavelength Dependence on the Formation of Electrically Conductive Fine Particles by Excimer Laser-Induced Ablative Photodecomposition of Monomeric Polynuclear Aromatic Solids
Authors: Akihiko Ouchi Akihiko Ouchi , Akira Yabe Akira Yabe
Published: February 2005

The reaction of reactive intermediates generated by excimer laser-induced ablative photodecomposition of solid monomers, namely, 3,4,9,10-perylenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic diimide, and 1,4,5,8-naphthalenetetracarboxylic dianhydride, yielded electrically conductive fine particles. The electrical conductivity was largely dependent on the wavelength of the lasers used. The fine particles had polymeric hydrocarbon moieties containing extended aromatic planes.