bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Characterization of Pb(ZrxTi1-x)O3 Thin Films by Reactive Sputtering Using an Alloy Target
Authors: Hayashi Koji , Shimizu Masaru , Shiosaki Tadashi
Published: February 2005

Pb(Zr
x
, Ti1-x
)O3 (PZT) thin films were deposited on Pt/SiO2/Si substrates by rf-magnetron sputtering using an alloy target consisting of Zr-Ti alloy and a Pb metal. When an alloy target was used in reactive sputtering, no change was observed in the Zr/Ti ratio of the films for up to 300 h for target uses. The (111)-oriented PZT films were successfully grown at substrate temperatures of 605-620°C. The coercive fields (E
c) and remanent polarizations (P
r) of the films with only the perovskite phase were in the range of 70-72 kV/cm and 20-22 µC/cm2, respectively. In fatigue behavior, switched charge density started to drop at 108 cycles.
Surface Acoustic Wave Transducer in a Layered Structure Composed of Thin Piezoelectric Ceramic Plate and Glass
Authors: Kohji Toda Kohji Toda , Yoshikiyo Yamamoto Yoshikiyo Yamamoto
Published: February 2005

Operation performance of a surface acoustic wave (SAW) interdigital transducer (IDT) in a layered structure composed of a thin piezoelectric ceramic plate and a glass substrate is described in terms of phase velocity, electromechanical coupling constant and mechanical displacement distributions. The numerical results of SAW phase velocities in the form of a function of the product of frequency and thickness of the piezoelectric ceramic plate are in good agreement with the measured velocities of the constructed layer-structured devices. The first-order SAW mode device has an excellent electromechanical coupling constant of greater than 15%, which is favorable for a SAW device exhibiting a satisfactory performance under single-mode operation in a SAW oscillator construction.
Normal Poling and High Poling of Ferroelectric Ceramics and Space-Charge Effects
Authors: Kiyoshi Okazaki Kiyoshi Okazaki
Published: February 2005

Poling treatment of field application below Curie point of ferroelectric ceramics is termed “normal poling” and a dc field application above Curie point is termed “high poling”. When a high poling is performed for BaTiO3 or (Sr, Ba)TiO3, a space-charge polarization (P2 type) in the direction of high poling field and an internal bias field E
-i with the direction opposite to high poling field are generated. When a ferroelectric sample such as BaTiO3 and Pb(Zr, Ti)O3 are aged at temperatures below T
c after normal poling, another space-charge polarization (-P2 type) in the direction opposite to that of the normal poling and the internal bias field E
i with the same direction as that of normal poling field are generated. In this paper, two kinds of space-charge models in ferroelectric ceramics and related phenomena such as space-charge-stabilized effects on the electromechanical strength, the pseudo-pyro-electric current of high-poled (Sr, Ba) TiO3 and asymmetric polarization reversal caused by the -P2 effects will be reviewed and discussed.
Crystal Structure and B-Site Ordering in Antiferroelectric Pb(Mg1/2W1/2)O3, Pb(Co1/2W1/2)O3 and Pb(Yb1/2Nb1/2)O3
Authors: Choo Woong Kil , Kim Hyo Jin , Yang Jae Ho , Lim Hoon , Lee Jeong Yong , Kwon Jeong Rok , Chun Chang Hwan
Published: February 2005

The high-temperature phase of Pb(Mg1/2W1/2)O3, Pb(Co1/2W1/2)O3 and Pb(Yb1/2Nb1/2)O3 belongs to the space group Fm3m with the unit cell size of 2a
c×2a
c×2a
c where a
c is the lattice parameter of the cubic perovskite unit cell. All these complex perovskites undergo phase transition into low-temperature orthorhombic structures with a shrunken lattice parameter along the c-axis and the approximate √2a lattice parameters along the a
0- and b
0-axes, which are, respectively, parallel to the prototype [110]
c
and [11̄0]
c
directions. The symmetry along the b
0-axis of the perovskites is most prominently distinguished from that along the a
0-axis in that the low-temperature structure is modulated in the b
0-axis direction. For Pb(Mg1/2W1/2)O3, a diffraction pattern detrimental to the crystal structure determination well below the Curie temperature is presented. At the same time, the crystal structures of lock-in phases of the aforementioned oxides are compared with the well-known structure of PbZrO3.
BaTiO3 Particle-Size Dependence of Ferroelectricity in BaTiO3/Polymer Composites
Authors: Yamamoto Takashi , Urabe Kazuyori , Banno Hisao
Published: February 2005

BaTiO3 particle-size dependence of ferroelectricity in BaTiO3/polymer composites was investigated from the viewpoints of the crystal phase in BaTiO3 powder and piezoelectric properties in BaTiO3/polymer composites. The crystal phase of BaTiO3 powder was transformed from tetragonal to pseudocubic at a critical particle size of 0.1 to 0.2 µm at room temperature. The piezoelectric charge constant (d
33) and hydrostatic piezoelectric constant (d
h) were obtained through poling treatment, although their values were small in BaTiO3/polymer composite using the pseudocubic BaTiO3 powder.
Observation of Light Scattering in Lithium Niobate
Authors: Chen Zhiming , Nakao Keisaku , Shiosaki Tadashi
Published: February 2005

Results of experiments on the dynamics of scattering in a quasi-c-cut plate of LiNbO3:Fe crystal are presented. With the incident laser beam along the +c direction, the back and forward-scattered light forms many spots and rings after a few seconds of illumination. The pattern is caused by the inter-reflection and photorefractive effect, and are explained with reference to theories of degenerated four-wave mixing and anisotropic light scattering in photorefractive materials. No scattering pattern is obtained when the incident beam is in the opposite direction.
Enhancement of Photoelastic Constant of Optical Thin-Film Waveguide Assisted by Surface Acoustic Wave
Authors: Nakagawa Yasuhiko , Hitoshi Ito Hitoshi Ito , Kouichi Kato Kouichi Kato
Published: February 2005

In the present research, we propose a method of controlling the photoelastic constant using surface acoustic waves. A Bragg diffraction is carried out to determine the photoelastic constants of Nb2O5. As a result, it is confirmed that the photoelastic constant of Nb2O5 thin film undergoing a sputtering process, during which surface acoustic waves were excited on the substrate, was about 3 to 6 times larger than those of thin films on which surface acoustic waves were not excited.
Low-Temperature-Fireable Dielectric Material Pb(Fe2/3W1/3)O3-(Pb, Ca)(Fe1/2Nb1/2)O3 for Microwave Use
Authors: Nakano Mutsuko , Suzuki Kazuaki , Taro Miura Taro Miura , Makoto Kobayashi Makoto Kobayashi
Published: February 2005

A ferroelectric Pb(Fe2/3W1/3)O3-Pb (Fe1/2Nb1/2)O3 (PFW-PFN) system has a low sintering temperature. A partial substitution of Ca for Pb in PFN shift the transition temperature sufficiently low, transforming this material into a paraelectric at room temperature. When paraelectric PFW-PCFN formed a single-phase (Pb, Ca)(W, Fe, Nb)O3 (PCWFN), this material was confirmed to have a high dielectric constant with temperature stability and low dissipation loss. There was a certain amount of difficulty associated with the synthesis of single-phased PCWFN. A process to overcome this difficulty is reported. Up to now, the sintering temperature of the best characterized material was 1000°C. This temperature is very low for the sintering of a glass-free dielectric material used as a microwave resonator.
Electrical and Optical Properties of Conducting Polymer-Ferroelectric Liquid Crystal Composite
Authors: Yin Xiao Hong , Masanori Ozaki Masanori Ozaki , Katsumi Yoshino Katsumi Yoshino
Published: February 2005

Conducting polymer-ferroelectric liquid crystal composites have been prepared for the first time. Properties of composites depend strongly on the combination of ferroelectric liquid crystal and conducting polymer. Characteristic ferroelectric properties have been found in these composites. Contributions of both the Goldstone mode and soft mode have been observed in the temperature dependence of the dielectric constant of the composite. Spontaneous polarization decreases markedly with increasing concentration of conducting polymer above about 10%, which is explained by taking the microstructure of the composite and a percolation model into consideration. Electrooptic effects such as the transient scattering mode have also been found.
Factors Controlling Pretilt Angles of Polyimide Alignment Film for Liquid Crystal Displays
Authors: Nozaki Chiyoshi , Naoya Imamura Naoya Imamura , Yasuhisa Sano Yasuhisa Sano
Published: February 2005

Factors controlling pretilt angles of polyimide (PI) alignment film for liquid crystal displays were studied by pretilt angle measurement of PI with various structural features and X-ray photoelectron spectroscopy (XPS). Structural features that resulted in high pretilt angles were: (1) rigid tetracarboxylic acid moiety, (2) diamine moiety containing hexafluoroisopropylidene group and -O- or -CH2- linkage, and (3) sufficient imidization ratio. XPS of PI's that gave high pretilt angles showed higher fluorine content at the surface than in the bulk of the film. The results implied that high pretilt angles result from orientation of the polymer chains within the film, and not simply from a high fluorine content in the material.
Low-Frequency Dielectric Responses of Proton-Exchanged LiTaO3
Authors: Ailie Tourlog Ailie Tourlog , Kiyoshi Nakamura Kiyoshi Nakamura
Published: February 2005

A space charge field model has been proposed for explaining the mechanism of domain inversion caused by heat treatment in proton-exchanged LiTaO3. The purpose of this study is to examine the existence of the space charges caused by proton exchange of LiTaO3. The low-frequency dielectric responses of proton-exchanged LiTaO3 measured at high temperatures are presented. It is shown that the dielectric constant and the dielectric loss are about one order of magnitude greater than those of unprocessed plates, and that the activation energy of proton-exchanged plates is different from that of unprocessed plates. These results indicate that a different species of defects arises in LiTaO3 due to proton exchange, and this results in a drastic increase of charged point defects.
Composition Variation of Optical Phonon Damping in Lithium Niobate Crystals
Authors: Seiji Kojima Seiji Kojima
Published: February 2005

Lattice vibrations have been studied by Raman scattering on stoichiometric, congruent and 5 mol% MgO doped lithium niobate crystals. The mode frequency of the optical phonon shows no marked composition variations, while the damping shows considerable composition dependence. The damping due to the scattering of phonons at defects was determined from the temperature dependence of the damping of A
1(z) modes, by the subtraction of the scattering due to the third- and fourth-order anharmonicity. The type of defects which scatter optical phonons was discussed in relation to the Li and Nb site vacancy models. The results strongly support the Li site vacancy model and suggest that the doped Mg atoms occupy the Li site.
Phase Transitions of Ba2NaNb5(1-x)Ta5xO15
Authors: Takashige Masaaki , Kojima Seiji , Hamazaki Sin-Ichi , Tsukioka Fuminao Shimizu
Published: February 2005

Ceramic samples of the mixed system Ba2NaNb5(1-x)Ta5x
O15 were investigated through dielectric and Raman scattering measurements. It was revealed that with the increase of x from 0 to 1, the ferroelectric Curie point decreases from 833 K to about 40 K, whereas the ferroelastic phase transition point decreases from 573 K to the 250 K range.
GaAs Quantum-Wire Laser Using Fractional Layer Superlattice
Authors: Saito Hisao , Kunihiko Uwai Kunihiko Uwai , Naoki Kobayashi Naoki Kobayashi
Published: February 2005

In (AlAs)
k/n
(GaAs)
l/n
(k+l=n) fractional layer superlattice (FLS) growth on the (001) GaAs vicinal surface 2° off toward [1̄10] by metal-organic chemical vapor deposition, using a (AlAs)
m
(GaAs)
n
(m, n>3) short period superlattice as the buffer layer very much improve the uniformity of lateral periodicity in the FLS near the FLS/buffer interface compared with using binary (GaAs and AlAs) and ternary AlGaAs as the buffer layers. This is due to the improvement in the uniformity of the terrace width on the surface of a short period superlattice by step-ordering. As a result, a large polarization anisotropy of about 50% is observed in the photoluminescence spectrum for the quantum-wire array structure oriented toward [110] in which a 4-nm-thick (AlAs)1/4(GaAs)3/4 FLS layer is sandwiched by (AlAs)3(GaAs)3 short period superlattice layers. Separated confinement heterostructures consisting of a 12-nm-thick undoped (AlAs)1/4(GaAs)3/4 FLS quantum-wire active layer, doped (AlAs)1(GaAs)2 carrier confinement layers, and doped Al0.6Ga0.4As optical confinement layers are grown. To prevent the disordering of the FLS layer induced by the diffusion of intentionally doped impurity atoms during the growth and the processing, low-diffusive Si and C atoms are used for n- and p-type doping into carrier and optical confinement layers. Lasing operation is obtained by current injection below 195 K for the electrode with simple stripe geometry. The lasing wavelength depends on the orientation of the stripe electrode. The electrode with [110] orientation which is parallel to the quantum wire array has a lasing wavelength of 662 nm, and the [1̄10] orientation which is perpendicular to the array has a lasing wavelength of 667 nm at 10 K.
Optical Constants of Amorphous Ga2Se3
Authors: Sadao Adachi Sadao Adachi , Shunji Ozaki Shunji Ozaki
Published: February 2005

The optical response in amorphous (a-)Ga2Se3 semiconductor in the 1.2-5.6-eV photon-energy range at room temperature has been measured by spectroscopic ellipsometry. It is found that the dielectric function ε=ε1+iε2 of a-Ga2Se3 strongly resembles those of amorphous tetrahedrally bonded semiconductors. The optical energy gap estimated from the plots of Eε2(E)1/2 versus E (photon energy) is 1.75 eV. Dielectric-related optical constants, such as the complex refractive index and absorption coefficient, of this amorphous semiconductor have also been presented.
Experimental Comparison of Off-State Current between High-Temperature- and Low-Temperature-Processed Undoped Channel Polysilicon Thin-Film Transistors
Authors: Yeh Ching-Fa , Yang Tzung-Zu , Chen Chun-Lin , Yang Tai-Ju Chen
Published: February 2005

Poly-Si thin-film transistors (TFT's) have a large off-state current that is unacceptable for pixel driver application. To quickly establish an effective solution to reduce the off-state current, systematic comparison and clarification of the mechanisms of off-state current are still insufficient. We will concentrate on an experimental comparison of off-state current mechanisms between low-temperature-processed (LTP) and high-temperature-processed (HTP) poly-Si TFT devices. Since all the off-state currents are found to be divided into three regions in LTP and HTP poly-Si TFT's, they are attributable to a resistive current in region I (low gate bias), pure thermal generation in region II (low drain bias) and Frenkel-Poole emission in region III (high gate bias, drain bias).
Substitution Effects of Fe and Zn for Cu in YBa2(Cu1-xMx)4O8
Authors: Meen Teen-Hang , Chen Ying-Chung , Liaw Ken-Whie , Juang Fung-Lung , Yang Hung-Duen
Published: February 2005

YBa2(Cu1-x
M
x
)4O8 (M=Fe, Zn; x=0 to 0.05) has been investigated by means of X-ray diffraction, thermogravimetric analysis, electrical resistivity and magnetic susceptibility measurements. X-ray diffraction patterns show that all samples contain the nearly single YBa2Cu4O8 phase. The results of structural analysis indicate that the orthorhombic-to-tetragonal transition occurs at about x=0.03 for M=Fe, whereas the structure remains orthorhombic until x=0.05 for M=Zn. Thermal stability is reduced with increasing Fe concentration, but is nearly unchanged in the case of Zn substitution. The suppressed rates of T
co with increasing dopant content are 17.81 K/at.% and 15.69 K/at.% for Fe and Zn. Effective magnetic moments of YBa2(Cu1-x
Fe
x
)4O8 are 5.99, 5.63 and 5.37 µB for x=0.01, 0.03 and 0.05, respectively. In addition, the similarities and differences between YBa2(Cu1-x
M
x
)4O8 and YBa2(Cu1-x
M
x
)3O7-y
are discussed.
Microwave Characteristics of TiO2-Bi2O3 Dielectric Resonator
Authors: Fukuda Koichi , Awai Ryozo Kitoh
Published: February 2005

The microwave characteristics of the binary-system TiO2-Bi2O3 ceramics, which is widely known to exhibit a comparatively high dielectric constant in the lower-frequency band, are investigated from a new standpoint. It is shown in this article that the composition of 0.919TiO2-0.081Bi2O3 has a high dielectric constant (εr=80), high Q (1800 at 5 GHz) and low temperature coefficient of resonant frequency (τf=+21 ppm/°C). From the X-ray diffraction and X-ray microanalysis, it is indicated that the crystal structure of this material is composed of two phases, TiO2 and Bi2Ti4O11, which possess a high εr with a negative temperature coefficient and a high εr with a positive temperature coefficient, respectively. The measurements of linear thermal expansion and temperature coefficient of capacitance are also carried out in order to study the behavior of temperature compensation in this system.
Optical Characterization of Quench-Deposited PbBr2 Films and Their Annealing Behavior
Authors: Kondo Shin-ichi , Tamotsu Arakawa Tamotsu Arakawa , Tadaaki Saito Tadaaki Saito
Published: February 2005

High-quality amorphous PbBr2 films were obtained by quench deposition onto fused-silica substrates cooled to 77 K. The films exhibited a well-defined crystallization temperature (T
c) of 335 K. The as-deposited films were stable at temperatures up to 160 K and relaxed to new stable random networks upon annealing at higher (but below T
c) temperatures. The optical spectra in the amorphous phase were characterized by a prominent first absorption band of nonexcitonic origin. Below the absorption edge, the amorphous films showed a very high transparency (absorption coefficients, less than 102 cm-1 below 3 eV) never achieved by deposition onto hot substrates.
Growth of Small Particles of Iron-Nickel Alloys Prepared by Gas-Evaporation Technique
Authors: Takehisa Ohno Takehisa Ohno
Published: February 2005

The crystal structure and habit of small particles of iron-nickel alloys prepared by the gas-evaporation technique were studied by electron microscopy. Most of the particles grown from Fe-36 at.%Ni foil consisted of a single phase of ferrite or austenite, and they formed alternating long chains.
In Situ X-Ray Monitoring of Metalorganic Vapor Phase Epitaxy
Authors: Tsuchiya Tomonobu , Taniwatari Tsuyoshi , Uomi Kazuhisa , Toshihiro Kawano Toshihiro Kawano , Yuuichi Ono Yuuichi Ono
Published: February 2005

We demonstrate the in situ X-ray monitoring of metalorganic vapor phase epitaxy by using a four-crystal monochromator. The in situ X-ray measurement of InGaAs with a thickness of 0.3 µm on an InP substrate was achieved even under growth conditions at 620°C. Moreover, this monitoring technique is not affected by the atmosphere of the reactant source gasses. Also, the X-ray peak of the InGaAs at 300°C, is clearly separated from the InP peak in spite of the small lattice mismatch (-0.09%) without aligning the wafer. The dependence of lattice mismatch on temperature measured by this X-ray monitoring technique agrees with the dependence calculated theoretically. This technique can also be used to measure the thickness dependence of lattice mismatch and temperature dependence of in-plane compressive strain for InP on GaAs heteroepitaxy.
Influence of Interface Structure between Overlayered Titanium Nitride Film and Aluminum on Multilayered Interconnects
Authors: Kageyama Makiko , Yasuyuki Tatara Yasuyuki Tatara , Hiroshi Onoda Hiroshi Onoda
Published: February 2005

Aluminum film with overlayered titanium nitride (TiN), which was formed as antireflective material, has been investigated. The effect of TiN film on aluminum film properties and the layered-metal line reliability as an interconnect depend on its deposition process. Aluminum grain enlargement after annealing was largely promoted by compressive stress of TiN, when TiN was deposited on aluminum after the aluminum was exposed to air. When TiN is deposited successively on aluminum in the same vacuum, aluminum grain size does not increase with TiN compressive stress. In this case, TiN has been found to have epitaxial continuity with the underlayer aluminum. This crystal continuity suppresses Al atom movement. Electromigration resistance of the TiN/Al/TiN layered line was found to have a longer lifetime when the overlayered TiN was deposited successively on aluminum. It is considered that this crystal continuity also influences the electromigration resistance of the layered-metal lines.
Observations of the Au/Si(111) System with a High-Resolution Ultrahigh-Vacuum Scanning Electron Microscope
Authors: Akira Endo Akira Endo , Shozo Ino Shozo Ino
Published: February 2005

Secondary electron (SE) imaging with a high-resolution ultrahigh-vacuum
scanning electron microscope (UHV-SEM) has been applied to the observation of
the Au/Si(111) system. Domains of the 5×2-Au or
√3×√3-Au structure partially covering a Si(111)-7×7
surface are clearly observed. Domains of 5×2-Au formed by Au
deposition onto a substrate held at ∼870 K show threefold elongation
corresponding to three equivalent kinds of domains rotated
120° to each other. On the other hand, 5×2-Au
regions formed by partial Au desorption by heating at ∼1270 K from an
entirely covered surface display larger size without such elongation.
Granular clusters, a few nm in size, of Au formed by deposition approximately
at room temperature, and large three-dimensional islands formed in the
Stranski-Krastanov growth mode are also clearly imaged.
X-Ray Diffraction Measurements of Lattice Strains in Co/Pd(001) Superlattice Films
Authors: Wu Lianjun , Nakayama Noriaki , Engel Brad N. , Falco Teruya Shinjo
Published: February 2005

Lattice spacings in fcc-Co/Pd(001) superlattice films grown on GaAs(001) substrates with a Ag(001) buffer layer were measured using a four-circle diffractometer. For samples with Co layers thinner than 9 Å and Pd layers thinner than 12 Å, the observed in-plane (110) lattice spacings were all 2.71±0.01 Å, indicating 8.0% lattice expansion of Co layers and 1.5% lattice contraction of Pd layers. The (002) lattice spacings along the growth direction were estimated from a profile fitting method, and they were 1.60±0.02 Å for Co layers and 1.98±0.02 Å for Pd layers. This means that Co layers are contracted nearly 10%, while Pd layers are expanded 2% along the growth direction of the superlattice films. The estimated large lattice strains are successfully applied to explain the large magnetovolume contribution to the magnetic anisotropy reported previously.
Interaction of Cesium-Potassium Antimonide Photocathode Materials with Oxygen: an X-Ray Photoelectron Spectroscopy Study
Authors: Leonardo Soriano Leonardo Soriano , Luis Galán Luis Galán
Published: February 2005

The interaction of oxygen with photocathode materials based on alkali antimonide at room temperature has been studied by means of X-ray photoelectron spectroscopy (XPS). In the first step, the antimonide is oxidized, forming alkali suboxide, (Cs11O3) and elemental Sb (Sb0) is segregated. Further oxidation (>20 L) causes the formation of an alkali oxide overlayer (i.e., Cs2O) and the oxidation of the elemental Sb to form Sb5+ species. The kinetics of oxidation has been found to be much faster than the logarithmic rate due to strong diffusion of alkali ions toward the surface. The in-depth distribution of alkali oxides for exposures larger than 20 L is the opposite of that which produces a good photoemissive surface (Cs11O3/semiconductor). However, slight oxidation (<20 L) improves the spectral response of the photocathode. A Cs suboxide overlayer (one-cluster size) has been proposed as the optimum activation surface.
Comparison between Atomic Force Microscopic Images of Ionic Crystal Surfaces in Air and in Dry Argon
Authors: Kouji Miura Kouji Miura , Yuko Shukuya Yuko Shukuya
Published: February 2005

We have observed cleavage surfaces of ionic crystals in air and in dry argon using atomic force microscopy (AFM). AFM images from cleavage surfaces of NaCl, KCl, LiF, CaF2 and BaF2 clearly exhibit atomically resolved images consisting of anions and cations for both conditions. The AFM image reveals that the force between tip and surface in dry argon is stronger than that in air.
Simulations of Electron Orbits in a Bucket-Type Ion Source
Authors: Ido Shunji , Hiroki Hasebe Hiroki Hasebe , Yoshihiro Fujita Yoshihiro Fujita
Published: February 2005

We developed a simulation code to calculate electron orbits with collisions between electrons and argon gas atoms. Simulations are applied to trace electron orbits in a bucket-type ion source. This paper introduces the numerical model. It discusses the lifetime of primary electrons and the effects of collisions.
Photoionization Spectra of Pd in High Rydberg States
Authors: Toshiaki Ishikawa Toshiaki Ishikawa
Published: February 2005

A series of Rydberg states of Pd in quantum numbers n=16 to 39 produced by a three-step selective excitation process using three tunable dye lasers are measured by a photoionization technique. It is found that the least squares fitting of the Rydberg formula to the observed Rydberg series yields the quantum defect δ=0.000068 and ionization potential E
i=67238.05 cm-1.
Nondestructive Depth Profile Analysis by Changing Escape Depth of Photoelectrons
Authors: Masaki Hasegawa Masaki Hasegawa , Ken Ninomiya Ken Ninomiya
Published: February 2005

Nondestructive depth profile analysis by changing the photoelectron escape depth was investigated at a soft X-ray beamline of the Photon Factory (KEK-PF). The escape depth was controlled by changing the energy of incident soft X-rays. The depth profile was determined from the observed photoelectron intensities based on the fact that the photoelectron intensity can be described by the Laplace transform of the depth profile. The oxidized silicon thin film on a silicon substrate was analyzed with this method, and depth profiles of SiO2 and Si were obtained. The depth resolution was 0.4 nm according to the 10-90% width of the transition region between the SiO2 and the Si. Improvement of depth resolution is discussed in terms of several simulations performed using a simple depth structure.
Observation of Fe-Mn Oxidation Process Using Specimen Transfer Chamber and Ultrahigh-Vacuum Transmission Electron Microscope
Authors: Koguchi Masanari , Hiroshi Kakibayashi Hiroshi Kakibayashi , Ryoichi Nakatani Ryoichi Nakatani
Published: February 2005

A specimen transfer chamber that enables a specimen to be transferred in vacuum from a thin-film growth apparatus to an ultrahigh-vacuum transmission electron microscope (UHV-TEM) was developed. This chamber was applied to observe, for the first time, the as-grown state of Fe-Mn thin films and the changes occurring during their oxidation. The oxidation process of 12-nm-thick Fe-Mn films on a carbon support film was observed by controlling the vacuum in the transfer chamber. Just after a film specimen was transferred, it had a polycrystalline single-phase structure. When the film was exposed to pressures from 3.8×10-6 Pa to 1 atm, (Fe-Mn)2O3 gradually appeared around the Fe-Mn grain boundaries. The Fe-Mn grains changed to (Fe-Mn)2O3 grains after 47 h of exposure to air.
Characteristics of Hall Accelerator for Helium-Ion Beam Extraction
Authors: Okada Morihiro , Toku Hisayuki , Yasushi Yamamoto Yasushi Yamamoto , Kiyoshi Yoshikawa Kiyoshi Yoshikawa
Published: February 2005

Discharge characteristics of a Hall accelerator-type ion source for low-voltage continuous operation (called HALOC), designed for film-coating purposes, have been studied for extracting helium-ion beams. Based on the energy distribution of helium-ion beams measured by a multigrid analyzer, the relationship between discharge conditions and the beam energy profiles has been discussed in terms of the electron mean free path, cycloidal length and neutralization of extracted ion beams. Experimental beam currents are also estimated by theoretical calculations.
The Initial Growth Stage of the InAs Quantum Well Structures on Variously Oriented GaAs Substrates
Authors: Lee Jeong-Sik , Kudo Kazuhiro , Niki Shigeru , Yamada Akimasa , Makita Yunosuke , Kuniaki Tanaka Kuniaki Tanaka
Published: February 2005

The InAs/GaAs strained quantum well structure growths by molecular beam epitaxy on variously oriented GaAs substrates have been investigated. X-ray diffraction and photoluminescence measurements have been used to examine the properties' dependence on the substrate orientation of a few monolayers of InAs quantum wells. Experimental results that show strong influence of substrate orientation on the growth mode and growth rate are obtained.
Optical Properties of Amorphous Si Partially Crystallized by Thermal Annealing
Authors: Takahiro Suzuki Takahiro Suzuki , Sadao Adachi Sadao Adachi
Published: February 2005

Spectroscopic ellipsometry (SE) has been used to study optical properties of amorphous (a-) Si partially crystallized by thermal annealing. The a-Si samples used were prepared by rf sputtering on (100)Si. A linear regression analysis (LRA) and a Bruggeman effective-medium approximation (EMA) indicate that the annealed layer consists of volume fractions of a-Si and microcrystalline (?c-) Si. Isothermal annealing experiments at 1100?C suggest that the crystallization starts to occur very quickly (?30 min) and then slows with an increase in the annealing time. The complex dielectric functions of ?c-Si deduced here differ appreciably from that of crystalline (c-) Si, especially in the vicinity of the sharp critical-point (CP) features. Analyses are also presented on the dielectric-function spectra of ?c-Si using a simplified model of the interband transitions.
Spectroscopic Ellipsometry Study of Si Surfaces Modified by Low-Energy Ar+-Ion Irradiation
Authors: Takayuki Miyazaki Takayuki Miyazaki , Sadao Adachi Sadao Adachi
Published: February 2005

Spectroscopic ellipsometry (SE) measurements are carried out to study structural modification of Si surfaces induced by low-energy Ar+-ion irradiation. The Ar+ ions are irradiated on Si(100) substrates at acceleration voltages between -150 and 0 V and substrate temperatures between 20 and 410?C. The SE data clearly suggest that the Ar+-ion irradiation modifies Si surfaces depending upon Ar+-ion energy and substrate temperature. An effective medium approximation (EMA) and a linear regression analysis (LRA) suggest that the surface layers modified with Ar+ ions at higher substrate temperatures consist of volume fractions of voids, crystalline and amorphous Si and those modified at lower substrate temperatures consist of volume fractions of SiO2, amorphous Si and voids. SE has thus proven to be an easy, fast and nondestructive technique that can be used to assess important structural parameters of Ar+-ion-modified Si surfaces.
Monte-Carlo Simulation of Surface Reactions in Plasma-Enhanced Chemical Vapor Deposition of Hydrogenated Amorphous Silicon Thin Films
Authors: Shirafuji Tatsuru , Chen Wei-ming , Mikio Yamamuka Mikio Yamamuka , Kunihide Tachibana Kunihide Tachibana
Published: February 2005

A three-dimensional Monte-Carlo simulation of surface reactions in plasma-enhanced chemical vapor deposition of hydrogenated amorphous silicon thin films has been carried out. The increase of Si-H2 bonds in the films with increase of SiH2 radical density was explained naturally in terms of surface roughness caused by high sticking probability of SiH2. The effective roughness monitored as voids by in situ ellipsometry supports the simulated results.
Superconducting Negative Resistance Switches
Authors: Adir M. Luiz Adir M. Luiz
Published: February 2005

A new type of superconducting switch using the negative differential resistance of the CVC (current-voltage characteristic) curve of a nontunneling Josephson junction is suggested. With the proper choice of the load resistor monostable or bistable switching circuits may be designed. The power consumption, the switching speed and other relevant characteristic features of the proposed superconducting switches are analyzed.
Measurement of Gas Temperature Profile in Discharge Region of Excimer Laser with Laser Schlieren Method
Authors: Kosugi Shinichiroh , Maeno Kazuo , Honma Hiroki
Published: February 2005

Shock waves are generated by pulse discharges in the cavity of excimer lasers. The shock waves cause arcing, nonhomogeneous excitation of laser gas and limitation of repetition rate of a high-repetition-rate excimer laser. Distribution of temperature rise by pulse discharge is an essential factor for generation and propagation of shock waves. Gas temperature profiles in the discharge region of the excimer laser cavity are measured by a laser schlieren method for single-pulse operations. The results show that the temperature distribution depends on the xenon concentration. In the cases of pure helium and higher xenon concentration, the temperature distributions are steeper than those in the cases of lower xenon concentration.
Novel Digital Photosensor Cell in GaAs IC Using Conversion of Light Intensity to Pulse Frequency
Authors: Tanaka Katsu , Ando Fumihiko , Taketoshi Kazuhisa , Ohishi Iwao , Asari Goro
Published: February 2005

A photoelectric GaAs integrated circuit that converts light intensity to digital signal frequency has been fabricated using the GaAs MES-FET process. The circuit includes a metal-semiconductor-metal photodiode (MSM-PD), a preamplifier (PA), a Schmitt trigger (ST), a flip-flop (FF) (1-bit digital counter) and a reset (Rst) FET. This sensor cell has a wide dynamic range of over 5 decades of incident light power and a ? characteristic suitable for an image pickup device.
Segregation of As on GaAs(100) Surface during Abrasion Process Studied by X-Ray Photoelectron Spectroscopy and Auger Electron Spectroscopy
Authors: Iijima Yoshitoki , Muramoto Koichi , Uemura Masao , Hiraoka Kenzo
Published: February 2005

When a GaAs(100) surface was mechanically scribed by a diamond tip in an ultrahigh vacuum (UHV), surface segregation of As was observed using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The same phenomenon was also seen when the surface was abraded in air using emery paper. In the latter case, angle-resolved XPS analysis of As3d and Ga3d spectra showed the formation of As-As bonds on the abraded surface. Ga-Ga bonds existed beneath the layer of As-As bonds isolated from Ga-As bonds. The mechanism of the surface segregation of As is discussed.
AC Photovoltaic Measurement of Charge Density Uniformity in Silicon Nitride Film Deposited on Si Wafer
Authors: Honma Noriaki , Kato Hisayuki
Published: February 2005

Charge density uniformities in an as-deposited silicon nitride film are evaluated using an ac photovoltaic method. The experimental results for photovoltages as a function of the thickness of a silicon nitride film showed that the net charge in silicon nitride is positive, and a negative charge is located near the interface between the silicon nitride and the ultrathin oxide on the silicon substrate. The photovoltages also greatly varied when the gas flow ratio of NH3 to SiH2Cl2 is changed from 5 to 50 while keeping the thickness constant. The ac photovoltaic measurement revealed a charge density inhomogeneity of 8-nm-thick silicon nitride films, which is attributed to local variations of the gas flow ratio.
Oxygen Exchange between Adsorbed CO2 and Perovskite-Type LaMnO3+? Surfaces
Authors: Taguchi Yasunori Yanagisawa
Published: February 2005

Using temperature-programmed desorption gas analysis, thermal desorption of C16O2 with a small amount of C16O18O is observed at about 730 K after C18O2 gas adsorption on LaMnO3+? (?=0.17) powders. This indicates that double oxygen exchange occurs between C18O2 gas and 16O atoms on LaMnO3+? surfaces.
Theoretical Exploration of Observed V-B Transitions between Magnetron Discharge and Anode-Obstructed Hollow-Cathode Discharge Mode
Authors: Shi Binxing , Yu Zengqi , Lumin Li Lumin Li , George Collins George Collins
Published: February 2005

The transition between the magnetron discharge and the anode-obstructed hollow-cathode discharge modes has been theoretically explored using the Monte Carlo method. The calculated discharge voltage versus magnetic field (V-B) transition curves are in agreement with the experimentally measured bimodal V-B characteristics. The calculated discharge voltage in the obstructed hollow-cathode mode increases with increasing magnetic field up to a critical value, B
c. Above this critical value the voltage required to sustain a discharge is dramatically lower and invariant to further increases in B. The latter behavior is characteristic of the well-known magnetron discharge mode. The B-field-induced variation of the sustaining voltage is judged to arise from a corresponding variation of the electron temperature of the plasma with applied magnetic field.
Applications of Quasi-Steady Magneto-Plasma-Dynamic Arcjets to Ceramic Coatings
Authors: Tahara Hirokazu , Abe Tomoyuki , Tsubaki Toshiyuki , Kagaya Yoichi , Tsubakishita Yasuji , Yoshikawa Takao , Kuwata Masayasu , Ueda Yasutoshi
Published: February 2005

For applications of quasi-steady magneto-plasma-dynamic (MPD) arcjets to material processing, an MPD arcjet with a cathode covered with ceramic materials was developed. In 100-shot operations at 5-10 kA, the ablation rates of the ceramic covers ranged from 2.5 to 5.0 mg/shot. The front velocities of ablated Al atoms inferred with a streak camera were much higher than velocities of 200-500 m/s for conventional plasma torches for material processing. This is effective for deposition of rigid films adhering strongly to substrate surfaces. The SEM photographs showed that a dense uniform film was deposited near the center of the substrate. From the XPS spectra, the peak area ratio of Ti/Al for the coating film almost equaled that for the cross section, and the valence numbers of Al and Ti did not change.
Fast Photothermal Relaxation Processes in Metals and Semiconductors Studied Using Transient Reflecting Gratings
Authors: Nishimura Hiroyuki , Akira Harata Akira Harata , Tsuguo Sawada Tsuguo Sawada
Published: February 2005

Dynamic processes forming the transient reflecting gratings are experimentally investigated in the picosecond time regime for both metals and semiconductors. The shapes of the initial parts of the grating signals were examined with respect to the pump and probe intensities, optical configurations of polarization directions and ion implantation doses. For metals, the rising part is influenced by the temperature grating independently of the corrugation grating due to surface acoustic waves. For silicon, the peak or shoulder at the initial part is attributed to the concentration grating of the photoexcited carriers, and it directly reflects the photothermal relaxation rate.
A Tip Approach System for a Scanning Tunneling Microscope Using an Inchworm
Authors: Kuroda Tatsuaki , Kuniyoshi Tanaka Kuniyoshi Tanaka , Miyoko O. Watanabe Miyoko O. Watanabe
Published: February 2005

We have developed an approach system for a scanning tunneling microscope, which provides approaches without tip crashing and with high immunity from vibrations. A commercial inchworm has been employed in this system and a controller has been developed to drive both the inchworm and the Z section of the piezoelectric scanner in such a manner as to avoid tip crashing caused by large glitches of the inchworm.
Read Laser Power Effects in Magneto-Optic Data Recording
Authors: H. Birecki H. Birecki
Published: February 2005

Nonlinear effects of laser power on readout signals from magnetooptic media are discussed. Impact on pulse width modulation recording is evaluated.
Recording and Erasing Characteristics at a Wavelength of 680 nm for a Phase-Change Disk Designed for 830 nm Wavelength
Authors: Inoue Kazuo , Ohta Takeo , Ishida Takashi , Gotoh Yoshikazu , Satoh Isao
Published: February 2005

A phase-change optical disk designed for use at 830 nm wavelength was examined for differences in recording and erasing characteristics at wavelengths of 830 nm and 680 nm. The saturated carrier-to-noise ratio (C/N) was more than 50 dB. The saturated erasability was near 30 dB. The laser spot is smaller at shorter wavelength. However, there was no marked difference depending on the laser spot size. This indicates that phase-change optical disks have good exchangeability regardless of the laser wavelength.
Future Trends in Frequency-Selective Optical Memories
Authors: Ao Rong , Lothar Kümmerl Lothar Kümmerl , Dietrich Haarer Dietrich Haarer
Published: February 2005

Several recent advances are reported in a study of a possible technical implementation of frequency-selective optical memories. After taking into account some engineering considerations, such memories can be constructed which have the potential of being operated at room temperature, with a gain of a factor of at least 10, most likely in both storage density and access rate, as compared to conventional optical memories.
Crosstalk Cancellation Using Differential Wax-Wane Focus Servo Technique
Authors: Mark S. Wang Mark S. Wang , Tom D. Milster Tom D. Milster
Published: February 2005

We present studies of crosstalk cancellation using the differential wax-wane focus servo technique. A scalar diffraction model is employed to accurately predict its performance. The measured wavefront is implemented in the diffraction model, and excellent agreement between experimental and modeling results is achieved. With measured system aberration, the tracking crosstalk is reduced from 0.7 µm in a single channel to less than 0.1 µm in the optimized differential channel. Comparisons to the astigmatic and pupil obscuration focus error detection techniques are given. Without any aberration, the differential wax-wane technique has a tracking crosstalk amplitude of 0.04 µm compared to about 0.25 µm in other techniques.
Optimum Reflectivity Design of Laser Diode Facets and Recording Medium for an Integrated Flying Optical Head
Authors: Hiroo Ukita Hiroo Ukita , Yoshitada Katagiri Yoshitada Katagiri
Published: February 2005

A reflectivity design of an integrated optical head is presented based on basic design quantities such as laser diode efficiency, write-erase power margin, phase-change medium sensitivity, and permissible read power. We obtain a reflectivity of R
1\fallingdotseq0.7 for the laser diode facet that faces the photodetector, R
2=0.01 for the same diode facet that faces the medium, 0.21≥R
3

h
≥0.14 for the medium, and a reflectivity difference between the two medium reflectivity states of R
3

h
-R
3

l
\fallingdotseq0.05.
High-Density Recording Characteristics of a 90 mm Phase-Change Optical Disk
Authors: Fujimoto Sadanari , Ikeda Ken-ichi , Taguchi Toyoki , Hasegawa Hiroshi , Kobori Hiromichi , Satoh Hiroharu , Sugaya Toshihiro , Kobayashi Tadashi , Suzuki Katsumi
Published: February 2005

A fairly reliable capacity of 300 Mbytes has been achieved on a single side of a 90 mm high-density phase-change optical disk, using a 0.6-mm-thick disk and an optical head which had a 690 nm laser diode and a 0.6 numerical aperture objective lens. The carrier-to-noise ratio (CNR), erasability, and the bit error rate (BER) of the optical disk were investigated. It has been confirmed that these parameters have a wide laser power tolerance for most inner and outer tracks.
Read Channel and Format for High-Density Magneto-Optical Disk System
Authors: Maeda Takeshi , Tsuchinaga Hiroyuki , Ide Hiroshi , Saito Atsushi , Toda Tsuyoshi , Kugiya Fumio , Ojima Masahiro , Mita Seiichi , Shigematsu Kazuo
Published: February 2005

Read/write technologies for the second-generation magneto-optical disk are developed. A large capacity of 1 GB on a 130-mm-diameter disk and high transfer rate of 2∼4 MB/s are attained by mark length recording and the zoned constant angular velocity (zoned CAV) method. Read technologies such as slice level adjustment in the direct slice detection method, the independent edge detection and resync patterns for DC free are combined with the (1-7) run-length limited (RLL) code to provide sufficient edge jitter margin of over 60% of the detection window.
High-Density Pulse Width Modulation Recording and Rewritable Capability in GeSbTe Phase-Change System Using Visible Laser Beam at Low Linear Velocity
Authors: Uchino Ken-ichi , Takada Ken-ichi , Ohno Takashi , Hidemi Yoshida Hidemi Yoshida , Yoshimitsu KObayashi Yoshimitsu KObayashi
Published: February 2005

Write and erase characteristics at low linear velocity in GeSbTe phase-change optical disks have been studied using 488 nm and 680 nm visible lasers. Good characteristics, which are carrier-to-noise ratio (CNR) of more than 50 dB and erasability of more than 25 dB, were obtained by optimizing the composition of GeSbTe and the layer structure. However, smaller erase power margin has been observed in comparison with the case of using a 780 nm laser. From transmission electron microscope (TEM) observation and numerical simulation, it is explained that these phenomena are mainly due to the difference in the temperature profile arising from the beam profile. For pulth width modulation (PWM) recording using a 680 nm laser, the resolution has been improved by 25% in comparison with the case of a 780 nm laser. Furthermore, a clear eye pattern of the eight-to-fourteen modulation (EFM) signal was observed at the 3 T mark length of 0.65 µm. Crosstalk of less than -26 dB was obtained even at 1.0 µm track pitch. In the overwrite cycle test using a 680 nm laser, no degradation of CNR up to 10000 cycles was observed.
Model-Following Digital Servo Using Multirate Sampling for an Optical Disk Drive
Authors: Tetsuo Semba Tetsuo Semba
Published: February 2005

In order to achieve faster seeks, a simple feedback method using classical control needs higher servo bandwidth to reduce the steady state tracking error and to maintain the stability of the objective lens positioning system. In a multi-input multi-output model-following servo controller, however, the tracking error and the instability of the objective lens positioning does not increase even when the faster seek is performed with the same actuators. Both simulation and experimental results show that the disturbances and the model mismatching are well reduced by the four feedback loops in the servo bandwidth. Although such multiple feedback loops makes the controller more complicated, a multi-rate sampling technique helps to decrease the load of the digital-signal-processing task without sacrificing the performance.
Multi-Beam Read-Verifying Optical Head for Parallel Recording
Authors: Watabe Akinori , Tanabe Takaya , Setsuko Murata Setsuko Murata , Kikuji Katoh Kikuji Katoh
Published: February 2005

A five-beam read-only optical head using a holographic beam splitter has been developed for instantaneous read-verification of parallel data recording. The holographic grating made of photo-resist film splits a 680-nm laser beam into five diffracted beams and an interval angle of 4 mrad. The average diffraction efficiency of the beams is about 13% and their spot diameters are 1.05±0.03 µm within a 70-µm image circle. A newly designed objective lens system composed of an aspherical lens and a chromatic lens can compensate 680 nm to 780 nm of chromatic aberration of wavelength to less than 0.4 µm. The carrier to noise (C/N) ratio of a 1.53-µm-pitch voltage-controlled frequency oscillation (VFO) signal is 49 dB, which is sufficient for magneto optical (MO) disk data retrieval.
Direct Overwriting Using Magnetooptical Trilayer Medium and One Magnet
Authors: Nakayama Junichiro , Mieda Michinobu , Katayama Hiroyuki , Takashi Akira , Kenji Ohta Kenji Ohta , Toshio Ishikawa Toshio Ishikawa
Published: February 2005

The magnetooptical trilayer medium DyFeCo/GdFeCo/GdDyFeCo which is overwritable by light intensity modulation using a single permanent magnet has been developed. The carrier-to-noise-ratio (CNR) of the medium was 46 dB and the erasability was -37 dB when a 0.65-µm-mark-length signal was written over a 1.0-µm-mark-length signal.