bluuebunny/crossref_metadata_2025 huggingface dataset:
An Optical Study of Interdiffusion in Strained InP-Based Heterostructures
Authors: Hamoudi Ali , Ougazzaden Abdallah , Krauz Philippe , Rao Krishna , Juhel Marc , Huguette Thibierge Huguette Thibierge
Published: October 2002

The interdiffusion behavior of In1-
x

Ga

x

As1-
y

P

y

/In1-
x

′
Ga

x

′
As1-
y

′
P

y

′
multiple quantum well heterostructures with varied built-in strain and layer thicknesses, has been investigated by monitoring their photoluminescence (PL) properties. All samples annealed at 850° C, have consistently exhibited a blueshift of the heavy hole exciton line as a result of atoms interdiffusion across the heterointerfaces. A quantitative analysis of their PL spectra permitted to deduce the following important characteristics of the interdiffusion process: (i) From the data on a nearly strain-compensated structure with constant P/As ratio and In-rich wells, studied here for the first time, we show that the blueshift of the excitonic line is consequent of group III atoms interdiffusion alone, like in GaAs/GaAlAs system, and the In-Ga interdiffusion can be described with a diffusion coefficient D
In-Ga≈4.72×10-16 cm2/s; (ii) In the case of lattice matched and compressively-strained structures, a simultaneous interdiffusion on group III and V sublattices has been assumed to yield an effective interdiffusion coefficient ranging from 3.83 to 5.51×10-16 cm2/s.
Behavior of Hydrogen at Charged Dislocation in NaCl
Authors: Tateno Hiroto , Nagasawa Mituru , Fukai Akira , Iwashita Youichirou
Published: October 2002

To study the structure of an edge dislocation core in an ionic crystal, we measured the amplitude dependence of internal friction by the automated Marx's composite oscillator method and the vibrational current caused by charged dislocations in a hydrogen-absorbed NaCl single crystal. The change of the sign of dislocation charge at the strain amplitude of 10-6 disappeared with absorption of hydrogen, while it was preserved using helium. These findings suggest that hydrogen exists as a positive ion in the dislocation core.
Transparent Conducting Boron-Doped Zinc Oxide Films Deposited by DC-Magnetron Sputtering in B2H6-Ar Mixtures
Authors: Nakada Tokio , Ohkubo Yukiyasu , Murakami Naoki , Akio Kunioka Akio Kunioka
Published: October 2002

Transparent conducting ZnO:B films for solar cells were produced by DC magnetron sputtering in B2H6-Ar mixtures. Low-resistivity textured films could be obtained at relatively low substrate temperatures of 150-200° C. The resistivity, electron mobility and carrier concentration were 4×10-4 Ω cm, 60 cm2/ Vs and 2×1020 cm-3, respectively. The 2-µ m-thick films showed a sheet resistance of 2 Ω/ sq and optical transmission of greater than 85% at wavelengths of 0.6-1.0 µ m. These films exhibited higher optical transmission in the near infrared region than ZnO:Al films with the same resistivity because of high electron mobility. No degradation of resistivity and optical transmission was observed after exposure at 85° C and 95%RH for 5 h.
Thermal and Ion-Induced Reactions on a Chlorine-Adsorbed GaAs(100) Surface Studied by Metastable-Atom De-excitation Electron Spectroscopy
Authors: Itabashi Naoshi , Ono Tetsuo , Ochiai Isao , Yamamoto Seiji , Kozo Mochiji Kozo Mochiji
Published: October 2002

Thermal and ion-induced reactions on a chlorine (Cl)-adsorbed GaAs(100) surface have been studied by metastable-atom de-excitation spectroscopy. The results show that Cl is bound to one site of a top-layer Ga atom, forming mono-chloride (GaCl), by exposing the surface to molecular chlorine ( Cl2) of less than 228 Langmuir (L) at 143 K. As the Cl2exposure dosage is further increased, one more Cl atom is bound to another site of the Ga atom of GaCl, forming di-chloride ( GaCl2). GaCl2is removed at a lower temperature than GaCl when heating the sample. On the other hand, both the chlorides are removed simultaneously when irradiated with Ar+ions at a kinetic energy of 500 eV. The difference between the two types of reactions is discussed in terms of desorption behaviors of the two chlorides.
Anisotropic Diffusion of Si Adsorbates on a Si(001) Surface
Authors: Doi Takahisa , Ichikawa Masakazu
Published: October 2002

The behavior of Si adsorbates evaporated on a Si(001) surface is studied by tracing their diffusion caused by radiative heating. A reflection electron microscope (REM) is used to observe denuded zones that are created at the terrace edge and grow with heating time. Diffusion constants of Si adsorbates are determined using the denuded zone widths on a Si(001) surface. The diffusion constants on the 2×1 terrace have directions parallel to a surface dimer connected to two nearest-neighbor atoms on the surface. Similarly, the diffusion constants on the 1×2 terrace have directions perpendicular to the dimer. Diffusion constants in the opposite directions are the same on both structures, so the isotropic diffusions in the opposite directions are observed on a Si(001) surface: u
D
2×1= d
D
2×1=D
2×1 and u
D
1×2= d
D
1×2=D
1×2. The index u indicates diffusion from the down-side to the up-side and d vice versa. However, a difference in diffusion constants between D
2×1 and D
1×2 is observed. It is concluded that D
1×2 is about 5-6 times as large as D
2×1 on the Si(001) surface.
Highly (100)-Oriented Thin Films of Sol-Gel Derived Pb[(Mg1/3Nb2/3)0.675Ti0.325]O3 Prepared on Textured LaNiO3 Electrode
Authors: Shyu Ming-Jyh , Hong Tian-Jue , Yang Tian-Juh , Tai-Bor Wu Tai-Bor Wu
Published: October 2002

Highly (100)-oriented thin films of Pb[(Mg1/3Nb2/3)0.675Ti0.325]O3 (PMNT) were fabricated by sol-gel method on (100)-textured LaNiO3 (LNO) metallic oxide electrode. The textured LaNiO3 layer was prepared by rf magnetron sputtering at 250° C on Si, SiO2/Si or Pt/Ti/SiO2/Si substrates. A well orientation match was found between the PMNT and LNO layers. The annealing temperature for obtaining a pure perovskite PMNT film was reduced for about 50° C by using the LNO-coated substrates comparing to that without. A well-developed grain structure was also formed for the former. Satisfactory dielectric and ferroelectric characteristics were observed from the (100)-oriented PMNT thin films prepared at 700° C on LNO, as compared to the randomly oriented one on Pt electrode. However, an increase of annealing temperature would cause a more serious out-diffusion of LNO which gradually deteriorated the property of PMNT films deposited on LNO.
Oxygen Adsorption Study on Rh(100) Surface by Electron-Stimulated Desorption Spectroscopy
Authors: Ueda Kazuyuki , Takano Akemi , Tanaka Ken-ichi
Published: October 2002

Adsorption states of oxygen on a Rh (100) surface have been studied by electron-stimulated desorption (ESD) spectroscopy. The ESD measurement was performed time sequentially during exposure of the surface to oxygen and heating of the surface. At least three adsorption states were distinguished for oxygen by ESD.
One state gave no ESD ions at low temperature. The other two states gave ESD oxygen ions of different kinetic energies. The yield of ESD oxygen ions changed drastically at 350 and 500 K.
Decrease of oxygen on the surface was clearly observed above 600 K in hydrogen gas.
Theoretical Analysis of Gas Breakdown Characteristic through a Narrow Discharge Tube
Authors: Ling Yi-Ming , Wan Zhu Wan Zhu
Published: October 2002

The breakdown characteristic through a narrow discharge tube, such as a plasma tube of gas lasers, is different from that between parallel electrodes given by Paschen's law. The physical modelling of the gas breakdown process in a narrow tube is established based on Townsend discharge theory. This kind of breakdown process can be divided into two stages. The first one is the changing process of the guiding electrical field of wall charges formed by the deposition of charged particles from the avalanche, and the second one is the electron avalanche process through the whole discharge tube. From the physical modelling mentioned above, the parameters just before breakdown and the breakdown characteristic through a narrow discharge tube will be analysed theoretically. It can be seen that the breakdown potential is dependent not only on the pressure, the tube length, and the species of gas but also on the diameter of the discharge tube. Finally, the calculated results are compared with the experimental results and the errors are discussed.
Mercury-Spectrum Measurement with a Handmade Negative-Film Diffraction Grating
Authors: Mikio Mimura Mikio Mimura , Masahiro Miyagi Masahiro Miyagi , Hiroshi Okada Hiroshi Okada , Takehiro Okumichi Takehiro Okumichi
Published: October 2002

A negative-film diffraction grating was made by taking a photograph of a pattern drawn using an XY-plotter connected to a personal computer. To check the performance of the negative-film grating, a simple monochromator system was built with it. Five spectrum lines in the light from a mercury lamp were observed with the monochromator system.
A Simple Electron Trap with Perpendicular Injection
Authors: Akira Tsushima Akira Tsushima
Published: October 2002

A simple electron trap with a uniform axial magnetic field was designed and constructed for stationary operation. Electrons from a small filament placed near the outer wall were continuously carried inside between electrostatic potential barriers by a positive bias to a center conductor.
A New Concept of X-Ray Microscopes with a Coded Aperture Imaging Mask
Authors: Matsuoka Masaru , Yoshiki Kohmura Yoshiki Kohmura
Published: October 2002

We propose a new concept of X-ray microscopes with a coded aperture imaging mask. This makes use of X-ray images through many pinholes, but requires neither reflection nor diffraction properties of X-rays. When an object is irradiated by a diffuse X-ray source, many objects images geometrically enlarged through coded holes can be deconvoluted to one image. The precision of the image is dependent on the size of each pinhole. The material and thickness of the coded mask constrain the energy of available X-rays for the present X-ray microscope.
Optical Measurement of Ultrasonic Nanometer Motion of Rough Surface by Two-Wave Mixing in Bi12SiO20
Authors: Honda Tokuyuki , Yamashita Toshihisa , Hirokazu Matsumoto Hirokazu Matsumoto
Published: October 2002

Motion of a rough surface of an ultrasonic transducer was measured using an optical interferometer based on photorefractive two-wave mixing in a Bi12SiO20 crystal. The displacement equivalent to noise was 0.10 nm in a band-width of 8.0 MHz. The low-frequency noise was automatically compensated by an adaptive property of the photorefractive grating without an electric feedback loop.
Temperature Rise and Heat Flux Induced by Laser Beam with Double-Gaussian Intensity Distribution
Authors: Yong-Feng Lu Yong-Feng Lu , Yoshinobu Aoyagi Yoshinobu Aoyagi
Published: October 2002

The temperature rise and heat flux induced by a CW (continuous wave) double-Gaussian-distributed laser beam have been investigated numerically in a semi-infinite substrate. The temperature-dependent thermal conductivity and surface reflectivity of the substrate material are incorporated in the calculation model. The results show that the double-Gaussian-distributed laser beam can provide a high temperature rise in a narrower region with low local heat flux, which implies low thermal stress at the irradiated area. One can change the temperature profile by manipulating the radiuses and powers of two portions in the double-Gaussian-distributed laser beam. The power of the individual beams in the double Gaussian can be used to control the resulting temperature and heat fluxes during processing of the electronic materials.
Electrochemomechanical Deformation of Polyaniline Films
Authors: Wataru Takashima Wataru Takashima , Masanori Fukui Masanori Fukui , Masamitsu Kaneko Masamitsu Kaneko , Keiichi Kaneto Keiichi Kaneto
Published: October 2002

The deformation of unstretched and stretched polyaniline (PANI) films by the electrochemical cycle has been studied. An anisotropic deformation is observed. The largest expansion and contraction upon oxidation and reduction, respectively, are observed for the direction perpendicular to the draw axis. The deformation parallel to the draw axis is the smallest for oxidation leucoemeraldine salt to emeraldine salt (ES), and shows even slight contraction upon oxidation from ES to pernigraniline salt. The expansion ratio Δℓ/ ℓ0, where Δℓ is the increment of expansion and ℓ0 is the original length, is found to be proportional to the degree of oxidation. In the unstretched film, Δℓ/ ℓ0 is about -2% at 20% reduction from the ES state. The results are discussed in terms of intercalation of dopant ions per repeating unit between chains and the conformational change of chains.
Fabrication of an Organic p-n Homojunction Diode Using Electrochemically Cation- and Photochemically Anion-Doped Polymer
Authors: Yamashita Kazuo , Kunugi Yoshihito , Harima Yutaka , Al-Nakib Chowdhury Al-Nakib Chowdhury
Published: October 2002

An organic p-n homojunction has been successfully constructed in a single strip of poly(3-methylthiophene) (PMT) film by electrochemical cation doping on one side and photosensitized anion doping on the other side. The rectifying effect observed with the Al/(cation:anion)-doped PMT/Au cell provides evidence for the formation of a p-n homojunction in the PMT film since both Al/cation-doped PMT/Al and Au/anion-doped PMT/Au cells exhibit ohmic behavior. The formation of p-n homojunction can be inferred from measured work functions of the electrochemically cation-doped PMT, photochemically anion-doped PMT, Al and Au films. The p-n homojunction cell yields a short-circuit photocurrent of 0.16 µ A· cm-2, an open-circuit photovoltage of 0.23 V and a fill factor of 0.30. These voltaic and photovoltaic properties are found to be superior to those of the polymer diode based on a p-n junction made by pressure contact of the p-doped PMT film with the n-doped PMT film.
Fermi Level Shift in Photoconductive Organic Pigment Films Measured by Kelvin Vibrating Capacitor Method
Authors: Hiramoto Masahiro , Ihara Kiyoaki , Masaaki Yokoyama Masaaki Yokoyama
Published: October 2002

Fermi level shift in n-type perylene pigment film was measured by the Kelvin vibrating capacitor method. Purification of pigment by reactive sublimation under methylamine atmosphere caused negative shift of the Fermi level due to the effective removal of unknown but specific impurity acting as an acceptor. On the other hand, bromine doping of pigment film caused marked positive shift of Fermi level to near the valence band, resulting in reversal of the photocurrent flow arising from the Schottky junction with Au. This is a clear demonstration of the control of conduction type from n-type to p-type, which was observed for the first time in pigment-based organic semiconductors. This result enabled construction of an organic homojunction composed of p- and n-type perylene pigment films.
Anomalous Transition in Charge Transport Behavior of Polysilane
Authors: Majima Yutaka , Nishizawa Hideyuki , Hiraoka Toshiro , Nakano Yoshihiko , Shuzi Hayase Shuzi Hayase
Published: October 2002

Anomalous transition of the dispersion parameter α was observed for the first time in poly( n-butyl- n-pentylsilane) (PBPS). Time-of-flight photocurrent (I) of PBPS was measured. The photocurrent transient was dispersive: I∝t
-(1-α). The dispersion parameter α dropped around the glass transition temperature T
g with increasing temperature, and became temperature-independent above T
g. The mobility was described within the framework of a formalism based on disorder due to Bässler and coworkers. Both the diagonal disorder parameter σ, the variance of the density of states, and the off-diagonal disorder parameter Σ, the degree of positional disorder, decreased around T
g. Nevertheless the ratio of the off-diagonal disorder parameter Σ to the diagonal disorder parameter σ was found to increase above the transition temperature. This anomalous transition is rationalized by the assumption that the off-diagonal disorder dominates charge transport in PBPS above T
g.
Large Molecule Epitaxy on Single Crystal Metals, Insulators and Single Crystal and MBE-Grown Layered Semiconductors
Authors: Schuerlein Thomas J. , Schmidt Albert , Lee Paul A. , Nebesny Kenneth W. , Armstrong Neal R.
Published: October 2002

We review the packing structures for a series of aromatic hydrocarbons, deposited by vacuum deposition methods as ordered monolayers→→multilayers, on a variety of metal, semiconductor and insulator surfaces. New results are presented for the adsorption of monolayers of perylenes, phthalocyanines, coronene, and pentacenes on the Cu(100) surface, along with the implications of these studies for the formation of ordered multilayers of these molecular systems. Aromatic molecules without heteroatoms appear to pack in a flat-lying motif, and exhibit approximately hexagonal close packing, even on a substrate with four-fold symmetry such as Cu(100). In general, aromatic systems whose bulk structures lend themselves to layer-by-layer growth during vacuum deposition appear to be the best candidates for ordered multilayer growth.
Two-Dimensional Crystal Growth Process of n-Alkane Molecules Observed Using Scanning Tunneling Microscope
Authors: Ishida Kenji , Taki Seiji , Okabe Hirotaka , Kazumi Matsushige Kazumi Matsushige
Published: October 2002

The growth stages of two-dimensional crystal in an n-alkane molecule (n- C33 H68) were investigated using a scanning tunneling microscope (STM) for the samples vacuum-deposited on a graphite substrate. The STM image revealed that the nuclei with a diameter of about 2 nm, which is coincident with the value estimated for the molecules with random conformation, arrange hexagonally in the initial growth stage. It is suggested that further growth was promoted by the increase in the density of the molecules adsorbed on the substrate as well as by their thermal and diffusible motions. Moreover, the mutual relationship between n-alkane molecules and the graphite lattice, namely an epitaxial effect, is discussed with respected to the atomic-resolution STM images.
Preparation and Characterization of 3,4,9,10-Perylenetetracarboxylic dianhydride (PTCDA) Films Deposited by Organic Molecular Beam Deposition Method
Authors: Fuchigami Hiroyuki , Tanimura Sachiko , Uehara Yasushi , Kurata Tetsuyuki , Sei Tsunoda Sei Tsunoda
Published: October 2002

The optical and structural properties for 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) films deposited on Au-coated substrates at the various growth temperatures by the organic molecular beam deposition (OMBD) method have been studied. The planar PTCDA molecules were oriented almost parallel to the substrate surface in the films deposited at the growth temperature of -160° C. Orientational disorder of the molecular planes occurred especially in the films grown at higher substrate temperatures. These films had basically large anisotropy of refractive indices which were evaluated by the prism attenuated total-reflection (ATR) method. The anisotropy of indices decreased for the film grown at the substrate temperature of 100° C. The optical anisotropy has been understood in terms of the molecular orientation.
Organic-Inorganic Hetero Nanosystems as an Approach to Molecular Optoelectronics
Authors: Jun Takada Jun Takada
Published: October 2002

A concept of organic-inorganic hetero nanosystems has been proposed as an approach to molecular optoelectronics. The direct use of the optical function of an individual organic molecule in a solid state is anticipated through the electronic function of inorganic materials. Basic information on the formation of hetero nanostructures by vacuum thin film technology was discussed. Various types of organic-inorganic hetero nanostructures consisting of copperphthalocyanine (CuPc) molecular crystals and metal oxides of TiO
x
and SiO2 were fabricated by evaporation and reactive evaporation techniques. Cross sectional transmission electron microscopy (TEM) directly revealed that the thickness of the mixing layer at the ceramics interface on a CuPc molecular crystal is at most a monolayer of CuPc in superlattice structures. The formation of nanoboxes of CuPc molecular crystal in a ceramic matrix which had been fabricated using the multilayer technique, was confirmed by observations of in-plane TEM and atomic force microscopy. Optoelectronic functions in organic-inorganic hetero nanosystems were discussed from the viewpoints of carrier generation at the interface, size effects, and molecular orientation.
Preparation of Large Single Crystal Thin Film of Polydiacetylene by Graphoepitaxy
Authors: Hattori Yasuhiro , Kubata Michiru , Uemiya Takafumi , Gotaro Tanaka Gotaro Tanaka
Published: October 2002

The crystal growth of a diacetylene monomer was investigated by graphoepitaxy, an orientation-controlled crystal growth using a substrate with an artificial surface pattern. The direction of crystal growth was controlled by grooves prepared on a part of a fused-silica substrate surface and single crystal growth followed it on a non-grooved area next to the grooves. A large single crystal thin film with the domain size of approximately 2×2 mm was finally obtained. The thin film could be polymerized by UV light irradiation without any morphological change. The obtained polydiacetylene thin film was large enough to apply in an optical waveguide for nonlinear optical devices.
Phospholipid and Protein Monolayers
Authors: Möhwald Helmuth , Baltes Hubert , Schwendler Michael , Helm Christiane A. , Brezesinski Gerald , Haas Heinrich
Published: October 2002

We report on X-ray reflectivity and diffraction studies using monolayers of phospholipids and of the protein streptavidin specifically bound to monolayers. For phospholipids with the phosphocholine head group attached to the glycerol backbone via (flexible) ethylene oxide spacers, we demonstrate that the lateral interactions can be reduced by increasing of the spacer length. This is reflected in a reduction of the tilt angle of aliphatic tails. Diffraction of the protein layer can be observedin situ. The data reveal that positional order is merely short-ranged and that the structure can be changed reversibly via film compression and expansion.
Phospholipid Film Electrodeposition of Quartz Resonator and Its Application to Odor Sensing
Authors: Hongyuan Xu Hongyuan Xu , Tatsuya Matsuda Tatsuya Matsuda , Takamichi Nakamoto Takamichi Nakamoto , Toyosaka Moriizumi Toyosaka Moriizumi
Published: October 2002

A new method for phospholipid film deposition has been developed. Anionic phospholipids such as phosphatidyl serine (PS) and phosphatidyl acid (PA) were deposited by an electrodeposition method onto one side of quartz-resonator platinum electrodes in an electrochemical cell, and the mass changes of these films were measured in situ by quartz crystal microbalance (QCM) technology. The QCMs with electrodeposition films were applicable to odor sensing both in gas phase and in liquid phase, whereas a conventional cast membrane was peeled off from the QCM surface and could not be used in liquid phase. Furthermore, the response of QCM with the electrodeposition film was much higher than that of QCM with a cast film in gas phase. The developed sensor has promising features in spite of its simple fabrication process.
Design of Intelligent Optical Sensors with Organized Bacteriorhodopsin Films
Authors: Tsutomu Miyasaka Tsutomu Miyasaka
Published: October 2002

Oriented purple membrane (PM) films comprised of the photosensitive retinal protein bacteriorhodopsin (bR) was immobilized in an electrochemical photocell by means of bioaffinity bonding with bispecific (BS) anitibodies that recognize bR.
Charge displacement photocurrent of significant efficiency was obtained from the homogeneously oriented PM film. Based on this technology, methods are described for the design of intelligent optoelectronic devices, which include image sensors for motion sensing, photoreceptor tips for visual prosthesis of human eyes, and environmental sensors for use in direction sensing and speed sensing.
Transient Photocurrent Based on Photoinduced Electron Transfer Processes in Flavin-Porphyrin Hetero Langmuir-Blodgett Monolayers
Authors: Akiyama Kouichi , Nishikawa Satoshi , Ueyama Satoshi , Satoru Isoda Satoru Isoda
Published: October 2002

Dynamic processes of photoinduced electron transfer in flavin-porphyrin hetero Langmuir-Blodgett monolayers, which are characterized both by the electronic properties of functional groups and by the structure of molecular organization, have been studied in terms of transient photocurrent properties. From an analysis of transient photocurrent with a kinetic model based on the organic quantum well structure, we can conclude that the photocarrier generation process is mainly due to charge separation from photoexcited flavin to porphyrin at the flavin-porphyrin molecular heterojunction, and that the charge shift in monolayers and charge transfer between monolayers and an electrode are controlled by applied electric field.
Measurable Range of Bulk Carrier Lifetime for a Thick Silicon Wafer by Induced Eddy Current Method
Authors: Maekawa Takao , Keisuke Fujiwara Keisuke Fujiwara
Published: October 2002

In contactless measurement for a wide range of bulk carrier lifetime τbwith a single wafer, it is preferable to use the thickest possible wafer since the maximum bulk lifetime is determined by the thickness of the wafer. For thick wafers with short bulk lifetime, the bulk lifetime must be determined after a reasonable time delay of photoconductive decay to avoid the effect of higher-order-mode recombination with shorter time constants. The appropriate range is examined in terms of the voltage signal during the photoconductive decay by computer simulations and experiments. It is shown that the measurable range is between 1/10 and 1/20 of the maximum voltage, i.e., τb=0.73-11 ms for p-type and τb=2.1-32 ms for n-type Si wafers with thickness 20 mm subject to non-monochromatic illumination of long duration.
A Novel Double-Pulse Excimer-Laser Crystallization Method of Silicon Thin-Films
Authors: Ryoichi Ishihara Ryoichi Ishihara , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

We propose a novel double-pulse excimer-laser crystallization method, where two laser light pulses successively irradiate the surface of thin silicon (Si) films. The first light pulse supplies thermal energy near the Si/substrate interface, and this energy reduces the heat removal rate in the melt-regrowth phase triggered by the second light pulse, resulting in large-grain growth of the Si film. The average grain size was enlarged up to 0.8 µm, i.e., more than 10 times larger than that obtained by the conventional method. Solidification characteristics were also investigated numerically.
Quantum Analysis of Hole Distribution in Multiple-Delta-Doped Diamond with a Deep Impurity Level
Authors: Yoshiharu Anda Yoshiharu Anda , Takuya Ariki Takuya Ariki , Takeshi Kobayashi Takeshi Kobayashi
Published: October 2002

Multiple-delta-doping (MDD) in synthetic diamond films is studied analytically from the quantum-mechanical point of view by solving Schroedinger's and Poisson's equations simultaneously and self-consistently. From the analysis, a series of wave functions and subbands are determined, and more accurate distribution of holes than from the classical-mechanical point of view is obtained. In MDD diamond films at 500 K, in spite of the deep impurity level, hole excitation efficiency rises to 4–5 times that of uniformly doped films. Moreover, 95% of holes are located in the nondoped layer where the mobility is high. These two beneficial features of MDD markedly improve the conductance as compared with that of uniformly doped diamond films.
Nondestructive Internal Observation of Metal-Oxide-Semiconductor LSI Chip Using Electron-Acoustic Microscopy
Authors: Mutsuo Kobayashi Mutsuo Kobayashi
Published: October 2002

Observation of a metal-oxide-semiconductor (MOS) LSI as a specimen was carried out by electron-acoustic microscopy (EAM) under various operating conditions of acceleration voltage (HV) as a parameter. The results are as follows. (1) The adjustment of the irradiation power of the electron beam should make it possible to achieve nondestructive internal observation of MOS-LSI specimens with ceramic packages. (2) EAM imaging was observed as a flat plane at H
V=14 kV. (3) When H
V=19 kV, both contact holes (0.8×0.8 µ m2) and via holes (0.8×0.8 µ m2) could be observed. (4) When H
V=15, 17 and 19 kV, depths (t
x) of the specimen observable by EAM were estimated as about 0.8, 1.1 and 1.5 µ m, respectively. (5) t
x corresponded to approximately 40% of the electron range of an excited electron beam as a function of H
V.
Annealing Temperature Dependence of MgO Substrates on the Quality of YBa2Cu3Ox Films Prepared by Pulsed Laser Ablation
Authors: Minamikawa Toshiharu , Suzuki Tenmin , Yonezawa Yasuto , Segawa Kazuhito , Morimoto Akiharu , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

The effect of annealing on a MgO substrate was systematically investigated, varying the annealing temperature, for preparation of high-quality YBa2Cu3O

x

(YBCO) films by pulsed laser ablation. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were carried out for characterization of the MgO substrate, and X-ray diffraction (XRD) measurement, including θ-2θ scan, ω-scan (rocking curve) and φ-scan, and electrical measurement were carried out for characterization of YBCO films. Thermal annealing of MgO above 1000° C in oxygen ambient was found to give rise to a great improvement of the crystallinity and the reproducibility of crystal orientation of YBCO films, while it was also found to induce Ca segregation on the surface of MgO and reduce the oxygen content of YBCO films. Annealing below 1000° C causes no outstanding improvement in the crystal structure of YBCO.
On the MgO substrate annealed at 1200° C c-axis-oriented YBCO film was found to reproducibly show a full width at half-maximum (FWHM) of the rocking curve of 0.3°, an FWHM of (005) diffraction of 0.1°, an epitaxial relation without in-plane misorientation, a critical zero temperature of 89 K, and a critical current density of 106 A/cm2 at 77.4 K and zero field.
Flip-Chip Bonding Using Superconducting Solder Bump
Authors: Ogashiwa Toshinori , Nakagawa Hiroshi , Akimoto Hideyuki , Shigyo Hiroyuki , Takada Susumu
Published: October 2002

Flip-chip bonding using superconducting solder bumps consists of two technologies: acid-free thermosonic compression ball bonding and face-down bonding of the chip on the substrate by means of thermosonic compression at 373 K.
A superconducting test chip with 68 bumps formed on Nb/Pd film pads was bonded on a ceramic substrate. The maximum shear strength of a single solder bump for the Nb/Pd films was found to be 26.5 MPa, which was about 3 times higher than that obtained for Nb/Au film pads. The flip-chip module did not undergo catastrophic failures in either prototype design or material combination during 20 thermal cyclings between 4.2 K and 273 K.
Electrical check tests at 4.2 K before and after the thermal cyclings suggest that the present superconducting solder bump can be put into practical use for superconducting IC chip connection.
Effects of Matrix Impedance on the Properties of Polymer Dispersed Liquid Crystal Cells
Authors: Chang Shoou-Jinn , Chiao Sun
Published: October 2002

We report the effects of matrix impedance on the electrical and optical properties of polymer dispersed liquid crystal (PDLC) samples. It was found that the impedance of a PDLC sample is a function of the applied dc bias and the frequency of the superimposed ac perturbation signal. Using the Randles equivalent circuit to model the PDLC samples, we found that samples having a higher matrix impedance have a much longer electrical decay time constant although the charge-up times are similar for all samples. PDLC samples with a longer electrical decay time constant also show slower optical switching behavior.
Violet and Near-UV Light Emission from GaN/Al 0.08Ga 0.92N Injection Diode Grown on (0001) 6H-SiC Substrate by Low-Pressure Metal-Organic Vapor Phase Epitaxy
Authors: Yuichiro Kuga Yuichiro Kuga , Toshio Shirai Toshio Shirai , Makiko Haruyama Makiko Haruyama , Hideo Kawanishi Hideo Kawanishi , Yasuharu Suematsu Yasuharu Suematsu
Published: October 2002

GaN/Al0.08Ga0.92N double-heterostructure (DH) was grown on (0001)-oriented 6H-SiC substrate by low-pressure metal-organic vapor phase epitaxy (LP MO-VPE). The main peak wavelength at room temperature from GaN/Al0.08Ga0.92N DH injection diode was 420 nm which originated in the band-to-impurity transition in GaN. A weak peak at 360 nm was also observed.
Li Planar Doping of ZnSe by Molecular Beam Epitaxy
Authors: Matsumura Nobuo , Yamawaki Kenro , Ichikawa Susumu , Junji Saraie Junji Saraie
Published: October 2002

Li planar-doped ZnSe epilayers were grown by molecular beam epitaxy. The saturation of the acceptor doping level was revealed ( Na-Nd∼1×1017 cm-3). Exciton emissions bound to Zn vacancy were observed in the planar-doped epilayers, which suggests the escape of Li atoms from the planar-doped layers. Emission intensities of the exciton bound to Li acceptor were increased by the planar doping compared with those in homogeneously doped samples.
Crystallization of Lanthanum-Modified Lead Zirconate Titanate (PLZT) Using Coprecipitated Gels
Authors: Lee Yao-Jung , Yen Fu-Su , Wu Jong-Ping , Hsing-I Hsiang Hsing-I Hsiang
Published: October 2002

Powders of lanthanum-modified lead zirconate titanate (Pb0.91La0.09)(Zr0.65Ti0.35)0.98O3 (PLZT 9/65/35) were obtained by calcination of various precursors via chemical coprecipitation methods. The precursors included the coprecipitated gel with the stoichiometric PLZT composition, PbO (powdered chemical reagent)+LZT coprecipitated gel, and mixture of Pb, La, Zr, and Ti individually precipitated gels. Crystallization behaviors of these precursors were examined over the temperature range of 400°-900° C using X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential thermal analysis/thermal gravimetric analysis (DTA/TGA) techniques. For coprecipitated PLZT gels, perovskite PLZT accompanied by pyrochlore crystallized at 500° C; further heating promoted the development of PLZT, and single-phase PLZT was achieved at 700° C. For PbO+LZT coprecipitated gels, PLZT began to form at 550° C. The formation reaction was complete at 800° C and only a limited amount of pyrochlore intermediate was detected by XRD.
For the mixture of Pb, La, Zr, and Ti gels, PLZT crystallized at 900° C, litharge, massicot, PbTiO3 (PT), and PbZrO3 (PZ) were formed as the intermediate phase instead of pyrochlore.
Low-Temperature Growth and Measurement of Oxygen in Reactively Sputtered AlN Thin Films
Authors: Kumar Sunil , T. L. Tansley T. L. Tansley
Published: October 2002

Aluminium nitride (AlN) thin films have been grown on a variety of substrates using low-temperature radio frequency reactive sputtering of aluminium in pure nitrogen plasma. Quantitative analyses of the film composition, carried out using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS), suggest the resulting films to be near stoichiometric with high amounts of oxygen present in them. The high concentration of oxygen in our films is attributed to the voided microstructure as revealed by cross-sectional scanning electron microscopy.
Formation of Hot Atomic Hydrogen Beam for Surface Diffraction Experiments
Authors: Sakurai Yuhji , Kotaki Kohichi , Kinugawa Tohru , Tatsuo Arikawa Tatsuo Arikawa
Published: October 2002

An attempt to generate a monoenergetic hot atomic hydrogen (H) beam for surface diffraction experiments was performed with photo-dissociation of hydrogen iodine (HI) molecules at 266 nm. The velocity and angular distributions of recoiling H fragments generated via two laser photolysis channels corresponding to the parallel and perpendicular transitions were investigated by means of resonantly enhanced multi-photon ionization (REMPI)-Doppler spectroscopy with the aid of tunable coherent VUV light around the Lyman-α line. Monoenergetic H beams with the velocities of 1.12×104 m/s for parallel transition and 1.75×104 m/s for perpendicular transition, having a sufficiently narrow velocity spread for surface diffraction experiments, were obtained.
Plasma Production Using Energetic Meandering Electrons
Authors: Zensho Yoshida Zensho Yoshida , Taijiro Uchida Taijiro Uchida
Published: October 2002

When an electron is accelerated by an oscillating electric field in an inhomogeneous magnetic field which has a null point, it meanders along a chaotic orbit. The kinetic energy becomes larger than that of regular motion in an off-resonant homogeneous magnetic field. This effect explains the high efficiency of plasma production in the neutral line discharge (NLD).
Discharge Positive Column with Elliptical Cross Section
Authors: Masumi Sato Masumi Sato
Published: October 2002

Analytical solutions are given for plasma parameters in the positive column with elliptical cross section in the high-pressure Schottky limit. The plasma density profile is described by a product of even radial and periodic Mathieu functions which can be expanded in terms of even Bessel functions. The plasma balance equation is derived from the boundary condition of zero plasma density at the elliptical tube wall and the electron temperature is calculated as functions of tube size and gas pressure. The solution for the elliptical positive column is shown to be a generalization of the circular positive column theory.
Relationship between Dissolution Inhibitors and Dissolution Rate of Resist in Chemically Amplified Three-Component Positive Resist
Authors: Horibe Hideo , Kumada Teruhiko , Kubota Shigeru , Kimura Yoshika
Published: October 2002

For chemically amplified electron beam (EB) resist composed of partially tert-butoxycarbonyl (tBOC) protected poly(p- vinylphenol) (PVP), a dissolution inhibitor, and an acid generator, the effect of the dissolution inhibitors on the dissolution characteristics of resist are investigated. As dissolution inhibitors, hydroquinone protected by a tert-butoxycarbonyl group (B-HQ) and isophthalic acid protected by a tert-butyl group (B-IP) are used. Dissolution inhibitors (B-HQ and B-IP) become dissolution promoters (HQ and IP) after exposure. The dissolution rate of the resist consisting of B-IP was faster than that of B-HQ in the exposed area. pKa of IP is smaller than that of HQ, and the acidity of IP is higher than that of HQ. Therefore IP enhances the solubility of the matrix resin in the alkaline developer. A 0.14 µ m line and space pattern is fabricated at 17.5 µ C/cm2 using 50 keV EB in the resist consisting of B-IP.
Effect of Native Oxide upon Formation of Amorphous SiOx Layer at the Interface of Directly Bonded Silicon Wafers
Authors: Ishigami Shun-ichiro , Kondoh Hideyuki , Ryuta Jiro , Kawai Yukio , Hisashi Furuya Hisashi Furuya
Published: October 2002

We have investigated the interface of directly bonded Czochralski silicon wafers with various thicknesses of initially grown native oxide film using high-resolution transmission electron microscopy (HR-TEM). It was found that the volume of the amorphous SiO

x

layer formed at the bonded interface decreased as the native oxide film thickness decreased. The estimated total number of oxygen atoms in the amorphous layer from HR-TEM observation was in fairly good agreement with the total number of oxygen atoms in the native oxide film. It is concluded, therefore, that the initial stage of the formation of the amorphous SiO

x

layer is mainly governed by the initially grown native oxide.
Time Domain Interferometry in X-Ray Region Using Nuclear Resonant Scattering
Authors: Izumi Koichi , Yoda Yoshitaka , Ishikawa Tetsuya , Zhang Xiao-Wei , Ando Masami , Seishi Kikuta Seishi Kikuta
Published: October 2002

Two basic examples of the externally controllable interferometry in the time domain in the X-ray region, which was carried out by the combination of nuclear resonant scattering with an X-ray interferometer, are shown. Time distributions of the scattered photons were measured with (i) two scatterers with different hyperfine structures inserted in respective beam paths, and (ii) two scatterers of the same kind in each beam path, one of which is translated to produce the Doppler shift. Modification of the time beat was observed, which is expected from standard theory assuming that the field amplitudes are superposed in the time domain.
Control of the Intensity of Polarized Light for Entire Visible Light Region Using Composite Half-Wave Plate
Authors: Yoshida Mitsuo , Ryuichi Shintani Ryuichi Shintani
Published: October 2002

The half-wave plate has been used to control the intensity of linearly polarized light in experiments. However this plate can be applied only to monochromatic light, because of the dependence of the action of the half-wave plate on wavelength. A new composite half-wave plate can be designed for the entire visible light region using two phase plates. Satisfied condition of the composite half-wave plate using two phase plates is obtained on the Poincaré sphere.
Collapse of Quantized Conductance in a Mesoscopic Tomonaga-Luttinger Liquid
Authors: Masao Ogata Masao Ogata , Hidetoshi Fukuyama Hidetoshi Fukuyama
Published: October 2002

The quantized value of conductance in a quantum wire is discussed near the Mott transition. The way in which the quantized value collapses is also predicted as a function of temperature and length of the wire by taking account of both impurity scattering and mutual Coulomb interactions, i.e. the case of dirty Tomonaga-Luttinger liquid.
Quantum Coherent Phenomena in Bilayer Quantum Hall Systems
Authors: Zyun F. Ezawa Zyun F. Ezawa
Published: October 2002

On the basis of the composite electron picture, we analyze bilayer quantum Hall systems at the Landau level filling factor ν=1/m with m an odd integer. A composite electron is an electron bound to statistics flux. It is shown that various Josephson phenomena occur, but not for the Meissner effect. A physical picture of the commensurate-incommensurate phase transition in the magnetic order is described by analogy with the superconductor Josephson junction. Plasmon excitations are analyzed in each phase. The activation energy anomaly which was recently discovered experimentally is accounted for by the change of the plasmon excitations associated with this phase transition.
Path Integral Technique for Inter-Landau Level Tunneling
Authors: Stopa Michael , Yoshinobu Aoyagi Yoshinobu Aoyagi , Takuo Sugano Takuo Sugano
Published: October 2002

We write a coherent state Feynman path integral for tunneling between Landau levels by developing a continuum representation for the Landau level index and also by showing that a gradient expansion of a sufficiently smooth potential can be written in terms of creation and annihilation operators for the cyclotron motion. We restrict our consideration to only the lowest two Landau levels, n=0 and n=1. We employ a steepest descent method for determining the coupled equations of motion for the path of the guiding center drift coordinate R(τ) and the single Landau index continuous coordinate θ(τ) in a smooth but otherwise arbitrary 2D potential.
Current-Direction-Dependent Commensurate Oscillations in GaAs/AlGaAs Antidot Superlattice
Authors: Kazuhito Tsukagoshi Kazuhito Tsukagoshi , Masaru Haraguchi Masaru Haraguchi , Kenichi Oto Kenichi Oto , Sadao Takaoka Sadao Takaoka , Kazuo Murase Kazuo Murase , Kenji Gamo Kenji Gamo
Published: October 2002

To explore commensurate oscillations in antidot lattice, the dependence on the antidot array number (N) perpendicular to the current flow direction is studied. With decreasingN, the peaks of the oscillations become small. Even atN=1, the peaks do not vanish. The relationship between the oscillations and the current flow direction is investigated in rectangular antidot lattices which are rotated at five different angles (θ) with respect to the current flow direction. At θ=0°, the shorter side of the cell is perpendicular to the current flow direction. The main peak magnetic field of the oscillations is determined by the period of the shorter side of the cell. The peak height decreases with increasing θ and vanishes at θ=90°.
Formation of Silicon and Cobalt Silicide Nanoparticles in CaF 2
Authors: Masahiro Watanabe Masahiro Watanabe , Fumitaka Iizuka Fumitaka Iizuka , Masahiro Asada Masahiro Asada
Published: October 2002

We have demonstrated a method of forming silicon and cobalt silicide nanoparticles (<10 nm) in CaF2 grown on a Si(111) substrate using codeposition of Si, Co and CaF2. It is shown that the size and density of silicon and silicide particles can be controlled by the substrate temperature and the evaporation rate of CaF2 and Si. At a growth temperature of around 200°C and a flux ratio of Co:Si:CaF2 of about 1:2:2, an average diameter of 7 nm was obtained.
Nano-Optical Studies of Individual Nanostructures
Authors: Lars Samuelson Lars Samuelson , Niclas Carlsson Niclas Carlsson , Pedro Castrillo Pedro Castrillo , Anders Gustafsson Anders Gustafsson , Dan Hessman Dan Hessman , Joakim Lindahl Joakim Lindahl , Lars Montelius Lars Montelius , Anders Petersson Anders Petersson , Mats-Erik Pistol Mats-Erik Pistol , Werner Seifert Werner Seifert
Published: October 2002

Optical techniques play a significant role in studies of nano-structures. The electronic structures of quantum dots, for example, vary with the geometric sizes in an ensemble, resulting in broadened spectral lines. Recently, different forms of local spectroscopic techniques have been applied to investigate such inhomogeneously broadened emission lines. In this paper we report on three methods for local spectroscopy: cathodo-luminescence, luminescence induced by a scanning tunnel microscope and microphotoluminescence. Each of these techniques is shown to have the capacity to investigate single quantum dots, with linewidths in the range 40–1000 µeV. Besides demonstrating the possibility of imaging and spectroscopically studing individual dots, we also demonstrate the possibility of investigating single impurity atoms, in imaging as well as in emission spectroscopy modes.
Evaluation of Hot Electron Coherent Length Using Well Width Dependence of the Resonance Characteristics of Resonant Tunneling Diodes
Authors: Young Cheul Kang Young Cheul Kang , Michihiko Suhara Michihiko Suhara , Kazuhito Furuya Kazuhito Furuya , Ryuya Koizumi Ryuya Koizumi
Published: October 2002

In order to evaluate the hot electron coherent length from the resonance characteristics of resonant tunneling diodes (RTDs), the dependence of the resonant level width on various broadening mechanisms is investigated. From the dependence of the resonant level width on the well width, it is shown that the individual contributions to resonant level broadening (phase relaxation and well width variation) can be analyzed separately. The resonant level widths were measured experimentally and compared with theoretical results, and the coherent length was evaluated to range from 80 to 120 nm at 4.2 K in GaInAs at hot electron energies of 50 to 100 meV.