bluuebunny/crossref_metadata_2025 huggingface dataset:
Auger Electron Spectroscopy Quantitative Analysis of Interfacial SiO2 Layer
Authors: Soh Ju-Won , Won-Jong Lee Won-Jong Lee
Published: October 2002

Auger electron spectroscopy (AES) depth profiles of the interfacial SiO2 and SiO2/Si3N4 layers formed between Ta2O5 film and Si substrate were quantitatively analyzed and the accuracy of the AES analysis was confirmed using a high-resolution cross-sectional transmission electron microscopy (TEM). It has been shown that the AES depth profiling technique is a convenient method for quantitative analysis of the ultrathin interfacial layers, enabling discrimination of the amorphous layers, SiO2/Si3N4.
Development of Polymers in O2Plasmas: Temperature Effects and Transition to Imperfect Anisotropy
Authors: Pons Michel , Pelletier Jacques , Joubert Olivier , Patrick Paniez Patrick Paniez
Published: October 2002

A parametric study of the etching of a photoresist is performed in an O2microwave multipolar plasma using a trilevel resist system. The etch rate and the anisotropy evolutions are reported as a function of ion energy, oxygen pressure and substrate temperature, which are important parameters likely to affect anisotropy. A transition from isotropic to imperfect anisotropic etching occurs when the ion energy is increased. However, residual lateral etching always subsists at room temperature, even at the lowest oxygen concentrations. Above room temperature, in contrast with ion-induced etching, the spontaneous lateral etch rate increases with temperature, suggesting a thermally activated reaction process. The phenomena are interpreted in terms of oxygen coverage on the polymer surface, with a threshold coverage being required for purely spontaneous chemical etching to occur, and on the assumption of a photon-induced desorption of volatile products proportional to the oxygen coverage.
Optimization of Object-Image Distance for Aberration and Space-Charge Effect in Symmetric Magnetic Doublet with Dynamically Compensated Field Aberrations
Authors: Nakasuji Mamoru , Hiroyasu Shimizu Hiroyasu Shimizu
Published: October 2002

Maximum beam currents are expected when the optimum object-image distances and beam semiangle are 840 mm and 0.53 mrad, 840 mm and 0.27 mrad, and 1008 mm and 0.16 mrad for the subfield sizes of 250, 500, and 1000 µ m squares, respectively, where main field size, beam energy, energy width, and beam blur specifications are assumed to be 20 mm, 100 keV, 3 eV, and 45 nm, respectively, and the space-charge effect is assumed to be proportional to the object-image distance, beam current and (beam semiangle)-1. The residual distortions after correction of the beam rotation and position are 5.2, 7.6, and 6.6 nm for the above respective object-image distance and field size conditions.
Novel Characteristics of Electroluminescent Diode with Organic Multiple-Quantum-Well Structure
Authors: Ohmori Yutaka , Fujii Akihiko , Yoshida Masayoshi , Katsumi Yoshino Katsumi Yoshino
Published: October 2002

Novel electroluminescent characteristics of the organic multiple-quantum-well (MQW) structure have been discussed in comparison with MQW structures which consist of cyclopentadiene derivatives (PPCP) and aromatic diamine (TPD) and of aluminum quinoline ( Alq3) and aromatic diamine (TPD). Energy transfer of excitons has been found in both PPCP/TPD and Alq3/TPD systems. Unique electroluminescent characteristics in terms of polarization characteristics and emission spectrum have been discussed for the PPCP/TPD MQW system in comparison with the Alq3/TPD MQW system.
Detection of Molecular Switching in Single Monolayers by Maxwell-Displacement-Current-Measuring Technique
Authors: Mitsumasa Iwamoto Mitsumasa Iwamoto , Koji Ohnishi Koji Ohnishi , Xiaobin Xu Xiaobin Xu
Published: October 2002

Molecular switching in mixed monolayer surface was investigated by means of Maxwell-displacement-current measurement. The condensation of pure azobenzene monolayers was loosened by the introduction of phospholipids into the monolayers, and the molecular aggregation in pure azobenzene monolayers was also weakened. As a result, transient displacement-current pulses were generated across the mixed monolayers in the entire range of molecular area due to the photoisomerization of azobenzene by alternating irradiation of ultraviolet and visible light.
Chaotic Laser Oscillation in Sequence Band of CO2 Molecule
Authors: Sugawara Toshiki , Tachikawa Maki , Shimizu Tadao
Published: October 2002

Deterministic chaos is observed in the passive Q-switching pulsation of a CO2 sequence-band laser. The period-doubling bifurcation to chaos is reproduced with good fidelity by use of our rate-equation model. It is revealed that the vibration-to-vibration energy transfer process in the ν3 mode gives an appreciable change in the chaotic behavior of the sequence-band oscillation.
Prediction of the Epitaxial Orientation of Ultrathin Organic Films on Graphite
Authors: Hoshino Akitaka , Isoda Seiji , Kurata Hiroki , Kobayashi Takashi , Yamashita Yoshiro
Published: October 2002

A method of predicting the epitaxial orientation of organic monolayer on graphite substrate was proposed together with a misfit defined appropriately for the prediction. This method is based on a lattice matching mode, point-on-line coincidence, that has been found through our scanning tunneling microscopy (STM) investigations of organic epitaxy on graphite. In order to examine efficiency of the method, epitaxial orientations of bis-1,2,5-thiadiazolo-tetracyano-quinodimethane (BTDA-TCNQ) and bis-1,2,5-selenadiazolo-tetracyano-quinodimethane (BSDA-TCNQ) were predicted and the predictions were compared with the orientations observed by STM.
In both cases, the orientation observed was found to be exactly one of the predicted orientations, which suggests not only the efficiency of the prediction method but also the importance of the point-on-line coincidence in organic epitaxy.
An Optimal Metric for Predicting Chaotic Time Series
Authors: Tanaka Naoki , Okamoto Hiroshi , Masayoshi Naito Masayoshi Naito
Published: October 2002

The optimal metric for predicting chaotic time series was derived. In the derivation, the effects on the metric of the modeling of dynamics and the state space reconstruction by embedding were taken into account. The obtained metric minimizes the error in prediction with the nearest neighbor approximation, when the metric is used to calculate the distance in the state space. It is shown that the Euclidean metric is not the best choice, in either the reconstructed space or the true state space. The validity of the obtained metric was shown using numerical examples.
Linear Arrangement of Motor Protein on a Mechanically Deposited Fluoropolymer Thin Film
Authors: Hitoshi Suzuki Hitoshi Suzuki , Kazuhiro Oiwa Kazuhiro Oiwa , Akira Yamada Akira Yamada , Hitoshi Sakakibara Hitoshi Sakakibara , Haruto Nakayama Haruto Nakayama , Shinro Mashiko Shinro Mashiko
Published: October 2002

Motor protein molecules such as heavy meromyosin (HMM), one of the major components of skeletal muscle, were arranged linearly on a mechanically deposited fluoropolymer thin film substrate in order to regulate the direction of movement generated by the motor protein. The fluoropolymer film consisted of many linear parallel ridges whose heights and widths were 10 to 20 nm and 10 to 100 nm, respectively. The fluoropolymer ridges adsorbed HMM molecules that were applied onto the film. Actin filaments labeled with rhodamine-phalloidin were observed under a fluorescence microscope moving linearly on the HMM-coated ridges. The observation indicates that HMM molecules were aligned on the fluoropolymer ridges while retaining their function. The velocity of actin movement was measured in this system.
GaAs Radiation Damage Induced by Electron Cyclotron Resonance Plasma Etching with SF6/CHF3
Authors: Mitani Katsuhiko , Oda Hiroto , Kasai Junichi , Imamura Yoshinori
Published: October 2002

After SF6/CHF3 plasma exposure, the sheet resistance of Si-doped GaAs layers is higher because of carrier reduction near the surface and sputter etched surface, and this electrical and physical damage is found to depend on rf-power and µ-wave power. The carrier reduction can be almost restored by annealing at 450° C for 30 min. Exposures to He plasma or CHF3 plasma cause more extreme carrier reduction than does exposure to SF6 plasma, indicating that the carrier reduction in the damaged layers is predominantly due to the bombardment by low-mass fragments such as H and He. Low-temperature (4.2 K) photoluminescence of SF6/CHF3-plasma-exposed GaAs shows a broad and complicated spectrum (ranging from 1.25 to 1.43 eV) related to defect-complex by incorporation of hydrogen.
Heteroepitaxial Growth of CuGaS 2 Layers by Low-Pressure Metalorganic Chemical Vapor Deposition
Authors: Chichibu Shigefusa , Shirakata Sho , Uchida Mei , Harada Yoshiyuki , Wakiyama Toshio , Matsumoto Satoru , Higuchi Hirofumi , Isomura Shigehiro
Published: October 2002

Heteroepitaxial growth of CuGaS2 was studied by low-pressure metalorganic chemical vapor deposition using normal-tripropylgallium as a new Ga precursor, combined with cyclopentadienylcoppertriethylphosphine and ditertiarybutylsulfide. Structural and optical properties were characterized in detail. The epilayer showed the c[001]-oriented growth on both GaAs(001) and GaP(001) substrates. The lattice parameter c of the epilayers was smaller than that of the bulk single crystal. Magnitude of the residual lattice strain for CuGaS2/GaP(001) was found to be larger than that for CuGaS2/GaAs(001), even though the lattice mismatch for the former was smaller than that for the latter. The strain is considered to be introduced during cooling after the growth. A photoluminescence peak at 2.493 eV (8 K) was assigned to a free exciton emission, because the peak energy agreed with A-exciton energy obtained from photoreflectance spectra.
Properties and Time Dependences of Silicon Oxynitride Films Deposited by Low-Temperature Photochemical Vapor Deposition
Authors: Noboru Shibata Noboru Shibata
Published: October 2002

Silicon oxynitride films ( SiN

x

O

y

) were deposited using mercury-sensitized photochemical vapor deposition. The photochemical vapor deposition (photo-CVD) SiN

x

O

y

film was used as an antireflective coating (ARC) for a single-crystal Si solar cell. It was found that the refractive index of SiN

x

O

y

film deposited at low temperatures showed maked time dependence.
Relationship between Overwrite Characteristics and Linear Velocity in Mark Edge Recording with Phase-Change Media
Authors: Ohkubo Shuichi , Ide Tatsunori , Mitsuya Okada Mitsuya Okada
Published: October 2002

In this paper, we describe the relationship between overwrite characteristics and linear velocity in mark edge recording with phase-change media. Overwrite jitter is reduced for a disk in which the absorptivity of the crystalline state (A
c) has been designed to be higher than that of the amorphous state (A
a). When linear velocity is lower than 6 m/s, however, overwrite jitter is suppressed even in disks with A
a higher than A
c. This jitter suppression at low linear velocity cannot be explained simply in terms of thermal diffusion or critical cooling rate. This paper presents a “preceding crystallization” model for a jitter-suppression mechanism in which a previously recorded amorphous mark crystallizes before the scanning laser spot reaches it. Computer simulation confirms the feasibility of this mechanism at linear velocities lower than 6 m/s.
Order-Disorder Transition and Microwave Dielectric Properties of Ba(Ni1/3Nb2/3)O3 Ceramics
Authors: Kim In-Tae , Kim Yoon-Ho , Chung Su Jin
Published: October 2002

Order-disorder transition of Ba(Ni1/3Nb2/3)O3 ceramics was investigated using X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy. Before sintering samples were pre-fired at 1300° C for 100 h to achieve higher chemical homogeneity. A transition from ordered to disordered state was observed at 1500° C and the transition was accompanied by the formation of liquid phases. The chemical compositions of liquid phases were analyzed using energy-dispersive spectroscopy. Microwave dielectric properties of ordered and disordered samples were measured using the post resonator method and the transmission cavity method. Variations of dielectric properties such as relative permittivity, quality factor, and temperature coefficient of resonant frequency with sintering temperature were discussed in terms of order-disorder transition, liquid-phase sintering, defect concentration, and grain size.
The Influence of Manganese on Negative Temperature Coefficient Effect of BaTiO3 Positive Temperature Coefficient Resistance
Authors: Lo Gun-Man , Chen Ying-Chung , Shih-Hsiung Chen Shih-Hsiung Chen
Published: October 2002

For La-Mn-codoped BaTiO3, the relationship of La and Mn which results in the minimum room-temperature resistivity is [ La+3]-5/3[ Mn+x
]∼0.275 mol%. The c/a ratio of crystal structure decreases with increased Mn content. The number of Mn+2 ions which diffuse in the grain, existing as Mn
T
i

′′, increases with increased Mn content and reduces the electron generation velocity. Moreover, when Mn content increases, the negative temperature coefficient effect of a BaTiO3 positive temperature coefficient resistance below T
c will be reduced.
Electric Nusselt Number in a Suspension of Spherical Hematite ( α-Fe2O3) Particles
Authors: Haque Mohammed Fazlul , Arajs Sigurds
Published: October 2002

An experiment has been devised to evaluate the electric Nusselt number in a suspension of spherical hematite particles (hematite in distilled water). The experiment was conducted using a single platinum wire (diameter=0.025 mm) mounted along the axis of a copper cylinder (diameter=53 mm). The Nusselt number was evaluated for various experimental parameters such as time, electric field, frequency, orientation, charge and concentration of the colloidal particles. An increase in Nusselt number was observed in an ac field, and the increase was extremely sharp for pH values largely different from the isoelectric point (i.e.p.). A similar effect was also noted in a dc field at a very weak field strength. An increase in concentration of the colloidal particles increased the Nusselt number and a similar effect was also noted when the cylinder was moved from the horizontal to the vertical position. An attempt was made to evaluate the efficiency of convection using an empirical relationship and the results for ac and dc fields are presented.
Minimal Glass Deformations with Rapid Thermal Annealing Control
Authors: Plevert Laurence , Mottet Serge , Bonnel Madeleine , Duhamel Nicole , Gy René , Haji Lazar , Bertrand Loisel Bertrand Loisel
Published: October 2002

A critical step in the fabrication of polycrystalline silicon thin-film transistors (TFT's) is to crystallize the amorphous silicon layer deposited on glass. This paper describes a complete rapid thermal annealing (RTA) process applied to the crystallization of the amorphous layer. The RTA heating and cooling rates have been optimized to minimize thermal gradients and to improve glass substrate stability. Numerical simulations taking into account the lamp characteristics, the annealing chamber configuration and the sample properties have been developed and allow elucidation of thermal nonuniformities in the sample during the RTA process. Although the transition point of a glass (Tg) is often considered as an upper limit in usual polysilicon TFT's processes, this paper shows that if the cooling rate is accurately controlled, annealing temperatures can be aboveTgwithout thermal damage to the glass.
Carbon Nanotubes Filled with Gadolinium and Hafnium Carbides
Authors: Ata Masafumi , Hudson Andrew J. , Yamaura Kiyoshi , Ken'ichi Kurihara Ken'ichi Kurihara
Published: October 2002

High-resolution transmission electron microscopy (HREM) has been used to examine the effect of metals on the ordering of carbon during fullerene generation by the the DC electric arc discharge of metal-composite graphite rods. Investigations of the carbonaceous deposits formed on the top edge of the negative electrode confirmed the existence of graphitic polyhedra and carbon nanotubes filled with hafnium (Hf) carbide and gadolinium (Gd) carbide crystals. X-ray diffraction measurements indicate that the metals are incorporated in the form of HfC and GdC2. Possible mechanisms leading to the different stuctures formed in the presence of Hf and Gd are discussed. The continuous supply of sufficient numbers of metal atoms into the arc plasma and moderate suppression of diffusion of the arc plasma flow by increased He pressure was found to enhance the growth of the carbon nanotubes filled with metal carbides.
Novel Formation Method of Quantum Dot Structures by Self-Limited Selective Area Metalorganic Vapor Phase Epitaxy
Authors: Kazuhide Kumakura Kazuhide Kumakura , Kazuaki Nakakoshi Kazuaki Nakakoshi , Junichi Motohisa Junichi Motohisa , Takashi Fukui Takashi Fukui , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

We have fabricated AlGaAs/GaAs quantum dot structures using selective area metalorganic vapor phase epitaxy (MOVPE). First, GaAs pyramidal structures with fourfold symmetric {011} facet sidewalls are formed on SiN
x
-masked (001) GaAs with square openings. Once the pyramidal structures were completely formed, no growth occurs on the top or sidewalls of the pyramids. Furthermore, the shape and width of the top area observed using a scanning electron microscope (SEM) and an atomic force microscope (AFM) is shown to be highly uniform. This indicates that self-limited growth occurs. Next, using these uniform pyramids, GaAs quantum dots are overgrown on top of the pyramids under different growth conditions. Sharp photoluminescence (PL) spectra are observed from uniform quantum dots.
Lateral-Size Control of Trench-Buried Quantum Wires Using GaAs/AlAs Superlattice Layers
Authors: Tetsuomi Sogawa Tetsuomi Sogawa , Seigo Ando Seigo Ando , Hiroshi Kanbe Hiroshi Kanbe
Published: October 2002

We demonstrated the lateral-size control of GaAs/AlAs trench-buried quantum wires (QWRs) in the region below 20 nm by using GaAs/AlAs superlattice layers (SLs). Scanning electron microscopy images and photoluminescence properties of the trench-buried QWRs revealed that the trench width can be controlled by varying the number of SLs and reduced to about 13 nm by growing 7 pairs of SLs. The GaAs wires in the trenches have a tendency to grow so as to maintain a constant cross-sectional area, which leads to reduction of the energetic broadening of the quantum sub-levels caused by pattern size fluctuation.
GaAs Metalorganic Vapour Phase Epitaxial Overgrowth over nm-Sized Tungsten Wires
Authors: Lars-Erik Wernersson Lars-Erik Wernersson , Kristina Georgsson Kristina Georgsson , Andrej Litwin Andrej Litwin , Lars Samuelson Lars Samuelson , Werner Seifert Werner Seifert
Published: October 2002

Epitaxial overgrowth of GaAs over nanometer-sized tungsten patterns is studied experimentally. The relationships between the quality of the overgrowth and geometrical parameters, such as crystallographic orientation, metal width, metal thickness, and grating period, are investigated. The overgrown structures are characterized using a scanning electron microscope at top surfaces and at cleaved edges, and by I-V measurements of Schottky diodes formed between the metal grid and the overgrown GaAs. It is established that it is possible to obtain a high-quality overgrowth layer with a completely planarized growth front within 200 nm of growth.
Mesoscopic Phenomena in Microstructures of IV–VI Epilayers
Authors: Grzegorz Grabecki Grzegorz Grabecki , Shojiro Takeyama Shojiro Takeyama , Satoru Adachi Satoru Adachi , Yoshihiro Takagi Yoshihiro Takagi , Tomasz Dietl Tomasz Dietl , Eliana Kamiń Eliana Kamiń , Anna Piotrowska Anna Piotrowska , Ewa Papis Ewa Papis , Norbert Frank Norbert Frank , Günther Bauer Günther Bauer
Published: October 2002

Precise magnetoresistance measurements on microstructures of photolithographically patterned PbSe epilayers have been performed in the magnetic field range up to 17 T. Unusual, reproducible magnetoconductance fluctuations have been observed. The fluctuation amplitude is about one order of magnitude greater than that predicted for universal conductance fluctuations. Moreover, the fluctuation frequency spectra correspond to the Aharonov-Bohm effect on electron trajectories up to 50 times smaller than the electron mean free path. This strongly points to the ballistic, not diffusive, origin of the observed phenomenon.
Transport through Discrete Energy Levels in Quantum Dots
Authors: Yoshimasa Isawa Yoshimasa Isawa , Futoshi Suwa Futoshi Suwa
Published: October 2002

The effect of potential fluctuations on a semiconductor quantum dot is exhibited. The height of a series of single peaks in the Coulomb oscillation (CLO) becomes irregular in the presence of potential fluctuations. As the source-drain voltage becomes larger than the quantized level spacing, a single peak broadens and turns into a multiple peak. The asymmetry of the barrier heights and the potential fluctuations in the dot are crucial in this regime. The influence of potential fluctuations on wave functions plays an important role in the transport phenomena in submicrometer devices near pinch-off.
Photon Emission from a False Vacuum of Semiconductors
Authors: Teruaki Okushima Teruaki Okushima , Akira Shimizu Akira Shimizu
Published: October 2002

We consider photon creation through the dynamical Casimir effect in a semiconductor material. Unlike previous studies, we evaluate the number of created photons using a microscopic model in which polarization degree of freedom is included in the theory as a microscopic variable, under realistic situations in which material parameters vary by a finite magnitude within a finite time, in a material which exhibits strong dispersions in the dielectric constant. Our results differ strikingly from previous results.
Valley Mixing and Interface Fluctuations in GaAs/AlAs Superlattices
Authors: Tsuneya Ando Tsuneya Ando
Published: October 2002

An interface matrix which incorporates mixing between Γ and X conduction-band valleys is used for calculation of optical intensities in GaAs/AlAs short-period superlattices. A characteristic oscillation of the intensity as a function of the monolayer number for superlattices with lower X states is destroyed easily in the presence of interface fluctuations.
Theoretical Study of Resonant Tunneling Transmission Characteristics in Symmetrical Rectangular Quadruple-Barrier Structures with	Deep Wells
Authors: Hiroaki Yamamoto Hiroaki Yamamoto , Youji Kanie Youji Kanie , Akira Kurita Akira Kurita , Keiji Taniguchi Keiji Taniguchi
Published: October 2002

Resonant tunneling transmission is studied theoretically for symmetrical rectangular quadruple-barrier structures with deep triple wells. Analytical expressions for the transmission coefficient and the resonance condition are derived for the first time. Two desired resonance levels may be obtained almost independently by selecting appropriate values of well width, which may be favorable for resonant tunneling device fabrication. The transmission coefficient versus electron energy is investigated, and it is shown analytically that the transmission spectrum is Lorentzian in shape near energies of resonance. Wave functions of an electron at the resonance level are examined, and the confining phenomenon is studied.
Transverse-Electric and Transverse-Magnetic Mode Switching in Tensile-Strained Quantum-Well Lasers Induced by the Quantum-Confined Stark Effect
Authors: Matsuto Ogawa Matsuto Ogawa , Tanroku Miyoshi Tanroku Miyoshi
Published: October 2002

Using a multiband effective-mass theory, we have calculated the transverse-electric (TE) and transverse-magnetic (TM) gains of a strained quantum-well laser subject to an external electric field. Our results show that when the well is under a moderate tensile strain, the field can switch the polarization of the room-temperature stimulated emission from the TE to the TM mode.
Effects of Lead Particles on the Magnetoresistance of a Two-Dimensional and Quasi-One-Dimensional Electron Gas
Authors: P. Omling P. Omling , H. Linke H. Linke , K. Deppert K. Deppert , L. Samuelson L. Samuelson , L. Theil Hansen L. Theil Hansen , P. E. Lindelof P. E. Lindelof
Published: October 2002

Very small lead particles have been deposited with random distribution on top of high mobility GaAs/AlGaAs two-dimensional electron gas (2DEG) samples, and the effects on the transport properties of the 2DEG have been studied. Particles more than 5 µm in diameter cause magnetic disorder in the 2DEG in their superconducting state, giving rise to prominent structures in the magnetoresistance. In contrast, spherical particles of 80 to 300 nm diameter do not cause magnetic effects. Electrostatic effects of the nm-sized particles on the transport properties of wide 2DEG structures are very weak, whereas the magnetoresistance properties of a narrow channel were altered significantly in the presence of only a few lead particles smaller than 300 nm. The influence of particles of diameter <300 nm on wide 2DEG samples could be strongly enhanced by melting the particles on the surface.
Electrical Properties of Ultralarge Grain Polycrystalline Silicon Film Produced by Excimer-Laser Recrystallization Method
Authors: Choi Do-Hyun , Imai Shigeru , Masakiyo Matsumura Masakiyo Matsumura
Published: October 2002

Electrical properties have been evaluated for polysilicon films from temperature dependence of the field-effect mobility. Density of the defect states at the grain boundary (GB) could be calculated as a function of energy for vacuum-, molecular-hydrogen- and atomic-hydrogen-annealed films. Defect states were distributed strongly near 0.14 eV below the conduction band and decreased steeply with more closer to the mid-gap. The GB was found to have no serious effect on electron and hole transport characteristics after hydrogenation.
Crystal Structure and Orientation of AlxIn 1-xN Epitaxial Layers Grown on (0001) \mbα-Al 2O 3 Substrates
Authors: Qixin Guo Qixin Guo , Nobuo Itoh Nobuo Itoh , Hiroshi Ogawa Hiroshi Ogawa , Akira Yoshida Akira Yoshida
Published: October 2002

The epitaxial layers of AlxIn1-x
N grown on (0001) α-Al2O3 substrates by microwave-excited metalorganic vapor phase epitaxy have been studied using the reflection high-energy electron diffraction and X-ray diffraction methods. All AlxIn1-x
N layers have a wurtzite structure, as expected from the structure of AlN and InN. The epitaxial relationship between the AlxIn1-x
N layers and the (0001) α-Al2O3 substrates is found to be (0001) Alx In1-x
N // (0001)α- Al2 O3
with [101̄0] Alx In1-x
N // [101̄0]α- Al2 O3
. The lattice constants of a and c axes of the epitaxial layers are determined. It is revealed that both the a lattice constant and c/a ratio of the epitaxial AlxIn1-x
N layers decrease with increasing molar fraction of x of the alloy.
Microstructural Characterization for Sputter-Deposited CuInSe2Films and Photovoltaic Devices
Authors: Nakada Tokio , Migita Kazuo , Niki Shigeru , Akio Kunioka Akio Kunioka
Published: October 2002

Comparative study on the microstructural and photoluminescence (PL) properties of CuInSe2films deposited by both three-source sputtering and hybrid sputtering was carried out by high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), PL spectroscopy and X-ray diffraction analysis. The CuInSe2films deposited by three-source sputtering exhibited small grain size and considerably high density of lattice defects, which led to poor cell performance. In contrast, hybrid-sputtered films showed relatively large grain size and low density of defects. Significant difference in PL spectra was also observed between CuInSe2films deposited by both methods. ZnO:Al/CdS/CuInSe2solar cell with an active-area efficiency of 11.3% was achieved using hybrid-sputtered material. The correlation between microstructural properties and device performance suggests that the decreasing defect density in CuInSe2films is essential for achieving high efficiency solar cells by sputtering process.
Characterization of Interdiffusion in SrTiO3/YBa2Cu3O7-x Multilayers by In Situ Auger Electron Spectroscopy
Authors: Nakamura Takao , Michitomo Iiyama Michitomo Iiyama
Published: October 2002

In situ deposition and surface characterization by Auger electron spectroscopy enabled precise surface composition analysis. The annealing temperature dependence of the surface composition in SrTiO3(2.8 nm)/YBa2Cu3O7-
x

and YBa2Cu3O7-
x

(2.7 nm)/SrTiO3 multilayers revealed the diffusion of each of the constituent atoms. The interdiffusion is negligible below 600° C. Ba atom diffusion into SrTiO3 was dominant in the temperature range from 600° C to 660° C. The activation energy was calculated to be 2.4 eV.
Ti atom diffusion into YBa2Cu3O7-
x

became distinctive above 660° C. The activation energy of Ti was 4.4 eV.
Fivefold Increase in Solar Laser Output with a Nonimaging Concentrator
Authors: Arashi Haruo , Cooke Dave , Hitoshi Naito Hitoshi Naito
Published: October 2002

A nonimaging concentrator (compound parabolic concentrator) has been employed to boost the output of a solar-pumped Nd:YAG laser crystal from 2 W to 10 W.
Since the nonimaging concentrator increased the solar power delivered to the laser, the reflectivity of the output coupler could be lowered from 95% to 90%. With the 90% output coupler in place, there was an additional increase in laser power, to 14 W.
Simple Modification of Positive-Branch Unstable Resonator for Diffraction-Limited XeCl Laser Beam
Authors: Chu Hong , Jhon Young Min , Choi Sang Sam , Park Dae Yoon
Published: October 2002

A simple modification of the output coupler to a standard positive-branch confocal unstable resonator (PBUR) was proposed and the output characteristics were investigated and compared with those of the standard PBUR. We utilized a small convex mirror of 1.8 mm diameter as an output coupler in order to reduce the beam divergence and to eliminate the subsidiary spot caused by the Fresnel reflection effect in the standard PBUR.
We obtained a single spot in the focal plane with a nearly diffraction-limited beam divergence of 0.09 mrad.
Closely Spaced Independently Addressable Dual-Beam Visible Lasers with Strained GaInP Quantum Wells
Authors: Yoshida Ichiro , Katsuyama Tsukuru , Hashimoto Jun-ichi , Hideki Hayashi Hideki Hayashi
Published: October 2002

Closely spaced (15 µ m center-to-center spacing) independently addressable dual-beam visible lasers were demonstrated using strained GaInP quantum well structures. Crosstalk characteristics were studied experimentally as well as theoretically. The estimated crosstalk of uncoated devices was around 3% with bias, and 10% without bias in CW-mode operation. The value of 3% was small enough for applications such as printers and optical disks.
B-Ion Substitution in (Pb-A)(Ti-B)O3 Systems with A=Na1/2Bi1/2 or K1/2Bi1/2 and B=Zr, Fe1/2Nb1/2, Zn1/3Nb2/3, Mg1/3Nb2/3 or Mg1/2W1/2
Authors: Ishii Yoshiaki , Nomura Koji , Fukuda Fumio , Asada Hiroshi , Aihara Tomomi , Mochizuki Shigeki , Fujiki Hiroyuki , Kakiyama Hiroyuki , Amakawa Takashi , Kitami Masaru , Hirota Ken-ichi , Takuro Ikeda Takuro Ikeda
Published: October 2002

Phase relation of the systems [Pb1-
y

(Na1/2Bi1/2)

y

](Ti1-
x

Zr

x

)O3 and [Pb1-
y

(K1/2Bi1/2)

y

](Ti1-
x

B

x

)O3 with B=Zr, Fe1/2Nb1/2, Zn1/3Nb2/3, Mg1/3Nb2/3 or Mg1/2W1/2 have been investigated. With increasing x and y, T
C decreased and peaks in ε-T curves became broader. Phase diagrams of all the systems at room temperature were determined. As the concentration y of Na1/2Bi1/2 or K1/2Bi1/2 was increased, the tetragonal-to-rhombohedral boundary shifted to smaller x and the tetragonal phase was suppressed within x∼0.1 on the ( K1/2Bi1/2) side. Piezoelectric response was examined in ceramic specimens with composition in the vicinity of the boundary in all systems, and a value of 0.18 as K(=C
1/C
0) was found in the [Pb-(K1/2Bi1/2)](Ti-Zr)O3 system.
Distribution Coefficient of Rare-Earth Active Ions in Calcium Niobium Gallium Garnet
Authors: Shimamura Kiyoshi , Sugiyama Kazumasa , Uda Satoshi , Tsuguo Fukuda Tsuguo Fukuda
Published: October 2002

Distribution coefficients of Nd3+, Tm3+ and Er3+ in calcium niobium gallium garnet (CNGG) single crystals have been investigated. The values of the equilibrium distribution coefficient, k
0, of Nd3+, Tm3+ and Er3+ in CNGG single crystals have been determined to be 0.55, 1.09 and 1.14, respectively. It is shown that the distribution coefficients of Nd3+ in CNGG single crystals are larger than those in other garnet crystals such as Y3Al5O12 and Gd3Ga5O12. The variation of the k
0 values is discussed in relation to the ionic radii of each of the cations.
Adsorption and Thermal or Photodecomposition of Triethylgallium and Trimethylgallium on Si(111)-7×7
Authors: Fukui Ken-ichi , Mizutani Wataru , Onishi Hiroshi , Ichimura Shingo , Shimizu Hazime , Iwasawa Yasuhiro
Published: October 2002

Adsorption and thermal or photodecomposition of triethylgallium (TEG) and trimethylgallium (TMG) on Si(111)-7×7 were investigated using a home-built scanning tunneling microscope (STM), Auger electron spectroscopy (AES), and thermal desorption spectroscopy (TDS). Adsorption of TEG and TMG at room temperature gave bright protrusions of Ga(C2H5)x(a) and Ga(CH3)x(a) (x=2, 3) on atop sites of Si adatoms with a slight preference for center adatoms over comer ones. The Ga(C2H5)x(a) and Ga(CH3)x(a) species were decomposed by UV irradiation probably due to absorption of UV photons by these adsorbates. Thermal decomposition of TEG on the 7×7 surface led to severe carbon deposition, particularly at low initial coverage of TEG, in contrast to the result reported on Si(100)-2×1.
Correlation between Adhesion Strength of Plasma-Polymerized Hexamethyldisiloxane Films to Polytetrafluoroethylene and Partial Discharge Resistance
Authors: Kusabiraki Minoru , Masao Aozasa Masao Aozasa
Published: October 2002

Polytetrafluoroethylene (PTFE) films were coated with plasma-polymerized hexamethyldisiloxane (PPHMDS) films in a dc glow discharge system. The correlation between the adhesion of the PPHMDS films to the PTFE films and the partial discharge resistance of the composite films was investigated. The voltage endurance of the composite films in the presence of partial discharges increased with the adhesion of the PPHMDS films. From an observation of the deteriorated surface scars, it was shown that the deterioration is affected by the formation of cracks in the PPHMDS film.
Nucleation of Polycrystalline Silicon Grains
Authors: Matsuo Naoto , Miyoshi Tadaki , Matsubara Kakuei
Published: October 2002

Influence of oxygen atoms in the atmosphere during in-situ annealing on the nucleation of polycrystalline silicon grains at the surface of amorphous silicon (a-Si) formed by low-pressure chemical vapour deposition is studied. The quantity of the oxygen atoms has a close relationship with the grain diameter. This is thought to be due to thin suboxide-islands produced on the a-Si surface during the annealing. The result calculated for the relationship between the density of the suboxide-islands and the annealing time by assuming that trap sites for oxygen atoms exist on the a-Si surface agrees with the experimental result for the density of the grains.
Quantitative Analysis of Trace Water in Highly Puified Nitrogen Gas by Atmospheric Pressure Ionization Mass Spectrometer
Authors: Mitsui Yasuhiro , Irie Takashi , Mizokami Kazuaki , Kuriyama Katsumi , Nakano Kazuo , Nakamura Yuko
Published: October 2002

Quantitative analysis of trace water, at ppb level and below, in highly purified nitrogen gas used in semiconductor fabrication processes was investigated using an atmospheric pressure ionization mass spectrometer (APIMS). Until recently, the trace analysis of strongly adhesive water was difficult because of the lack of a standard gas for calibration and high background water levels. The standard gas was prepared by using a gas containing a ppm level of water evaporated from a water bottle, and diluting it 105 times using a two-step dilution system. To reduce the background, a simplified SUS316L electropolished gas line with no valves, mass flow controllers or connectors was assembled. Using this method, a calibration curve applicable to the low ppm to ppt range was obtained. The background obtained was 40 ppt. The curve was fitted with a theoretical curve calculated from ion-molecule reactions.
Ellipsometric Measurements and its Alignment: Using the Intensity Ratio Technique
Authors: Chao Yu-Faye , Wei Chi-Shin , Lee Wen-Chi , Lin Shy-Chaung , Chao Tien Shen
Published: October 2002

Using first-order treatment on azimuth errors of the polarizer (P) and analyzer (A) with respect to the plane of incidence (POI), we construct two intensity ratios around a certain configuration, such as P=±π/4 and A=0 as compared to A=π/2. These expressions can be used not only to align the azimuths of the polarizer and analyzer to the POI, but also to obtain the ellipsometric parameter ψ without locating the minimum intensity. BK7 glass and SiO2/Si thin film are ultilized to evaluate this technique.
Analysis of Laser Beam Propagation Effects in Atomic Laser Isotope Separation
Authors: Chen Yen-Wei , Izawa Yasukazu , Nakai Sadao , Chiyoe Yamanaka Chiyoe Yamanaka
Published: October 2002

In the atomic laser isotope separation process, the laser beams propagate through the atomic vapor over a long distance. It has been shown that the laser-atom interactions significantly modify the laser pulse shape and propagation velocity, resulting in degradation of the isotope separation efficiency. These propagation effects have been analyzed quantitatively, and a simple scaling formula has been derived to estimate the necessary laser energy for such optically thick atomic vapor. The optimum conditions of incident laser pulse have also been discussed.
Combined Gas Microflowmeter and Potentiometric Sensor
Authors: Domanský Karel , Jiří Janata Jiří Janata
Published: October 2002

A gas microflowmeter based on a potentiometric chemical sensor is demonstrated. The flowmeter operates on the hot-wire principle. Electric current is passed through a platinum microbridge. A preset bridge resistance is kept constant by regulating the heating current. By measuring the changes in the heating current, the calibration flow curve can be obtained. The temperature profiles of both the electrically heated microbridge and the substrate in its vicinity, measured with an infrared microscope, are presented.
Influence of Buffer Layers and Excess Pb/Zr+Ti Ratios on Fatigue Characteristics of Sol-Gel-Derived Pb(Zr, Ti)O3 Thin Films
Authors: Doi Hidekazu , Atsuki Tsutomu
Published: October 2002

Since fatigue of the Pb(Zr, Ti)O3 (PZT) films is closely related to the movement of defects generated due to interdiffusion of atoms through the ferroelectric/electrode interface, studies on the effect of excess Pb content, defined as R= Pb/(Zr+Ti), in the PZT films or insertion of a PZT buffer layer with a large R or of a La-bearing PZT buffer layer between the films and electrode may be effective for diminution of fatigue. Another important aspect is lowering the annealing temperature as much as possible when making the films, so as to reduce interdiffusion. In the present work, annealing temperature for making sol-gel-derived ferroelectric films was fixed at 550° C, and fatigue tests of PZT films with and without buffer layers were carried out. Fatigue tests of the PZT(52/48) films with various values of R have shown that although polarization of the PZT(52/48) film increases with R, fatigue life does not significantly improve due to an increase in fatigue rate with increasing switching cycles. Insertion of the PbTiO3 (PT) buffer layer, 4 nm thick, somewhat amplified the R dependence of ferroelectric properties of the films. Insertion of a 40-nm-thick PZT (120/52/48) buffer layer substantially increased (P
*
r-P
∧
r), the difference between switched and nonswitched polarizations, for the PZT(100-110/52/48) or PZT(110/70/30) film in early stages of the fatigue life profile; however, an enhanced fatigue rate followed and eventually resulted in an insignificant improvement of fatigue life. AES depth profile analysis has revealed that diffusion of excess Pb in the buffer layer towards the surface removes or greatly reduces Pb deficiency which is typically generates in the vicinity of the surface of the films without buffer layers. The resulting reduction of the amount of the defects is thought to have caused substantial increase of (P
*
r-P
∧
r) in early stages of the fatigue life profile. Insertion of double buffer layers of PZT(120/52/48) and PLZT(5/65/35), each 20 nm thick, produced a conspicuous bulge in the polarization fatigue life profile, although fatigue life was not much improved. The origin of the bulge was discussed.
Growth and Photoluminescence of Cr4+-DopedCa3Ga2Ge3O12 Single Crystals
Authors: Peicong Pan , Yamazaki Takafumi , Sugimoto Akiko , Yamagishi Kiyoshi , Humihiko Takei Humihiko Takei
Published: October 2002

Pure and Cr-doped single crystals of Ca3Ga2Ge3O12 have been prepared by the Czochralski method in oxygen gas of 1-1.2 atm. The pure crystals are colorless and transparent, whereas the doped ones are green. Photoluminescence with a broad peak around 1400 nm is observed on the Cr-doped crystals by optical excitation with a Nd:Y3Al5O12 laser beam of 1064 nm. This spectrum is ascribable to an electronic transition of Cr4+ in the tetrahedral Ge4+ sites.
Effect of Oxygen Pressure on (BaxSr1-x)TiO3 Thin Films by Pulsed Laser Ablation
Authors: Nakamura Takanori , Yamanaka Yasuhiro , Morimoto Akiharu , Shimizu Tatsuo
Published: October 2002

(Ba

x

Sr1-
x

)TiO3 (x=0-1.0) (BST) thin films were prepared on (111)Pt/Ti/SiO2/Si substrates by pulsed laser ablation (PLA) using an ArF excimer laser at various oxygen pressures. The film compositions agree well with those of the targets. For all the film compositions, the crystalline structure of the thin films is a single perovskite phase. The thin films prepared at 133 Pa are randomly oriented. The films preferentially oriented along the [111] direction are obtained at low oxygen pressures (6.67 and 13.3 Pa). The surface morphology of the thin films becomes rougher with increasing oxygen pressure. Moreover, this roughening is prominent with low Ba content. The excessively high oxygen pressure during PLA deposition deteriorates the crystal structure and the dielectric property of BST films. The dielectric constant of BST (x=0.6) thin film prepared at the oxygen pressure of 6.67 Pa is 800 at 1 MHz.
Deposition and Electrical Characterization of Very Thin SrTiO3 Films for Ultra Large Scale Integrated Dynamic Random Access Memory Application
Authors: Hwang Cheol Seong , Park Soon Oh , Kang Chang Seok , Cho Hag-Ju , Kang Ho-Kyu , Ahn Sung Tae , Moon Yong Lee Moon Yong Lee
Published: October 2002

SrTiO3 thin films are deposited on Pt/SiO2/Si substrates using RF magnetron sputtering in a temperature range from 200° C to 600° C. The film deposited at 600° C shows the best dielectric property and leakage current characteristics due to its good crystallinity and stoichiometric composition. Dielectric constant of the film deposited at 600° C decreases with decreasing thickness from 235 at 120 nm to 145 at 30 nm. Leakage current shows a constant value of about 30 nA/cm2 at 1.6 V in a thickness range from 50 nm to 120 nm but increases rapidly to 5 µ A/cm2 at 30 nm. The electrical properties of the films are explained by a model of the Pt/SrTiO3/Pt capacitor based on the band structure.
Preparation of Dielectric Thin Films of Pb[(Mg1/3Nb2/3)0.9Ti0.1]O3 by Screen Printing Method
Authors: Futakuchi Tomoaki , Katsumi Tanino Katsumi Tanino
Published: October 2002

Dielectric thin films of Pb[(Mg1/3Nb2/3)0.9Ti0.1]O3 were obtained by a screen printing method. A screen-printable dielectric paste was synthesized using submicron-sized powder and a metalorganic compound, which acted as an organic vehicle and a sintering aid. The crystal structure and dielectric properties of the thin films were greatly influenced by the bottom electrodes and substrate materials and also by firing conditions.
Hydrothermal Syntheses of Lead Zirconate Titanate Thin Films Fabricated by a Continuous-Supply Autoclave
Authors: Ohba Yoko , Miyauchi Masahiro , Sakai Etsuo , Masaki Daimon Masaki Daimon
Published: October 2002

Crystalline lead zirconate titanate (PZT) films formed hydrothermally in a test-tube autoclave have heterogeneous chemical composition, because the concentration of each ion (Pb, Zr and Ti) in solution cannot be controlled. A continuous-supply autoclave system was used to obtain PZT films with desirable chemical compositions. A solution was sampled from the reactor during the reaction, and the change in concentration of elements was measured. Based on the results, the appropriate composition and concentration were determined. The obtained PZT film has an intermediate layer between the film and titanium substrate. The layer was much thinner than that obtained with a test-tube autoclave.
Preparation and Properties of Niobium-Doped Pb[(Sc1/2Nb1/2)0.58Ti0.42]O3 Ceramics Using Hot Isostatic Pressing
Authors: Adachi Masatoshi , Toshima Takeshi , Takahashi Megumi , Yamashita Yohachi , Akira Kawabata Akira Kawabata
Published: October 2002

1 mol% Nb-doped Pb[(Sc1/2Nb1/2)0.58Ti0.42]O3 (PSNTN) ceramics with the morphotropic phase boundary (MPB) composition were prepared by the hot isostatic pressing (HIP) method to improve their physical and ferroelectric properties. Sintering, hot isostatic pressing, and annealing conditions were optimized to produce high-density PSNTN ceramics and utilize their excellent dielectric and piezoelectric properties. Using hot isostatic pressing after conventional sintering at 1275° C for 2 h, the achieved density of PSNTN hot-isostatically pressed at 1000° C was 8.00 g/cm3, which was approximately 99.5% of the theoretical value. The maximum dielectric constant of ε
T
33/ε
0 was 2900 at room temperature, and its dissipation factor was 1.5%. Large electromechanical coupling factors of k
p=70% and k
t=55% were obtained. The remanent polarization P
r and coercive field E
c were 27 µ C/cm2 and 6.9 kV/cm, respectively. The PSNTN ceramic is a promising material for applications to electromechanical bulk transducers, because of its large coupling, high dielectric constant and low mechanical quality factor.
Thermoelectric Power Studies on 1% Excess Te Doped Pb0.8Sn0.2Te Thin Films
Authors: V. Damodara Das V. Damodara Das , C. Bahulayan C. Bahulayan
Published: October 2002

Thin films of Pb0.8Sn0.2Te of thicknesses varying between 360 Å and 3400 Å have been prepared by flash evaporation on cleaned glass substrates held at room temperature. Thermoelectric power (TEP) of these films has been evaluated by measuring the thermal emf developed by the integral method in the temperature range 300 K to 500 K. It has been found that TEP of all the films is positive and increases with temperature in the low temperature region and tends to saturate at high temperatures, beyond 400 K. This has been attributed to the pinning of the Fermi level at high temperatures. It was also found that these films did not show the expected linear dependence of TEP on the inverse film thickness.