bluuebunny/crossref_metadata_2025 huggingface dataset:
Epitaxial Si on Al2O3 Films Grown with O2 Gas by the Ultrahigh-Vacuum Chemical Vapor Deposition Method
Authors: Takayuki Kimura Takayuki Kimura , Hideki Yaginuma Hideki Yaginuma , Atsuhiro Sengoku Atsuhiro Sengoku , Yoshitaka Moriyasu Yoshitaka Moriyasu , Makoto Ishida Makoto Ishida
Published: October 2002

By an improved Al2O3(100) growth on Si(100) using O2 gas instead of N2O gas, high-crystalline quality silicon on insulator (SOI) and multistacked SOI structures were successfully fabricated on a 2-inch Si(100) wafer by the ultrahigh-vacuum chemical vapor deposition (UHV-CVD) method. The surface morphology of the Si top layer of the fabricated SOI structure is better than that of the silicon on sapphire (SOS) structure grown by the UHV-CVD method. The transistor action was confirmed from the electrical properties of the MOSFET, and the field effect mobility of 748 cm2/V s was obtained. These results were similar to those obtained from bulk Si. This improved Si top layer of SOI and multistacked SOI structures is due to the improved surface morphology and crystalline quality of the Al2O3 layer grown on Si with O2 gas.
Reduction of Remote Impurity Scattering in Heavily Modulation-Doped GaAs and (GaIn)As Quantum Wells with AlAs/GaAs Type-II-Superlattice Barriers
Authors: Friedland Klaus-Juergen , Hey R. , Kostial H. , Ploog K. H.
Published: October 2002

We present a new semiconductor heterostructure to reduce impurity scattering in remotely doped GaAs and (GaIn)As single quantum wells. By using heavy-mass X-electrons in the short-period AlAs/GaAs superlattice barriers, the potential fluctuations of the ionized Si dopants are smoothed. In 10 nm GaAs and (InGa)As single quantum wells, respective densities of about 2×1016 m-2 and 3 ×1016 m-2 can be achieved with a low level of remote impurity scattering. For (InGa)As single quantum wells, the reduction of the impurity scattering manifests itself as an increase of the single particle relaxation time. Structure design and growth parameters for achieving ultrahigh conductivities are discussed.
Pressure Induced Phase Transitions in Spinel and Wurtzite Phases of ZnAl2S4 Compound
Authors: V. Ursaki Veacheslav , I. Burlakov Igor , M. Tiginyanu Ivan , S. Raptis Yannis , Anastassakis Evangelos , Igor Aksenov Igor Aksenov , Katsuaki Sato Katsuaki Sato
Published: October 2002

ZnAl2S4 single crystals with spinel (α-phase) and wurtzite (w-phase) structures have been studied by Raman spectroscopy under hydrostatic pressures of up to 300 kbar. Significant changes in the phonon spectrum of the α-phase have been observed at the critical pressure of 230 kbar, which are attributed to a reversible phase transition to a denser high-pressure phase, having a similar structure to that of calcium ferrite. In the pressure interval of 180 to 230 kbar, the two phases coexist. The irreversible disappearance of the Raman signal of w-ZnAl2S4 doped by Cd at pressures above 90 kbar was attributed to a phase transition to a rocksalt-type structure. This critical pressure is 40 kbar lower than that in undoped w-ZnAl2S4 and is explained on the basis of crystal structure quality. Different structures were realized upon removing the pressure, depending on the highest pressure previously reached, such as a mixture of wurtzite and spinel phases, a spinel quasi-crystalline structure, or a pressure-induced amorphous phase. The behavior of the quasi-crystalline spinel structure upon repeating the pressure cycle was found to be different from that of the α-phase single crystal.
Enhanced Current-Voltage Characteristics of Al0.25Ga0.75As/In0.25Ga0.75As/GaAs P-HEMTs Using an Inverted Double Channel Structure
Authors: Ahn Kwang-Ho , Jeon Young-Jin , Jeong Yoon-Ha , Yun Chan-Eui , Pyo Hyun-Myung
Published: October 2002

An inverted double channel Al0.25Ga0.75As/In0.25Ga0.75As/GaAs pseudomorphic high electron mobility transistor (P-HEMT) grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD) has been demonstrated for the first time. The inverted double channel heterostructure shows a high two-dimensional electron gas (2-DEG) concentration of 4.53×1012 cm-2 along with a large mobility of 5010 cm2/V·s at 300 K, respectively. The fabricated P-HEMT device with a gate dimension of 1.8×200 µm2 shows a maximum drain current of as high as 820 mA/mm and a maximum extrinsic transconductance of 320 mS/mm at 300 K. Also, extrinsic transconductance is sustained over a wide range of gate voltages from -2.0 V to 1.8 V. In addition, a high two-terminal gate-drain reverse breakdown voltage of -17 V is obtained. The results obtained show a great potential of the inverted double channel P-HEMT for power applications.
Selective Oxidation of AlGaAs/GaAs Structure and Its Application to Vertical Cavity Lasers
Authors: Yang Gye Mo , Lim Dae Ho , Kim Jong-Hee , Lim Kee Young , Lee Hyung Jae
Published: October 2002

We report on vertical-cavity surface-emitting lasers (VCSELs) fabricated using selective oxidation to form a current aperture and an oxide surface barrier to seal buried AlAs layers in distributed Bragg reflectors. The lateral selective oxidation of the AlAs layer is strongly influenced by its thickness and heterointerface structures. The oxidation rate decreases rapidly with decreasing AlAs thickness in the range of < 80 nm, and the presence of AlGaAs layers on both sides of the AlAs layer reduces the oxidation rate. In addition, an oxide surface barrier with a thickness of ∼1 µm is formed by a brief wet oxidation which blocks diffusing oxygen species during the second wet oxidation. The effectiveness of the seal is demonstrated by using the oxide barrier as a mask against wet oxidation in the fabrication of oxide-confined VCSELs. The 8×8 µm2 devices with three quantum wells exhibit a threshold current of 400 µA, and the 4×4 µm2 single-quantum devices possess a threshold current as low as 85 µA.
Characterization of InP Air/Semiconductor Gratings Formed by Mass-Transport Assisted Wafer Fusion Technique and Its Application to Distributed Feedback Laser
Authors: Masahiro Imada Masahiro Imada , Toyotsugu Ishibashi Toyotsugu Ishibashi , Susumu Noda Susumu Noda
Published: October 2002

InP air/semiconductor gratings formed by the wafer fusion technique is investigated for implementation in novel structures. The grating shape after wafer fusion is changed depending on the duty cycle and/or the fused temperature. The cross-sectional view of the fused interface, observed using transmission electron microscopy (TEM), shows that there is no threading dislocation and the fused interface is not flat but curved, due to the mass-transport phenomenon. We also find that no voltage barrier exists at the n-n fused interface, but a voltage barrier exists at the p-p fused interface. The mass-transport has a significant influence on the electrical characteristics of the fused interface. A single longitudinal mode oscillation of a distributed feedback (DFB) laser with air/semiconductor gratings embedded by wafer fusion technique is demonstrated under pulsed condition at room temperature. The lasing wavelength is about 1.28 µm. The threshold current is 180 mA and the threshold current density is estimated to be about 1.3 kA/cm2.
High Power Performance of Nonbiased Optical Bistable Devices Using Multiple Shallow Quantum Well p-i-n-i-p Diodes
Authors: Kwon O-Kyun , Lee Kyu-Seok , Lee El-Hang , Ahn Byung-Tae
Published: October 2002

We studied the laser power dependence of the performance of nonbiased optical bistable devices (NOBDs) which are composed of two identical multiple shallow quantum wells p-i-n-i-p diodes connected in series. Under the illumination of the laser of a wavelength corresponding to that of the exciton absorption, the diode revealed both the maximum photocurrent and the large negative differential resistance in the forward bias region, fulfilling the conditions of the nonbiased optical bistable operation without any external bias voltage. With the laser power up to 2 mW in a circle of 10 µm diameter, the reflectivity change of ∼20% and the contrast ratio of 2:1 were maintained between the on- and off-states of the NOBD. These results ensure that the proposed device is a good candidate for high-speed optical bistable operation using a high power laser.
Organic Light Emitting Diodes with Reduced Spectral and Spacial Halfwidths
Authors: Siegfried Dirr Siegfried Dirr , Achim Böhler Achim Böhler , Stefan Wiese Stefan Wiese , Hans-Hermann Johannes Hans-Hermann Johannes , Wolfgang Kowalsky Wolfgang Kowalsky
Published: October 2002

Organic light emitting diodes (OLEDs) with reduced spectral and spacial halfwidths for full-color imaging applications are investigated. The electroluminescence behaviour of the lanthanide complexes Eu(TTFA)3Phen and Tb(ACAC)3Phen having sharp emission lines in the red and green spectrum, respectively, is examined for different OLED structures. Device optimization criteria with respect to multilayer design and material choice for this type of device are given. A Fabry-Pérot microcavity OLED is investigated to narrow the spectral width of commonly used organic materials (e.g. Alq3) from 100 nm to only 13 nm, demonstrating blue and green emission. In addition, the forward emission at the resonance wavelength is 8 times higher in intensity accompanied by a reduced spacial halfwidth. The directivity is further improved using materials with inherent narrow spectral widths. A spacial full-width at half maximum (FWHM) of 12° is demonstrated if the europium complex Eu(TTFA)3Phen is embedded into a microcavity structure. Compared to a non-cavity device as a reference, the emission intensity in this direction is significantly enhanced by a factor of about 8.
GaAs/AlGaAs Quantum Structures Grown in Tetrahedral-Shaped Recesses on GaAs (111)B Substrates by Metalorganic Vapor Phase Epitaxy
Authors: Tsujikawa Tomoko , Momma Keishi , Yaguchi Hiroyuki , Onabe Kentaro , Shiraki Yasuhiro , Ito Ryoichi
Published: October 2002

GaAs/AlGaAs quantum structures were grown in tetrahedral-shaped recesses (TSRs) on GaAs (111)B substrates at different growth rates by metalorganic vapor phase epitaxy. Observation of cathodoluminescence revealed that GaAs quantum structures with different layer thicknesses were formed at {100} edge regions, {110} and {111}A sidewalls and the {111} bottom region of the TSR. The luminescence from the bottom region of the TSRs was clearly seen in the sample grown at a large growth rate. With increasing growth rate, the thickness in the bottom region increased, whereas the thickness at the edge regions decreased. This is explained by a reduction in the migration distance of Ga adatoms from the {111} bottom region to the other regions.
Multitunneling Junction of Metal Droplets Formed on CaF2 Step Edges in a Self-Assembling Manner
Authors: Koji Kawasaki Koji Kawasaki , Marie Mochizuki Marie Mochizuki , Jun Takeshita Jun Takeshita , Kazuo Tsutsui Kazuo Tsutsui
Published: October 2002

One-dimensional metal droplet arrays of Ga and Al, the mean size of which was smaller than 8 nm, were formed along step edges on the surface of epitaxial CaF2 film in a self-assembling manner. The two-step method by which Al and Ga were sequentially deposited to grow Ga/Al double layer droplets was examined, and it was shown to be suitable to reduce gap spacing between neighboring droplets. A multitunnelling junction (MTJ) of Ga/Al droplets was formed by a two-step method and a MTJ diode was fabricated by a conventional lift-off process. Current–voltage characteristic of the device showed a Coulomb staircase at 25 K and room temperature.
Wrapped Alignment Marks for Fabrication of Interference/Diffraction Hot Electron Devices
Authors: Hiroo Hongo Hiroo Hongo , Yasuyuki Miyamoto Yasuyuki Miyamoto , Jun Suzuki Jun Suzuki , Michihiko Suhara Michihiko Suhara , Kazuhito Furuya Kazuhito Furuya
Published: October 2002

A wrapped alignment mark structure is proposed for a nano-fabrication process by e-beam lithography (EBL) with organometallic vapor phase epitaxy regrowth. To protect the alignment marks during regrowth, a SiO2 layer covers the surface of the gold mark and a thin tungsten layer is inserted between the mark and the substrate. The waveform serving as a mark detection signal is not significantly reduced after regrowth. By employing this mark system in EBL, an aligned nanostructure with a buried double-slit heterostructure and fine multi-electrodes is fabricated successfully to show the feasibility of this alignment mark method of wrapping. The center to center spacings of the double-slit and the fine electrodes are 40 nm and 50 nm, respectively.
AlGaAs/GaAs Laser Diodes with GaAs Islands Active Regions on Si Grown by Droplet Epitaxy
Authors: Egawa Takashi , Ogawa Akira , Jimbo Takashi , Umeno Masayoshi
Published: October 2002

The AlGaAs/GaAs laser diodes with the self-formed GaAs islands active regions on the Si substrates, showed a threshold current (I
th) of 260 mA, a threshold current density (J
th) of 5.4 kA/cm2 and a lasing wavelength of 791 nm with the full width at half-maximum (FWHM) of 2.8 nm under pulsed condition at 300 K and an I
th of 110 mA, a J
th of 3.9 kA/cm2 and a lasing wavelength of 771 nm with the FWHM of 1.8 nm under a continuous-wave condition at 100 K. The self-formed GaAs islands on Si, grown by the droplet epitaxy, exhibited a conical shape with heights of 8 nm and effective diameters of 300 nm. Compared with the conventional quantum well laser diode on Si, the self-formed laser diode on Si exhibited an improved reliability due to the reduction of the dislocation number in the active region.
Computer Analysis of Surface Recombination Process at Si and Compound Semiconductor Surfaces and Behavior of Surface Recombination Velocity
Authors: Adamowicz Boguslawa , Hasegawa Hideki
Published: October 2002

A theoretical analysis of the surface recombination is performed for n-Si, GaAs and InP surfaces under photo-excitation in terms of the so-called effective surface recombination velocity S
eff. A very strong dependence of S
eff both on the excitation light intensity and the surface fixed charge density has been found. S
eff reaches its maximum when n
s≈p
s, independently on the light intensity. S
eff can be significantly reduced by shift of the surface Fermi level towards band edges by means of the surface fixed charge Q
FC or by appropriately reducing or reshaping the surface state density distribution.
Terahertz Emission from Quantum Beats in Coupled Quantum Wells
Authors: Norihiko Sekine Norihiko Sekine , Kazuhiko Hirakawa Kazuhiko Hirakawa , Yasuhiko Arakawa Yasuhiko Arakawa
Published: October 2002

We have investigated the terahertz (THz) emission from quantum beats in coupled quantum wells by time-resolved THz spectroscopy. It is found that the intensity of the THz emission exhibits a clear resonance in the excitation wavelength, suggesting that quantum beats in coupled quantum wells are caused by excitons. It is also found that the dephasing time of quantum beats is almost constant (∼6 ps) up to 50 K and decreases rapidly with increasing temperature, indicating that the coherence of quantum beats is broken by impurity and/or roughness scattering at low temperatures and by optical phonon scattering at high temperatures.
Ballistic Weak Localization and Wave Function Scarring in Quantum Wires
Authors: P. Bird Yuichi Ochiai , K. Ferry Koji Ishibashi
Published: October 2002

Magneto-transports in a ballistic transport regime were studied in a double-sided corrugation-gated wire. A central peak at zero field was observed along with several symmetric peaks in the low temperature magneto-resistance. Although the side peaks were considered to have come from a multiple back scattering of electrons, the central peak depends strongly on the temperature, and could be explained by a ballistic weak localization effect. It can also be discussed by a numerical simulation of the wave function scarring in the corrugation units. It was observed that the relationship between the ballistic weak localization and the wave function scarring imparted important information on the dynamic behavior of electron transport in the corrugation wire.
Prebreakdown Light Emission and Current Pulses in Liquid Nitrogen
Authors: Kazuaki Yamazawa Kazuaki Yamazawa , Hisanao Yamashita Hisanao Yamashita
Published: October 2002

Prebreakdown light emission phenomena and current pulses in liquid nitrogen under positive and negative impulse voltages of both polarities were simultaneously observed. Two structures of light emission, bush-like and filamentary, were observed in both polarities. The light pulses could be classified into a few patterns. A close relation between these patterns and the structures of the light emission was found. From the streak photographs using the image converter camera, it was found that light emission appears intermittently and propagates in a stepwise manner. The prebreakdown current pulses occur prior to the corresponding light pulses, and the time difference between them is 40 ns for both polarities. From the results of these observations, the mechanisms that cause the difference of the light emission structures is considered. For the negative polarity, the structure is determined by the pulse activity after the initiation of the phenomena. In contrast, the structure is already determined at the instance of the initiation for the positive polarity.
A Critical Assessment of Different Models of the Metastability in a-Si:H
Authors: Rosa Chierchia Rosa Chierchia , Stefano Loreti Stefano Loreti , Vittorio Loreto Vittorio Loreto , Luigi Mariucci Luigi Mariucci , Carla Minarini Carla Minarini , Alberto Mittiga Alberto Mittiga
Published: October 2002

We have studied the light degradation and the thermal annealing of a-Si:H at different light intensities and temperatures monitoring both the defect density and the photoconductivity. This large set of data is used as a benchmark for the models of the metastability in a-Si:H. We show that an entire class of these models (which predict stretched exponential kinetics) is not in good agreement with our data. We discuss the mathematical and physical basis of these models pointing out some weak points that could explain these failures. The data are in better agreement with the “recombination induced bond breaking" models if an accurate description of annealing processes is included. The annealing rate must be computed considering a broad distribution of energy barriers. It must be also taken into account that the energy barrier for the annealing of a metastable defect can be reduced by a monomolecular trapping event at the defect itself. Our calculations show that this reduction amounts to an energy of about half the gap and lasts for a time of the order of 1 ps.
A Compact Buried-Channel Lightly-Doped-Drain Metal-Oxide-Semiconductor- Field-Effect-Transistor Model
Authors: Jang Sheng-Lyang , Chyau Chwan-Gwo , Liu Shau-Shen , Chiu Chung-Ming
Published: October 2002

In this paper, we report a complete, single-piece, and analytical drain current model for submicrometer buried-channel (BC) lightly-doped drain (LDD) metal oxide semiconductor field effect transistors (MOSFETs). The model is valid in all regions of operation, is suitable for a circuit simulator, and is developed using the quasi-two-dimensional approach. The BC device physics, bias-dependent LDD resistance, velocity saturation, drain induced barrier lowering and channel length modulation have been taken into account in the model. The accuracy of the resulting LDD BC MOSFET model has been checked by the experimental LDD data.
Influence of Microwave on Methane-Air Laminar Flames
Authors: Ogawa Satoru , Sakai Yasuhiro , Kenji Sato Kenji Sato , Setuko Sega Setuko Sega
Published: October 2002

The influence of microwave on methane-air premixed and diffusion flames was investigated in this work. The burned-gas temperature, brightness and electron temperature were measured for a flame situated in a cavity resonator excited in the TE011 microwave (2.45 GHz) resonant mode. The burned-gas temperature was measured with a radiation thermometer by observing the radiation from the end of the optical fiber inserted into the flame. The change of brightness was obtained with a photomultiplier tube. The electron temperature was estimated by the equivalent resistance method with double-floating electrostatic probes. While the burned-gas temperature increases by a few degrees, the electron temperature increases substantially with an increase of the microwave power introduced to the cavity. The brightness of the diffusion flame which is ascribed to the radiation of carbon particles, increases with an increase of microwave power.
Polymer-Dispersed Cholesteric Liquid-Crystal Device Containing Directly Stacked Right- and Left-Handed Layers
Authors: Kato Kinya , Tanaka Keiji
Published: October 2002

Right- and left-handed polymer-dispersed cholesteric (chiral nematic) liquid-crystal (PDCLC) layers are stacked directly between a pair of substrates. Each layer in a device containing these stacked layers exhibits independent characteristics. This is because the PDCLC structure confines the liquid crystal (LC) within small cavities (droplets) surrounded by polymer, preventing LC mixing between layers. This technique makes PDCLC devices polarization free and effectively increases the reflectivity of such devices.
(Pb,La)(Zr,Ti)O3 Thin Films Prepared by Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition for the Charge Storage Capacitor of a Gigabit-scale Dynamic Random Access Memory
Authors: Joong-Shik Shin Joong-Shik Shin , Won-Jong Lee Won-Jong Lee
Published: October 2002

Perovskite single phase (Pb,La)(Zr,Ti)O3 (PLZT) (0–22/60/40) thin films with a stoichiometric composition were successfully fabricated on Pt/Ti/SiO2/Si substrates at 490°C by the electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD). The characteristics of PLZT films for various La concentrations were investigated for the application to the charge storage capacitor of a gigabit-scale dynamic random access memory (DRAM). The La doped films showed paraelectric-like slim loop P–V hysteresis curves and almost no frequency dependence of permittivity. The doping of La caused the film surface to be very smooth. After rapid thermal annealing at 650°C for 1 min, the capacitance as well as the leakage current characteristics of the films were greatly improved. The 50-nm-thick PLZT(5.5/56/44) film had an effective capacitance of 133 fF/mm2 and an SiO2 equivalent thickness of 0.26 nm.
Initial Silicide Formation Process of Single Oriented (002) Hf Film on Si and Its Diffusion Barrier Property
Authors: Satoko Shinkai Satoko Shinkai , Katsutaka Sasaki Katsutaka Sasaki , Yoshio Abe Yoshio Abe , Hideto Yanagisawa Hideto Yanagisawa
Published: October 2002

We have investigated the initial silicide formation process of the single oriented (002) Hf film on (001) Si and compared it with that of the polycrystalline Hf film. From the results of X-ray diffraction analysis, we found that the first nucleation phase of Hf silicide is the multiphase silicides of Hf3Si2 containing a small amount of Hf5Si3 and the silicidation temperature is 420°C which is much lower than the values reported so far.The chemical nature of the silicide phase formed was evaluated by means of Auger electron spectroscopy and X-ray photoelectron spectroscopy. It is seen from these analyses that the chemical bonding state is the same as that of Hf3Si2, which has the lowest contact resistivity. Furthermore, it is also revealed that the diffusion barrier property of the single oriented (002) Hf film is superior to that of the polycrystalline Hf film, in which a rapid out-diffusion of Si occurs.
New Recordable Optical Discs with Metal Thin Film and Organic Film on Polycarbonate
Authors: Min Kyung Sun , Huh Youngjae Jae , Kim Sung Hoon , Wijk Robert Jan van , Dubbledam Gert , Maaskant Nico
Published: October 2002

A new recordable optical disc which has the advantages
of low material cost and wavelength dependence was proposed.
It consists of a polycarbonate (PC) substrate, a metal thin film,
an organic buffer layer, a metal reflective layer and an overcoat.
Its recording mechanism was investigated
by atomic force microscopy observation of each layer surface and
the recording characteristics were evaluated.
It was observed that the recording mechanism involves the thermal
deformations of the PC substrate, the thin metal film and the
organic buffer layer and the recording characteristics are equal
to those of a dye-based CD-R.
High-Density Optical Disc Mastering Using Photobleachable Dye
Authors: Higuchi Takanobu , Okumura Youichi , Iida Tetsuya
Published: October 2002

The authors earlier developed a UV laser beam recorder (UV-LBR) and the mastering process for a high-density optical disc. Although it has sufficient resolution for the current digital versatile disc
(DVD), the available resolution is not sufficient for the next generation DVD. Therefore, the authors have developed a new mastering process that can extend the resolution limit of the UV-LBR to realize the
next generation DVD. It uses photobleachable dye (PBD) coated over a photoresist layer. In this paper, the effectiveness of the new multilayer mastering process is
discussed, especially the writing ability of random data using 8/16-modulation. From the results of the experiments, the authors confirmed that the new process, which
consists of a multilayer using PBD, has an advantage over the conventional process in the high-density recording, for a recording capacity of 13 Gbytes or greater.
An Analysis of Noise Power Spectrum Due to Mark Variations of an Optical Disk System
Authors: Oh Sei-Joon , Jo Soonchul , Kim Soon-Gwang
Published: October 2002

Readout signal and noise power spectrum of an optical disk system
were simulated and the results were compared with the measured power
spectrum to analyze the major sources of noise in the system.
The readout signal and power spectrum were calculated by varying
the mark shape and position as well as beam off-track range.
The variations of mark length, position and beam off-track range were
assumed to have a Gaussian probability distribution.
The power spectrum of the readout signal was calculated by executing
a discrete fast Fourier transform algorithm.
From the fitting of the measured signal power spectrum,
the major sources of noise in our optical disk system were deduced to be
the variations of mark length, position and beam off-track range.
Persistent Spectral Hole Burning of Eu3+ Ions in Silicate Glasses
Authors: Koji Fujita Koji Fujita , Kazuyuki Hirao Kazuyuki Hirao , Katsuhisa Tanaka Katsuhisa Tanaka , Naohiro Soga Naohiro Soga , Hiroko Sasaki Hiroko Sasaki
Published: October 2002

Measurements of spectral hole burning have been carried out for
glasses with compositions of (75 - x)SiO2·xAlO3/2· 25NaO1/2·1.0EuO3/2(x = 0, 10, 15,
20, 25, 35) at 4.2 K. A persistent spectral hole can only be burned
in silicate glass containing Al2O3. The hole burning is accompanied
with no antiholes and lasts for 30 min to 1 h. This phenomenon is in
contrast to the hole shape and lifetime observed in an optical
pumping mechanism due to population redistribution among the
hyperfine levels previously reported for Eu3+-doped silicate
glass. With an increase in Al2O3content, the hole linewidth
becomes narrower and the hole depth increases. The variation in the
hole linewidth can be explained in terms of the structural changes
in the aluminosilicate glass.
Full-Multiple-Scattering Approach to L3 X-Ray Absorption Near Edge Structures of Amorphous Germanium
Authors: Yanagisawa Osami , Fujikawa Takashi , Naoe Shun-ichi
Published: October 2002

The observed L3 X-ray absorption near edge structures (XANES) spectra for crystalline and amorphous germanium are analyzed using full-multiple-scattering calculations. The prominent first peak found in the crystalline Ge spectra are absent in the amorphous Ge spectra. The difference in the spectra is accounted for by the bond-angle fluctuation in amorphous Ge where the Ge–Ge bond distance is fixed, but a bond-angle fluctuation of 10° should be taken into account. This angular fluctuation is in good agreement with that oserved in previous studies. Other effects, such as the electronic structure and core-hole potential are also investigated, and we find that the latter effect plays an important role in XANES analyses.
High Density Aluminum Etcher Process Window Characterization and Comparison
Authors: Jacobs John , Saito Kazumi , Yamamoto Jiro
Published: October 2002

The process characteristics of four, high density, aluminum, plasma etchers using three types of plasma sources
have been experimentally studied. Aluminum etch rate was found to depend mainly on process pressure, total flow rate,
chamber volume, and chlorine flow rate. In addition, when etching with a BCl3/Cl2 chemistry, aluminum line profile
appears to be comparable between plasma sources. Electrical breakdown on a IC capacitor, aluminum line critical
dimensions, and aluminum and photoresist etch rate uniformities were found to differ between etcher types. Since etch
rate uniformities and aluminum line critical dimensions appear to be determined by ion current flux, chamber design
and process parameters, and similar ion current flux values and process parameters can be obtained with different
plasma sources, it is suggested that the plasma source has limited affect on these characteristics. Only breakdown
voltage appears to depend on the plasma source.
Monitoring of Electron Energy Distribution Change from Optical Emission for Nonmagnetic Ultrahigh-Frequency Plasma
Authors: Kinoshita Keizo , Noda Shuichi , Okigawa Mitsuru , Hikosaka Yukinobu , Itabashi Naoshi , Inoue Masami
Published: October 2002

Fractional electron density, which is partial electron density in energy distribution, has been
measured in a high-density non-magnetic ultrahigh-frequency (UHF) plasma from optical emission
of rare gases (Xe, Ar, He). The technique was applied to rare gas mixed plasma, as well as
fluorocarbon gas containing plasma. In the calculation procedure, the fractional electron density was
assumed to be constant between the two threshold energies of the different emissions. In the
experiment, total electron density was changed by changing the UHF source power without changing
electron temperature measured by a single probe. However, in UHF plasma, the fractional electron
density between the threshold energy of ArI and HeI emissions increased more than total electron
density increase. This result was obtained both for Ar/He plasma and Ar/C4F8/He/Xe plasma. On the
other hand, fractional electron density over the threshold energy of He increased at about the same
rate of or less than the total electron density increase. In addition, the fractional electron density
between the threshold energy of XeI and ArI in Ar/C4F8/He/Xe plasma increased less than total
electron density increase. These results indicate that the electron temperature, which is commonly
used as a typical index value of electron energy of the plasma, does not reflect the fine structure of
EEDF. The optical technique can supplement this point, especially at the high energy tail of EEDF.
Electron Microscopy Study of Surfactant-Mediated Solid Phase Epitaxy of Ge on Si(111)
Authors: Aizawa Noriyuki , Homma Yoshikazu , Tomita Masahito
Published: October 2002

The effect of As surfactant on solid phase epitaxy (SPE) of Ge on Si(111) has
been investigated using in situ scanning electron microscopy and ex situ
transmission electron microscopy. As surfactant is supplied to an amorphous Ge
film in four different ways: co-deposition with the Ge film, deposition on the Si
substrate, deposition on each interface of 3-nm-thick Ge films in a multilayered
structure, and deposition on the surface of a Ge film. As at the Ge/Si interface
has a limited effect in suppressing island growth with a critical thickness of
about 20 monolayers (ML). Thicker film growth is achieved by the other three
SPE methods. Although the surface morphology slightly differs, the crystalline
quality is almost the same for all cases. An As surfactant on the surface of
amorphous Ge increases the crystallization temperature by 100°C compared to
the Ge islands temperature without As. This indicates that an As overlayer
inhibits structural relaxation on amorphous film by suppressing surface
diffusion of Ge atoms, thus changing the growth mode. In other SPE methods,
surface passivation with As due to segregation during deposition may also be
responsible for the suppression of islands.
X-Ray Photoelectron Spectroscopy Study of Junction Interface in In/BaRbBiO Films
Authors: Fumihiko Toda Fumihiko Toda , Tomoyuki Yamada Tomoyuki Yamada , Satoru Kishida Satoru Kishida , Heizo Tokutaka Heizo Tokutaka
Published: October 2002

The In/BRBO/STO specimens were fabricated by depositing
Ba0.6Rb0.4Bi1.0Oy (BRBO) on the SrTiO3 (STO) substrates
by means of molecular beam epitaxy
using 100% pure ozone and then, by depositing In metal.
From the X-ray photoelectron spectroscopy results,
we found that the In metal deposited on the BRBO/STO specimen removed the
oxygen from BRBO and produced InOx layer at the interface between
In metal and BRBO.
Dynamic Behavior in the Angular Distribution of Emission from a Micrometer-Sized Asymmetric Liquid Jet
Authors: Moon Hee-Jong , Lee Sang-Bum , Ko Kwang-Hoon , Kim Guang-Hoon , Lee Jai-Hyung , Chang Joon-Sung , Yi Jonghoon , Lee Jongmin
Published: October 2002

The dynamic behavior in the angular distribution of emission was measured from an asymmetrically
distorted liquid jet which was induced by laterally flowing gas. We observed that
the intensity pattern was restricted to around φ∼90°,
above 2% of the distortion parameter η. The fine structure of
the intensity pattern was also restricted to φ∼90°,
which is evidence of the directional emission of MDR (morphology-dependent resonance) lights. As η
increases, the intensity profile narrows down to φ∼90°
and then broadens at η≥5%. We found that a
broad peak shifts continuously with a linear relationship to η, which should
be related to the detailed shape of deformation. Broad split peaks were observed when the
intensity of emission was substantially enhanced for efficient coupling, which is not expected from
the ray-optics model for an ideal elliptical microcavity.
In-Plane Liquid Crystal Beam Steering Devices with a Beam Separation Structure
Authors: Okada Hiroyuki , Bos Philip J. , Onnagawa Hiroyoshi
Published: October 2002

In-plane liquid crystal beam steering devices with a beam separation structure have been
investigated. The separation between ordinary and extraordinary beams could be realized by using
a liquid crystal director inclined by 45° to an air-liquid crystal interface. Successful analog beam
control of 8° is obtained under an application of in-plane electric field. Reflection and
confinement phenomena are also obtained at the interface of the spatial distribution of the
refractive index.
Epitaxial Growth of Aluminum on Silicon Substrates by Metalorganic Molecular Beam Epitaxy using Dimethyl-Ethylamine Alane
Authors: Neo Yoichiro , Otoda Toshihiro , Sagae Katumi , Mimura Hidenori , Yokoo Kuniyoshi
Published: October 2002

In this paper, the growth process of aluminum on a silicon
substrate by metalorganic molecular beam epitaxy using dimethyl-ethylamine alane has been described. The crystallographic orientation of the
aluminum grains strongly depends on the substrate temperature. The
epitaxial single crystalline (111) Al grains grow on a (111) Si substrate at a
substrate temperature between 450 and 500°C. The bi-crystalline (110) Al
grains grow on a (100) Si substrate at the substrate temperature between
350 and 450°C. For a (100) Si substrate, the orientation of Al is related to the
reconstruction of the Si substrate. Furthermore, the selective growth of Al
into 1.5-µm-diameter via-holes is shown to be possible.
Growth Mode and Characteristics of the O2-Oxidized Si(100) Surface Oxide Layer Observed by Real Time Photoemission Measurement
Authors: Youichi Takegawa Youichi Takegawa , Yoshiharu Enta Yoshiharu Enta , Maki Suemitsu Maki Suemitsu , Nobuo Miyamoto Nobuo Miyamoto , Hiroo Kato Hiroo Kato
Published: October 2002

The initial thermal oxidation on Si(100)2×1 surfaces using oxygen have been investigated with real-time ultraviolet and synchrotron-radiation photoelectron spectroscopies at substrate temperatures (T
s) of 350–730°C and at O2 pressures of 3×10-7–1×10-5 Torr. At T
s below 600°C, the oxidation proceeded following a Langmuir-type adsorption mode, while at T
s above 700°C it indicated a two-dimensional island growth mode. The characteristics of the grown oxide also differ between the two temperature regions: the oxide grown in the high temperature region shows a rougher oxide/Si interface as well as a higher thermal stability against thermal decomposition as compared to the one grown in the low temperature region. These differences in the oxidation mode and the film characteristics between the two temperature regions are understood in terms of the presence of simultaneous oxide decomposition in the high temperature region.
Photoalignment Films of Polyesters with Photoreactive Main Chain
Authors: Song Soyoung , Watabe Mamoru , Adachi Takahiro , Kobae Takashi , Chen Yaohong , Kawabata Masami , Ishida Yutaka , Takahara Shigeru , Yamaoka Tsuguo
Published: October 2002

The photoreactive thin films of poly(oxyalkyleneoxy-1,4-phenylenediacryloyl), a PDA-n polyester
(n=2–5), were prepared. Their photoreactions and the liquid crystal (LC) photoalignment by irradiation
of linearly polarized UV light (LPL) were investigated. The PDA-n polyesters have photoreactive sites in
the polymer main chain and not in the side chain which is different from poly(vinyl cinnamate) (PVCi), a
well-known photoalignment polymer. These PDA-n thin films show different photoreactivities depending
on the number of methylene units, n. Odd-numbered PDA-n polyesters with higher photosensitivity than
even-numbered PDA-n polyesters show a dichroism due to irradiation with LPL which results in a
homogeneous alignment of the nematic LC.
Inelastic Rainbow Scattering of CH4 Molecules from a LiF(001) Surface
Authors: Yagyu Shinjiro , Murakami Fumiaki , Kino Yasunobu , Yamamoto Shigehiko
Published: October 2002

Angular intensity and velocity distributions of CH4 scattered from a LiF(001) surface have
been measured using CH4 molecular beams with energies in the range of E
i=190–570 meV. Rainbow scattering of CH4 molecules has been obtained for the [100] incident azimuthal
direction and the results are compared with the “Washboard” model proposed by Tully [J. Chem. Phys. 92 (1990) 680]. A qualitative agreement between our experimental
results and the model has been observed as far as the dependence of angular intensity
distribution of scattered CH4 molecules on both incident energy and surface temperature are
concerned. It is found that the attractive potential acting on CH4 at the LiF surface plays an
important role in determining the rainbow peak position. The model also explains the angular
velocity distribution of scattered CH4 molecules.
Comparison of Resolution between Lens Projection Optical and X-Ray Proximity Lithographies
Authors: Horiuchi Toshiyuki
Published: October 2002

Fundamental research on comparing the resolution between optical and X-ray
lithographies is carried out. It is difficult to print highly accurate patterns with fine
sizes of 0.1–0.15 µm by optical lithography, and X-ray proximity printing is expected
to be a candidate for the next generation technology. However, it is necessary for X-ray
lithography to have a great technological advantage at least in resolution to be
considered as a practical alternate method, but it is also not very easy to replicate such
highly precise patterns by X-ray lithography. Accordingly, the resolution should be
compared between optical and X-ray lithographies, and the improvement in
resolution must be clarified clearly and quantitatively. In this study, image intensity
curves for single slit patterns are compared between lens projection optical and X-ray
proximity lithographies. By investigating the exposure conditions when the
intensity curve widths at 30% relative intensity are equal to each other, a universal
relationship for obtaining approximately the same intensity curve profiles can be
shown in a simple graph. Using this relationship, resolution limits of the ArF excimer
laser and X-ray lithographies are roughly compared as an example.
A Multilayer-Coated Reflection Mirror for Microfabrication
Authors: Kinoshita Hiroo , Kimpara Yachiyo , Watanabe Takeo , Platonov Yuriy , Wood James. L.
Published: October 2002

We propose a multilayer-coated mirror for the first mirror of a beamline. Calculated
reflectivities of over 80% for B4C/W and C/Ni constant d-spacing multilayer-coated mirrors are
obtained at 6 keV. Moreover, by using the constant d-spacing multilayer-coated mirror, a
monochromatic light source with high reflectivity and high resolution is obtained at the glancing
angle of 1.5°. Furthermore, it is determined that a graded d-spacing multilayer-coated mirror,
i.e., a supermirror, is effective in this photon energy region since the half-width at half-maximum of the reflectivity increases. A multilayer-coated reflection mirror for beamline
optics is promising for applications in microfabrication and structure analysis of materials.
Quartz Crystal Microbalance Odor Sensor Coated with Mixed-Thiol-Compound Sensing Film
Authors: Saitoh Atsushi , Nomura Tooru , Munoz Severino , Moriizumi Toyosaka
Published: October 2002

The relationship between the sensing film material and odor sensor selectivity, as
measured using quartz crystal microbalance, has been examined in previous studies.
However, selectivity depends not only on the film material, but also on the structure of the
sensing films. In the present study, the relationship between the structure of sensing film
and the response characteristics observed during film is investigated. Thiol compounds with
different molecular structures and atomic groups were mixed and used as sensing film
materials. The mixing ratio was varied to produce different film structures. In addition, we
demonstrated a new self-assembly method for making a sensing film with the desired
specific response property, using the interaction between odor molecules and sensing film
molecules due to their affinity. The experimental results indicate that the sensor response is
influenced by the sensing film structure, and that sensors with specific response properties
can be produced by controlling the film structure.
Proximity Sensors Utilizing an Evanescent Acoustic Field Formed by a Piezoelectric Bending Vibrator
Authors: Kiyoshi Nakamura Kiyoshi Nakamura , Satoshi Hongo Satoshi Hongo
Published: October 2002

A proximity sensor utilizing an evanescent acoustic field formed by flexural plate waves is proposed. When the velocity of a flexural wave propagating in a thin plate is lower than that of air, an evanescent acoustic field can be formed in the air near a major surface of the plate. When an object comes into the evanescent field, the acoustic radiation admittance of the plate can be changed. Hence, proximity sensing can be achieved by measuring the electrical admittance of the piezoelectric bending vibrator. To confirm the characteristics of the proximity sensor, some experiments were carried out using a bending vibrator consisting of a 140° rotated Y-cut LiNbO3 plate with a polarization-inverted layer. It is demonstrated that when an object approached the surface of the vibrator, the admittance at the resonances of the bending vibrator decreased drastically as the distance d between the object and the vibrator decreased.
Vibratory Gyro-Sensor Using a Flexural Same-Form Double-Mode Disk Resonator
Authors: Hideki Tamura Hideki Tamura , Yoshiro Tomikawa Yoshiro Tomikawa , Takayuki Kikuchi Takayuki Kikuchi , Sumio Sugawara Sumio Sugawara
Published: October 2002

This paper deals with a new type of vibratory gyro-sensor using a flexural same-form double-mode disk resonator with additional inertia.
This vibratory gyro-sensor can be supported at its center of gravity, and has a flat structure to meet, at a right angle, the axis of the angular velocity to be measured.
The principle of the basic operation and the practical structure of the vibratory gyro-sensor are described in the first part of this paper.
In the second part of the paper the experimental results of a prototype gyro-sensor are explained.
Moreover, the modified vibratory gyro-sensor of the diaphragm type is also described in this paper.
The results obtained proved that the disk-resonator proposed by us operated as a gyro-sensor and showed relatively good gyro-sensor characteristics.
Propagation Characteristics of Surface Acoustic Waves on Langasite
Authors: Inoue Kenji , Sato Katsuo
Published: October 2002

The propagation characteristics of surface acoustic waves (SAW) on La3Ga5SiO14
were investigated by both experimental and numerical methods. The experimental results
of the SAW velocity and the coupling coefficient (k
2) on X-cut and Y-cut substrates were
in good agreement with the numerical results using the material constants reported
previously. However, the experimental results of the temperature coefficient of delay
(TCD) differed from that of the numerical calculations. So, a modification of the
temperature coefficients of the material constants was performed numerically by the
measured data using the direct search of optimization method. The numerical results
obtained using the new constants were in good agreement with the experiment result on
the X-cut and Y-cut substrates. Other cuts were also studied using the new constants.
Then it was confirmed theoretically and experimentally that the temperature stable cut
was located at (0°, 140°, 22.5°) cut with k
2 of 0.32% and TCD (second-order
coefficient) of 5.2×10-8/°C2.
Load Characteristics and Vibration Loci at the Driving Surfaces of Ultrasonic Rotary Motor using a Longitudinal-Torsional Vibration Converter
Authors: Tsujino Jiromaru , Nakai Kentaro , Sako Kazuhide , Ikegami Noritada , Noda Kohsuke , Suzuki Ryo
Published: October 2002

Characteristics of ultrasonic rotary motors using a longitudinal-torsional vibration converter,
15 to 50 mm in diameter, are studied. To obtain a large torque, ultrasonic motors using one-dimensional
longitudinal-torsional converters with diagonal slits are proposed. The converters
have simple and tough structures and are driven using only a longitudinal vibration transducer.
The vibration converters are fabricated from metal materials and have diagonal slits cut along the
converter circumference, adjacent to a nodal position of longitudinal vibration. The ultrasonic
motors consist of a vibration converter having a driving part at its free edge, and a rotor part
statically pressed to the driving surface using corned disk springs. The vibration characteristics
and vibration loci at the driving surfaces of these converters and motors are measured under
loaded and nonloaded conditions and at forward and reverse rotating conditions, using two laser
Doppler vibrometers. Vibration locus shapes are changed according to the load conditions and
frequencies. Maximum torques of over 0.2 N·m are obtained by the converters, 15 to 20 mm
in diameter, and at frequencies of 56 to 65 kHz. The maximum revolution speed obtained is
over 550 r.p.m. using a 15-mm-diameter motor of 56 kHz.