bluuebunny/crossref_metadata_2025 huggingface dataset:
Roles of Atomic Hydrogen in Chemical Annealing
Authors: Nakamura Kenjiro , Yoshino Kunihiko , Takeoka Shinya , Isamu Shimizu Isamu Shimizu
Published: October 2002

A systematic study has been performed to reveal the role of atomic hydrogen in chemical annealing, where the deposition of a thin layer and treatment with atomic hydrogen are repeated alternately, for the fabrication of a stable structure. Structural relaxation resulting from impingement of atomic hydrogen on the growing surface is differentiated into two processes: the structural promoted relaxation on the surface and changes caused within the sub-surface depending on the conditions for deposition of the thin layer and the flux of atomic hydrogen. The structural changes within the sub-surface resulted in either the widening of the optical gap or crystallization at rather low substrate temperatures (T
s: 100-150° C). High-quality a-Si:H with the optical gap of 1.87 eV exhibiting rather high stability against light soaking was successfully fabricated by this technique. The defect density of the film was 4×1015 cm-3 in its well annealed state and 6×1016 cm-3 in the saturated state. At high T
s, on the other hand, the hydrogen treatment mainly enhanced chemical activities of the growing surface and resulted in either narrowing of the optical gap or promotion of the grain growth.
Nanoscale Lithography with Electron Exposure of SiO 2 Resists
Authors: Thomas K. Whidden Thomas K. Whidden , John Allgair John Allgair , Angela Jenkins-Gray Angela Jenkins-Gray , Maroun Khoury Maroun Khoury , Michael N. Kozicki Michael N. Kozicki , David K. Ferry David K. Ferry
Published: October 2002

We report on electron-beam patterned hydrocarbon residues on silicon dioxide as chemical initiators in high temperature HF vapor etching for the production of nanolithographic masks (∼20 nm feature size). These are of utility in reactive ion etching based pattern transfer to the underlying substrate and, potentially, as dielectric components in nanoscale devices. Metallic cobalt, deposited through the oxide mask, has been used to generate 12–20 nm wide lines of cobalt silicide.
Difference of Si Selective Growth on Al 2O 3 and SiO 2 Substrates by Electron Beam Irradiation Method
Authors: Makoto Ishida Makoto Ishida , Hirosi Tayanaka Hirosi Tayanaka , Shunichi Yanagiya Shunichi Yanagiya , Tetsuro Nakamura Tetsuro Nakamura
Published: October 2002

Based on a proposed growth model of Si selective epitaxy on Al2O3, the selective epitaxy of Si on both Al2O3 and SiO2/Si substrates was investigated. It is clarified that the incubation time for the Si growth on Al2O3 depends on electron dose density and growth conditions. The incubation time increased with increasing electron dose density from 1015 to 1018 electrons/cm2. Thickness of the selectively grown layer is determined by taking the product of the growth rate and the incubation time difference. Selective Si deposition on SiO2/Si substrates was studied using an electron-beam irradiation method, because SiO2 is also the oxide material as Al2O3, and the same phenomena could be expected from our proposed mechanism. It was confirmed that the selective growth of Si was possible on the SiO2/Si substrate modified by electron beam irradiation. However, Si deposition on SiO2 occurred on the irradiated area, in contrast to the case of Si on Al2O3.
Coherent Transport through Electron Wave Directional Coupling Structures
Authors: Shinya Suzuki Shinya Suzuki , Lindor E. Henrickson Lindor E. Henrickson , Kazuhiko Hirakawa Kazuhiko Hirakawa , Toshiaki Ikoma Toshiaki Ikoma
Published: October 2002

We have theoretically investigated the coherent transport in quantum-mechanically coupled quantum wire structures by using the tight-binding Green's function method. Extension of the method to a four-terminal geometry is found to be essential in predicting transmission characteristics of quantum-wire electron wave directional coupling structures. It is found that the interwire transmission probability can be tuned from 0.02 to 0.95 by applying external gate electric fields. Thus, we have confirmed the basic operation of field-effect switching action. Furthermore, we have investigated the effect of a potential gradient along the channel on the transmission coefficients and found that the potential gradient significantly improves the interwire transmission probabilities.
Quantum Interference Effects in an Aharonov-Bohm Ring with a Gate
Authors: Mincheol Shin Mincheol Shin , Kyoung Wan Park Kyoung Wan Park , Seongjae Lee Seongjae Lee , El-Hang Lee El-Hang Lee
Published: October 2002

We have exactly treated the problem of the multichannel electrostatic Aharonov-Bohm effect in a ring structure with a voltage-controlling gate. We have found that, at zero temperature, the conductance oscillation patterns are complex because of contributions from individual channels. However, as the temperature is raised, the oscillations originated from the lower channels quickly vanish, and the overall conductance is almost completely governed by the topmost channel only, thereby making the situation very similar to the single-channel case in characteristics.
Low-Energy Focused Ion Beam Doping during Molecular Beam Epitaxial Growth for the Fabrication of Three-Dimensional Devices: The Effect of Dopant Surface Segregation
Authors: James H. Thompson James H. Thompson , Pier J. Sazio Pier J. Sazio , Harvey E.Beere Harvey E.Beere , Geraint A. C. Jones Geraint A. C. Jones , David A. Ritchie David A. Ritchie , Edmund H. Linfield Edmund H. Linfield , Gilbert W. Smith Gilbert W. Smith , Michael Houlton Michael Houlton , Colin R. Whitehouse Colin R. Whitehouse
Published: October 2002

An extreme example of surface segregation is found in Sn-doped GaAs grown by molecular beam epitaxy (MBE). Abrupt changes in the doping profile are not possible, instead the dopant concentration decreases exponentially towards the wafer surface from the point at which doping was terminated. In this work it is shown that segregation can be suppressed by implanting the Sn from a very-low-energy (50 to 300 eV) ion beam during growth. The effect of ion implantation energy is studied using secondary ion mass spectroscopy (SIMS) to measure the depth profile of the implanted Sn. It is found that the level of incorporation can be increased by up to a factor of eight using a 300 eV ion energy.
Role of Displacement Current in Quantum-Dot Turnstile Devices
Authors: Tuyoshi Hatano Tuyoshi Hatano , Kazuya Fujimoto Kazuya Fujimoto , Yoshimasa Isawa Yoshimasa Isawa
Published: October 2002

The dynamics of the current and the electron number in quantum-dot turnstile devices, in which the heights of the tunneling barriers are modulated by external rf signals, is studied theoretically within the adiabatic approximation. The displacement current is more accurately quantized than the tunneling currents flowing through both the left and the right barriers, since the leakage current is compensated. We find numerically that an electron tunnels through the barrier before its height reaches the minimum value. The tunneling phases of rf signals, at which an electron can actually tunnel, change as the amplitude of rf signals and the barrier height and width are varied. We also discuss the conditions for the current quantization. The dcI-Vcurve which we obtain shows a plateau at each quantized currentnefwith widthe2/C+ΔEand sharp steps between neighboring plateaus. Whenever the dc current is quantized, the change of the number of electrons in the quantum dot during one half-period of rf signal is an integer.
Theoretical Calculation of Photonic Gap in Semiconductor 2-Dimensional Photonic Crystals with Various Shapes of Optical Atoms
Authors: Toshihiko Baba Toshihiko Baba , Tomomi Matsuzaki Tomomi Matsuzaki
Published: October 2002

Photonic band gaps are calculated for various structures of semiconductor 2-dimensional (2D) photonic crystals for effective control of spontaneous emission. When the structure consists of a semiconductor and air, only circular holes periodically formed on the semiconductor substrate show the absolute 2D photonic gaps. However, it was seen that circular rods whose surface is covered with a dielectric film show a wide TM absolute gap. The latter is a promising structure due to the ease of fabrication and the small nonradiative recombination expected by the passivated semiconductor surface.
Photoluminescence and X-Ray Photoelectron Study of AlGaAs/GaAs Near-Surface Quantum Wells Passivated by a Novel Interface Control Technique
Authors: Satoshi Kodama Satoshi Kodama , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

Photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) study is performed on unpassivated and passivated AlGaAs/GaAs near-surface quantum wells (QWs) in order to clarify the mechanism of the recently found large PL intensity increase which was achieved by a novel interface control technique utilizing a SiO2/Si3N4/Si structure including an ultrathin silicon interface control layer (Si ICL). It is shown that the novel Si ICL technique produces a coherent interface structure free of oxides and nitrides, and this removes surface states without introducing additional confined electronic states that interfere with the fundamental e1-hh1 transition of the near-surface QW. The present technique seems to be applicable to passivation of various kinds of compound semiconductor quantum structures.
Charge Kosterlitz-Thouless Transition in Two-Dimensional Arrays of Small Tunnel Junctions
Authors: Shun-ichi Kobayashi Shun-ichi Kobayashi , Akinobu Kanda Akinobu Kanda , Ren-ichi Yamada Ren-ichi Yamada
Published: October 2002

We observed temperature dependence of resistance in two-dimensional random and regular small tunnel junction arrays, in the normal and superconducting states. Precursor behaviors of the charge Kosterlitz-Thouless (K-T) transitions were observed for the first time. We also observed the vortex K-T transition in random arrays. The results are consistent with theoretical phase diagrams.
Critical-Current Oscillations due to Interference Effects in a Clean-Limit Superconductor-Two-Dimensional-Electron-Gas-Superconductor Junction
Authors: Hideaki Takayanagi Hideaki Takayanagi , Tatsushi Akazaki Tatsushi Akazaki
Published: October 2002

We have confirmed the effects of interference on the superconducting critical current of a gate-fitted superconductor-normal metal-superconductor junction in the clean limit. As the normal metal, the junction uses a two-dimensional electron gas (2DEG), which is well confined in an InAs-inserted-channel InAlAs/InGaAs heterostructure. The superconducting critical current is measured as a function of the gate voltage and shows oscillations as a function of the 2DEG carrier concentration. This oscillation is explained by the Fabry-Pérot interference of the quasi-particles that undergo two normal reflections between two Andreev reflections.
Bound States in Superconductors
Authors: Satoshi Kashiwaya Satoshi Kashiwaya , Yukio Tanaka Yukio Tanaka , Masao Koyanagi Masao Koyanagi , Koji Kajimura Koji Kajimura
Published: October 2002

Bound states of quasiparticles in a normal metal placed between two different pair potentials are investigated. The energy levels of the bound states become discrete to satisfy a quantum condition, and are strongly affected by the macroscopic phases of pair potentials in the superconductors. The most interesting feature is formation of bound states on the Fermi level. Our model intuitively and systematically explains qualitative features of the bound states in various situations such as vortex cores and surfaces.
Quantization and Confinement Effects in Superconducting Films with an Antidot Lattice
Authors: Victor V. Moshchalkov Victor V. Moshchalkov , Marijke Baert Marijke Baert , Vitaly V. Metlushko Vitaly V. Metlushko , Erik Rosseel Erik Rosseel , Margriet Van Bael Margriet Van Bael , Kristiaan Temst Kristiaan Temst , Xiang-gang Qiu Xiang-gang Qiu , Rik Jonckheere Rik Jonckheere , Yvan Bruynseraede Yvan Bruynseraede
Published: October 2002

We have studied flux line confinement by regular arrays of submicron holes (triangular and square antidot lattices) in superconducting films. Critical current density j
c and pinning force f
p are very strongly enhanced due to pinning of single or multi-quanta vortices by the antidots. Direct measurements of j
c and f
p for several well-defined antidot diameters D, proves that pinning centers with size considerably larger than the temperature-dependent coherence length ξ(T) are much more efficient than those with D\congξ(T).
Platinum as Recombination-Generation Centers in Silicon
Authors: Bei Deng Bei Deng , Hiroshi Kuwano Hiroshi Kuwano
Published: October 2002

The general equations of steady-state lifetime in semiconductors with multiple deep impurity levels are derived based on the recombination theory. From the obtained equations the six capture cross sections of three Pt-induced levels in silicon are experimentally determined. The behaviors of minority carrier lifetime and leakage current in Pt-diffused devices are also discussed. It is found that the minority carrier lifetime is influenced by the three Pt-related levels and that the major contribution to the leakage current arises from the level ofEc-0.52 eV.
Effect of As Pressure on Se \mbδ-Doped in GaAs by Molecular Beam Epitaxy
Authors: Eriko Sano Eriko Sano , Yoshiji Horikoshi Yoshiji Horikoshi
Published: October 2002

Using elementary Se as an n-type dopant, Se δ-doped GaAs films were grown on (001) GaAs substrates by molecular beam epitaxy. The results of secondary ion mass spectroscopy and capacitance-voltage measurement show that it is necessary to use adequate As pressure during Se deposition to form a sharp interface. The Se concentration in the films did not change monotonically and reached a maximum value followed by a minimum value as a function of Se deposition time. The Se incorporation rate decrease over long Se deposition time is probably caused by Se condensation on the surface to form more volatile molecules. A possible model of the Se-adsorbed surface is proposed by considering the reflection high-energy electron diffraction patterns.
Photoluminescence Studies of Wurtzite Type W-ZnAl 2S 4 Single Crystals
Authors: Tetsuya Kai Tetsuya Kai , Masakazu Kaifuku Masakazu Kaifuku , Igor Aksenov Igor Aksenov , Katsuaki Sato Katsuaki Sato
Published: October 2002

Single crystals of wurtzite-type W-ZnAl2S4 have been grown by the chemical vapor transport technique. Structural studies of the obtained crystals using powder X-ray diffraction analysis revealed their wurtzite structure with random distribution of cations at tetrahedral sites, whereas optical experiments showed that the crystals obtained had a direct band gap of ∼3.7 eV and exhibited a strong blue photoluminescence (PL) even at room temperature, with two different luminescence peaks, each of which had a different excitation band. In order to explain the PL results, the configuration coordinate model for the radiative transitions involved in the formation of the PL bands has been proposed. The model takes into account a lattice relaxation around the deep center responsible for the blue emissions, as well as the splitting of the valence band of W-ZnAl2S4 caused by the effect of the noncubic crystal field and spin-orbit interaction.
Superconductivity at 63 K in YSr2.2Cu2.6Fe0.25Oy
Authors: Sheen Shyang-Roeng , Chen Dian-Hau , Chang Chau-Ting , Chen Yung-Fang , Chien Fan-Z. , Maw-Kuen Wu Maw-Kuen Wu
Published: October 2002

The iron doped Y-Sr-Cu-O superconductor was prepared via the oxalate coprecipitation method. The superconducting transition temperature is 63 K and the zero resistivity temperature is 55 K for YSr2.2Cu2.6Fe0.25O

y

. The superconductor has a tetragonal structure with the lattice constants of a=3.8022(10) Å and c=11.4206(36) Å. Preliminary characterization of the properties such as X-ray diffraction, resistivity, magnetic properties, lattice constants and oxygen content of the Y-Sr-Fe-Cu-O obtained after high-temperature treatment are reported.
Correlation between Hall Numbers and Tc in Y1-xCaxBa2Cu3O7-δ ( 0≤x≤0.5) Thin Films Prepared by RF Thermal Plasma Deposition Method
Authors: Yakabe Hisataka , Kosuge Michikazu , Tsujino Jiroh , Shiohara Yuh , Naoki Koshizuka Naoki Koshizuka
Published: October 2002

The temperature dependence of the resistivity and the Hall coefficient R
H was measured for Y1-
x

Ca

x

Ba2Cu3O7-δ thin films prepared on SrTiO3 substrates using the RF thermal plasma deposition method. Transition temperature T
c and resistivity of the as-grown film decrease with increasing Ca concentration. However, oxygen treatment affects the transport properties of the films and a slight increase in oxygen deficiency δ increases T
c in heavily Ca-doped samples through changes in the hole density. There is a maximum T
c of about 90 K with variation of the carrier density and further reduction of the oxygen content lowers T
c again. The value of the maximum T
c is independent of Ca concentration and a parabolic relationship between Hall number and T
c exists in the Y1-
x

Ca

x

Ba2Cu3O7-δ system.
One-Dimensional Model of Magnetic Domain Wall with Self-Induced Anisotropy
Authors: Pant Bharat B. , Matsuyama Kimihide , Yamasaki Jiro , Humphrey Floyd B.
Published: October 2002

A one-dimensional model of the domain wall with a spatially varying easy axis angle is presented. First, the easy axis profile is set to the ideal Bloch wall profile, and the resulting wall profile and wall energy are calculated. This procedure of setting the easy axis profile to the domain wall profile is performed iteratively using numerical techniques. At each iteration the wall profile is calculated using energy minimization. A more gradual evolution of the easy axis profile is also modelled, tilting the easy axis profile towards the domain wall profile with increasing iteration number. For both the abrupt and the gradual evolution, the domain wall width continues to increase and domain wall energy continues to decrease with increasing iteration number. Except for the initial ideal Bloch wall, the exchange energy of the wall is greater than its anisotropy energy. The depinning field to free the pinned wall is also calculated and found to reach an asymptotic value of ≃0.55 H

K
.
Electro- and Cathodoluminescent Properties of ZnS:Cu,Mn and ZnS:Cu,Tb Thin Films
Authors: Djazovski Oleg N. , Tanaka Shosaku , Kobayashi Hiroshi , Semienov Nikolay N. , Pasynkov Vladimir V.
Published: October 2002

The electroluminescent (EL) and cathodoluminescent (CL) characteristics of ITO-ZnS:Cu,Mn(Tb)-Al DC EL thin films were investigated. The experimental results showed that efficient resonant energy transfer takes place from self-activated ZnS and Cu centers to Mn ions resulting in high luminance of ZnS:Mn,Cu cells. EL properties of ZnS:Cu,Tb cells can be explained on the basis of the direct impact excitation model, while the energy transfer mechanism makes a negligible contribution to the excitation process. This accounts for the comparatively low EL luminance of Tb-doped cells.
Thermal and Dielectric Properties of Amorphous LiNbO 3
Authors: Kim Seong Hyun , Yang Yong Suk , Kim Ho Jong , Min Soo Kang Min Soo Kang , Min Su Jang Min Su Jang
Published: October 2002

Amorphous LiNbO3 was produced by the twin-roller quenching method and X-ray diffraction, trace of differential thermal analysis, and temperature- and frequency-dependent dielectric constants were measured. After glass transition and crystallization temperatures were confirmed by differential thermal analysis experiments, activation energies of both processes were calculated using Ozawa's non-isothermal method. From the results of temperature- and frequency-dependent dielectric constant measurements, dielectric relaxation mechanisms below and above glass transition and crystallization temperatures were considered.
A New Method of Evaluating the Resistance of Cross-Linked Polyethylene Compounds to Water Treeing
Authors: Zong-huai Fan , Noboru Yoshimura Noboru Yoshimura
Published: October 2002

In this paper, a new method of evaluating the resistance to water trees of various cross-linked polyethylene (XLPE) insulation compounds is presented. The new method is that water trees are grown in XLPE materials which are immersed in AgNO3 solution used as needle electrode. Water trees grown by this method have several characteristic properties such as spontaneous colouring and fast growth during the formation of water trees, as well as retention of their original structures after removal of the electric field. Several XLPE insulation compounds, whose water-tree-resistant properties are known, have been used to test and verify that the growth of water trees in AgNO3 solution is a very effective test method for evaluating the water-tree-resistant properties of different XLPE compounds.
Structural Study of Molten Silicon by Energy Dispersive X-Ray Diffraction Method
Authors: Susumu Takeda Susumu Takeda
Published: October 2002

Energy dispersive X-ray diffraction (EDXD) measurement on molten silicon has been carried out at three temperatures of 1693 K, 1733 K and 1768 K.
Three structure factors of molten silicon show the characteristic shoulder on the higher-wave-vector side of the first peak. Amplitudes of the structure factors in the first and second peaks are smaller than those obtained by the angular dispersive X-ray diffraction (ADXD) method. The analysis of the distribution function (RDF) shows that the coordination number of the first two neighbors is 5.7(3.7+2.0) at 1693 K, 5.4(3.7+1.7) at 1733 K and 5.7(3.7+2.0) at 1768 K.
These values suggest that the temperature dependence of the local atomic rearrangement is very weak in the temperature region investigated here.
Fabrication of Dye-Adsorbed Merocyanine Thin Films by a Bias Voltage Langmuir-Blodgett Technique
Authors: Itadera Kazuhiko , Kuniyoshi Shigekazu , Kudo Kazuhiro , Kuniaki Tanaka Kuniaki Tanaka
Published: October 2002

We have investigated the effect of bias voltage applied to an electrically conductive substrate on the formation of adsorption Langmuir-Blodgett (LB) films. In fabricating the adsorption LB films, a merocyanine dye with a long alkyl chain and a triphenylmethane dye are employed as spreading and adsorbing molecules from an aqueous subphase, respectively. The results demonstrate that the bias voltage LB technique is a powerful tool for controlling the adsorption ratio of a variety of functional dyes and the formation of dye aggregates.
Characterization of Spray Pyrolysed CdS Thin Film Doped with Cu
Authors: Mathew Sunny , Mukerjee P. S. , K. P. Vijayakumar K. P. Vijayakumar
Published: October 2002

Spray pyrolysed CdS thin film have been converted into p-type by diffusing Cu atoms for the first time. Copper atoms diffuse into CdS film when Cu/CdS bilayer system is annealed. The hot probe and Hall effect studies show that the n-type CdS film is converted into p-type. The resistivity of these films is quite high at low Cu concentration while further addition of Cu causes a drastic decrease in the resistivity value. The X-ray Diffraction (XRD), X-ray Photonelectron Spectroscopy (XPS) and optical absorption studies show that Cu merely diffuses into CdS and does not form any chemical reaction with sulphur to form new compounds. The Variable Angle Spectroscopic Ellipsometric (VASE) studies confirm the diffusion of copper into CdS and also shows that the Cu atoms diffuse ∼500 n
m into CdS due to annealing at 350° C.
Study on Microstructures and Interdiffusion Behavior in Pt/Ti/SiO2/Si and Pb(Zr, Ti)O3/Pt/Ti/SiO2/Si Multilayer Systems
Authors: Kim Sung-Tae , Kim Cha-Yeon , Park Kyu-Ho , Kim Kwang-Young , Lee Jeong Soo , Jeong Young Woo , Hyun Ja Kwon Hyun Ja Kwon
Published: October 2002

Interfacial phenomena in the O2-annealed multilayer systems of Pt/Ti/SiO2/Si and Pb(Zr, Ti)O3/Pt/Ti/SiO2/Si have been studied using Auger electron spectroscopy, X-ray diffraction and transmission electron microscopy (TEM). Emphasis has been placed on the microstructural analysis of interfaces. The strong tendency of titanium diffusion into platinum appeared to be responsible for the formation of an isolated platinum layer when the samples were annealed in O2 for 4 h at 450° C or higher. The formation of a TiO2 phase was confirmed at the annealing temperature of 600° C or higher. TEM analysis of the 650° C annealed sample confirmed the presence of a Pt-containing layer sandwiched by TiO2 layers. Rapid thermal annealing is strongly recommended to suppress undesirable interdiffusions and the resultant chemical reactions.
Preparation of Rutile TiO2Films by RF Magnetron Sputtering
Authors: Kunio Okimura Kunio Okimura , Akira Shibata Akira Shibata , Naohiro Maeda Naohiro Maeda , Kunihide Tachibana Kunihide Tachibana , Youichiro Noguchi Youichiro Noguchi , Kouzou Tsuchida Kouzou Tsuchida
Published: October 2002

TiO2films were prepared by rf (13.56 MHz) magnetron sputtering using a mixture of Ar and O2gases. At a total pressure of 2 mTorr, 100% rutile TiO2films were successfully obtained on non heated substrates with rf power of 200 W, while 100% anatase TiO2films were deposited at a pressure of 20 mTorr. Spatial profiles of both emission of excited species and plasma parameters were measured by optical emission spectroscopy (OES) and the Langmuir probe method. At a pressure of 2 mTorr, it was found that high-energy electrons are generated at a certain radial position near the cathode surface where the transverse magnetic field is maximum, and the strong localization of plasma was observed. It was proven that the energetic species impinging on the growing film are responsible for the formation of the rutile phase even if the substrate is at room temperature.
Simulation of Kinetic Electron Emission from Beryllium by keV Ion Impacts
Authors: Kawata Jun , Ohya Kaoru
Published: October 2002

A Monte Carlo simulation model of ion-induced kinetic secondary electron emission from beryllium, a candidate material for plasma-facing components in thermonuclear fusion devices, is developed. In the model, the conduction electron excitation by a projectile ion and the cascade multiplication process of the excited electrons are involved in production of secondary electrons in the solid. Due to increase in the excitation probability, the secondary electron yield increases with increasing impact energy and initial charge state of the projectile, and decreasing mass of the projectile. Nevertheless, the majority of secondary electrons are produced through the cascade process, so that the peak of the energy distribution of secondary electrons depends little on the impact energy and the species of the projectile. Due to increase in the energy transferred from the projectile to the electrons, however, the distribution progressively broadens towards the high-energy side as the impact energy is increased or as the mass of the projectile is reduced.
Bunch-Shape Monitor for a Picosecond Single-Bunch Beam of a 35 MeV Electron Linear Accelerator
Authors: Hosono Yoneichi , Nakazawa Masaharu , Iguchi Tetsuo , Ueda Touru , Kobayashi Tosiaki , Kozawa Takahiro , Uesaka Mitsuru , Ohkuma Juzo , Okuda Shuichi , Yamamoto Tamotsu , Suemine Shoji
Published: October 2002

A non-interactive-type bunch-shape and beam intensity monitor for a 35 MeV electron linear accelerator (linac) has been developed. The monitor consists of an electric SMA-type connector and an Al pipe of 50 mm inner diameter. Test measurements of the present monitor have been made under the conditions of the accelerated charges of lower than 27 nC/pulse and the pulse width ranging from 6 to 30 ps (Full Width at Half Maximum). The results show that the present monitor is applicable to bunch-shape measurement of the picosecond single-bunch beam. The monitor output is also found to be proportional to the beam intensity of more than 0.05 nC/pulse.
Electron Distribution Functions in a Sputtering Magnetron Discharge
Authors: Sheridan T. E. , Goeckner M. J. , J. Goree J. Goree
Published: October 2002

The electron distribution function g(v

z
) in a cylindrically symmetric, planar, sputtering magnetron has been characterized using a one-sided, planar Langmuir probe. Measurements were made above the magnetic trap at six radial locations in the direction normal to the cathode. The distribution function is found to be non-Maxwellian, with a shape that depends sensitively on radial position. Near the symmetry axis, g(v

z
) is anisotropic and exhibits a strong electron drift from the cathode to the anode. Off axis, g(v

z
) is nearly symmetric and has two components: a dense, cold Maxwellian component, and a tenuous, energetic shell component.
Observation of Polymer Alloy by Spectral Soft X-Ray Microscopy with Laser Plasma X-Ray Source
Authors: Takeichi Akihiro , Azuma Hirozumi , Shoji Noda Shoji Noda
Published: October 2002

A polymer alloy film on a photographic plate (ILFORD, Q-plate) was exposed to the dispersed soft X-rays in the wavelength region between 8.1 nm and 33.6 nm. A direct image recorded on the Q-plate was magnified by means of an optical microscope. The microscopic images for one of the component polymers in the polymer alloy containing silicon had circular spots of about 50 µ m in diameter scattered in a matrix with certain wavelengths of soft X-rays. A change in image contrast of the microstructure was observed in the wavelength range between 8.6 nm and 13.2 nm. This reversal of contrast suggests that these circular spots, or islands, are silicon-rich phases because the L-absorption edge of silicon is 12.3 nm. Spectral soft X-ray contact microscopy is useful in determining the wavelength region suitable for clear microstructure imaging, as well as in identifying constituent elements.
Atomic Species Analysis and Three-Dimensional Observation by High-Angle Hollow-Cone Dark-Field Transmission Electron Microscopy
Authors: Kakibayashi Hiroshi , Nakamura Kuniyasu , Tsuneta Ruriko , Mitsui Yasuhiro
Published: October 2002

Methods of determining atomic species and reconstructing three-dimensional images of the specimen structure were examined by high-angle hollow-cone dark-field transmission electron microscopy (HADF-TEM). The contrast of the HADF image systematically changed depending on the atomic number and the size of particles deposited on carbon films. The relationship between the contrast and the atomic number was well simulated using the theory of multiple electron scattering. The specimens, which were Cu particles precipitated in Si crystal, were observed with an inclination from -50 to 50° by steps of 2°. The images were processed using computed tomography. It became clear that the spatial distribution of the Cu particles differed depending on whether the precipitated position was a dislocation or a (111) stacking fault.
Effects of Postetching Treatments on Electrical Characteristics of Thermal Oxides on Reactive-Ion-Etched Silicon Substrates
Authors: Cheng Huang Chung , Ueng Shih Yuan , Wang Ping Wei , Kang Tzong Kuei , Chao Tien Sheng
Published: October 2002

Thin oxides thermally grown on the reactive-ion-etched (RIE) silicon substrates in N2O and diluted O2 ambients have been studied. The RIE will strongly affect the silicon surface microroughness and lead to poor oxides properties. Using the after-treatment-chamber (ATC) process, CF4 addition in the O2 plasma can further improve the time-zero-to-dielectric-breakdown (TZDB) characteristics of the thin oxides as compared with pure O2 plasma. This is because CF4 addition in the ATC can remove the damaged silicon layer and smooth the silicon surface since the O2 plasma can effectively only strip the polymeric layer. In addition, the N2O-grown oxides can enlarge the process window of the CF4/O2 ATC treatments with respect to pure oxides.
Surface Morphologies and Electrical Properties of (Ba, Sr)TiO3 Films Prepared by Two-Step Deposition of Liquid Source Chemical Vapor Deposition
Authors: Kawahara Takaaki , Yamamuka Mikio , Yuuki Akimasa , Kouichi Ono Kouichi Ono
Published: October 2002

Protrusions of (Ba, Sr)TiO3 (BST) crystallites were found to appear on BST film surfaces prepared by liquid source chemical vapor deposition (CVD) at a substrate temperature T
s=420° C and a reactor pressure P=1.5 Torr. Such protrusions were successfully suppressed by two-step deposition, where BST films consisted of a buffer layer and a main layer; the buffer layer was a CVD-BST film about 60 Å thick annealed in N2 ambient. By this two-step deposition on Pt electrodes, the BST film properties of equivalent SiO2 thickness t
eq=0.56 nm, leakage current J
L=1.2×10-8 A/cm2 at +1.1 V and dielectric loss tan
δ=0.011 were achieved at a total film thickness of 230 Å, along with a coverage of 80% at a trench of aspect ratio 0.65 and sufficiently low absorption current.
Effect of Substrate Temperature on Electrical Characteristics of (Pb, La)(Zr, Ti)O3 Ultrathin Films Deposited by Metalorganic Chemical Vapor Deposition
Authors: Hazumi Shigeki , Asano Takayuki , Hattori Masaya , Nakashima Hiroshi , Kobayashi Ichizo , Masaru Okada Masaru Okada
Published: October 2002

Lanthanum-modified lead zirconate titanate (PLZT) thin films (50-200 nm) were deposited on Pt/SiO2/Si substrates by metalorganic chemical vapor deposition (MOCVD). The electrical properties of the films were investigated as functions of the La content and substrate temperature. Ferroelectric PZT films were obtained at a substrate temperature as low as 500° C, and their electric characteristics were improved with increasing substrate temperature. La was adequately solid-dissolved into the PZT above 650° C. PLZT(15/45/55) films having a thickness of 100 nm were found to have good properties for application to capacitors of dynamic random access memory (DRAM), i.e., effective charge density of 80 fF/µ m2, dielectric constant of 1000, SiO2 equivalent thickness of 0.4 nm and leakage current density of 5×10-8 A/cm2. La addition to PZT was effective in reducing the leakage current with an increase in the registration rate.
Characteristic Change due to Argon Ion Etching and Heat Treatment of (Pb, La)TiO3 Thin Films Fabricated by Multiple Cathode Sputtering
Authors: Maiwa Hiroshi , Ichinose Noboru , Kiyoshi Okazaki Kiyoshi Okazaki
Published: October 2002

The ferroelectric properties of (Pb, La)TiO3 thin films fabricated by multiple cathode rf-magnetron sputtering were investigated. After argon ion etching of the (Pb, La)TiO3 thin films, the reduction of Pb-O bonds, shift of hysteresis loop on the E-axis and the decrease of remanent polarization was induced. After heat treatment at 700° C in N2, squareness and saturation of the loop worsened, and remanent polarization decreased. After reheat treatment of the films at 400° C for 1 h, the coercive field decreased, and the squareness of the loop was improved. These results were discussed from the viewpoint of the behavior of space charge.
Highly Oriented Pb(Zr, Ti)O3 Thin Films Prepared by Pulsed Laser Ablation on GaAs and Si Substrates with MgO Buffer Layer
Authors: Masuda Atsushi , Yamanaka Yasuhiro , Tazoe Mitsutoshi , Yonezawa Yasuto , Morimoto Akiharu , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

Highly [100]-oriented Pb(Zr, Ti)O3 (PZT) films were prepared on (100) GaAs and (100) Si substrates with MgO buffer layer by pulsed laser ablation (PLA). The depth profile of the constituent elements observed by X-ray photoelectron spectroscopy (XPS) shows that there are no remarkable interdiffusion and/or no formation of an alloying layer at both interfaces between PZT and MgO and between MgO and GaAs substrate. The [100]-oriented perovskite PZT films which exhibit the ferroelectric hysteresis loop were obtained on (100) Si substrate with MgO buffer layer with the thickness of only 50 Å, showing that this technique promises the realization of metal-ferroelectric-semiconductor field-effect transistors (MFS-FETs).
Epitaxial Orientation Control of LiTaO3 Film and Interfacial Coulomb's Potential
Authors: Fujimura Norifumi , Tsuboi Hiroshi , Taichiro Ito Taichiro Ito
Published: October 2002

A lithium tantalate film with a new epitaxial orientation, (112̄0), on R-cut (011̄2) sapphire, prepared by the rf magnetron sputtering method, has been confirmed. Growth orientation was controlled by paying attention to the state of sharing between octahedra in the structure and to the formation of the octahedra containing lithium and tantalum ions. The orientation of the film on (011̄2) sapphire changes from (011̄2) to (112̄0) upon increasing the Li concentration in the film. Lithium concentration can be increased by increasing the rf power, O2 partial pressure and total gas pressure, and by decreasing the substrate temperature during sputtering. Based on the consideration of the degree of freedom in sharing of octahedra containing Li and Ta, it can be shown that the (011̄2) epitaxial film can be formed even under a Li-poor condition, but stoichiometric Li concentration is needed to form the (112̄0) epitaxial films. The epitaxial relationship in the growth plane was confirmed to be 20°-rotated [0001] and [0001̄] LiTaO3ł[2̄110] sapphire, using an X-ray Laue method and reflection high energy electron diffraction. Although it is an unusual relationship, it is well explained in relation to the cohesive energies at the (112̄0) epitaxial film/(011̄2) sapphire interface.
Preparation and Rapid Thermal Annealing Effect of (Ba, Sr)TiO3 Thin Films
Authors: Ichinose Noboru , Takashi Ogiwara Takashi Ogiwara
Published: October 2002

In this paper, we describes the effect of rapid thermal annealing on the electrical properties of (Ba0.5Sr0.5)TiO3 (BST) thin films. BST thin films were grown by the rf magnetron sputtering method with rapid thermal annealing (RTA) at various temperatures. When BST thin films were deposited directly on boron-doped Si(100) (P-type) substrate, silicon-diffused oxide interlayers were formed between BST and P-type Si(100) depending on the RTA temperature. The dielectric constant of BST thin film was improved by RTA and the maximum value (∼100) was obtained at 700° C.
Transient Emission Mechanisms in Thin-Film Electroluminescent Devices with Rare-Earth-Ion-Activated SrS Phosphor Layers
Authors: Okamoto Shinji , Nakazawa Eiichiro
Published: October 2002

Transient emission processes in rare-earth-ion-activated SrS thin-film electroluminescent (TFEL) devices have been investigated by measuring emitted light waveforms. The rare-earth-ion activators are Ce3+, Pr3+, Nd3+, Eu2+, Sm3+, Tb3+, Dy3+, Er3+, Ho3+ and Tm3+. The waveforms can be classified into three groups according to light emission responsibility (LER) to applied voltage pulse. In Group 1, Tb and Dy with slow LER show abrupt decay at the trailing edge of each driving voltage pulse. This is due to the Auger process with strong interaction of the excited ions with electrons flowing backward in the SrS conduction band. In Group 2, Ce, Pr, Nd, and Eu with fast LER cause secondary emission at the edge. In Group 3, other ions show slower LER than in Group 2. In particular, Er decay curves indicate a single luminous center.
Measurement of Piezoelectric Constant of ZnO Thin Film on Si Microstructure
Authors: Tanaka Katsuhiko , Kubo Ryuichi , Ohwada Kuniki , Umeda Akira , Ueda Kazunaga , Usuda Takashi
Published: October 2002

The piezoelectric constant of a zinc oxide thin film on a silicon fixed beam was evaluated by a new method using a metal bar (Davies' bar) and a laser interferometer. The beam was fabricated by silicon micromachining techniques, and the ZnO film was deposited on it by rf sputtering. The film attached to the end of the Davies' bar was accelerated by striking the other end of the bar with a projectile, and the piezoelectric constant of the film was calculated from the strain and the electric charge. A reasonable value of e
31=0.43 C/m2 was obtained for the test specimen.
Preparation of Ferroelectric Thin Films of Bismuth Layer Structured Compounds
Authors: Watanabe Hitoshi , Mihara Takashi , Yoshimori Hiroyuki , Araujo Carlos A. Paz de
Published: October 2002

Ferroelectric thin films of bismuth layer structured compounds, SrBi2Ta2O9, SrBi2Nb2O9, SrBi4Ti4O15 and their solid solutions, were formed onto a sputtered platinum layer on a silicon substrate using spin-on technique and metal-organic decomposition (MOD) method. X-ray diffraction (XRD) analysis and some electrical measurements were performed on the prepared thin films. XRD results of SrBi2(Ta1-
x

, Nb

x

)2O9 films (0≤x≤1) showed that niobium ions substitute for tantalum ions in an arbitrary ratio without any change of the layer structure and lattice constants. Furthermore, XRD results of SrBi2
x

Ta2O9 films (0≤x≤1.5) indicated that the formation of the bismuth layer structure does not always require an accurate bismuth content. The layer structure was formed above 50% of the stoichiometric bismuth content in the general formula. SrBi2(Ta1-
x

, Nb

x

)2O9 films with various Ta/Nb ratios have large enough remanent polarization for nonvolatile memory application and have shown high fatigue resistance against 1011 cycles of full switching of the remanent polarization. Mixture films of the three compounds were also investigated.
Electrical Comparison of Sol-Gel Derived Lead-Zirconate-Titanate Capacitors with Ir and Pt Electrodes
Authors: Aoki Katsuhiro , Fukuda Yukio , Numata Ken , Akitoshi Nishimura Akitoshi Nishimura
Published: October 2002

The electrical properties of sol-gel-derived Ir/lead-zirconate-titanate (PZT)/Ir and Pt/PZT/Pt capacitors were carefully investigated. PZTs with columnar structures were well crystallized on both Ir and Pt substrates. 250-nm-thick PZT films deposited on Ir and Pt showed random and <111>-preferred orientations, respectively. The Ir/PZT/Ir capacitor showed large remanent polarization density of 20.7 µ C/cm2 at applied voltage of 2.5 V even though this PZT is randomly oriented. This value is almost equal to that of <111>-oriented film prepared on Pt. Furthermore, coercive field of the Ir/PZT/Ir capacitor is much lower than that of the Pt/PZT/Pt one. For endurance property for switching, Pr of Pt/PZT/Pt capacitor was degraded to 45% of the initial value by switching of 1×105 cycles. On the other hand, that of Ir/PZT/Ir capacitor was decreased to 45% by 1×107 switching cycles. Degradation of remanent polarization density by switching was reduced considerably by using Ir electrodes.
Relationship between Lifetime of Multilayer Ceramic Actuator and Temperature
Authors: Nagata Kunihiro , Shuichi Kinoshita Shuichi Kinoshita
Published: October 2002

The lifetime characteristics of the multilayer ceramic actuator (MCA) with applied DC or unipolar AC voltage at various temperatures are investigated. The relationship between the logarithm of the lifetime and the reciprocal of absolute temperature for the MCA with applied DC voltage showed linear characteristics similar to the Arrhenius type. The relationship between logarithm of lifetime and logarithm of applied DC voltage also showed linear characteristics. The lifetime decreases as the applied voltage increases. For an applied unipolar AC voltage of 50 Hz, the lifetime characteristic of MCA was similar to that obtained with DC voltage.
Improvement in Durability of Piezoelectric Ceramics for Actuator
Authors: Sakai Takenobu , Terai Youichi , Mamoru Ishikiriyama Mamoru Ishikiriyama
Published: October 2002

High-durability lead zirconate titanate (PZT) ceramics have been developed in order to prevent time-dependent degradation in displacement or failure under operation. The coercive field (E
c) and mechanical strength of PZT have been improved by doping various additives such as In, La, and Pr, in this study. Neither decrease of displacement nor formation of cracks took place in this new PZT after over 108 cycles of dynamic durability tests. The results indicated that both E
c and mechanical strength were important factors in improving the durability of PZT ceramics.
Rod-Type Ultrasonic Motor Using Two Degenerate Second Flexural Vibration Modes and Characteristic Consideration Using Its Equivalent Circuit Expression
Authors: Manabu Aoyagi Manabu Aoyagi , Yuuichi Nakano Yuuichi Nakano , Yoshiro Tomikawa Yoshiro Tomikawa
Published: October 2002

This paper deals with a simplified equivalent circuit of an ultrasonic motor and its application to the estimation of motor characteristics. Investigation of this equivalent circuit is conducted from the viewpoint of systematization of research on ultrasonic motors. The equivalent circuit must follow the principle of motor operation and must be expressed simply. We have considered the characteristics of an ultrasonic motor using its equivalent circuit expression. We propose simplified equivalent circuits of a rod-type ultrasonic motor using the two degenerate second flexural vibration modes; moreover, we show that the maximum torque, the suitable load, and power transmission can be easily estimated. As a result, we found that the estimated maximum torque was sufficiently close to the measured one and that the power transmission could be estimated by correction of the measured value of internal resistance.
Oxygen-Atmosphere Firing of Piezoelectric Lead Zirconate Titanate Ceramics Substituted with Lead Antimonate Niobate Having Submicron Particle Sizes
Authors: Kudo Satoru , Tashiro Shinjiro , Hideji Igarashi Hideji Igarashi
Published: October 2002

Piezoelectric lead zirconate titanate (PZT) partially substituted with Pb(Sb, Nb)O3 was used to obtain piezoelectric ceramics having high piezoelectricity and fine grains. Furthermore, the calcined powder was ground to submicron sizes and fired in oxygen atmosphere. Densification was promoted by this method, and dense ceramics were consequently obtained at low firing temperatures. Thus, it was clarified that oxygen-atmosphere firing of submicron-size powder was effective in obtaining piezoelectric ceramics with submicron-size grains.
Varistor Characteristics of (Ba, Sr)TiO3 Semiconducting Ceramics Fired in Reducing-Reoxidizing Atmosphere
Authors: Ishiya Tomohiro , Tashiro Shinjiro , Hideji Igarashi Hideji Igarashi
Published: October 2002

Varistor characteristics at room temperature were estimated for (Ba, Sr)TiO3 semiconducting ceramics having positive temperature coefficient of resistivity (PTCR) characteristics and a low Curie point less than -100° C. The samples were sintered in a reducing atmosphere at 1350 or 1400° C for 2 h and then annealed in an oxygen atmosphere at 1200° C for 2 h in the cooling process. These samples showed high permittivity originating from the barrier capacitance at grain boundaries in addition to the varistor characteristics. The varistor characteristics and dielectric properties depended on the potential barrier formed by the annealing in oxygen atmosphere.
Operation Performance of Self-Oscillation Ultrasonic Vibrating Device for Liquid Atomization
Authors: Toda Kohji , Jun Ishii Jun Ishii
Published: October 2002

An ultrasonic vibrating device, composed of a rectangular piezoelectric ceramic plate and a metal plate is described for liquid atomization. The resonance is used for the self-oscillation, which arises from the coupling between two vibration modes in the ceramic plate. The best operation occurs when one of the resonant frequencies of the vibrating device is equal to that of the piezoelectric ceramic plate without the metal plate. The ceramic plate has two electrodes on one of the two surfaces. A power feeding circuit is composed of the piezoelectric ceramic plate with three electrode terminals, which functions as a resonant element as well as a vibration source, and a power amplification transistor. The metal plate with minute holes functions effectively for liquid atomization.
Hydrothermal Crystal Growth of Lanthanum-Modified Lead Zirconate Titanate
Authors: Yanagisawa Kazumichi , Kanai Hideyuki , Yamashita Yohachi
Published: October 2002

Single crystals of lanthanum-modified lead zirconate titanate (PLZT) were grown under hydrothermal conditions. The starting nutrient at the bottom of the capsule dissolved in KF solution at 640° C, and recrystallized at the top of the capsule at 600° C. The basic shape of the grown crystals was cubic and they were black in color. The content of Zr in the crystals was markedly reduced in comparison with that of starting PLZT nutrient.