bluuebunny/crossref_metadata_2025 huggingface dataset:
Discrimination of Compound Semiconductor Heterointerfaces by Simultaneous Observations of Atomic Force Microscopy and Lateral Force Microscopy
Authors: Ikuo Suemune Ikuo Suemune , Mitsuo Hoshiyama Mitsuo Hoshiyama
Published: October 2002

ZnSe/GaAs heterointerfaces were studied with simultaneous probing by atomic force microscopy (AFM) and lateral force microscopy (LFM). Surface flatness of the (110) cleaved facets was examined with AFM and the frictional force was measured across the heterointerfaces with LFM. On (110) cleaved facets where ZnSe and GaAs surfaces are located on the same horizontal plane with atomic precision and are not distinguishable with AFM, different frictional forces between ZnSe and GaAs surfaces are observed with LFM. This demonstrates the possibility that the geometrical flatness and the difference of semiconductors on cleaved facets of semiconductor heterointerfaces are distinguished with the simultaneous probing of AFM and LFM, respectively. Abruptness of the ZnSe/GaAs heterointerfaces was found to be drastically improved by replacing ZnSe with ZnSe/ZnS0.18Se0.82 superlattices lattice-matched to GaAs.
Fluctuation in Two-Dimensional Stick-Slip Phenomenon Observed with Two-Dimensional Frictional Force Microscope
Authors: Fujisawa Satoru , Kishi Eigo , Yasuhiro Sugawara Yasuhiro Sugawara , Seizo Morita Seizo Morita
Published: October 2002

We used an atomic force microscope combined with a lateral force microscope (AFM/LFM) as a two-dimensional frictional force microscope (2D-FFM) to investigate the two-dimensional behavior of the atomic-scale friction between the cleaved surface of MoS2 and the Si3N4 tip apex of the microcantilever based on the two-dimensional stick-slip model. As a result, for the scan direction along the row of the stick-points, we found the unstable state where the tip apex shows fluctuation between two adjacent rows of stick-points. On the other hand, near the row of the stick-points, we also found the stable state where the tip apex takes a straight walk on a row of the stick-points without fluctuation.
Local Properties of Phase-Separated Polymer Surfaces by Force Microscopy
Authors: Motomatsu Makoto , Nie Heng-Yong , Mizutani Wataru , Tokumoto Hiroshi
Published: October 2002

Force microscopy techniques such as atomic force microscopy (AFM), friction force microscopy (FFM), and force modulation microscopy (FMM) were applied to polymer blend and copolymer surfaces to observe phase-separated structures and distinguish the individual components. We observed a continuous phase-separated structure of polystyrene (PS)/polyethyleneoxide (PEO) polymer blend, a micro-phase-separated structure of styrene (S)/butadiene (B) S-B-S-B block copolymer, and islands-sea phase-separated structures of PS/polymethylmethacrylate (PMMA) polymer blend and diblock copolymer with AFM. FFM and FMM were applied to PS/PMMA polymer blend and diblock copolymer, and FFM differentiated PS from PMMA.
Scanning Near-Field Optical Microscopy and Scanning Thermal Microscopy
Authors: Pylkki Russell J. , Patrick J. Moyer Patrick J. Moyer , Paul E. West Paul E. West
Published: October 2002

The development of the scanning tunneling microscopy has led to the development of related techniques which include the scanning near-field microscopy (SNOM) and the scanning thermal microscopy (SThM). These techniques provide sample information in addition to the simultaneously obtained topography. With SNOM normal optical microscopy contrast mechanisms (adsorbance, fluorescence, polarization, etc.) can be used. The principles and design of a SNOM are presented. Subwavelength resolution (better than λ/20) is demonstrated. In SThM, the contrast is provided by temperature and thermal conductivity. The design of a resistive thermal probe is described. Several operating modes are described and image contrast due to thermal conductivity is demonstrated.
Molecular Beam Epitaxy of Silicon-Based Heterostructure and Its Application to Novel Devices
Authors: Masanobu Miyao Masanobu Miyao , Kiyokazu Nakagawa Kiyokazu Nakagawa
Published: October 2002

Recent progress in Si heterostructure engineering is reviewed from physical and technological viewpoints. Advanced methods to fabricate atomic layer doping structures, Si on insulator structures, and strain controlled double heterostructures, i.e. Si/SiGe/Si and Si/silicide/Si using molecular beam epitaxy, are developed. Detailed characterization provides a comprehensive understanding of the physical phenomena behind these new crystal growth techniques. Application of these advanced methods to novel device fabrication is also discussed.
Alternating Magnetic Field Shielding of YBCO Tubes in Static Field
Authors: Soonchil Lee Soonchil Lee , Youngjo Go Youngjo Go , Dongyeon Won Dongyeon Won , Gyewon Hong Gyewon Hong , Sunchil Kwon Sunchil Kwon
Published: October 2002

The alternating magnetic field shielding efficiency of a YBCO tube was measured in a static field of up to 1 kG, bearing the possibility of its application as a field regulator in mind. The shielding efficiency is higher when the sample is field-cooled than when it is zero-field-cooled, as predicted by the critical state model. In the case of field cooling, the tube still shields about 25% of ac field of 1 kHz even in 500 G dc field. Shielding efficiency monotonously increases with increasing frequency from 10 Hz to 1 kHz.
Magnon Brillouin Scattering from an Amorphous CoNbZr Thin Film
Authors: Yoshihara Akira , Takanashi Katsutoshi , Shimoda Mamoru , Osamu Kitakami Osamu Kitakami , Yutaka Shimada Yutaka Shimada
Published: October 2002

Spin waves in a sputtered Co85Nb12Zr3 amorphous thin film have been studied by Brillouin scattering in external magnetic fields of up to 3.5 kOe. The spin wave and exchange stiffness constants of the CoNbZr film are determined as D
B=(2.47±0.3)×10-9 Oe ·cm2 and A=(0.98±0.14)×10-6 erg/cm, respectively.
Optical Pickup Using Blazed Holographic Optical Element for Video Disc Players
Authors: Yoshida Yoshio , Miyake Takahiro , Keiji Sakai Keiji Sakai , Yukio Kurata Yukio Kurata
Published: October 2002

A blazed holographic optical element (HOE) was used in the development of an optical pickup for video disc players. In the analysis, an optical utilization efficiency of 13.2% was obtained by optimizing the groove profile, although the HOE includes various grating pitches (from 1.6 to 2.2 µm). The blazed HOE was fabricated on a glass substrate by the ion-milling technique with CHF3 gas etching. The signal-to-noise ratio of the video signal reproduced with this optical pickup was more than 48 dB, and the pickup showed good environmental stability.
A Thin Film of an Ni–NiO Heterogeneous System for an Optical Recording Medium
Authors: Atsuko Iida Atsuko Iida , Reiji Nishikawa Reiji Nishikawa
Published: October 2002

The authors have found a write once read many (WORM) type new optical recording medium of an Ni–NiO heterogeneous system thin film. The structure of the recording medium is a single layer Ni–NiO heterogeneous thin film on a transparent resin substrate. Irradiation of a converged laser diode beam causes a volume expansion of the film to form a swell. Information reading is done by using its reduction in reflectivity. The recordable composition region of this film is considered to be the transitive region from the metal to the oxide. The volume expansion is assumed to be induced by the oxidation of the Ni–NiO heterogeneous thin film and the height of the swell is estimated. This value agrees well with the measured top height of the swell.
Calculation of Band Structures for Perovskite-Type Crystals Using Discrete Variational Xα Method
Authors: Kamiya Toshio , Tanaka Takeshi , Takaaki Tsurumi Takaaki Tsurumi , Masaki Daimon Masaki Daimon
Published: October 2002

Electronic structures of perovskite-type oxides were calculated using the discrete variational X α method. First, band structures and densities of states (DOS) were calculated for SrTiO3 and tetragonal BaTiO3. The calculated band structures agreed well with the previous reports and the DOS explained the XPS spectra measured well. Furthermore, band structures of SrTiO3/SrZrO3 superlattices with double period of SrTiO3 along [001], [011] and [111] directions were calculated. As a result, it was confirmed that the SrTiO3 and the [001] superlattice showed an indirect transition between the conduction band at the Γ point and valence band at the M or R point, while the [011] or the [111] superlattice showed a direct transition at the Γ point.
Influence of Interface Barrier on Lateral Transport Properties for Metal/Semiconductor Systems
Authors: Sekika Yamamoto Sekika Yamamoto , Tyuzi Ohyama Tyuzi Ohyama , Eizo Otsuka Eizo Otsuka , Syouichi Yamauchi Syouichi Yamauchi , Motohiro Iwami Motohiro Iwami
Published: October 2002

This work reports on an investigation of the transport properties of metal semiconductor systems in the direction parallel to the interface. Anomalies caused by the shunting effect for resistivity and Hall coefficient measurement on metal semiconductor systems were analyzed in detail. It is found that the above-mentioned anomalies are closely related with the Schottky barrier height as well as the current density across the metal semiconductor interface. The critical temperature at which a distinct indication of the shunting effect appears is around 200 K for NiSi2/p-Si system.
Polarization Fatigue Characteristics of Sol-Gel Ferroelectric Pb(Zr0.4Ti0.6)O3 Thin-Film Capacitors
Authors: Mihara Takashi , Paz de Araujo Hitoshi Watanabe
Published: October 2002

Fatigue characteristics of PbZr0.4Ti0.6O3 (PZT) thin-film capacitors made by sol-gel spin coating have been evaluated using hysteresis measurement by bipolar continuous pulses. The following three stages were found according to the cumulative polarization switching cycles: (1) slow fatigue stage at the initial switching cycles, (2) logarithmic fatigue stage at middle switching cycles which is recognized in general, (3) saturated stage at extremely large number of switching cycles. The decays of the nonswitched parts started in the middle of the logarithmic fatigue stage. The switching cycles at half of the initial remanent polarization are exponentially proportional to reverse electric field, and the degradation is explained in terms of an “electric-field-activating process” with an accelerating factor of 1.2×10-3 in units of decade kV/cm on our PZT thin-film capacitors. Temperature dependence of fatigue characteristics was unexpectedly small and activation energy was estimated to be 0.051 eV. A plausible fatigue model is proposed in which injected charge initiates the polarization fatigue.
Relationship between Film Thickness and Electro-Optical Properties in Polymer Dispersed Liquid Crystal Films
Authors: Rumiko Yamaguchi Rumiko Yamaguchi , Susumu Sato Susumu Sato
Published: October 2002

Dependences of turbidity and dielectric constant on film thickness in polymer dispersed liquid crystal (PDLC) films are measured for a polymer ball type and a droplet type morphology. Liquid crystal molecules tend to align parallel to a substrate at the interface between the film and the substrate for the polymer ball type PDLC film, where contrast ratio in the thinner film becomes larger than that of the droplet type films. Electro-optical properties are represented using turbidity and electric field instead of transmittance and applied voltage. The electro-optical properties for the droplet type PDLC film are independent of film thickness, and a relationship between the driving voltage and the contrast ratio can be estimated for an arbitrary film thickness.
Carbon Microfibers Grown on Graphite Electrode During Fullerene Generation Using Composite Graphite Rods
Authors: Ata Masafumi , Kijima Yasunori , Imoto Hiroshi , Nobuyuki Matsuzawa Nobuyuki Matsuzawa , Noboru Takahashi Noboru Takahashi
Published: October 2002

Using carbon/metal composite electrodes, silver-colored carbon deposits were obtained on the top edges of negative electrodes during electric arc vaporization for fullerene generation. Needle-shaped, rod-shaped, and winding carbon fibers 20–30 µm in length and 3–4 µm in diameter were observed on the surface of the deposits, using a scanning electron microscope (SEM). The results of energy-dispersive X-ray (EDX) microanalysis on the fibers showed that metal carbides exist at the top portions of these fibers. It was suggested that the growth of such fibers was induced by the catalytic activity of small clusters of metal carbides which act as seeds. The structures of the fibers were discussed based on these experimental results.
Location and Motion of Isotropic Paramagnetic Centres in Synthetic Monohydrocalcite
Authors: Callens Freddy , Debuyst René , Dejehet Fernand , Idrissi Samira , Peter Moens Peter Moens
Published: October 2002

The isotropic CO-
2 and CO-
3 centres in CaCO3·H2O were examined with electron spin resonance (ESR), electron-nuclear double resonance (ENDOR) and thermogravimetric analysis (TGA). From the absence of anisotropy and the small value of the 1H ENDOR splitting ( ∼0.3 MHz), the effect of crushing and/or thermal annealing on the ESR and TGA spectra, it is concluded that both isotropic centres are located in the occluded water, surrounding the constituent crystallites of the spherulites. ESR line width and 13C hyperfine coupling parameter measurements yield approximate values for the rotation activation energy (ΔE( CO3
-<ΔE( CO2
-) with ΔE∼ 0.2 eV) and for the vibrational frequency ( ∼2.1012 Hz for CO2
-).
Growth Behavior of Y1B a2C u3O7-xSuperconducting Thin Films Using Laser Ablation Technique
Authors: Huang Chin-Shih , Lin I-Nan , Lee Joseph Yan-min , Tseung-Yuen Tseng Tseung-Yuen Tseng
Published: October 2002

The growth behavior of Y1Ba2Cu3O7-x(YBCO) thin films on MgO substrates synthesized by laser ablation deposition techniques has been investigated. The effects of important parameters, i.e., substrate temperature, post annealing schemes, laser beam fluence and deposition chamber atmosphere on the crystal structure, microstructure and superconductivity of the deposited films have been studied. Among those important depositing parameters, the plume to film interaction was observed to impose the most prominent effect on the film characteristics. The films were found to consist mainly of a noncrystalline phase whenever the substrates were located either in the invisible or the supersonic zones of the plume. Only when the substrates are positioned in the reactive zone does the crystalline phase grow rapidly via a nucleation and growth mechanism. The (013) grains nucleate preferentially and are subsequently transformed into a (00m) orientation, possibly by diffusion. The number of (013) grains transformed increases with temperature used for step annealing and with time at that temperature.
Surface Morphologies of BaTiO3 Thin Films by Atomic Force Microscopy
Authors: Yoon Young Soo , Yoon Young-Ku , Lee Jeong Yong , Sang Seop Yom Sang Seop Yom
Published: October 2002

Surface morphologies of BaTiO3 thin films have been studied by atomic force microscopy (AFM). The films on (111)InSb, indium tin oxide (ITO)-coated glass and (100)Si substrates are deposited by in-situ metalorganic chemical vapor deposition (MOCVD) at different deposition temperatures of 300°C, 400°C and 600°C, respectively. AFM under ambient conditions showed that the BaTiO3 film deposited on the ITO-coated glass had a smooth surface consisting of large hemispherical grains, while the film on (100)Si had a slightly rough surface with <110> textured rectangular grains. As-grown film on the (111)InSb substrate was in the amorphous phase except near the interface, resulting in a rough surface. Our results of dependence on the kind of substrates and growth temperature suggest that the surface morphology of the as-grown films is strongly influenced by the crystallinity and growing characteristic of the film. For low-temperature growth below the deposition temperature of 600°C, surface roughness of the BaTiO3 film is strongly dependent on growth temperature rather than crystallinity of the films related to substrates.
Extended X-Ray Absorption Fine Structure Study on Local Structure around Fe Atoms in Fe/Ag Granular Materials
Authors: Sakurai Masaki , Makhlouf Salah A. , Sumiyama Kenji , Kimio Wakoh Kimio Wakoh , Kenji Suzuki Kenji Suzuki
Published: October 2002

The short-range structure of Fe/Ag granular materials has been studied by means of extended X-ray absorption fine structure (EXAFS). The local structure around Fe atoms is a distorted bcc structure for the as-deposited state of Fe/Ag granular films produced by the ionized cluster beam (ICB) deposition technique. Fe atoms are rather randomly distributed in the Fe/Ag alloy films produced by cosputtering. With increasing annealing temperature and time, the local structure around Fe atoms becomes a strain-free bcc structure in the ICB-deposited films, while Fe clusters are formed in the sputter-deposited films. The formation of small Fe clusters and rough interfaces between the Fe cluster and the Ag matrix is responsible for giant magnetoresistance (GMR) in Fe/Ag granular materials.
Magneto-Optical Characteristics of Bi-Substituted Rare-Earth Iron Garnet Films Prepared by Laser Ablation
Authors: Kidoh Hideo , Yashima Hideyuki , Akiharu Morimoto Akiharu Morimoto , Tatsuo Shimizu Tatsuo Shimizu
Published: October 2002

Bismuth substituted rare-earth iron garnet (Bi:RIG) films were prepared on (111) gadolinium gallium garnet (GGG) and glass substrates b laser ablation using the ArF excimer laser. Crystal structure of the garnet phase was obtained above the substrate temperature of about 500° C on GGG substrate without postdeposition annealing and on glass substrate with postdeposition rapid thermal annealing. Films with the easy magnetization axis normal to the film plane were obtained for Bi:DyIG and Ga- or Al-substituted Bi-YIG on GGG substrate. The Faraday hyster- esis loops and the magnetic domain were observed. On the other hand, the easy magnetization axis normal to the film plane was obtained for Bi:DyIG films on the glass substrate with postdeposition rapid thermal annealing.
Determination of Charge and Energy for Particles Penetrating a Silicon ΔE×E Telescope in Space Radiation
Authors: Hayashi Takayoshi , Doke Tadayoshi , Hasebe Nobuyuki , Fujiki Ken'ichi
Published: October 2002

A method of determination of charge and energy for energetic particles penetrating (not stopping) a multilayer silicon Δ E×E telescope with a finite thickness (12 mm) is examined in the energy region up to several hundreds of MeV/nucleon. From the results of the accelerator experiment, an energy resolution σ
E
of 1.2% in rms and a charge resolution σ
Z
of 0.11 charge unit in rms for Fe-group nuclei with energies between 190 and 230 MeV/nucleon are obtained. For lighter elements such as hydrogens and helium ions, an energy resolution σ
E
of 2.9% is obtained in the energy region between 33 and 42 MeV/nucleon and even their individual isotopes are separated. Also, the energy dependences of these resolutions suggest that this method can be utilized for particles with energies about two times larger than that corresponding to the range of telescope thickness for the evaluation of the space radiation effects even under the limitations of weight, size, and electric power supply.
Measurements of Diffusion Coefficient of CF2 Radical in DC Pulsed CF4/O2 Discharge Plasma
Authors: Arai Toshihiko , Goto Miki , Takayama Daisuke , Tetsuya Shimizu Tetsuya Shimizu , Masahiko Murakami Masahiko Murakami
Published: October 2002

Laser-induced fluorescence has been used to measure the CF2 radical ground-state densities after extinction of DC pulsed CF4/O2 discharge plasma. From the measurement, the CF2 radical was shown to be removed mainly by a diffusion process. Its diffusion coefficients are found to be D=150 cm2·Torr·s-1 in O2 and D=65 cm2·Torr·s-1 in CF4 at room temperature.
Time-Dependent RF Swarm Transport by Direct Numerical Procedure of the Boltzmann Equation
Authors: Kenji Maeda Kenji Maeda , Toshiaki Makabe Toshiaki Makabe
Published: October 2002

Electron swarm transport in rf fields under spatial homogeneity has been investigated by a direct numerical procedure (DNP) of the Boltzmann equation. The accuracy and validity of the DNP is examined by comparison with the previous results in Reid's inelastic ramp model gas in dc fields. The electron velocity distribution with strong nonlinear time variation and high anisotropy is demonstrated and discussed in Ar with the rf swarm parameter in order to show the power of the DNP over a wide range of frequency.
Plasma-Induced Chemisorption of Nitrogen and Its Chemical Reactivity on Alumina
Authors: Kunimori Kimio , Kuriyama Takashi , Shin-ichi Ito Shin-ichi Ito , Satoshi Kameoka Satoshi Kameoka
Published: October 2002

Nitrogen was chemisorbed on an alumina ( Al2O3) surface by plasma discharge of N2, and the chemical behavior of chemisorbed nitrogen was studied by temperature-programmed desorption (TPD) and infrared (IR) spectroscopy. Molecular nitrogen N2(ad) chemisorbed on an Al2O3 surface showed a high reactivity with hydrogen even at room temperature, if Pt is present on the Al2O3 surface. Hydrogenated species, NH

x

(ad) (x=1 or 2) and NH3(ad), were formed on the Al2O3 surface, as evidenced by IR spectroscopy. It is suggested that hydrogen spill-over from the Pt surface onto the Al2O3 catalyst plays an important role in the mechanism of hydrogenation reaction.
Electronic and Structural Characterisation of Boron-Doped Hydrogenated Silicon Thin and Ultrathin Films Prepared by RF Magnetron Sputtering
Authors: Sharma Shailesh N. , Bose Subhasis , Banerjee Ratnabali , Batabyal Ajit K. , Banerjee Dipali , Bhattacharya Ramen
Published: October 2002

Boron-doped hydrogenated silicon films were deposited by the rf magnetron sputtering techique using a poly-Si target and a sputtering gas mixture of argon, hydrogen and 1% diborane in argon. The effects of rf power density and substrate temperature on the properties of thin and ultrathin films were studied. The films were characterised by conductivity, Hall effect, optical transmission measurements, X-ray diffractometry, transmission electron microscopy and infrared vibrational spectroscopy. With suitable parametric optimisation, maximum conductivity values of 20 S cm-1 and 0.3 S cm-1 were realised for thin and ultrathin films, respectively. Highly conducting films ( ≥5 S cm-1) showed (220) orientation of silicon parallel to the substrate. Low power densities ( ≈0.9 W/cm2) resulted in a homogeneous growth and with increase in power density, evidence of boron crystal segregation was obtained. Conditions where conducting ultrathin films could be deposited on transparent conducting oxide without apparent degradation were determined.
High-Resolution Infrared Spectroscopy Applied to Powder Formation, Plasma Transport and Surface Processes
Authors: Boer Marco Haverlag , Gerrit Kroesen Gerrit Kroesen , Frits de Hoog Frits de Hoog
Published: October 2002

Infrared absorption spectroscopy using both a Fourier transform spectrometer and a tunable diode laser arrangement has been performed to study the growth of particles in an rf (13.56 MHz) plasma at pressures from 25 to 200 mTorr in mixtures of CF4, CF2Cl2 and CHF3 with argon. A planar configuration has been used, with a silicon wafer on the powered electrode. Absorption bands at 750–1300 cm-1 have been found and attributed to C-F, Si-F, C-Cl and Si-C absorption. Furthermore continuous extinction due to Rayleigh and Mie scattering has been observed. The CF2 concentration appears to decrease strongly when powder growth begins. The SiF4 concentration shows a maximum then. Considering all these results, we arrive at the conclusion that particle growth is initiated by micromasking at the Si surface combined with a highly directional etching process. Due to residual isotropic etching the particles are released from the surface and enter the plasma. Furthermore, it has been found that the powder production continues and even accelerates after the freon flow is stopped, due to sputtering of remaining structures on the surface.
Study on Growth Processes of Subnanometer Particles in Early Phase of Silane RF Discharge
Authors: Fukuzawa Tsuyoshi , Kawasaki Hiroharu , Masaharu Shiratani Masaharu Shiratani , Yukio Watanabe Yukio Watanabe
Published: October 2002

Growth processes of particles formed in an early phase of silane RF plasmas are investigated using the modified Langmuir probe, spectroscopic and photodetachment methods. From the probe measurements, the particles are estimated to be on the order of subnanometer size, and they are found to nucleate and grow principally around the plasma/sheath boundary near the RF electrode, where optical emission intensity of SiH radicals is high. These spatial profiles are different from those of positive and negative ion densities during discharging periods. These results suggest that many short-lifetime neutral radicals are necessary for the nucleation and subsequent growth of a particle. The photodetachment experiments and scanning electron microscope (SEM) observation also show that the particles are in the size ranges below about 200 atoms and about 1 nm. Spatial profile measurements of probe currents and negatively charged particle density obtained by the photodetachment method confirm that the mass of the particles around the plasma/sheath boundary near the RF electrode is large.
Overdense Plasmas Produced by Electron Cyclotron Heating in a Linear Multipole
Authors: Masayuki Fukao Masayuki Fukao , Ken-ichi Matsuura Ken-ichi Matsuura
Published: October 2002

A report is given of characteristics of a plasma produced by electron cyclotron heating (ECH) in a linear multipole (LMP) field configuration. The electron density measured by a 6 mm microwave interferometer reached 2×1012 cm-3, which corresponds to 30 times the cutoff density for the 2.45 GHz RF source. On the basis of the spatial distributions of electron density, electron temperature and space potential measured with Langmuir and emissive probes, the mechanism of overdense plasma production is discussed. Consideration is also given to steady operation of this configuration, which is essential for practical plasma process applications.
Effect of Axial Magnetic Fields on Electrical Characteristics of Low-Pressure Wire Discharge
Authors: S. Maeyama Hajime Urai , Hiroyuki Yasui Hiroyuki Yasui , Tohru Tamagawa Tohru Tamagawa
Published: October 2002

In order to reveal the potential of wire discharge as a high-density-plasma source, electrical characteristics of a wire discharge plasma were investigated, in particular, taking note of the effect of axial magnetic fields. The dc breakdown voltage and the delay time of a pulse discharge were measured in the presence of an axial magnetic field. When a single-wire anode is adopted, the effect of the magnetic field is very small. On the contrary, in the case of adopting two parallel anode wires, the axial magnetic field affects the discharge properties considerably.
A Study of the Sustaining Mechanism in an Inductively Coupled Plasma
Authors: Kenji Kond Kenji Kond , Hidehiko Kuroda Hidehiko Kuroda , Toshiaki Makabe Toshiaki Makabe
Published: October 2002

Inductively coupled plasma (ICP) has recently been of special interest in material processing reactors. We have developed a theoretical model based on the relaxation continuum (RCT) model for a collision-dominated ICP. The spatiotemporal behavior of ICP is investigated at 13.56 MHz in Ar under the crossed electric and magnetic fields. Electrons in time-varying electric and magnetic fields are transported in a complicated manner due to the appearance ofE×B-drift originating due to the Larmor motion. As a result, the electron energy gain and loss mechanism is controlled by the Larmor motion and the plasma is mainly sustained near the reactor wall during the phase when the external magnetic field is weakened. The space-time requirements for the maintenance of an ICP are investigated in terms of the net ionization rate and the electron flux.
Coupling of Excited-State Kinetics and Boltzmann Equation in Non-Equilibrium Plasmas
Authors: Capitelli Mario , Celiberto Roberto , Gorse Claudine , Savino Longo Savino Longo , Franco Paniccia Franco Paniccia
Published: October 2002

The need for coupling heavy-particle excited-state kinetics and electron dynamics in molecular and atomic plasmas is illustrated for different plasma conditions, such as DC (direct current). RF (radio frequency), laser pumping circuit, afterglow and multipole magnetic plasmas. Different systems ( N2, H2, O2, He, He–CO, He–CO–CO2–N2, SiH4, Ne–Xe–HCl) are discussed with emphasis on the role of excited states in shaping the electron energy distribution function under various plasma conditions.
Three-Dimensional Simulation of Target Erosion in DC Magnetron Sputtering
Authors: Shidoji Eiji , Nemoto Masaharu , Takuji Nomura Takuji Nomura , Yukio Yoshikawa Yukio Yoshikawa
Published: October 2002

We simulate the erosion profiles of a rectangular planar target in the DC magnetron sputtering system. The simulation model assumes time-independent magnetic and electric fields that are not disturbed by the magnetron plasma. The electron trajectories are obtained by integrating partial orbits. The Monte Carlo technique, taking account of the differential cross section, is used to discriminate the ionization collision from the excitation and elastic collisions. Thus we determine the coordinates where an argon ion and an electron appear to indicate the erosion profiles. The calculated 3D erosion profiles are in very good agreement with those of the target actually used. This simulation technique for the sputtering process will be valuable in designing the magnet arrangement of a magnetron sputter target.
Harmony Between Simple Fluid and Particle Models of Radio-Frequency Parallel-Plate Discharge
Authors: Savino Longo Savino Longo , Mario Capitelli Mario Capitelli
Published: October 2002

Parallel-plate radio-frequency (RF) discharge in low-pressure pure helium is studied using two different models: (1) a local, one-electron group fluid model, and (2) single-particle dynamics with Monte Carlo collisions assuming a harmonic oscillatorlike ambipolar field. It is found that the field parameters in the particle model can be selected in order to fit the experimental eedf in the bulk plasma. The bulk field found is near that of the fluid model. With change to a molecular gas (nitrogen), this two-stage approach allows for self-consistent coupling of the electron dynamics with the vibrational kinetics. When molecules are deactivated mainly through superelastic collisions with electrons, the coupling with the vibrational kinetics changes the eedf in the bulk plasma.
Radical Beams Produced by Laser Ablation and Their Application
Authors: Yoshiki Nakata Yoshiki Nakata , Yoshiyuki Sasaki Yoshiyuki Sasaki , Tatsuo Okada Tatsuo Okada , Mitsuo Maeda Mitsuo Maeda
Published: October 2002

A variety of solid targets such as Al2O3, Si3N4, YBa2Cu3O

x

and polymers were ablated with an ArF or KrF excimer laser. Laser-induced fluorescence spectroscopy (LIF) was used to detect species ejected from ablated targets and to characterize their kinetic properties. An aluminum radical beam produced from Al2O3 was applied to the measurement of the reactive cross section of Al with oxygen gas and to the study of the radical-surface interaction.
Cyclotron Resonance Mass Spectrometry of Ionic Radicals in Magnetized CF4Plasma
Authors: Tetsu Mieno Tetsu Mieno
Published: October 2002

The mass distribution of ionic radicals in a magnetized CF4plasma is measured by a newly developed ion cyclotron resonance mass spectrometer (ICR-MS). The density ratio of CF+to CF3+increases with plasma density for DC discharge and decreases with CF4pressure for electron cyclotron resonance discharge. Negative ions F-and F2-are detected at a CF4gas pressure of 3–9×10-4Torr for DC discharge. Fragmentation of a CF4gas by electron beam injection is also measured by this spectrometer.
Spatiotemporal Profiles of Optical Emission Spectra in CF4Discharges at 1 MHz
Authors: Ishikawa Itsuo , Kusunoki Hideki , Kobayashi Hidehiko , Yukinori Saito Yukinori Saito , Shinji Suganomata Shinji Suganomata
Published: October 2002

Spatiotemporally resolved observation of optical emission spectra was made in 1 MHz discharges in CF4and in CF4/N2mixture at the pressure of 0.5 Torr. The emission intensity peaks around phases ωt=0 and π of the applied voltage (Vsin ωt) were observed in addition to those around phases ωt=π/2 and 3π/2. These results are similar to those in electronegative SF6/N2mixture discharges, while their electrical properties are rather similar to those in electropositive N2discharges. Those characteristic optical emissions indicate the existence of a relatively intense field due to the space charge which is yielded by the presence of negative ions in the discharge space.
Time-Resolved Measurements of RF Plasmas Using Electrostatic Probe Having Compensation Circuits for Space Potential Fluctuation
Authors: Takashi Tatsuno Takashi Tatsuno , Toshiki Taniguchi Toshiki Taniguchi , Shosaku Matsumura Shosaku Matsumura
Published: October 2002

The time-resolved Langmuir probe method using a laser-heated emissive probe to compensate space potential fluctuation is modified to improve the limit of amplitude for compensation and reliability of current detection in order to experimentally study RF plasma under various conditions. Time-resolved electron temperatures and electron densities are measured at various input powers and pressures of Ar and He in 13.56 MHz RF asymmetric discharge. Not only the electron temperature but also the electron density change was synchronized with excitation RF. The period of variation is not the same as second harmonics, but is a fundamental period of 13.56 MHz. The electron temperature and the self-bias depend on the excitation RF power. Such evidence may indicate that plasma parameters are closely related with the electron acceleration in the electrode sheath and the plasma caused by the self-bias field.
Experimental Studies on Electrostatic Probe Responce for Large and Rapid Voltage Swing
Authors: Hideki Yoshii Hideki Yoshii , Suui Sasaki Suui Sasaki , Shousaku Matsumura Shousaku Matsumura
Published: October 2002

An electrostatic probe current response for large and rapid voltage swing of probe voltage is investigated experimentally. The probe current overshoot for the positive step voltage is greater than that for the negative step voltage even if the final value is the same in the electron and the ion saturation regions. The instantaneous probe current for the sinusoidal probe voltage begins to shift when the frequency exceeds the ion plasma frequency. Therefore, it has become clear that time-resolved measurement is not applicable to reduce distortion of the conventional time-averaged probe characteristics when the space potentials fluctuate rapidly.
Fundamental Studies of Ozone Generation and Its Characteristics Using New Type of Ozonizer
Authors: Yamabe Chobei , Satoshi Ihara Satoshi Ihara , Masashi Ishimine Masashi Ishimine
Published: October 2002

Fundamental studies of a new type of ozonizer, which has no dielectrics between main metal electrodes and has a circuit called charge transfer, have been carried out. The rate constant k
1 for the reaction of O+O2+O2→O3+O2 has been measured through absorption measurements using the 253 nm line of a mercury lamp in He/O2 mixtures at atmospheric pressure.
Electrical Properties of Planar RF Discharges Including the Second Harmonic Frequency
Authors: Kawata Hiroaki , Takashi Kubo Takashi Kubo , Kenji Murata Kenji Murata
Published: October 2002

The second harmonics in both voltage and current waveforms are measured for RF Ar discharges in an asymmetry parallel-plate-type reactor. These values greatly depend on the matching network impedance at the second harmonic frequency. We mainly measure the second harmonic voltage and current under a small second harmonic current. The second harmonic voltage is calculated based on an equivalent circuit model of the discharge with nonlinear components. Although the sheath voltage distortion due to the sheath dynamics in the nonuniform ion density distribution is a main source of the second harmonic component, the power loss through inelastic collisions, which depends on the RF phase, is also important.
Preparation and Properties of (ZnS)3(ZnSe)42 Ordered Alloys Fabricated by Plasma-Enhanced Low-Temperature Growth Technique
Authors: Fujiwara Hiroyuki , Nabeta Toshiyuki , Hideaki Kiryu Hideaki Kiryu , Isamu Shimizu Isamu Shimizu
Published: October 2002

Gallium-doped ZnSe and ordered alloys, (ZnS)3(ZnSe)42, were grown on a GaAs substrate. Low-temperature growth (T
g=200° C) of ZnSe and ZnS films was performed by hydrogen radical-enhanced chemical vapor deposition (HRCVD) using triethylgallium (TEGa) as the dopant source. Atomic hydrogen generated by RF plasma is used to enhance the formation of the depositing species. Two-dimensional ordered structures on the atomic scale were achieved by atomic layer epitaxy (ALE). In photoluminescence (PL) measurements of doped ZnSe films, the emission intensity attributed to the neutral donor-bound exciton increases with increasing TEGa flow rates. Strong blue PL emission was observed for the doped ZnSe film with optimized TEGa flow rate at room temperature. In X-ray diffraction (XRD) spectra of the ordered alloys, satellite peaks due to the layered structure were observed. A carrier concentration of 3×1016 cm-3 and a Hall mobility of 154 cm2/Vs were obtained for the ordered alloy, (ZnS)3(ZnSe)42, at room temperature.
Study of Deposition Process in Modulated RF Silane Plasma
Authors: Kirimura Hiroya , Maeda Hiroshi , Murakami Hiroshi , Nakahigashi Takahiro , Ohtani Satoshi , Tabata Takao , Hayashi Tsukasa , Kobayashi Masanao , Mitsuda Yoshie , Nakamura Nobuyuki , Hajime Kuwahara Hajime Kuwahara , Akira Doi Akira Doi
Published: October 2002

The influences of plasma parameters on the deposition of a-Si:H film and particle growth have been studied with silane discharge using amplitude-modulated RF methods. Plasma parameters have been measured with the Langmuir probe system and optical emission spectrometer. Behaviors and generation processes of particles have been observed by the laser scattering method. The deposited thin film has been characterized by various techniques such as Fourier-transform infrared (FT-IR) spectrometry, ESR and the constant photocurrent method (CPM). High deposition rate with low particle density as well as high film quality has been realized for a-Si:H film by amplitude-modulated RF methods.
Deposition Mechanisms of SiO2 in Remote Plasma Chemical Vapor Deposition Analyzed by Spatially Resolved Mass Spectroscopy
Authors: Fuyuki Takashi , Tohru Oka Tohru Oka , Hiroyuki Matsunami Hiroyuki Matsunami
Published: October 2002

The decomposition of silane ( SiH4) with activated neutral oxygen is investigated by spatially resolved quadrupole mass spectroscopy (QMS). SiH4 molecules were found to be decomposed in the vapor phase by collisions with activated neutral oxygen. Generation of hydroxyls (OH, H2O) is discussed in relation to the chemical reactions in the vapor phase and on the substrate surface. The analysis of activation energy in the evolution of hydroxyls from growing surfaces infers that Si–O bonds form on substrate surfaces releasing OH and H2O into the vapor.
Chemical Kinetics of Chlorine in Electron Cyclotron Resonance Plasma Etching of Si
Authors: Ono Kouichi , Tuda Mutumi , Nishikawa Kazuyasu , Tatsuo Oomori Tatsuo Oomori , Keisuke Namba Keisuke Namba
Published: October 2002

Electron cyclotron resonance (ECR) plasma etching of Si in Cl2 has been studied from the viewpoint of plasma chemistry. Experiments were performed over a wide pressure range (0.2–10 mTorr), using a divergent magnetic-field ECR plasma reactor supplied with 2.45-GHz microwaves; a floating electrode or substrate holder was located ∼30 cm downstream (B≈150 G) of the 875-G ECR resonance region, and samples of polycrystalline Si were etched with no additional wafer biasing. Several diagnostics were employed to characterize the plasma around the wafer position, including two-photon laser-induced fluorescence (LIF) for detection of Cl atoms and Fourier transform infrared (FTIR) absorption spectroscopy for etch products or SiCl

x

(x=1–4) molecules. The Si etch rate behavior obtained is interpreted in terms of a modified adsorption-reaction-ion-stimulated desorption process model based on these diagnostics.
Multilayer Resist Profile Control in Oxygen Reactive Ion Etching Using Ethanol Gas Mixture
Authors: Kimura Yasuki , Ryouichi Aoyama Ryouichi Aoyama , Seki Suzuki Seki Suzuki
Published: October 2002

By adding ethanol gas to oxygen-based chemistry, the controllability of resist profile and the overetch characteristic, under the condition with nearly no areas of material to be etched (etchable area), are improved. A model for resist profile control in which the resist profile is determined by the ratio of the sum of the isotropic etching component and the isotropic deposition component to the anisotropic etching component, is examined by evaluating the dependence of the resist profile and the etching rate on gas composition, the product of ion energy and ion current density (ion impact), and line and space (L & S) width. Both the gas composition and L & S width affect the sum of isotropic components. Ion impact affects the anisotropic etching component. When the isotropic components are balanced, resist profile is independent of ion impact and L & S width.
Effect of Magnetic Field to Etching Characteristics of Inductively Coupled Plasma
Authors: Jiwari Nobuhiro , Fukasawa Takayuki , Nakamura Akihiro , Kubota Kazuhiro , Shindo Haruo , Yasuhiro Horiike Yasuhiro Horiike
Published: October 2002

As a first attempt, SiO2 etching characteristic is studied in a plasma produced by partially propagating helicon wave. The plasma is produced employing a ring magnet whose field profile has a zero point. Highly selective SiO2 etching is attainable in a down stream where the electron energy is fairly low, because no propagation of helicon wave and thus no radio frequency (RF) field exist there. The propagation is found by the wave pattern measurements.
Interband Tunneling Mechanisms and Effects of AlSb Center-Barrier Layer on Light Particle Coupling and Reverse I-V Characteristics of GaSb/AlSb/InAs/AlSb/GaSb/AlSb/InAs Triple-Barrier Structures
Authors: Hwang Liu Meng , Yeong Her Wang Yeong Her Wang , Mau Phon Houng Mau Phon Houng
Published: October 2002

Light particle coupling-induced tunneling has been proven to contribute to the peak current density. The overlap carrier distribution combined with the transmission coefficient is utilized to interpret the interband tunneling mechanisms. The incorporation of an AlSb layer into the GaSb/InAs interface of GaSb/AlSb/InAs/GaSb/AlSb/InAs broken-gap structures results in GaSb/AlSb/InAs/AlSb/GaSb/AlSb/InAs triple-barrier interband tunneling structures, which have been demonstrated previously. The effects of the incorporated AlSb layer on the light particle coupling are theoretically investigated with the three-band model. It was found that, while incorporating the AlSb layer into the GaSb/InAs interface, the light-particle coupling at the interface becomes weaker, and the active region finally degenerates into two separate InAs and GaSb quantum wells. In addition, the AlSb center barrier also affects the reverse I-V characteristics of the triple-barrier structures, leading to a negative differential resistance in the reverse characteristics. The effect of the AlSb center barrier on the reverse I-V characteristics of the triple-barrier structure is also discussed.
Observation of HCl- and HF-Treated GaAs Surfaces by Measuring Contact Angles of Water Droplets
Authors: Matsushita Koichi , Miyazaki Shuji , Sumio Okuyama Sumio Okuyama , Yasuji Kumagai Yasuji Kumagai
Published: October 2002

A GaAs surface chemically treated with hydrochloric acid (HCl) or hydrofluoric acid (HF) has been characterized by measurements of the contact angle between the surface and a water droplet on it in air. The contact angle measured from the GaAs samples dipped into water shows the formation of a thin surface layer on the GaAs surface and the subsequent removal of the layer upon chemical treatment with HCl or HF solution. Annealing in nitrogen atmosphere is shown to be effective in stabilizing the surface against water.
Coercivity Acquisition in Permanent Magnet Materials: an Exchange-Controlled Mechanism
Authors: Jesús Marí a Gonzalez Jesús Marí a Gonzalez , Federico Cebollada Federico Cebollada
Published: October 2002

In this work we present an experimental study on the acquisition of coercivity in REFeB (RE=rare earth) finely microstructured hard magnetic materials with grain sizes below the single-domain critical dimensions. By measuring the volume percentage of the samples that became coercive upon application of a given magnetic field, we have obtained the values of the fields required to develop coercivity in 50% of the grains of the hard phase. These fields were clearly lower than those obtained in previous works for materials of similar composition and larger mean grain size (multidomain grains). In order to account for the experimental behavior, we have considered the results obtained from a simple model of the evolution with the magnetic field of the moment distribution at the grain boundary regions. From this we suggest that the acquisition of coercivity in our samples is closely linked to the occurrence of exchange-driven, collective magnetization and demagnetization processes.
Absorption Lines of Vibrationally Excited O2 and HF in ArF Laser Spectrum
Authors: Shimauchi Midori , Miura Tokiwa , Hiroshi Takuma Hiroshi Takuma
Published: October 2002

In a N2 atmosphere the ArF laser spectrum is observed in various spectral resolutions. Many absorption lines sensitive to the O2 impurity produced by shots of the pulsed discharge are observed. All absorption lines are assigned to the rotational lines of HF B–X (3–11) and (4–10), and O2
B–X (14–3), (15–3), (16–3), (17–3) and (10–2) bands; some O2 lines in the high-resolution spectrum are resolved into triplet components, and their wavelengths in N2 and relative intensities are given. Quantitative studies on R
2,3(5) and R
1(5) (14–3) lines are found to satisfy the severe conditions for estimating σ, the absorption cross section. The obtained σ value, and the population ratio in the v=3 to v=2 levels of the ground state, suggest fairly high populations in these excited levels. The HF absorption lines are the strongest, though they decay along with the shot number.
Density of Vaporized Atoms of Zinc in Top-Heating Furnace
Authors: Shinya Sawai Shinya Sawai , Nobuhiko Wada Nobuhiko Wada
Published: October 2002

Zinc was evaporated in a top-heating furnace filled with helium or argon gas and the density of vaporized zinc atoms was measured by atomic absorption spectroscopy. The density of zinc monomers does not depend greatly on the helium gas pressure in the range of 1.33 ×102–1.33 ×104 Pa, and it does not change if the furnace is filled with argon gas of 1.33 ×103 Pa. However, its density depends on the temperature in the furnace. The evaporation rate increases with decreasing gas pressure.
Preparation of SrTiO3 Thin Films by Metalorganic Chemical Vapor Deposition
Authors: Kobayashi Ichizo , Wakao Yoshihiro , Tominaga Koji , Okada Masaru
Published: October 2002

Strontium titanate ( SrTiO3) thin films were grown by means of the metalorganic chemical vapor deposition (MOCVD) method using dipivaloylmethane (DPM) chelate of strontium (II) [ Sr(DPM)2] and titanium tetraisopropoxide as source materials. In the preliminary experiments, the deposition behaviors of SrO and TiO2 films from respective sources were examined separately. As-grown perovskite single-phase SrTiO3 films were obtained at the substrate temperature of 750° C under the reduced pressure of 530 Pa. The films deposited on the MgO (100) substrate showed high (100) orientation and good optical transmission spectra, with the refractive index of 2.35. The dielectric constant and dielectric loss were 150–250 and 0.01–0.04, respectively. The leakage current density of the 0.38 µ m-thick films was approximately 3×10-8 A/cm2 at 3 V.