bluuebunny/crossref_metadata_2025 huggingface dataset:
Particulate Suspension Flow Induced by Sinusoidal Peristaltic Waves
Authors: Meenu Saxena Meenu Saxena , Vijai P. Srivastava Vijai P. Srivastava
Published: October 2002

The flow of a particle-fluid suspension induced by simusoidal peristaltic waves in an axisymmetric tube and in a two-dimensional channel under long wavelength approximation, is studied. The equations governing the flow for both the fluid and particle phase are solved and the expressions for the dimensionless flow rate, pressure drop and friction force are derived. The results obtained are discussed briefly and compared with other studies to observe the effect of particle concentration in the fluid. It is shown that pressure drop decreases with flow rate and its minimal is achieved at zero flow rate. Pressure drop increases with particle concentration but decreases with increasing amplitude ratio. Pressure-flow rate relationships are found to be linear for any given set of parameters. Friction force posseses a similar character to pressure drop and qualitatively the results of two-dimensional geometry is similar to axisymmetric case. Besides its applications to wide range of engineering and biological problems, it is hoped that the axisymmetric tube analysis may be used to study the two-phase peristaltic induced flow of blood.
Local Tunneling Barrier Height Imaging on Si(111) Surface
Authors: Nobuhiro Horiguchi Nobuhiro Horiguchi , Kazunori Yonei Kazunori Yonei , Masahiro Miyao Masahiro Miyao
Published: October 2002

We measured the spatial distribution of a local tunneling barrier height by means of the AC height modulation method. We performed this measurement on clean Si(111)7×7 surfaces and the surfaces exposed to O2 gas. On clean surfaces, 7×7 structures, which are the same as those in topographic images, were observed in the tunneling barrier height mode. It was found that the spatial distribution of local tunneling barrier height was modified along a step. It was also found that the topography and the spatial distribution of local tunneling barrier height were modified by exposure to O2 gas.
Double Quantum Dots as Dissipative Two Level Systems
Authors: Tomosuke Aono Tomosuke Aono , Kiyoshi Kawamura Kiyoshi Kawamura
Published: October 2002

A double quantum dot system is a typical example of a dissipative two level system. The ratio of the coupling of the two dots and the width of the energy level is the important parameter determining whether the quantum coherence can be seen clearly. Indications of quantum coherence between two dots appear not only in the stationary states but also in the relaxation processes from non-stationary states.
Aharonov-Bohm Effect in Quantum Dots
Authors: Hiroshi Akera Hiroshi Akera
Published: October 2002

The Aharonov-Bohm oscillations of the conductance through two quantum dots in parallel is studied theoretically in the limit of large one-electron level separations in each dot. An electron tunnels through a single energy level in each dot, which is closest to the chemical potential (µ) of the emitter and collector electrodes. It is assumed that the level in the first dot is well above µ, while that in the second dot is close to µ. The conductance is calculated by solving the equations of motion for the Green function at temperatures higher than the level broadening due to tunneling. It is shown that the ratio of an oscillating component to a nonoscillating component of the conductance in this case is not changed by the interaction at the second dot.
Wave Function Scarring in Open Ballistic Quantum Dots
Authors: Akis Richard , Ferry David K. , Bird Jonathan P.
Published: October 2002

Numerical simulations of the quantum mechanical transport and corresponding wave functions ofopenquantum dots, with leads supporting a small number of propagating modes, have been carried out. We have found that the wave functions that coincide with some of the resonance features in the transport appear to showscarring, that is, the amplitude of the wave functions arehighlyconcentrated along underlyingsingle,classical trajectories. We discuss some of the conditions necessary for dot shape and size and the magnetic field for this scarring effect to become apparent. In particular, we find the nature of the leads to be quite important, with injection of the electrons viaan angled,collimated beambeing crucial for the excitation of a preferred set of regular, semiclassical trajectories.
Interface Characterization of Semiconductor Quantum Nanostructures
Authors: Klaus H. Ploog Klaus H. Ploog
Published: October 2002

The correlation between the actual interface structure and the observed distinct electronic properties resulting from carrier confinement becomes crucial with the increase of confinement in semiconductor quantum nanostructures. We present two case studies for the necessity of a more critical assessment of the properties of such nanostructures. First, we discuss the problem of exciton localization in GaAs quantum wells. Second, we critically evaluate the area of strained InAs insertions in a GaAs matrix to realize quantum dot structures. We show that unintentional exciton (carrier) localization at growth related potential fluctuations often masks the desired quantum confinement effects.
Fabrication of Nanocrystalline Silicon with Small Spread of Particle Size by Pulsed Gas Plasma
Authors: Toru Ifuku Toru Ifuku , Masanori Otobe Masanori Otobe , Akira Itoh Akira Itoh , Shunri Oda Shunri Oda
Published: October 2002

We have investigated the formation of nanocrystalline Si (nc-Si) in SiH4 plasma using a pulsed-H2 gas supply by very-high-frequency (VHF; 144 MHz) excitation. Nanocrystalline Si is formed in the gas phase of a SiH4 plasma cell by the coalescence of radicals. The particle size of nc-Si is determined by the growth time of nc-Si in the plasma cell. Supplying H2 into SiH4 plasma enhances nucleation of nc-Si. When the H2 gas supply is turned off, nucleated nc-Si particles grow larger in SiH4 plasma. In the next cycle of H2 gas supply, nc-Si particles grown in the previous cycle are pushed out of the cell into the deposition chamber. Using this method, fabrication of nc-Si with a diameter around 8 nm and a narrow spread (±1 nm) of particle size was realized.
Creation of Highly-Ordered Si Nanocrystal Dots Suspended in SiO2 by Molecular Beam Epitaxy with Low Energy Oxygen Implantation
Authors: Ishikawa Yukari , Fukatsu Noriyoshi Shibata
Published: October 2002

Low energy oxygen implantation during Si molecular beam epitaxy (MBE) allows the formation of highly-oriented Si nanocrystal dots (NCDs) suspended in SiO2. Transmission electron microscopy reveals the unusual facet morphology of NCD while the spontaneous orientation of the crystal axis of NCD toward [100] is clearly observed. Well-developed {100} and {111} facets are characterized by nearly perfect Si/SiO2 interfaces. Compelling evidence is found for the epitaxial origin of NCD inherited from the parental two-dimensional Si slabs.
Proposal of a Micro-Fabrication Process for Al Nanostructures
Authors: Tadatsugu Hoshino Tadatsugu Hoshino , Nobuyuki Enomoto Nobuyuki Enomoto , Kaori Okano Kaori Okano , Minoru Tsuda Minoru Tsuda
Published: October 2002

The mechanism of migration of Al adatoms on H-terminated Si(111) surfaces has been investigated by ab initio calculations using density functional theory. The positions of Al adatoms in the potential energy minima and the energy change along the least potential energy path for Al adatom migration have been obtained. Furthermore, we demonstrate the difference between the migration processes on H-terminated and bare Si surfaces. The activation energy required for Al adatom migration has been estimated to be 1.0 eV on bare Si surfaces, but the energy required is very small (2 meV) for Al adatom migration on H-terminated surfaces. Energetic stabilization originating from Al adsorption on H-terminated surfaces is very slight compared with that originating from Al adsorption on bare Si surfaces. Based on these theoretical results, a micro fabrication technique has been proposed for the production of Al nanostructures on H-terminated Si(111) surfaces by selective growth of Al dots only at bare Si areas.
Artificial Control of Dot Sites for Ga Droplet Arrays on CaF 2 Films by Surface Steps and Electron Beam Modifications
Authors: Kazuya Uejima Kazuya Uejima , Jun Takeshita Jun Takeshita , Koji Kawasaki Koji Kawasaki , Kazuo Tsutsui Kazuo Tsutsui
Published: October 2002

The control of formation sites for Ga droplets on epitaxial CaF2 films was investigated by two approaches: alignment on step edges, and local surface modification by focused electron beam exposure. Ga droplets 10 nm in diameter were formed with spacings of 5–30 nm on monolayer step edges on CaF2 surface. Straight and parallel multi-steps were formed using vicinal substrates, and the preferential formation of Ga droplets on these steps was observed. Site control by surface modifications of CaF2 using a focused electron beam exposure was also achieved. Two dimensional dot matrix arrays of Ga droplets were fabricated using this technique. Preliminary results indicating the formation of a GaAs quantum dot array from these site controlled Ga droplets by supplying a molecular beam of As4 were obtained.
Lateral Positioning and Vertical Stacking of InAs Islands on GaAs Substrates: Designing Quantum Transport Devices
Authors: Mark S. Miller Mark S. Miller
Published: October 2002

Some prospects and constraints for coupling strained islands into strongly modulated one-dimensional electronic systems and using them as quantum transport devices are assessed. Two device structures, a diode and a triode, are proposed for the InAs on GaAs system. The proposals rely on published evidence of vertical island coupling on flat substrates and lateral island positioning on patterned substrates. An aim of this report is to connect the properties and requirements for quantum transport devices to the electronic structure parameters and technology coming from crystal growth experiments.
Vertical Single Electron Transistors With Separate Gates
Authors: Austing David Guy , Takashi Honda Takashi Honda , Seigo Tarucha Seigo Tarucha
Published: October 2002

We demonstrate independent gate action in a vertical sub-micron single electron transistor with four separate gates fabricated by a new technology from a double barrier structure starting material. When the gate voltage is swept over a given range, the number of conductance oscillations increases systematically as the number of gates “squeezing” the quantum dot is varied from one to four. Alternatively, the average period of the conductance oscillations is essentially independent of the number of “squeezing” gates if the gate voltage is appropriately scaled to an “effective gate voltage”. We show that subtle changes occur in the appearance of the conductance oscillations when the lateral geometry of the quantum dot is controllably deformed.
Basic Control Characteristics of Novel Schottky In-Plane and Wrap Gate Structures Studied by Simulation and Transport Measurements in GaAs and InGaAs Quantum Wires
Authors: Hiroshi Okada Hiroshi Okada , Seiya Kasai Seiya Kasai , Hajime Fujikura Hajime Fujikura , Tamotsu Hashizume Tamotsu Hashizume , Hideki Hasegawa Hideki Hasegawa
Published: October 2002

To clarify the control properties of Schottky in-plane gates (IPGs) and Schottky wrap-gates (WPGs) recently employed in the high-temperature operation of compound semiconductor single electron devices, computer simulations and transport measurements were carried out for gated quantum wires (QWRs). Both types of QWRs showed clear Shubnikov-de Haas oscillations. Non-linear Landau plots confirmed gate-controlled 1D transport in the QWRs. In the GaAs IPG QWR, the effective wire width was found to change linearly with gate bias, whereas this was not observed in the InGaAs WPG QWR. These gate control behaviors are in excellent agreement with theory. Near pinch-off, clear conductance oscillation was seen in both QWRs.
Correlated Electron-Hole Transport in Capacitively-Coupled One-Dimensional Tunnel Junction Arrays
Authors: Shuhei Amakawa Shuhei Amakawa , Minoru Fujishima Minoru Fujishima , Koichiro Hoh Koichiro Hoh
Published: October 2002

Correlated electron-hole transport in two capacitively-coupled one-dimensional tunnel junction arrays is studied by simulation. A simple model of the orthodox theory in conjunction with the theory of cotunneling is applied. The conflict between existing theories about the three-junction array circuit is resolved by carefully examining the dynamic process of charge transport. We evaluate the accuracy of correlated electron-hole transport. Accuracy is improved and high-precision correlated transport occurs over a wider range as the arrays get longer. The response speed of the circuit is not very fast and the transient response does not follow steady-state characteristics when driven fast. Our simulation shows that dynamic analysis is important in studying structures of tunnel junction arrays. As an example of applications, the operation of a dc current transformer that consists of two capacitively coupled tunnel junction arrays is presented. Problems in integrating the circuit into a larger system are also discussed.
Spectroscopy, Imaging and Switching Behaviour of Individual InP/GaInP Quantum Dots
Authors: Castrillo Pedro , Hessman Dan , Pistol Mats-Erik , Prieto Jose Antonio , Craig Pryor Craig Pryor , Lars Samuelson Lars Samuelson
Published: October 2002

We have measured the photoluminescence of individual quantum dots grown by the Stranski-Krastanow growth mode. Studies of many individual quantum dots reveal that about one quantum dot in a thousand switches between two emission intensity levels on a time-scale of seconds. The switching is temperature and excitation power activated. For each set of experimental conditions, the statistics is consistent with random telegraph noise. By strong illumination it is possible to turn the switching off, after which the quantum dot emits continuously.
Observation of Excited Biexciton States in CuCl Quantum Dots: Control of the Quantum Dot Energy by a Photon
Authors: Michio Ikezawa Michio Ikezawa , Yasuaki Masumoto Yasuaki Masumoto
Published: October 2002

Experimental observations of the excited biexciton states in CuCl quantum dots embedded in a NaCl crystal are presented. An increased absorption due to the transition from the exciton state to the excited biexciton states was clearly observed on the high-energy side of the exciton resonance in subpicosecond pump-and-probe spectra at 77 K. The energy difference between it and the exciton resonance largely increased with decreasing dot size. Temporal evolution of the induced absorption band was studied and the results were consistent with the identification of the excited biexciton states.
Effects of Dimensionality on Radiative Recombination Lifetime of Excitons in Thin Quantum Boxes of Intermediate Regime between Zero and Two Dimensions
Authors: Gotoh Hideki , Ando Hiroaki , Takagahara Toshihide , Kamada Hidehiko , Temmyo Arturo Chavez-Pirson
Published: October 2002

We report on effects of dimensionality on radiative recombination lifetime in thin quantum boxes of intermediate regime between 0D and 2D. The temperature dependence of the recombination lifetime is calculated using a theoretical analysis that rigorously treats the electron-hole Coulomb interaction. We show how the dependence evolves from 2D to 0D with a decrease in the lateral width of the box. We also examine the effects of exciton localization, which arises from structural defects in the boxes, on the radiative recombination lifetime. These theoretical results are compared with experimental data obtained from InGaAs quantum disks on a (311)B GaAs substrate. Good agreement between theoretical results and the experimental data is obtained.
Observation of Excited State Excitons in CuCl Quantum Cubes
Authors: Naru Sakakura Naru Sakakura , Yasuaki Masumoto Yasuaki Masumoto
Published: October 2002

Persistent spectral hole burning (PSHB) spectroscopy was utilized to investigate excited state excitons confined in CuCl quantum dots embedded in NaCl crystals. In the PSHB spectra of CuCl quantum dots, a resonantly burned hole and lower energy satellite holes were observed. These satellite holes are thought to originate from hole burning of the ground state excitons which results from site-selective excitation of excited state excitons confined in CuCl quantum dots. Relations between energy positions of the resonantly burned hole and that of each satellite hole are explained well in terms of the simple concept of a particle in a quantum cube with infinitely high potential barriers. Spectral profiles of the ground state excitons and the first excited state excitons confined in CuCl quantum dots were obtained. The Z3 exciton luminescence spectrum showed that the excited state excitons are in a majority in the higher energy region of the Z3 exciton absorption band.
InGaAs/GaAs Quantum Dot Lasers with Ultrahigh Characteristic Temperature (T 0= 385 K) Grown by Metal Organic Chemical Vapour Deposition
Authors: Maximov Mikhail V. , Kochnev Igor V. , Shernyakov Yuri M. , Zaitsev Sergei V. , Gordeev Nikita Yu. , Tsatsul'nikov Andrew F. , Sakharov Alexey V. , Krestnikov Igor L. , Kop'ev Petr S. , Alferov Zhores I. , Ledentsov Nikolai N. , Bimberg Dieter , Kosogov Alexander O. , Werner Peter , Gösele Ulrich
Published: October 2002

Low threshold current density (AlInGa)As/GaAs lasers based on InGaAs quantum dots (QDs) are grown by metal organic chemical vapour deposition (MOCVD). Quantum dots deposited at 490° C and covered with GaAs are directly revealed in the active region. On a transmission electron microscopy (TEM) image of the laser structure no large clusters or dislocations are found over a macroscopic distance. We show that the properties of QD lasers can be strongly improved if the QDs are confined by Al0.3Ga0.7As barriers and the cladding layers are grown at high temperature. Optimisation of the laser structure geometry allows extension of the range of ultrahigh temperature stability (T
0=385 K) of the threshold current to 50° C.
Crystal Structure of GaN Grown on 3C-SiC Substrates by Metalorganic Vapor Phase Epitaxy
Authors: Wu Jun , Yaguchi Hiroyuki , Nagasawa Hiroyuki , Yamaguchi Yoichi , Onabe Kentaro , Shiraki Yasuhiro , Ryoichi Ito Ryoichi Ito
Published: October 2002

GaN films were grown on 3C-SiC substrates by metalorganic vapor phase epitaxy (MOVPE) using 1,1-dimethylhydrazine (DMHy) as the N source. The crystal structure was strongly affected by both the growth temperature and the V/III ratio. At 600° C, only hexagonal GaN films with their c-axis perpendicular to the substrate surface were grown. At 800° C, relatively high V/III ratios resulted in the growth of hexagonal GaN with their c-axis oriented in the [111] direction while cubic GaN films were obtained at lower V/III ratios. The origin of [111]-oriented hexagonal GaN is also discussed.
Simulation for the Microcrystalline Silicon Thin Film Transistors by Considering the Change of Acceptor-Like State and Microcrystal Grain Size Effect
Authors: Jenq Fenq-Lin , Chen Jiann-Ruey , Chen Bor-Yir , Fon-Shan Yeh Fon-Shan Yeh
Published: October 2002

A numerical simulation to predict and analyze the characteristics of microcrystalline silicon thin-film transistors have been proposed. This model is derived from the Poisson's equation, with the consideration of the effect of microcrystal grain size. The microcrystalline silicon acceptor-like state characteristic energies are modified by the change of energy gap. This proposed model conforms fairly well with the experimental data.
Ferromagnetic Resonance in Epitaxial α′-martensite Fe–N Films
Authors: Kohmoto Osamu , Okamoto Satoshi , Kitakami Osamu , Shimada Yutaka , Takeshi Tsuda Takeshi Tsuda
Published: October 2002

Ferromagnetic resonance at 35 GHz was studied in 200-Å-thick single-crystal α′-martensite Fe90N10 (001) films grown on (001) GaAs substrates. From the resonance fields in both (001) basal and (100) vertical planes and the saturation magnetization (4πM) value of 23.0 kG, a large uniaxial anisotropy (K
u) along the [001] axis of 6.36×106 erg/cm3, a cubic anisotropy (K
1) of 2.2×105 erg/cm3 and the gyromagnetic ratio (g-value) of 2.07 have been determined.
Characterisation of Long M-State Lifetime Bacteriorhodopsin Thin Films for Optical Cache Memory
Authors: Wang Changhai , Bacon Mark , Kar Ajoy. K. , Baxter Brian S. Wherrett
Published: October 2002

We report the optical characterisation of bacteriorhodopsin (BR) films of long intermediate-state lifetimes. The M-state lifetime is extended from 10 ms for the native BR protein to ∼20 minutes for our BR films, by chemical and physical modifications of the material. Optical cache memory characteristics of thin films are studied in excite-probe experiments in which nanosecond-duration pulses are used to excite a BR film and cw monochromatic light used to monitor the transmission dynamics. The memory read-time is found to vary significantly with the probe wavelength; it is of the order of milliseconds at 633 nm and of the order of 100 µs for probe wavelengths of 600 nm and below. The memory erase-time is ∼50 µs. Contrast ratios and insertion losses are measured at different probe wavelengths, with a maximum contrast ratio following nanosecond excitation of ∼3:1 obtained in the peak absorption region of the B-state ( ∼570 nm), at an excitation fluence of 30 mJcm-2. The implications of these results for the application of BR films as optical cache memory devices are discussed.
Hydrogen Plasma Resistive and Highly Textured SnO2:F/ZnO:In Bilayer Films Prepared by the Pyrosol Method
Authors: Lee Chang Hyun , Song Koeng Su Lim
Published: October 2002

Indium doped ZnO (ZnO:In) thin films were prepared on corning 7059 glass by the pyrosol method and the hydrogen plasma durability of the films was investigated. We found that the ZnO:In films prepared at the higher substrate temperature of 425° C to 475° C have better hydrogen plasma durability because its denser surface with smaller grain boundary region kept energetic hydrogen ions from diffusing into the grain boundaries. Two kinds of SnO2:F/ZnO:In bilayer films were fabricated at the temperature of 425° C through a successive process by the pyrosol method: the SnO2:F/ZnO:In with thin (580 Å) ZnO:In and the SnO2:F/ZnO:In with thick (2000 Å) ZnO:In. The former has excellent durability owing to its thin (580 Å) ZnO:In layer which acts as a barrier against hydrogen ions. It has a resistivity of 6.6×10-4 Ω cm and a transmittance of 83.8% at the wavelength of 550 nm. The latter is a bilayer film of the SnO2:F/ZnO:In with thick (2000 Å) ZnO:In which acts not only as a barrier but as a light scattering layer due to the highly textured thick (2000 Å) ZnO:In film.
Fabrication and Physical Properties of Radio Frequency Sputtered ZnMnSe Thin Films
Authors: Tsai Cheng-Tzung , Chuu Der-San , Chou Jiun-Yueh Leou
Published: October 2002

Zn1-x
MnxSe thin films with various Mn concentrations were produced by the radio frequency sputtering technique. As the Mn concentration increased, it was found that two types of crystal structures (zinc blende and wurtzite) compete with each other. The grain size of the Zn1-x
Mnx Se thin films decreased as Mn concentration x was increased. Moreover, the zone-center optical phonons of Zn1-x
MnxSe thin films exhibit an intermediate mode behavior which is consistent with that of the bulk crystals.
Collisionless Heating of Electrons by Meandering Chaos and Its Application to a Low-Pressure Plasma Source
Authors: Hiroaki Asakura Hiroaki Asakura , Ko Takemura Ko Takemura , Zensho Yoshida Zensho Yoshida , Taijiro Uchida Taijiro Uchida
Published: October 2002

Near a magnetic neutral line, where the magnetic field vanishes, the adiabatic invariants of charged particle motion are destroyed, and hence the number of degrees of freedom increases. When a radio-frequency electric field is applied to the system, the particle motion becomes strongly chaotic. This effect can be used to produce heat in a plasma in the absence of any collisional process. The kinetic entropy of an electron orbit increases very rapidly by the mixing effect. The velocity distribution is approximated by a Gaussian function, so the thermodynamic entropy production can also be estimated. This collisionless heating mechanism enables high-efficiency plasma production at a low gas pressure.
Electron Heating and Control of RF-Produced Plasma Parameters Excited by a Planar, Spiral Antenna
Authors: Seiji Takechi Seiji Takechi , Shunjiro Shinohara Shunjiro Shinohara , Yoshinobu Kawai Yoshinobu Kawai
Published: October 2002

Electron heating in inductively coupled plasma with use of a planar, spiral antenna is investigated by measurement of the skin depth of evanescent waves and antenna-plasma coupling. It is shown that for plasma production, both a collisionless and a collisional heating mechanism play an important role in a wide range of collision frequencies. In addition, control of plasma parameters such as uniformity and density by adjustment of the antenna configuration and the external magnetic field is demonstrated.
Angle Resolved Mass Spectrometry of Positive Ions Transmitted through High Aspect Ratio Channels in a Radio Frequency Discharge
Authors: Stoffels Eva , Stoffels Winfred Willem , Imai Kunihide Tachibana
Published: October 2002

The behavior of positive ions in high aspect ratio structures, relevant to the reactive ion etching of deep trenches, has been studied by means of energy resolved mass spectrometry. High aspect ratio trenches are simulated by capillary plates with various aspect ratios. Angle resolved measurements of the ion current passing through the channels in the capillary plates have been performed in low pressure argon and helium radio frequency plasmas. The angular distribution of the ion counts becomes strongly anisotropic after the ions have passed through the channels. The narrowing of the ion distribution with increasing aspect ratio is explained by the loss of ions at the side walls of the channel. This loss is mainly a consequence of geometrical shadowing; ion loss due to deflection by surface charge on the capillary plates has only little effect at moderate power inputs. At high power inputs ion losses become extremely high, so the transmission through the channel plate decreases almost to zero.
Study of Ion-Induced Secondary Photon Emission in Reactive Ion Etching Experiment
Authors: Moshkalyov Stanislav A. , Munemasa Machida Munemasa Machida , Delton O. Campos Delton O. Campos
Published: October 2002

Optical emission spectroscopy with high spatial resolution was employed for the study of surface sputtering under reactive ion etching conditions in chlorine-containing gas mixtures. Secondary photon emission (both atomic and molecular) from the processed material was found to be strongly localized near the surface. A simple model, considering the observed features of the secondary photon emission as induced by ion sputtering of the processed surface, has been presented. This technique can give new opportunities for in-situ diagnostics and modeling of plasma-surface interaction in various plasma technologies.
Spectroscopic Measurement of High-Pressure Argon Plasma Produced by Excimer Laser
Authors: Tsuda Norio , Yoshihisa Uchida Yoshihisa Uchida , Jun Yamada Jun Yamada
Published: October 2002

When a XeCl excimer laser beam was focused in a high-pressure gas of up to 100 atm, a hot and dense plasma was produced at the focal spot. The plasma developed not only backward but also forward. The forward plasma developed by means of a forward breakdown wave. The radius of the forward plasma becomes smaller further from the focal spot because the laser beam transmitted through the plasma was further focused by the plasma. The radiation intensity from plasma produced by an ultraviolet laser was observed using a spectrometer. The temporal spectral intensity signal had two peaks. The first peak was a signal from the plasma produced at the observed point, but the second peak was that diffused from the back. The electron temperature was measured from the ratio of the spectral intensity of Ar II lines. The electron temperature on the order of 105 K was obtained.
Propagating Wave Characteristics for Plasma Production in Plasma Processing Field
Authors: Shunjiro Shinohara Shunjiro Shinohara
Published: October 2002

In this review paper, general wave characteristics and plasma production through excitation by propagating waves are outlined, with emphasis on plasma processing. First, the basic wave classification, characteristics and wave phenomena are summarized, with descriptions of resonance (damping), cutoff, polarization, wave energy and energy flux after introduction of a dispersion relation. Next, an analysis of various propagating waves and methods of plasma production and/or heating by these waves are presented followed by a summary of typical wave diagnostics. Finally, after a description of the characteristics of propagating waves and current research in the plasma processing field, i.e., with a focus on electron cyclotron, surface and helicon waves, experimental helicon wave studies are described for the introduction of typical propagating wave measurements.
Volt Ampere Characteristics of Low Current DC Discharges in Ar, H 2, CH 4 and SF 6
Authors: Ilija Stefanović Ilija Stefanović , Zoran Lj. Petrović Zoran Lj. Petrović
Published: October 2002

In this paper we show new results for a wide range of characteristics of low current diffuse (Townsend-dark discharge regime) discharges in Ar, H2, CH4, SF6. The measured observables include: volt-ampere characteristics, ranges of free running oscillations, frequency and damping of induced oscillations and we also determine the negative differential resistance (the negative differential voltage to current ratio). The measurements were performed for pressures between 0.027 and 1 Torr and for distances between electrodes in the range from 1 to 3 cm.
Dual Focus Optical Head with a Hologram-Integrated Lens
Authors: Komma Yoshiaki , Tanaka Yasuhiro , Urairi Kenichiro , Seiji Nishino Seiji Nishino , Sadao Mizuno Sadao Mizuno
Published: October 2002

A dual focus optical head with a holographic optical element (HOE) that can read both 0.6 mm disks and 1.2 mm disks has been developed. To ensure practicality and mass-producibility of the head, we examined servo-signal characteristics and evaluated allowable ranges for the misalignment of the HOE, the wavelength deviation, the disk tilt angle and the defocus distance. It was found that stable servo operation can be obtained and that except for the issue of coma aberration, the allowable ranges are wide enough for mass-production. When an objective lens having initial coma aberration is used with a plane-type HOE, coma aberration still remains for the 1.2 mm disk after performing skew adjustment for the 0.6 mm disk. We found that the aberration can be reduced by integrating an HOE with the objective lens on its first surface.
Two-Dimensional Nonequilibrium Plasma Modeling Based on the Particle-Boltzmann Hybrid Model for RF Glow Discharges
Authors: Koji Satake Koji Satake , Toshiaki Monaka Toshiaki Monaka , Osamu Ukai Osamu Ukai , Yoshiaki Takeuchi Yoshiaki Takeuchi , Masayoshi Murata Masayoshi Murata
Published: October 2002

A two-dimensional self-consistent nonequilibrium numerical method based on the particle and Boltzmann equation hybrid model has been developed to study the radio-frequency (rf) glow discharge. In this paper, the presented particle-Boltzmann hybrid model has been applied to two types of rf glow discharge. One is the parallel-plate capacitively coupled plasma (CCP) of Ar gas. The model predicted the spatial profile of Ar(3
p
5) density, which shows good agreement with the experimental emission profile of ArI (λ=419.8 nm). The other is the ladder electrode inductively coupled plasma (LICP) of SiH4 gas. It is found that electrons obtain their energy from both the electrostatic field enhanced by the edge effect and the induced electric field.
Digital Video Disc/Compact Disc Compatible Pick-up With Liquid Crystal Shutter
Authors: Tsuchiya Yoichi , Kajiyama Seiji , Kano Yasuyuki , Yoshiyuki Matsumura Yoshiyuki Matsumura , Syuichi Ichiura Syuichi Ichiura
Published: October 2002

We have developed an optical pick-up with a liquid crystal shutter that can read both digital video discs (DVDs) and compact discs (CDs). An objective lens which is designed for reading DVDs with a numerical aperture ( NA ) of 0.6 is used in this optical pick-up. The pick-up can be used to read CDs by changing the diameter of the laser beam which enters the objective lens, using the liquid crystal shutter. The wavelength of the laser diode is 635 nm. When a CD is read, the NA of the objective lens is 0.35. For focus error detection when reading CDs, an astigma method was used, and for tracking error detection, a 3-beam method was used. We have confirmed that both DVDs and CDs can be successfully read by changing the NA of the objective lens according to the thickness of the disc substrate.
Effects of O2 Addition on BCl3/Cl2 Plasma Chemistry for Al Etching
Authors: Banjo Toshinobu , Tsuchihashi Masaaki , Hanazaki Minoru , Tuda Mutumi , Ono Kouichi
Published: October 2002

Effects of low level (0.5–20%) O2 addition on BCl3/Cl2 plasma chemistry have been investigated using several diagnostic tools: optical emission spectroscopy, microwave interferometry, and mass spectrometry. Experiments were performed using a magnetically enhanced planar 13.56-MHz rf plasma reactor, where aluminum etching was also performed using samples masked with a photoresist pattern of lines and spaces. As O2 was added into a BCl3/Cl2 plasma, the Al etch rate first increased and then dropped above ≈3% O2 added; a transition from reactive-ion-etching (RIE) lag to inverse RIE lag occurred at an O2 percentage of ∼8%. Optical and mass spectrometric measurements indicated that the Cl concentration increases as O2 is added into a BCl3/Cl2 plasma, and that above a critical O2 percentage (∼6% O2) B

x

O

y

species are formed in the plasma through a reaction between boron chlorides and oxygen and then deposit onto the wafer surface during etching. The Al etching characteristics obtained in BCl3/Cl2/O2 plasmas are interpreted in terms of competitive effects of increased concentrations of Cl and B

x

O

y

.
Radical Behavior in Inductively Coupled Fluorocarbon Plasma for SiO2 Etching
Authors: Nakagawa Shigenori Hayashi , Michinari Yamanaka Michinari Yamanaka , Masafumi Kubota Masafumi Kubota
Published: October 2002

Silicon dioxide etching in an inductively coupled plasma (ICP) using a multispiral coil (MSC) has been studied on the basis of CF

x

(x=1, 2) radical measurement employing a laser-induced fluorescence (LIF) technique. Fundamental radical behaviors in the MSC-ICP including a pulsed operation have been investigated for CF4 gas chemistry; radical composition and distribution are strongly dependent on chamber wall conditions and on the pulse modulation period as well as the time-averaged ICP power, because of dissociation and extinction kinetics. Moreover, radical behaviors in fluorocarbon plasmas including C4F8 and CHF3 have been examined in relation to the SiO2 etching characteristics. The dependence of radical densities on gas chemistry and on ICP power in the MSC-ICP has been characterized and has been found to correlate with the SiO2 etch rate and selectivity to Si. The results demonstrate that the control of radical behavior is crucial in realizing selective SiO2 etching using the MSC-ICP.
Formation of Carbon Nitride Films by the Radio-Frequency Plasma Chemical Vapor Deposition Method
Authors: Mei Zhang Mei Zhang , Ping Wang Ping Wang , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

Carbon nitride films are deposited both on the cathode and anode in a CH4-N2 atmosphere by radio frequency plasma chemical vapor deposition. An increase in rf power and a decrease in gas pressure lead to an increase in the self-bias voltage, which increases ion energy and ion bombardment. The films grown on the cathode and anode definitely show different properties with or without ion bombardment under the same deposition conditions. The films produced with efficient ion bombardment have lower hydrogen content, higher electrical conductivity and greater hardness. The conductivity is affected by characteristics of the films such as the bonding state of the carbon, nitrogen and hydrogen and by the number of defects in the films. It is likely that conductivity is not dominated by band conduction but by hopping conduction. It is clear that efficient ion bombardment and ion energy during film growth are important factors in producing electrically conductive and hard carbon nitride films.
Reducing the Effects of Plasma Proximity in Plasma Immersion Ion Implantation
Authors: Jones Erin C. , Shao Jiqun , Denholm A. Stuart , Cheung Nathan W.
Published: October 2002

Plasma Immersion Ion Implantation is shown to be a promising candidate for low-energy, high-dose ultra large-scale integration (ULSI) applications like ultra-shallow junction processing. Junctions shallower than 65 nm at a background concentration of 1018 cm-3 have been made with BF3 PIII (p-type) and PH3/H2 PIII (n-type). Remaining concerns about PIII processing include impurity contamination, surface erosion, charging of thin oxide devices, and interaction with photoresist. Contamination can be reduced through proper machine design and cleaning. Surface erosion is minimized by using higher frequency implantation: although the erosion rate rises, the dose rate increases faster. Charging becomes severe at higher frequencies, so a moderate frequency (around 10–20 kHz) is recommended to minimize both effects. The effect of PIII-photoresist interaction on devices is comparable to that seen with conventional implantation.
Spectroscopic Study of Vapor-Phase Reactions in Preparation of YBa2Cu3O7-x Oxide Thin Film Using Pulsed Laser Deposition
Authors: Yamagata Yukihiko , Kurogi Hiromitsu , Tsuchiya Keisuke , Tomoaki Ikegami Tomoaki Ikegami , Kenji Ebihara Kenji Ebihara
Published: October 2002

Vapor-phase reactions in plasma plume during preparation of YBa2Cu3O7-
x

superconducting thin film are investigated using optical emission spectroscopy. Argon/oxygen gas mixtures of various ratios are used as ambient to study the formation of diatomic oxides. Most of YO and some of BaO molecules are formed in the vapor, while CuO molecules are not formed in the vapor but only ejected from the target. To obtain high-quality oxide thin films, fluxes of the oxide molecules, atoms and ions reaching a substrate, which are dependent on laser energy density, argon mixture ratio and total pressure, should be controlled.
High-Density Recording Mechanism of Magnetooptical Disks
Authors: Takeshi Maeda Takeshi Maeda
Published: October 2002

Models which can be used to explain the mechanism of recording on magnetooptical disks within the accuracy required for our drive system are described. Guide rules for understanding the mechanism of recording on magnetooptical disks through the read and write processes are developed based on these models. These guide rules are useful for simulation of the mechanism and prediction of system performance. According to these guide rules, these models of the read and write processes are reduced and simplified so that we can easily construct and develop a high-density recording system. Furthermore, an example of analysis based on this simplified model and a new method for high density recording based on these guide rule are described.
Removal of Oxygen from the Si(100) Surface in a DC Hydrogen Plasma
Authors: Ron Kroon Ron Kroon
Published: October 2002

This paper focuses on the removal of oxygen from a Si(100) surface by hydrogen plasma etching under high-vacuum conditions, i.e., the reaction-chamber base pressure is ≈10-7 mbar. The efficiency of oxygen removal from the Si(100) surface in the employed DC hydrogen glow discharge, with the sample at room temperature, is found to depend on the ratio of H2- and H2O partial pressures, the latter of which depends on the reaction-chamber base pressure and the amount of H2O liberated from the reaction-chamber walls by the plasma. This ratio reflects the competition between reduction of the Si surface by atomic hydrogen and reoxidation of the Si surface by residual H2O. A low-energy hydrogen ion bombardment is found to facilitate the reduction of the Si surface oxides. This process is most efficient when the sample potential is kept at 25 V below the plasma potential, i.e., when the surface is struck by 25-V protons.
Convergent Beam Electron Diffraction Measurement for Local Strain Distribution in Si around a NiSi2 Island
Authors: Wakayama Yutaka , Yumiko Takahashi Yumiko Takahashi , Shun-ichiro Tanaka Shun-ichiro Tanaka
Published: October 2002

Lattice strain distribution was measured in Si substrates near NiSi2 islands. Using the convergent beam electron diffraction (CBED) technique, quantitative and highly spatially resolved evaluations were carried out. Variations in the CBED patterns were found to be due to a combination of stress components with different orientations and magnitude. As a result, it was revealed that, in addition to normal stress components, singular stress with characteristic orientation or extremely high strain concentration was observed, especially near the NiSi2 island corner. This actual strain distribution was considered to be highly influenced by the shape, size and orientation of the NiSi2 island on Si substrates.
Modulation Characteristics of the Negative Nonlinear Absorption Effect in Erbium-Yttrium Aluminum Garnet
Authors: Yoshinobu Maeda Yoshinobu Maeda , Masatoshi Migitaka Masatoshi Migitaka
Published: October 2002

Dependence of the negative nonlinear absorption effect on both modulation degree and frequency was investigated in erbium yttrium aluminum garnet crystals. For a modulation frequency of 1 MHz, two peaks, A and B, were observed in the transmitted waveform. With a decreasing modulation degree, peak C which consists of peaks A and B appeared and a reversed-phase waveform was obtained in the transmitted waveform. Peak A decreased as the modulation frequency increased, and peak B was only observed for modulation frequencies above 50 MHz. In the case of a modulation degree under 35%, the transmitted waveform changed to the opposite phase of incident one for modulation frequencies up to 100 MHz. In addition, the negative nonlinear absorption effect was dependent on the product of the composition of erbium and the sample length. It was suggested that the enhanced absorption was due to stimulated emission in three excited states of Er3+.
Temporal Characteristics of Short Pulse Dye Mixture Lasers
Authors: Tou Teckyong , Kwongkeong Tham Kwongkeong Tham , Weeong Siew Weeong Siew
Published: October 2002

Time delays in superradiant emissions from five binary dye mixtures were measured to be linearly dependent on the spectral overlap between the donor fluorescence band and the acceptor absorption band. Temporally intervealed subnanosecond pulses were observed in the DF/R640 dye mixture owing to an efficient DF-to-R640 energy transfer, in which the DF laser emission could be briefly terminated while R640 was lasing. When R640 was photobleached, the DF laser emission was restored. In the tenary dye mixture, C460/DF/R640, mode locked laser emission was observed for the donor, C460, while less number of laser pulses were observed for DF and R640.
Analyses of an Oriented Diamond Nucleation Processes on Si Substrate by Hot Filament Chemical Vapor Deposition
Authors: Xi Li Xi Li , Yasuaki Hayashi Yasuaki Hayashi , Shigehiro Nishino Shigehiro Nishino
Published: October 2002

Bias-enhanced nucleation (BEN) of oriented diamond on Si(100) substrates was investigated by ellipsometric monitoring using hot-filament chemical vapor deposition (HF-CVD). A plasma was observed above the substrate on the Mo holder by a glow discharge during the BEN process. We confirm that this plasma plays a critical role in the BEN process. A diamond film growth boundary was present when the initial bias voltage was below -250 V. The results of the ellipsometric monitoring indicate that the BEN process includes the following stages: carbonization, incubation, nucleation, nuclei growth and film growth. A scanning electron micrograph showed that biasing for too long induces twinned crystals. It is showed that the biasing time is a very important factor in oriented nucleation.
Fabrication of Pb(Zr, Ti)O3 Microscopic Capacitors by Electron Beam Lithography
Authors: Hiratani Masahiko , Okazaki Choichiro , Hasegawa Haruhiro , Sugii Nobuyuki , Tarutani Yoshinobu , Takagi Kazumasa
Published: October 2002

An epitaxial microscopic capacitor array of Pb(Zr, Ti)O3/SrRuO3 with 0.5-to 2-µ m squares was fabricated by electron-beam lithography and Ar-ion etching on a SrTiO3(001) substrate. Atomic force microscopic observation revealed that line-and-spacing larger than 1 µ m assures adequate separation between capacitors. A thin barrier is formed on the terrace edge of the capacitors due to re-deposition of Ar-ion etched oxide.
X-ray Photoelectron Spectroscopy Study of the Interactions of O+ and N+ Ions with Polyimide Films
Authors: Lulu Zhang Lulu Zhang , Toshiaki Yasui Toshiaki Yasui , Hirokazu Tahara Hirokazu Tahara , Takao Yoshikawa Takao Yoshikawa
Published: October 2002

With an increase in the use of polyimides in aerospace applications, the degradation of polyimides caused in the space environment is receiving more attention. In this paper, a ground experiment in which polyimides were exposed to high-energy ions in the space plasma environment was carried out. The effects of oxygen or nitrogen ion bombardment on the chemical structure of polyimide films were investigated by X-ray photoelectron spectroscopy (XPS). The polyimides were exposed to ion beams with energies in the range of 0.5–1.0 keV and in doses between 1.7 ×1015 and 8.2 ×1016 ions/cm2. An in-situ XPS analysis was also carried out, and showed that the ion bombardment changed the chemical structure of the polyimides due to the addition of oxygen and nitrogen ions and the desorption of other components.
Feasibility of Fabricating a Modified Volcano-Shaped Field Emitter
Authors: Su-Hua Yang Su-Hua Yang , Meiso Yokoyama Meiso Yokoyama
Published: October 2002

We fabricate modified volcano-shaped field emission arrays (MVSFEAs) using one photomask process and self-aligned technology. Because the enhanced electric field at the tips causes a larger value of β, the resulting onset voltage is lower and the emission current is higher for MVSFEA than for conventional FEA. According to our results, the emission current density at a gate voltage of 380 V is 8.64×106 A/cm2 and emits about 58 nA/tip when the radius of the volcano aperture, a, is equal to 0.75 µ m. The emission current density of MVSFEAs for a=0.75 µ m is 37.9-fold larger in magnitude than that of a=0 µ m owing to the larger value of β for MVSFEAs.
Positive Ions in C 4F 8 RF Discharge in a Planar Diode
Authors: Shinya Sasaki Shinya Sasaki , Yuji Hirose Yuji Hirose , Itsuo Ishikawa Itsuo Ishikawa , Kazuya Nagaseki Kazuya Nagaseki , Yukinori Saito Yukinori Saito , Shinji Suganomata Shinji Suganomata
Published: October 2002

Positive ions were measured in situ by direct sampling from C4F8 discharge at 13.56 MHz using a quadrupole mass spectrometer. Major positive ions in the discharge plasma are CF+, CF2
+, CF3
+, C2F4
+, C2F5
+ and C3F5
+. When the gas flow rate increases, the signal intensity of C2F4
+ increases. The intensity variation of C3F5
+ is similar to that of C2F4
+. However, those of CF3
+ and C2F5
+ decrease with increasing gas flow rate, and those of CF+ and CF2
+ are almost constant. The difference in intensity variations is considered to result from the production processes of ions.