bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectral Change in Acoustic Pressure and Cavitation Inception
Authors: Hirose Akihiro , Nobuaki Takahashi Nobuaki Takahashi , Sumio Takahashi Sumio Takahashi
Published: October 2002

Acoustic pressure spectra were measured against the excitation level of the piezoelectric transducer in order to investigate the relationship between acoustic spectra and cavitation inception at an excitation frequency of 20 kHz. Measurements were conducted on degassed and nondegassed distilled water using an acoustooptic detection system. The results of the measurements suggest that the observation of n/2 (n: 3, 5, 7…) order subharmonics is useful to monitor the inception of transient cavitation.
Fracture Strength Measurement of Silicon Chips
Authors: Lee Seong-Min , Sim Sung-Min , Chung Yong-Wuk , Young-Kwan Jang Young-Kwan Jang , Hee-Kang Cho Hee-Kang Cho
Published: October 2002

In this study, a three point bending test is used to determine how the susceptivity of large chips to brittle fracture correlates with chip thickness and backend process quality. Four sets of wafer backend processes, including the commonly used mechanical grinding, were used in this experimental work. In the mechanical grinding process, chip strength was more significantly influenced by the geometry of the machine mark than by the depth of the scratched groove. This experimental result indicates that a limitation exists in the enhancement of the mechanical stability of Si chips by the control of chip thickness because cracks in chips have a tendency to seek out deep scratches rather than typical flaws. Therefore, the mechanical instability associated with increasing chip size should be compensated for by optimization of the backlap process.
High Quality GaAs Epitaxial Layers Grown from Ga–As–Bi Solutions by Liquid Phase Epitaxy
Authors: Saravanan S. , Jeganathan K. , Baskar K. , Kumar J. , Subramanian C. , Soga T. , Jimbo T. , Arora B. M. , Umeno M.
Published: October 2002

The liquidus isotherms for the Ga–As–Bi system were determined at 973 and 923 K in the Ga–As–GaAs region. The liquid phase epitaxial growth of GaAs from Ga–As and Ga–As–Bi solutions were investigated. The addition of ten atomic percent of Bi to the Ga–As solution increase the growth rate of the grown epilayers nearly 4.4 times than in the case of GaAs layers from Bi solution. Above 9 at.% of Bi in Ga solution the problems associated with the edge growth were almost eliminated. Optical measurements at 4.2 K revealed that Bi does not alter the band gap energy value of the GaAs epitaxial layers. The photoluminescence (PL) intensity and full width at half maximum (FWHM) revealed the good quality of undoped GaAs epilayers from Bi solvents compared to that of Ga solvents even though the purity of the Bi was relatively less.
Effect of Buried Oxide Thickness in a Thin-Film Silicon on Insulator Power Metal-Oxide-Semiconductor Field-Effect Transistor
Authors: Satoshi Matsumoto Satoshi Matsumoto , Toshiaki Yachi Toshiaki Yachi
Published: October 2002

Effect of buried oxide thickness in a thin-film silicon on insulator (SOI) power metal-oxide-semiconductor field-effect (MOSFET) transistor is demonstrated. In the thin-film SOI power MOSFETs fabricated on a separation by implanted oxygen (SIMOX) substrate, devices with a thin buried oxide showed higher performance than ones with a thick buried oxide. The device with thinner top silicon layer operated in a fully depleted mode. The minimum specific on-resistance of the fabricated device was 66 m Ω· mm2 at a breakdown voltage of 32 V.
Analysis of Overlay Accuracy in 0.14 µm Device Fabrication using Synchrotron Radiation Lithography
Authors: Hifumi Takashi , Sumitani Hiroaki , Itoga Kenji , Watanabe Hiroshi , Inoue Masami , Marumoto Kenji , Ohsawa Hiroshi , Saitoh Kenji
Published: October 2002

We applied synchrotron radiation lithography to the fabrication of a 0.14 µ m rule dynamic random access memory structure using high dielectric film capacitor and trench isolation techniques. An overlay accuracy of 80 nm was obtained. In order to clarify the contributions of the error causes to the overlay accuracy, we mathematically classified the overlay error into four components: rotation, translation, magnification and in-plane deformation (IPD). A rotation and translation error was estimated to be 38 nm. A wafer process-induced error such as a rotation and translation due to a degradation of the alignment mark worsens the overlay error by 33 nm. We have also found that the maximum magnification error including the mask magnification was 4 ppm and the magnification correction was necessary to achieve an overlay accuracy less than 50 nm. The IPD was estimated to be 60 nm, and the major cause was a mask overlay error. The analyzed results suggest that an IPD less than 30 nm and a rotation/translation component less than 30 nm are required to achieve an overlay error less than 50 nm.
A Hybrid-Integrated Two-Dimensional ( 3×24) High-Efficiency High-Power Laser Diode Array
Authors: Nemoto Kazuhiko , Ogawa Masamichi , Toshimasa Kobayashi Toshimasa Kobayashi , Osamu Matsuda Osamu Matsuda
Published: October 2002

Using buried-heterostructure laser diodes grown by one-step metal organic chemical vapor deposition and a structure designed to dissipate heat, we have realized a hybrid-integrated two-dimensional high-power laser diode array. The array consists of 3×24 elements, which are individually addressed in a simple matrix. The laser emits at 850 nm and each element operates at 30 mW. The laser characteristics have good uniformity and an energy-conversion efficiency of 45% was achieved. Finite element analysis was used to calculate the thermal characteristics and it was shown that the laser array can be a practical device. The array was operated for more than 1100 h under constant current at room temperature without an external cooler, when the initial power of each laser element was 30 mW, the pulse width was 0.1 ms and the duty cycle was 25%.
Optical Emission Spectra from Laser Ablation of Graphite at 266 nm and 1064 nm under a Magnetic Field
Authors: Fumio Kokai Fumio Kokai
Published: October 2002

Optical emission spectra were measured during laser ablation of graphite at 266 nm and 1064 nm at fluences of 1.7–12.2 J/cm2 with or without a magnetic field of ∼0.1 T. In the presence of magnetic field, the intensity distribution of C, C+, and C2+ emission lines varied considerably and some of the emission lines which originated from higher excited states became obscure. In addition, the C2 Swan band emission appeared, particularly during 1064 nm laser ablation. These changes in emission spectra are explained in terms of the promotion of ionization of C and C+, formation of C2, and deexcitation of electronically excited states, resulting from enhanced collisions between ablated species due to cyclotron motions under a magnetic field. We will discuss the formation and excitation of C2 and C2+, and deexcitation of electronically excited C+ and C2+.
The Influence of CuO–BaO Mixtures Addition on the Grain Growth of BaTiO3 Ceramics
Authors: Cheng-Fu Yang Cheng-Fu Yang
Published: October 2002

Densification and grain growth development in CuO–BaO mixture doped BaTiO3 have been studied on the effect of the ratio of CuO–BaO mixtures (molar ratio, CuO/BaO=1, 2, and 2.5). Grain growth for BaTiO3 with 1 wt% CuO–BaO mixtures addition is studied for sintering from 950° C to 1250° C in air. The average grain size of BaTiO3 ceramics is the functions of sintering temperature, sintering time, and CuO/BaO ratio. The results are discussed in terms of the kinetic growth equation: G

n
=K
0
t exp
(-Q/R
T). The grain growth exponents decrease with the increasing of CuO/BaO ratio and sintering temperature. For BaTiO3 fluxed with CuO/BaO=1, 2, and 2.5, the average grain-growth exponents are determined to be 5.3, 5, and 4.3 and the activation energies are estimated to be 290±60, 314±40, and 348±19 kJ/mol, respectively. The molar ratio of CuO–BaO mixture will affect the average grain size, grain growth kinetic exponent, and activation energy of BaTiO3 ceramics.
Agglomeration Resistant Self-Aligned Silicide Process Using N 2 Implantation into TiSi 2
Authors: Akira Nishiyama Akira Nishiyama , Yasushi Akasaka Yasushi Akasaka , Yukihiro Ushiku Yukihiro Ushiku , Kenji Hishioka Kenji Hishioka , Yasumasa Suizu Yasumasa Suizu , Masakazu Shiozaki Masakazu Shiozaki
Published: October 2002

An agglomeration resistant self-aligned silicide (SALICIDE) process using N2 implantation into TiSi2 films has been developed. The film morphology and the film sheet resistance after high-temperature annealing in an Ar ambient were evaluated as a function of implanted nitrogen doses. High implantation doses of 5×1016 cm-2 or more realized the completely flat film after the annealing; however there is an optimum dose of approximately 1×1016 cm-2 for maintaining the film sheet resistance at its minimum value. This phenomenon could be explained by the fact that the main composition of the film was changed from TiSi2 (C54) to TiN with a 5×1016 cm-2 or more nitrogen implantation and that the TiN film contains Si crystals. A successful application of this technique to a 0.8 µm n-MOS transistor is also presented.
DV-Xα Calculations of Charge Exchange between D+ and TiC, TiCxO(1-x), and SrO Surfaces during Low Energy D+ Scattering
Authors: Tilley Barbara , Souda Ryutaro , Yamamoto Kazuo , Hayami Wataru , Aizawa Takashi , Otani Shigeki , Isizawa Yoshio
Published: October 2002

Electronic structures for D+ ( H+) interacting with surface clusters of TiC (001), oxygenated TiC (001) ( TiC

x

O(1-
x
)), and SrO (001) have been calculated using self-consistent-charge discrete variational Xα methods, and the results used to successfully explain local charge exchange during low energy D+ scattering from the anionic component of the surfaces. The calculations show that the character of the surface peak formed in the D+ energy spectrum is target specific and is largely controlled by the size of the energy difference between the highest occupied molecular orbital (HOMO) and the antibonding molecular orbital containing the majority of the H 1s character (H-MABO). Calculations also demonstrate that the energy difference between the HOMO and the H-MABO is dependent on the charge of the cluster, which can be modified in covalent and metallic bonds by electron flow from atoms outside the cluster.
Magnetite Ores with Steel or Basalt for Concrete Radiation Shielding
Authors: Bashter I. I. , Abdo A. El-Sayed , Abdel-Azim M. Samir
Published: October 2002

This paper is concerned with the study of the leakage spectra of total gamma rays and fast neutrons from two types of heavy concretes made from local magnetite ores. The two types are the steel-magnetite concrete (ρ=5.11 g/cm3) and the basalt-magnetite concrete (ρ=3.05 g/cm3). The radiation source used was a collimated beam emitted from one of the horizontal channels of the ET-RR-1 reactor. Total gamma rays and fast neutrons were measured using a gamma-neutron spectrometer with a stilbene scintillator. Gamma ray or neutron events were rejected by a pulse shape discriminator based on the zero cross over method. The obtained data were displayed in the form of spatial fluxes and energy distributions and attenuation curves. The linear attenuation coefficients for total gamma rays, macroscopic removal cross sections for fast neutrons and half-value layers for gamma rays and neutrons have been obtained for the whole energy range and at different energies. Comparison with other published data has been done when such data are available. For comparison, the steel-magnetite concrete is a much better radiation attenuator than the magnetite and basalt-magnetite concretes, especially for thick shields.
Fabrication of a Narrow Gold Wire Using Scanning Tunneling Microscopy
Authors: Okamoto Hiroshi , Itakura Akiko , Taro Yakabe Taro Yakabe , Hitoshi Nejoh Hitoshi Nejoh
Published: October 2002

A new method for fabricating a narrow gold wire is presented. The resultant wire has width around 200 nm and length up to several microns. The wire is fabricated by using a tungsten tip to `pull' gold atoms from a gold thin film towards a bare silicon region. This method is believed to be based on the electro-migration effect. Moreover, the method can be used as a fabrication method for closely separated electrodes for future atomic devices because the whole process can be done in an ultra-high-vacuum (UHV) environment.
Nanometer-Scale Layer Removal of Aluminum and Polystyrene Surfaces by Ultrasonic Scratching
Authors: Iwata Futoshi , Kawaguchi Makoto , Hisayuki Aoyama Hisayuki Aoyama , Akira Sasaki Akira Sasaki
Published: October 2002

An atomic force microscope combined with a quartz crystal resonator have been employed for nanometer-scale layer removal by ultrasonic scratching. The atomic force microscope has a very sharp diamond tip mounted on the end of a cantilever for surface scratching. Sample thin films are deposited on the surface of an AT-cut quartz crystal resonator which is able to oscillate the surface laterally at its resonance frequency of 5 MHz. Surfaces of aluminum and polystyrene were scratched withx-yscanning of 3×3 µ m2with a micronewton loading force, and the topographies of the scratched areas were observed. Scratching with surface oscillation can result in deep carving of the surface in spite of a low loading force which is not sufficient for removal of the surface without oscillation. The hollow bottom of the polystyrene surface which was scratched with surface oscillation was obviously flat in comparison with the surface scratched without oscillation.
Scanning Auger Electron Microscopy Evaluation and Composition Control of Cantilevers for Ultrahigh Vacuum Atomic Force Microscopy
Authors: Toyoko Arai Toyoko Arai , Masahiko Tomitori Masahiko Tomitori
Published: October 2002

Atomic force microscopy (AFM) tips have been evaluated on a submicrometer scale using a scanning Auger electron microscope (SAM) with a field emission electron gun. The commercially available AFM tips on the cantilever as supplied were usually covered with carbon and oxide layers as identified by the Auger spectra. A piezoresistive cantilever can be easily heated by passing a small current into the resistive film on the lever. The carbon and oxide layers can be reduced by heating the cantilever at temperatures higher than 700°C and simultaneously irradiating with an electron beam. However, the layer in which carbon is strongly combined with the Si substrate cannot be completely removed by the above method. The tip then was cleaned by Ar ion sputtering and thermally oxidized to form a clean Si oxide layer. The oxide layer was removed only by heating at 700°C. Thus a clean Si tip can be obtained in an ultrahigh vacuum (UHV) AFM chamber by heating the tip, which is then covered with clean Si oxide as a protective layer.
Practical Scan Speed in Atomic Force Microscopy for Live Neurons in a Physiological Solution
Authors: Nagayama Shin , Tojima Takuro , Morimoto Mayumi , Sasaki Shigeo , Kawabata Kazushige , Ushiki Tatsuo , Abe Kazuhiro , Etsuro Ito Etsuro Ito
Published: October 2002

We examined the practical scan speed for the observation of live neurons in a physiological solution using atomic force microscopy (AFM) with a desired vertical resolution of the order of 10-8 m, which was reasonable when taking into account that a flicker of extracellular protein and saccharide on the neurons in the solution occurred during an observation period of a couple of minutes. The practical scan speed was found to be under 40 µ m/s, therefore, if we applied AFM using 100 lines and 100 pixels per line to an observation area of 20 µ m×20 µ m, the minimum period for acquiring one image was estimated to be about 2 min. This procedure gave us good images that represented the slow three-dimensional dynamics in live neurons, such as the retrograde movement of surface protuberances, but suggested that another approach was required to detect fast structural changes induced by stimulation.
Pattern Selection of Cracks in Directionally Drying Fracture
Authors: Sasa Teruhisa S. Komatsu
Published: October 2002

We study pattern selection of cracks in directionally drying fractures by analyzing the experimental systems recently devised by C. Allain and L. Limat [Phys. Rev. Lett. 74 (1995) 2981]. Proposing a simple picture of crack formation, we clarify the mechanism of how cracks become regularly arrayed and find that the interval between neighboring cracks is proportional to the 2/3 power of the cell thickness. This result explains well the experimental data of Allain and Limat.
Quantum Transport in Single and Multiple Quantum Dots
Authors: Ferry David K. , Bird Jonathan P. , Akis Richard , Pivin David P. , Connolly Jr. , Ishibashi Koji , Aoyagi Yoshinobu , Sugano Takuo , Ochiai Yuichi
Published: October 2002

Ballistic quantum dots have been used in a wide variety of studies ranging from single-electron charging to chaotic systems. However, in open, ballistic quantum dots, the behavior is significantly different. Here, we discuss (1) the observation of regular, periodic fluctuations arising from the existence of stable orbits, (2) the regular and chaotic behavior of coupled dots, and (3) the theory of such dots. The regular orbit properties of these dots are their most stable, generic property, and are clearly reflected in the magnetoresistance. These give rise to periodic fluctuations, which are the result of a very few, periodic orbits within the dot that give rise to scarred wave functions and harmonically related frequencies in the Fourier spectrum. The orbits arise from the role of regular trajectories in the oscillatory density of states and the crucial collimation effects of the quantum point contacts.
Periodic Conductance Oscillations and Geometrical Commensurability in an Open Ballistic Square
Authors: Zozoulenko Igor V. , Schuster Ralf , Karl-Fredrik Berggren Karl-Fredrik Berggren , Klaus Ensslin Klaus Ensslin
Published: October 2002

We report experimental and numerical studies of the magnetotransport in a four-probe square quantum dot. Low-field magnetoresistance is dominated by the classical ballistic electron trajectories traversing the dot. Scanning the Fermi energy we find periodic conductance oscillations superimposed on these classical effects. Theory shows that, at the given Fermi energy, transport through the dot is effectively mediated by just a few eigenstates of the corresponding isolated square. This holds even in the case of many propagating modes in the leads. The geometry of the injecting leads plays a decisive role in the selection of a particular set of eigenstates of the square. This defines a specific period of oscillations observed in the experiment.
Multiple Photon Assisted Tunneling between Two Coupled Quantum Dots
Authors: Toshimasa Fujisawa Toshimasa Fujisawa , Seigo Tarucha Seigo Tarucha
Published: October 2002

We describe photon-assisted tunneling (PAT) between discrete zero-dimensional (0D) levels in two weakly coupled quantum dots. Resonant tunneling current with multiple (up to three) photon absorption is observed when the two 0D levels are separated by a multiple of the microwave photon energy. The PAT current shows a Bessel function dependence on the microwave power, which is in agreement with time-dependent tunneling theory. The sharp PAT peaks can be well resolved even when the high microwave power increases electron temperature in the reservoirs.
Tunneling Transfer and Energy Relaxation Rate of Photo-Excited Carriers in Coupled Quantum Wells
Authors: Sawaki Nobuhiko , Anzai Noritaka , Murakami Tsutomu , Yamaguchi Masahito , Takeshi Ikeda Takeshi Ikeda , Masatoshi Taya Masatoshi Taya
Published: October 2002

Tunneling transfer rate between coupled quantum wells/dots and the energy relaxation rate are studied as a function of the density of excited carriers. Both are expected to be determined by the emission rate of LO/LA phonons. It is found that if the carrier density is reduced, the tunneling escape time decreases but the energy relaxation time increases. This suggests that the emission of LO phonons produces non-equilibrium phonons which reduce the effective LO phonon emission rate, but carrier-carrier interaction enhances the scattering rate due to LA phonons. By reducing the size of the tunneling structure, i.e., in a quasi-zero-dimensional structure, the LA phonon emission rate is also reduced.
Atomic-Scale Negative Differential Conductance Observed at B -Type Surface Steps on the Si(001)–2×1 Surface
Authors: Yoshimura Takuji Komura , Takafumi Yao Takafumi Yao
Published: October 2002

We have found that the I–V characteristics at a rebonded B -type step on a Si(001)–2×1 surface show negative differential conductance (NDC), as a result of a detailed study of the atomic and electronic structures of rebonded B -type steps using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). The rebonded B -type step is characteristically observed with bright protrusions in an empty-state STM image. From the differetial conductance spectra at the rebonded B -type step, the NDC is caused by a strong enhancement in the local density of the antibonding state.
Magnetoresistance in a Superconducting Single-Electron Transistor with a Multiply Connected Coulomb Island
Authors: Hideki Sato Hideki Sato , Mitsuru Kimura Mitsuru Kimura , Singo Katsumoto Singo Katsumoto
Published: October 2002

The influence of phase fluctuation on fluxoid quantization in a small superconducting ring has been evaluated. In an isolated mesoscopic-sized superconductor, the number of Cooper pairs is fixed and the phase of the order parameter largely fluctuates due to Heisenberg's uncertainty principle. Under such conditions, it is not trivial whether the single-valuedness of the order parameter is kept and the fluxoid is quantized in the superconductor. We examined the problem experimentally using a superconducting single-electron transistor with a ring-shaped Coulomb island. We found that even when the fluctuation in the number of Cooper pairs is very small and a clear Coulomb oscillation is observed, the magnetic flux which goes through the ring is quantized.
Size Quantization and Zero Dimensional Effects in Self Assembled Semiconductor Quantum Dots
Authors: Petroff Pierre M. , Ribeiro Klaus H. Schmidt , Kotthaus Axel Lorke
Published: October 2002

In this paper we discuss size quantization effects in InAs self assembled quantum dots deposited by molecular beam epitaxy (MBE) on (100) GaAs. The quantum dot size measurements are performed by transmission electron microscopy while the energy levels from the same samples are measured by capacitance, photoluminescence, photovoltage and electroluminescence techniques. Size quantization effects are observed, however variations in the quantum dot shapes, composition fluctuations and non uniform size distribution, which are deposition dependent prevent complete and accurate quantification of these effects. Through infrared absorption measurements together with capacitance measurements, the zero dimensional character of the quantum dots and “the atomic like” shell structure of the electronic levels in the quantum dots are established.
High Resolution X-Ray Diffraction and Reflectivity Studies of Vertical and Lateral Ordering in Multiple Self-Organized InGaAs Quantum Dots
Authors: A. Darhuber Anton , S. Kop'ev Vaclav Holy , A. O. Kosogov A. O. Kosogov , P. Werner P. Werner
Published: October 2002

We have investigated multiple layers of self-assembled InGaAs quantum dots by high-resolution X-ray diffraction reciprocal space mapping and reflectivity. An anisotropy in the dot spacing was found, which proves an ordering of the islands in a disordered two-dimensional square lattice with main axes parallel to the <100 > direction and a lateral lattice parameter of 55 nm. Vertical correlations in the dot multilayers were investigated nondestructively in the regime of total external reflection of X-rays.
Thermal Response Design for High Recording Density Magnetooptical Media
Authors: Abiko Toru , Konishi Ayumi , Masaki Kagawa Masaki Kagawa , Shuichi Igarashi Shuichi Igarashi
Published: October 2002

For the light intensity modulation recording process of magnetooptical (MO) disks, we have investigated the thermal response of the recording layer for high linear density recording. By means of a computer simulation, we found that the thermal response is improved by using a 6-layer structure which has an extra thermal flow control layer composed of a thermal buffer and an extra heat sink layer, unlike the conventional 4-layer structure. The thermal response improvement was also confirmed experimentally. It is possible to optimize both the thermal response and the optical requirements separately using our 6-layer structure which will be useful when designing higher density recording MO disks.
Dephasing Processes in Self-Organized Strained InGaAs Single-Dots on (311)B-GaAs Substrate
Authors: Kamada Hidehiko , Temmyo Jiro , Notomi Masaya , Furuta Tomofumi , Tamamura Toshiaki
Published: October 2002

Single-dot photoluminescence measurements are undertaken on a number of individual InGaAs disks spontaneously formed on the GaAs-(311)B face. Well-isolated distinctive narrow single-dot luminescence lines, the narrowest of which is 34 µ eV in FWHM, is measured using a microscope and their evolution with excitation density is examined. Under very low excitation, individual dot luminescence is well approximated by the Lorentzian lineshape. Excitation via the barrier continuum results in very low luminescence saturation density and simultaneous broadening into a non-Lorentzian lineshape. In contrast, excitation resonant with excited states, causes no such broadening, but saturation power is about three orders of magnitude larger than under barrier excitation. Such phenomena are explained by different carrier flows into the dot states. Carrier-carrier scattering is discussed as a primary dephasing process that causes line broadening.
Electrical Characteristics and the X-ray Photoelectron Spectroscopy of AlN/InP Structure Fabricated by Helicon-Wave-Excited Plasma Nitridation of Vacuum-Evaporated Al
Authors: Hidematsu Hayashi Hidematsu Hayashi , Ichirou Hatanaka Ichirou Hatanaka , Singo Sato Singo Sato , Hideaki Ikoma Hideaki Ikoma
Published: October 2002

Aluminum nitride/n-type InP (100) metal-insulator-semiconductor (MIS) structures were fabricated by helicon-wave-excited plasma nitridation of vacuum-evaporated Al on an InP substrate. Nitridations were performed in both N2 plasma and N2 + Ar mixed plasma. For comparison's sake, the Al/InP structure was exposed to the helicon-wave-excited O2 plasma to fabricate the Al2O3/InP MIS structure. Relatively good capacitance-voltage (C–V) characteristics were obtained for the N2-plasma-treated Al/InP sample, which were superior to those obtained for the O2-plasma- and N2 + Ar-mixed-plasma-treated ones. The leakage current was also the smallest for the N2-plasma-treated sample. X-ray photoelectron spectroscopic (XPS) measurements indicated that AlN and/or AlN
x
O
y
was formed nearly throughout the entire film depth in both N2- and N2 + Ar-plasma treatments, while Al2O3 was found to be formed in the case of the O2-plasma treatment.
Photochemical and Spectroscopic Properties of Naphthacenequinones as Candidates for 3D Optical Data Storage
Authors: Koroteev Nikolay I. , Magnitskii Sergey A. , Vladimir V. Shubin Vladimir V. Shubin , Nataliya T. Sokolyuk Nataliya T. Sokolyuk
Published: October 2002

More than 30 peri-aryloxy-p-quinone derivatives have been synthesized for possible application in 3D optical memory devices. Extinction coefficients, fluorescence, photochromism and photo-decomposition quantum yields of 15 naphthacenequinone derivatives for both isomeric forms have been measured.
Enhanced Degradation During Static Stressing of a Metal Oxide Semiconductor Field Effect Transistor Embedded in a Circuit
Authors: Gupta Ashawant , Sugiharto Dewi S. , Yang Cary Y. , Matsuzaki Nozomu , Minami Masataka , Yamanaka Toshiaki , Nagano Takahiro
Published: October 2002

We have observed a unique phenomenon during low-gate voltage (V
G) static stressing of metal-oxide-semiconductor-field-effect-transistors (MOSFETs). Static stressing has been performed by probing n-MOSFET devices that are discrete, as well as devices that are embedded in a circuit. Although the measured substrate current for the circuit and discrete devices is similar, significantly more hole trapping is observed under low-V
G static stressing of circuit devices. It is clear that the extent of hole trapping is circuit dependent, and that in actual operation the devices will not undergo such static stressing. Nevertheless, these devices provided a unique opportunity to study the role of hole trapping in interface-state formation. Thus, rather than identifying the cause for increased hole trapping, we focused our efforts on understanding the mechanisms of interface-state formation. It is found that while both electrons and holes are needed for the formation of interface states, it is hole trapping that is the rate-limiting factor in device degradation.
Thermal Characteristics of a Continuous-Wave Cr:LiSAF Laser
Authors: Sadao Uemura Sadao Uemura , Kenzo Miyazaki Kenzo Miyazaki
Published: October 2002

Thermal power density produced in the laser medium of a continuous-wave (cw) Cr:LiSAF laser has been investigated to clarify the laser output characteristics. For the cw Cr:LiSAF laser using axially symmetrical end pumping, the available pump power density has been found to be limited to less than ∼100 W/mm3. Based on the thermal characteristics studied, an efficient diode-pumped cw Cr:LiSAF laser has been developed.
Structural and Electrical Characters of Sintered Ba–Ti–Al–Si Ferroelectric Glass-Ceramic Prepared From Sol–Gel Derived Powders
Authors: Yao Kui , Zhu Weiguang , Zhang Liangying , Yao Xi
Published: October 2002

Ferroelectric BaTiO3 based Ba–Ti–Al–Si glass-ceramics were successfully fabricated by the chemical sol–gel technique. The structural features, dielectric and ferroelectric properties, such as dielectric constant and loss, leakage current and ferroelectric hysteresis loop, were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and electrical measurements. It is found from experimental results that electrical properties of the BaTiO3 glass-ceramic samples strongly depend upon their microstructure evolution. By optimizing the process conditions, the high dielectric constant at room-temperature is obtained and such glass-ceramic samples exhibit high resistivity and low dielectric loss. The partial dielectric constant of the BaTiO3 phase grown in the glass-ceramic is estimated and it obeys the Curie-Weiss law. The effect of the glass phase distribution in the glass-ceramics on electrical properties is also discussed.
Domain Structure Investigations of Triglycine Sulfo-Phosphate Single Crystal: Evidence of Domain Motion with Time at Room Temperature
Authors: Balakumar Subramanian , Xu Jian Bin , Wilson Ian Howard , Arunmozhi Gnanasundaram , Nakatani Noriyuki , Yamazaki Toshinari
Published: October 2002

Ferroelectric domain dynamics of triglycine sulfo-phosphate (TGSP) single crystals have been studied by atomic force microscopy (AFM). Lenticular domains have been observed on a cleaved (010) surface at room temperature. Time evolution of surface topography with domain motion has been studied systematically for the first time. Due to spontaneous movement of the domain boundary, there is a removal of the top most layer SO4-G1. Consequently the second top layer (G2-G3) is exposed. Additionally, continuous variations in the refraction of cleavage layers at the domain boundary are documented.
Formation of a Lead Zirconate Titanate (PZT)/Pt Interfacial Layer and Structural Changes in the Pt/Ti/SiO 2/Si Substrate during the Deposition of PZT Thin Film by Electron Cyclotron Resonance Plasma-Enhanced Chemical Vapor Deposition
Authors: Whan Kim Su-Ock Chung , Hong Kim Geun , Chong Ook Park Chong Ook Park , Won Jong Lee Won Jong Lee
Published: October 2002

Lead zirconate titanate (PZT) thin films were fabricated on Pt(70 nm)/Ti(100 nm)/SiO2/Si substrates at 470°C by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD). A Pb-deficient interfacial layer approximately 25 nm thick was found between the PZT film and the Pt substrate by high magnification transmission electron microscopy (TEM) examination. It was concluded that the interfacial layer was produced by the short residence time of Pb oxide molecules on the Pt substrate during the early stage of the PZT film growth. During the deposition of PZT film, the Pt/Ti/SiO2/Si substrate was altered into the Pt/TiO2/Pt/TiO2/TiSi2/SiO2 structure. The structural change was attributed to the Ti out-diffusion into the Pt layer, the oxidation of Ti by the in-diffused oxygen, and the formation of TiO2/Ti-silicide by the reaction between the SiO2 and Ti layers.
Alignment of Liquid Crystal on Poly(Vinyl Cinnamate) Photopolymer and Anchoring Direction
Authors: Kumar Rajesh Kumar Rajesh , Shin Masuda Shin Masuda , Rumiko Yamaguchi Rumiko Yamaguchi , Susumu Sato Susumu Sato
Published: October 2002

A poly(vinyl cinnamate) photopolymer under irradiation of linearly polarized UV light acts as an aligning agent inducing orientation in adjacent liquid crystals. We have promoted the homogeneous as well as homeotropic alignment of liquid crystal using poly(vinyl cinnamate) as an aligning agent, under different experimental conditions. The anticipated orientation mechanism for the promotion of homeotropic alignment in the case of a liquid crystal/photopolymer composite system is discussed. From our observations we infer that in a liquid crystal/photopolymer composite system with a change of curing condition, the boundary surface condition at the substrates changes, which in turn affects the mode of alignment.
Anomalous IR Absorption of the System Gold Island Film in Water or Methanol
Authors: Suzuki Yushi , Kobayashi Masakazu , Otto Aritada Hatta
Published: October 2002

Experimental reflectivities in Kretschmann configuration of vacuum-evaporated Au films immersed in water in the infrared spectral range are not consistent with a theory involving bulk optical constants, effective media models and the classical electromagnetic theory based on Fresnel's equations. However the experimental ratio of reflectivities of the Au film in methanol and that in water in the spectral range of the methanol C–H stretch vibrations can be fitted by the classical electromagnetic theory. Surprisingly, this is not possible in the spectral range of the C–O stretch vibration of methanol.
Estimation of Lateral Resolution in Scanning Hot Electron Microscopy
Authors: Kobayashi Daisuke , Furuya Kazuhito , Vazquez Nobutaka Kikegawa
Published: October 2002

Scanning hot electron microscopy (SHEM) was introduced as a method of observing the spatial distribution of hot electrons in solids. In this short note we estimate the spatial resolution of the technique. Assuming that the tip radius is 30 nm, SHEM can be expected to attain a spatial resolution on the order of 5 nm.
High-Sensitive Spectroscopy of Molecular Iodine by Means of Power-Stabilized Light from a Diode Laser Spectrometer
Authors: Kurosu Takayuki , Jun Ishikawa Jun Ishikawa , Nobuhiko Ito Nobuhiko Ito
Published: October 2002

The hyperfine features of molecular iodine at 657 nm were observed with a high S/N ratio using a diode laser spectrometer whose intensity noise was reduced by feedback stabilization. The spectrometer consisted of a master/slave laser system, which enabled to stabilize the power independently of the frequency as well as to obtain stable single mode oscillation with moderate output power. The quantum limit of the sensitivity attainable by the power-stabilized laser was also calculated. The power-stabilized diode laser is available for the development of compact length standards having an output with very low intensity noise.
Design of High-Tc Sintered Superconductor Pipe Lenses (Supertrons) for Charged-Particle Beams
Authors: Peter Roth Peter Roth
Published: October 2002

To facilitate the design of high-T
c sintered superconductor pipe lenses (Supertrons), we suggest a so-called Supertron number S
u which is numerically found to be a similarity number. The Supertron number S
u is computed as a function of the accelerating voltage U of charged particles travelling through the Supertron. Using this dependence S
u(U), the focal length of Supertrons having given dimensions can be estimated.
Electron and Ion Energy Controls in a Radio Frequency Discharge Plasma with Silane
Authors: Kohgi Kato Kohgi Kato , Satoru Iizuka Satoru Iizuka , Gautam Ganguly Gautam Ganguly , Tohru Ikeda Tohru Ikeda , Akihisa Matsuda Akihisa Matsuda , Noriyoshi Sato Noriyoshi Sato
Published: October 2002

Electron and ion energy distribution functions are controlled in a radio-frequency (rf) discharge plasma with silane for production of hydrogenated amorphous silicon films. We apply the grid-bias method to an rf silane plasma in order to obtain a low electron-temperature (T
e≃0.2 eV) and low ion-temperature (T
i≃0.1 eV) plasma. The ion beam energy is controlled by biasing the substrate. We find that the room temperature hole drift mobility is increased by two orders of magnitude compared to the conventional value at an ion beam energy between 23 eV and 24 eV.
Production of Inductively Coupled RF Plasma Using a Ladder-Shaped Antenna
Authors: Murata Masayoshi , Mashima Hiroshi , Yoshioka Masao , Nishida Seiichi , Morita Syoji , Yoshinobu Kawai Yoshinobu Kawai
Published: October 2002

A radio-frequency (RF) excited H2 plasma is produced using a ladder-shaped antenna which is positioned within a plasma chamber and the fundamental characteristics of the plasma are examined. The potential and current fed to the antenna are almost in phase. The plasma parameters are measured as a function of RF power, gas pressure and gas flow rate with a Langmuir probe. It is found that the plasma density is uniform within ±10% over 300 mm. Furthermore, increases in the frequency of the RF power source lead to increases in the plasma density. When a mesh grid is installed between the antenna and the substrate, the plasma density and the plasma potential decrease.
Measurement of the Electron Energy Distribution in Asymmetric Radio-Frequency Plasmas with a Self-Compensating Langmuir Probe
Authors: Kubo Takashi , Hiroaki Kawata Hiroaki Kawata , Kenji Murata Kenji Murata
Published: October 2002

The electron energy distribution function (EEDF) of an asymmetric parallel plate radio-frequency discharge has been measured with a modified self-compensating Langmuir probe. The measurements are taken for argon gas discharges at pressures between 50 mTorr and 0.4 Torr. The applied discharge powers are between 5 W and 50 W. It is found that at low pressures the EEDF consists of two electron energy groups. The spatial dependence of plasma parameters is also investigated.
Measurement of a Three-Dimensional Distribution of Microwave Electric Field in Electron Cyclotron Resonance Plasmas
Authors: Furuse Mumeo , Tamura Hitoshi , Fukumasa Seiichi Watanabe
Published: October 2002

We have developed an apparatus that can measure the three-dimensional distribution of microwave electric field intensity in electron cyclotron resonance (ECR) plasmas. The reflection edge of the incident microwaves depends on the plasma density in the etching chamber: it is the ECR zone when the electron density (n
e) is above 1×1011 cm-3 and the electrode when n
e is below 1×1011 cm-3. The spatial distribution of the ion saturation current density at the electrode is the same as that of the microwave electric field intensity at the ECR zone. Therefore, in order to obtain uniform ion saturation current density, the intensity of the microwave electric field at the ECR zone must be kept uniform.
Negative Ion Density Determination Using Probe to Detect Photo-Detached Electron by Continuous Wave Laser
Authors: Masaharu Maeda Masaharu Maeda , Kenji Higuchi Kenji Higuchi , Shosaku Matsumura Shosaku Matsumura
Published: October 2002

Theoretical calculation of probe current increase caused by photo-detachment of electrons by laser irradiation in a plasma and experimental studies have been done in order to determine the absolute negative ion density. The positive column of a hollow cathode DC Ar:O2 discharge is used in the experiment. During laser irradiation of the anode, detected photo-detached electron current increases with increase of the laser on-off frequency because of temporal space potential change. The O- densities determined from the theoretical calculation show good agreement with those theoretically predicted based on Ichikawa's theory when the laser does not irradiate the anode.
Potential Oscillations in an Electronegative Plasma Driven by an Asymmetry RF Discharge
Authors: Mahmood Nasser Mahmood Nasser , Yasunori Ohtsu Yasunori Ohtsu , Gen Tochitani Gen Tochitani , Hiroharu Fujita Hiroharu Fujita
Published: October 2002

Potential oscillations of electronegative plasmas have been experimentally studied in a strongly asymmetric rf (13.56 MHz) discharge. Oscillation amplitudes in the plasma were found to increase suddenly from 10 to 60 V with increasing concentration of SF6 gas in He gas, while gradually from 10 to 40 V in CF4 mixed plasma. The electron energy distribution functions (EEDFs) measurement predicted an electron beam travelling from the plasma towards the rf electrode because of the potential double layer in the sheath picked up by an emissive probe. A clear difference in potential formation and EEDFs profiles in comparison to those in electropositive plasmas has been detected. A more marked gas concentration dependence was obtained in a SF6 gas than in a CF4 one due to the more active production of negative ions in a SF6 plasma.
Modeling of a Pulsed-Power SF6 Plasma
Authors: M. Meyyappan M. Meyyappan
Published: October 2002

Pulsing the input power has received much attention to eliminate anomalous side wall etching problems in high density discharges. A simple model consisting of mass conservation equations for ions, neutrals, and electrons and a power balance is used to analyze the characteristics of a pulsed-power SF6 plasma. The model shows an abundant production of negative ions in the after glow and a strong modulation of their density and production rate for a wide range of pulse periods and duty ratios. The results suggest that a pulse period of 100–250 µ s with a duty cycle 25–50% is sufficient to maintain low electron temperature and plasma potential and produce a high concentration of negative ions during the off-part of the cycle.
A Method for Identifying Sources of Reactive Ion Etch Lag and Loading in a Magnetically Enhanced Reactive Ion Etcher
Authors: Buie Melisa J. , Ventzek Jeremiah T. P. Pender
Published: October 2002

The objective of this paper is to establish a diagnostic method for etch processes which involves identification of the possible sources of reactive ion etch (RIE) lag and loading and the systematic examination and elimination as appropriate for a magnetically enhanced reactive ion etch (MERIE) chamber. A statistical model based on experimental data from the process window is built. Analysis of the model will provide the important experimental control parameters which impact the response variables of interest. With this information, the ion and/or neutral transport mechanisms which cause RIE lag and loading can be identified. This method is applied to an experimental MERIE chamber and can be used to eliminate lag for a standard contact type process.
Profile Evolution during Cold Plasma Beam Etching of Silicon
Authors: Kouichi Ono Kouichi Ono , Mutumi Tuda Mutumi Tuda
Published: October 2002

Processing characteristics of cold, directional plasma beams have been studied by numerical simulation of the profile evolution of trenches etched in silicon with chlorine, where the cold plasma beams were characterized by highly directional fluxes of neutrals as well as ions with their low temperatures or random thermal energies. The model included ion and neutral transport in microstructures and ion-assisted surface chemistry for the chlorine-silicon system. The numerical results demonstrate that the cold plasma beams achieve high etch anisotropy and microscopic uniformity: a tapered profile, inversely tapered profile, and reactive-ion-etching (RIE) lag, which often occur in usual plasma etching environments, are significantly suppressed owing to preferential incidence of neutral reactants as well as ions onto the bottom of microstructural features. In addition, the increased directionality of neutral fluxes not only offsets the RIE lag, but also further causes a weak inverse RIE lag without relying on surface inhibitors. Experimental techniques are also discussed for generation of such cold, directional beams of reactive plasmas.
Amorphous Hydrogenated Carbon-Nitrogen Films Deposited by Plasma-Enhanced Chemical Vapor Deposition
Authors: Fernando Lázaro Freire Jr. Fernando Lázaro Freire Jr.
Published: October 2002

Recent results on the composition, structural characterization and mechanical properties of amorphous hydrogenated carbon-nitrogen films (a-C(N):H) deposited by plasma enhanced chemical vapor deposition (PECVD) have been discussed. The use of different nitrogen-containing gases, ammonia, methylamine or nitrogen itself, combined with methane or acetylene, results in films with similar microstructures. As a general rule, the incorporation of nitrogen into the amorphous network increases with the partial pressure of the nitrogen-precursor gas at the expense of the carbon content. This increase is followed by a substantial reduction of the deposition rate. The nitrogen incorporation also reduces both the compressive internal stress and the fraction of carbon atoms in a s
p
3 state of hybridization. The stability of those films when submitted to thermal annealing or to energetic ion bombardment is also discussed.
Carbon Nitride Films Produced Using Electron Cyclotron Resonance Nitrogen Plasmas
Authors: Mei Zhang Mei Zhang , Lujun Pan Lujun Pan , Tsutomu Miyazaki Tsutomu Miyazaki , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

Carbon nitride films have been produced using electron cyclotron resonance (ECR) nitrogen plasmas. The results of optical emission spectroscopy indicate that reactive nitrogen species are more easily generated than methane-derived species downstream in an ECR plasma. The effect of varying the gas ratio of N2 to CH4 as well as the substrate temperature on the N/C composition ratio in the film and on the film structure have been investigated. The film growth rate decreases but the concentration of nitrogen in the film increases as the gas ratio of N2 to CH4 increases. At lower substrate temperatures, both the deposition rate and the nitrogen concentration increase. The ratio of carbon to nitrogen in the film increases from 12% to 40% as the substrate temperature is lowered from 26°C to 5°C.
Relation between Plasma Parameters and Film Properties in DC Reactive Magnetron Sputtering of Indium-Tin-Oxide
Authors: Yoshinobu Matsuda Yoshinobu Matsuda , Yasunari Yamori Yasunari Yamori , Madoka Muta Madoka Muta , Shinichi Ohgushi Shinichi Ohgushi , Hiroshi Fujiyama Hiroshi Fujiyama
Published: October 2002

The dc magnetron sputtering process of an indium-tin-oxide (ITO) target in Ar/O2 is studied. Experimental results from laser induced fluorescence measurements of sputtered indium atoms, optical emission measurements of various atomic and molecular species in the excited states, probe measurements of plasma ion density and potential, and measurements of deposited film properties (transmittance, resistivity and deposition rate) are reported. Effects of the preset pressure of introduced O2 on these parameters are investigated over a wide range of preset pressures.