bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Sputter Process on a New ZrTi+PbO Target System and Its Application to Low-Temperature Deposition of Ferroelectric Pb(Zr,Ti)O3 Films
Authors: WeiXiao Zhang WeiXiao Zhang , Kimihiro Sasaki Kimihiro Sasaki , Tomonobu Hata Tomonobu Hata
Published: October 2002

An rf reactive sputter deposition technique was adopted to deposit ferroelectric lead zirconate titanate (PZT) thin films from a ZrTi (50%/50%) alloy target combined with PbO pellets. Deposition characteristics including the effects of PbO area ratio were discussed. A new deposition mode called the near-metallic mode was observed. The crystallinity and the composition of the films prepared in the near-metallic mode were investigated as functions of PbO area ratio and substrate temperature. Excess Pb supply tended to enhance perovskite phase formation. Near-stoichiometric perovskite PZT films were obtained at a substrate temperature as low as 450° C. On the other hand, for a PZT+PbO target, perovskite PZT films were obtained only at temperatures higher than 540° C. Deposition rate of perovskite films from the ZrTi+PbO target was 2–3 times higher than that from the PZT+PbO target.
Stress in Amorphous SiOx:H Films Prepared by Plasma-Enhanced Chemical Vapor Deposition
Authors: Le-Nian He Le-Nian He , Takao Inokuma Takao Inokuma , Yoshihiro Kurata Yoshihiro Kurata , Seiichi Hasegawa Seiichi Hasegawa
Published: October 2002

Amorphous SiO

x

(a- SiO

x

) films were deposited on single-crystal Si (c-Si) and fused quartz substrates by a plasma-enhanced chemical vapor deposition technique using SiH4–O2 mixtures. For stoichiometric films (a- SiO2) deposited on c-Si substrates, the observed stress is compressive, and its magnitude increases with increasing deposition rate or with decreasing deposition temperature T
d. The elastic constant, deduced from the stress values for films on two different substrates, decreases with increasing T
d between 100 and 300° C, and is constant independent of the deposition rate when T
d is fixed at 300° C. It is found that there are close relationships among the stress, the Si–O stretching absorption, the buffered HF etch rate, the density of Si dangling bonds and the deposition rate. As a consequence, for stoichiometric films deposited at T
d ≥300° C, it is concluded that the Si–O–Si bond angle decreases with increasing deposition rate, leading to a decrease in the peak frequency of the infrared absorption, and that films with higher deposition rates are more defective, showing relatively high compressive stress.
Validity of Double and Triple Gaussian Functions for Proximity Effect Correction in X-ray Mask Writing
Authors: Aya Sunao , Kise Koji , Hideki Yabe Hideki Yabe , Kenji Marumoto Kenji Marumoto
Published: October 2002

An improved function is proposed to express the deposited energy intensity distribution for fine patterns or that for heavy metals such as X-ray absorbers. An experimental method is also proposed for obtaining the function parameters, and the optimal parameters are obtained for Si and W–Ti substrates at acceleration voltage of 25 kV. Using the improved function with the best-fit parameters, the validity of the double and triple Gaussian functions for the proximity effect correction is evaluated. The dose modulation ratios for ninety line-and-space patterns on the two substrates are calculated using the double Gaussian, triple Gaussian, and improved functions. From the comparison among the ratios, the following are found: for the double Gaussian function the ranges of correction errors on W–Ti and Si substrates are 8 and 30%, respectively; for the triple Gaussian function the ranges of errors on W–Ti and Si substrates are 6 and 12%, respectively.
In-Situ Measurement of He + Stopping in Si Layers by Low-Energy Ion-Scattering Spectroscopy
Authors: Matsui Miyako , Uchida Fumihiko , Kiyokazu Nakagawa Kiyokazu Nakagawa , Akio Nishida Akio Nishida
Published: October 2002

We investigated the energy loss process for 2.0-keV He+ beams in amorphous Si(a-Si) by using low-energy ion-scattering spectroscopy. A-Si layers with thicknesses ranging from 2.0 to 8.0 nm were formed on Ge(2 monolayers)/Si(100) by molecular beam epitaxy under ultrahigh vacuum conditions. Backscattering measurements were performed in situ so as not to change their surfaces. The Ge peak shifted with the thickness of the a-Si overlayer, indicating an energy loss from 1.3 to 2.0-keV He+ in the a-Si layer. The obtained experimental energy shifts were compared with those calculated by Lindhard and Scharff (LS) and Ziegler, Biersack and Littmark (ZBL). The present results generally agree with their theoretical calculations.
Application of In-Situ Al-Flow Process for Triple-level Metallization
Authors: Lee Ki-Young , Su-Cheon Lee Su-Cheon Lee , Young-Wug Kim Young-Wug Kim
Published: October 2002

Triple-level metal structure for half-micron application specific integrated circuit (ASIC) devices was fabricated by employing in-situ Al-flow process for each interconnect. Uniformity of resistance distribution and electromigration resistance of metal lines were greatly enhanced by utilizing in-situ Al-flow technique. Mean time to failure (MTTF) value for the in-situ flowed Al film was about 4 times larger than that for conventionally sputtered Al film. This enhancement of electromigration resistance was due to the coarse grain size of the Al film in-situ flowed. Failure rates of vias were also drastically decreased after in-situ Al-flow treatment. The MTTF value for Al-flowed via was about 8 times larger than that for conventional via formed by sputtered Al film due to the via filling. It was found that the optimum flow temperature was 560° C to achieve the adequate resistance of metal line and good via reliability. In-situ Al-flow technique also showed the excellent flow characteristics in via filling, promising its application in the formation of multiple (over triple) stacked via in the future.
Effects of Recoil-Implanted Oxygen on Depth Profiles of Defects and Annealing Processes in P+-Implanted Si Studied Using Monoenergetic Positron Beams
Authors: Uedono Akira , Kitano Tomohisa , Watanabe Masahito , Moriya Tsuyoshi , Kawano Takao , Tanigawa Shoichiro , Suzuki Ryoichi , Ohdaira Toshiyuki , Mikado Tomohisa
Published: October 2002

Effects of oxygen atoms recoiled from SiO2 films on depth profiles of defects and annealing processes in P+-implanted Si were studied using monoenergetic positron beams. For an epitaxial Si specimen, the depth profile of defects was found to be shifted toward the surface by recoil implantation of oxygen atoms. This was attributed to the formation of vacancy-oxygen complexes and a resultant decrease in the diffusion length of vacancy-type defects. The recoiled oxygen atoms stabilized amorphous regions introduced by P+-implantation, and the annealing of these regions was observed after rapid thermal annealing (RTA) at 700° C. For a Czochralski-grown Si specimen fabricated by through-oxide implantation, the recoiled oxygen atoms introduced interstitial-type defects upon RTA below the SiO2/Si interface, and such defects were dissociated by annealing at 1000° C.
New Developments of Less Toxic Group-V Precursors for the Metalorganic Vapour Phase Epitaxy of III–V-Semiconductors: In -Situ-Formation of As–H Functions by Thermal β-Elimination of Specific As-Trialkyl Compounds
Authors: Zimmermann Gunnar , Spika Zeljko , Marschner Thomas , Stolz Wolfgang , Göbel Ernst O. , Gimmnich Peter , Becker Ralf , Lorberth Jörg , Greiling Arnd , Salzmann Andreas
Published: October 2002

Thermal decomposition studies and low pressure metalorganic vapour phase epitaxy (MOVPE) growth experiments have been performed using novel, less toxic arsinetrialkyl sources, which decompose by the β-hydride elimination process. Therefore, As–H functions are automatically formed in the hot temperature zone of the MOVPE reactor to enable high quality layer deposition. Decomposition studies have been carried out under growth conditions in the MOVPE reactor by quadrupole mass spectroscopy (QMS). The β-elimination decomposition of the novel As-sources diethyltertiarybutyl-arsine (DE t BAs) and diethylisopropyl-arsine (DE i PrAs) is proven by the detection of the cracking products diethylarsine (DEAsH) and the corresponding alkene fragments isobutene ( C4H8) and propene ( C3H6), respectively. The alkene-to-radical formation for different As- and P-precursors indicate a β-elimination efficiency of about 60% for tertiarybutyl- and 40% for isopropyl-groups, whereas for ethyl groups no significant indication of a β-elimination has been observed. GaAs bulk layers were grown by using trimethylgallium (TMGa) in combination with the β-eliminating As-trialkyl sources DE t BAs and DE i PrAs, respectively, as well as by using TEAs or DEAsH, both decomposing under ethyl-radical formation. In addition, the partially fluorinated source pentafluorethyl-diisopropyl-arsine (PFED i PrAs) has been investigated, however, only an etching of the GaAs substrate surface could be detected independently of the growth conditions. The use of β-eliminating As-trialkyl compounds leads to significantly improved layer properties as compared to TEAs-grown structures. GaAs layers, grown with DE t BAs or DE i PrAs at substrate temperatures of 600–650° C and V/III ratios between 8 and 80 exhibit p-type behaviour with net carrier concentrations of 3–5×1015 cm-3 and hole mobilities of 350–400 cm2/ V·s at 300 K and 3500–4100 cm2/ V·s at 77 K. Carbon is the dominant acceptor impurity in GaAs layers at present, as determined by PL spectroscopy. These results indicate a promising potential of the class of β-eliminating As-compounds as replacements for arsine in the MOVPE.
High Efficiency Double Sided Buried Contact Silicon Solar Cells
Authors: Ebong Abasifreke U. , Lee Soo H. , Honsberg Christiana , Wenham Stuart R.
Published: October 2002

A double sided buried contact (DSBC) silicon solar cell structure is currently developed at the University of New South Wales. This structure provides an improved surface passivation without the use of photolithography. It is bifacial in nature and can be illuminated from both sides. Because of the improved rear passivation, cells have been fabricated using a wide range of substrate resistivity with little variation in performance, especially the open circuit voltage. This paper reports the demonstration of 19% efficiency (measured under AM1.5, 100 mW/cm2, 25°C at the University of New South Wales) for this structure fabricated on 1 Ω·cm, p-type crystalline silicon substrate.
Field-Effect Conductance Activation Energy in Polycrystalline Silicon Thin-Film Transistors after Bias Stress
Authors: Seo-Yoon Kim Seo-Yoon Kim , Yoon-Ho Song Yoon-Ho Song , Kee-Soo Nam Kee-Soo Nam , Choochon Lee Choochon Lee
Published: October 2002

We have bias-stressed hydrogen-passivated polycrystalline silicon thin-film transistors by varying the bias condition and have measured the change in the field-effect conductance activation energy as a result of the bias stress. For stress by a high gate bias voltage, a slight broadening occurs in the activation energy curve, while stress by a low gate bias voltage gives rise to a shoulder. Numerical calculation shows that the change in activation energy is due to defect generation in the poly-Si layer and for stress by low gate voltage, defects are localized near the drain region. The energy distribution of defects cannot be obtained accurately, but its position is higher than 0.2 eV above midgap.
Properties of High Quality InP Epilayers Grown by Solid Source Molecular Beam Epitaxy using Polycrystalline GaP as a Phosphorous Source
Authors: Missous Adarsh Sandhu
Published: October 2002

We report on the properties of high quality epitaxial InP grown by solid source molecular beam epitaxy (MBE) using polycrystalline GaP as a phosphorous source. The as-grown InP was n-type with a background impurity concentration of 1.2×1015 cm-3 and mobility of 4500 cm2/Vs at room temperature. Low temperature photoluminescence at 5 K showed free exciton together with donor and acceptor related band-edge emission. These results show that high quality InP can be grown by solid source MBE without the need for high temperature crackers or toxic hydride phosphorous sources.
Comparison of Atmospheric Boundary Layer Structure Mesured with a Microwave Temperature Profiler and a Mie Scattering Lidar
Authors: Matsui Ichiro , Sugimoto Nobuo , Maksyutov Shamil , Inoue Gen , Kadygrov Evgeny , Vyazankin Sergei
Published: October 2002

Measurements of the atmospheric boundary layer using a microwave temperature profiler and a Mie scattering lidar were conducted simultaneously. The atmospheric mixed layer height obtained from the aerosol concentration measured using the lidar agreed very well with the height of the unstable layer measured using the microwave temperature profiler.
Temperature Decrease Caused by Voltage Generation in Metal-Insulator-Metal Structure of Polyimide Langmuir-Blodgett Insulating Film: Possibility of a New Phenomenon of Energy Conversion
Authors: Taro Hino Taro Hino
Published: October 2002

Voltage was generated in metal-insulator-metal (MIM) structures of Al/polyimide Langmuir-Blodgett insulating film/Au which were fabricated in 1986. Temperature decrease caused by the voltage generation was ascertained by noncontact temperature measurements using a vacuum avalanche photodiode. The voltage is still being generated today. Electron diffusion via the Langmuir-Blodgett (LB) film was observed and was considered to be the cause of the voltage generation. From the experimental results, it was found that the present MIM is a new microscopic element that transduces heat energy to electrical energy.
Heat Flow and Detectivity of Multilayer Thin-Film Pyroelectric Detector
Authors: Kang Qing , Liangying Zhang Liangying Zhang , Xi Yao Xi Yao
Published: October 2002

The pyroelectric responses of a multilayer, thin-film pyroelectric detector under both isolated and heat-sink boundary conditions are completely analyzed. Exact mathematical solutions of the heat flow equation are derived. The multilayer detector is composed of pyroelectric layer/thermal isolation layer/silicon substrate. The analytical result shows that when the thickness of the isolation layer is increased, the detectivity, D
*, at low frequencies will be improved, and as the thickness of the pyroelectric layer is decreased, the high-frequency response is improved. D
* of a detector with 1 µm PLZT((Pb, La)(Zr, Ti)O3)/10 µm porous silica/0.5 mm silicon is higher than that of the detector with 10 µm PLZT/1 µm porous silica/0.5 mm silicon in a wide frequency range. In order to achieve better performance of a multilayer thin-film detector, the thicknesses of the two layers should be chosen very carefully. This analysis provides a guide for the preparation of multilayer thin-film pyroelectric detectors.
Electron Microscopic Studies and Microchemical Analysis of Se 10Sb 10Te 80 Ternary Alloy Thin Films
Authors: Raju V. Damodara Das
Published: October 2002

Thin Films of thicknesses less than 1000 Å have been deposited in a vacuum of 5 ×10-5 Torr by the very fast evaporation (∼50 Å/s) of the ternary Se10Sb10Te80 bulk alloy pieces onto cleaned glass plates which were held at room temperature vertically above the evaporation source (at a distance of 25 cm). From the energy dispersive X-ray analysis (EDAX) patterns of the films, the presence of Te, Sb and Se has been confirmed and the semi-quantitative content of the constituent elements in the alloy films has been determined. Film specimens for transmission electron microscopy have been detached from these glass substrates by dippping the latter in very dilute HF solution. These film specimens have been examined in an electron microscope. Electron diffraction patterns reveal that the films are not amorphous but are polycrystalline in most of the regions, but also single crystalline in some regions which have a darker contrast in bright field transmission electron micrographs. Analysis of the single crystalline (spot) patterns obtained reveals that the single crystalline microcrystallites in different regions are oriented differently. The orientations of these microcrystallites have been determined.
Characterization of Diamond Films Grown on Amorphous SiO 2
Authors: Chen Chia-Fu , Leu Shye-Yuh , Sheng-Hsiung Chen Sheng-Hsiung Chen , Wen-Kuan Yeh Wen-Kuan Yeh
Published: October 2002

Continuous diamond film growth on SiO2 was achieved by an effective pretreatment. Carbon implantation and diamond powder abrasion were used to enhance diamond nucleation on SiO2. The possibility of using two gas mixtures (CH4–CO2 and CH4–H2) in order to achieve the growth of continuous diamond films on SiO2 was examined. The diamond film growth rate obtained using the CH4–CO2 gas mixture was 0.6 µm/h which is roughly three times higher than that of the CH4–H2 gas mixture. CH4–H2 gas mixtures had a lower etching reaction rate than that of CH4–CO2 gas mixtures. The higher etching rate of the CH4–CO2 gas mixture was considered to be due to a higher concentration of active carbon radicals or carbon-containing species in the plasma. Scanning electron microscopy (SEM) and optical emission spectroscopy (OES) indicated that active carbon radicals and carbon-containing species are the major cause of pits arising at the surface. Using CH4–H2 gas mixtures at a low microwave power gave the optimum reaction conditions for depositing diamond films on SiO2 layers.
Three-Dimensional Distribution Measurement of Electric Fields using Stark Effect in NaK
Authors: Yoshitaka Takahashi Yoshitaka Takahashi , Toshihiko Yoshino Toshihiko Yoshino , Kazuya Kawasaki Kazuya Kawasaki
Published: October 2002

Three-dimensional distribution measurement of electric fields has been demonstrated by applying the Stark effect of sodium-potassium (NaK) molecules. The magnitude of the electric field is determined from the intensity ratio of the Q-branch line to that of the P- and R-branch lines in the laser-induced fluorescence (LIF) spectrum because the Stark level mixing effect gives rise to the appearance of the “forbidden” Q line. A method for determining the field polarity is also proposed, in which the intensity variation of the LIF is phase-sensitively detected by superimposing a reference ac field on the dc field to be measured.
Fundamental Aspects of the Reactions of Thermal and Hyperthermal F, F2, Cl, and Cl2 with Si Surfaces
Authors: Thomas Engel Thomas Engel
Published: October 2002

Reactive neutral halogen interactions with silicon surfaces are being investigated as possibilities for processing technologies which minimize damage and the exposure of ultrathin dielectric films to charged particles. In order to assess the feasibility of this method, it is necessary to determine reactive adsorption probabilities for halogen atoms and molecules as a function of their kinetic and internal energy. In addition, it would be advantageous to determine atomic level mechanisms for the etching reactions under different surface conditions and for both equilibrium and nonequilibrium reactive interactions. In this article, a summary of this information is given for the interaction of silicon surfaces with fluorine and chlorine.
Notch Profile Defect in Aluminum Alloy Etching Using High-Density Plasma
Authors: Suguru Tabara Suguru Tabara
Published: October 2002

An etching profile distortion called a “notch” was observed in Al alloy etching using inductively coupled plasma and electron cyclotron resonance plasma etcher. Mechanisms of notch formation and reduction were discussed. Electron charge up and the lowered electrical potential of the specific patterns are the reasons for the notch occurrence. Notches are smaller at the Al/Ti(O)N stacked structure. A new etching method is proposed for eliminating notches and achieving high selectivity employing an ICP etcher.
Analysis of Fluorocarbon Deposition during SiO2 Etching
Authors: Maruyama Takahiro , Fujiwara Nobuo , Ken-itiro Siozawa Ken-itiro Siozawa , Masahiro Yoneda Masahiro Yoneda
Published: October 2002

Fluorocarbon film deposition during SiO2 etching affects etching profile and etch selectivity with respect to the photoresist and the underlayer. The fluorocarbon deposition rate with and without ion irradiation is investigated by employing a pair of permanent magnets on the wafer. From the result of this experiment, film deposition rate is almost 0 in the absence of ion irradiation. X-ray photoelectron spectroscopy analysis indicates that ion irradiation suppresses the fluorine/carbon ratio. We discuss the possibility of ion deposition and ion-assisted polymerization. We also investigate the amounts of adsorbed particles using a quadrupole mass spectrometer.
Influence of Gas Chemistry and Ion Energy on Contact Resistance
Authors: Hashimi Kazuo , Matsunaga Daisuke , Kanazawa Masao , Tomoyasu Masayuki , Koshiishi Akira , Ogasawara Masahiro
Published: October 2002

Reactive ion etching (RIE) damage in contact hole etching is studied. The significant oxidation retardation layer (ORL) on Si surfaces is observed followed by high V
pp (peak-to-peak voltage of 380 kHz RF) RIE. The depth of the ORL is linearly proportional to V
pp, and it consists of a Si–C bond layer, according to X-ray photoelectron spectroscopy (XPS) analysis. The increase in contact resistance is found to be due to the existence of the ORL, using the sacrificial oxidation method and secondary ion mass spectroscopy (SIMS) analysis. The etch chemistries based on fluorocarbon-containing gas mixtures are characterized in terms of contact resistance and ORL. When hydride-containing gas mixtures are used in RIE, the contact resistance is low and the ORL depth is small. When CO-containing gas mixtures are used, the contact resistance is high and ORL depth is large. These different properties result from the different amounts of carbon implanted at the silicon surface.
Dry-Etching Mechanism of Sputtered Pb(Zr1-xTix)O3 Film
Authors: Ikegami Naokatsu , Takayuki Matsui Takayuki Matsui , Jun Kanamori Jun Kanamori
Published: October 2002

The Pb(Zr1-
x

Ti

x

)O3 (PZT) etching mechanism involving an ion-assisted etching reaction in a Cl2 helicon wave plasma environment was studied in terms of the physical-bombardment-induced structural change of the film and chemical interaction of the damaged surface with halogen. In-situ X-ray photoelectron spectroscopic analysis of a 1 keV- Ar+-irradiated PZT surface used in combination with Rutherford backscattering spectrometry revealed that the physical bombardment preferentially breaks Pb–O bonds, releasing Pb in the crystal which is subsequently sputtered from the surface, resulting in low Pb concentration on the surface. Thermal reaction study at 600° C of Cl+-, F+- and Ar+-implanted PZT using X-ray diffraction indicated that the induced low Pb concentration initiates the subsequent reaction with existing halogen on the damaged surface, which is accompanied by a structural change in the film.
Structural Study of Amorphous SiNx:H Films Produced by Plasma-Enhanced Chemical Vapor Deposition
Authors: Kazuki Wakita Kazuki Wakita , Hideki Hayashi Hideki Hayashi , Yoshikazu Nakayama Yoshikazu Nakayama
Published: October 2002

The structure of amorphous SiNx:H films prepared by glow discharge decomposition of SiH4 and NH3 has been investigated by measurements of X-ray diffraction intensity. The first peak in atomic density function obtained by analysis of diffraction intensity indicates a nearest-neighbor distance of 1.74 Å which corresponds to the Si–N bond length of 1.730–1.745 Å in β-Si3N4 crystal. We have also estimated the Si–N–Si–N bond configuration by comparing the corrected observed scattering intensity with the scattering intensity calculated using a simple bonding model. It has been shown that a Si atom bonded to a N atom with a coplanar bond has two tetrahedral bonds in the plane of the coplanar bonds.
An Analytical Velocity Overshoot Model for 0.1 µm N-Channel Metal-Oxide-Silicon Devices Considering Energy Transport
Authors: Kuo James B. , Yao-Wen Chang Yao-Wen Chang , Yu-Guang Chen Yu-Guang Chen
Published: October 2002

We report an analytical velocity overshoot model for 0.1µm N-channel metal-oxide-silicon (NMOS) devices taking into account energy transport. As verified by 2D simulation results, the analytical velocity overshoot model gives a good prediction of the IV characteristics.
Transient Voltage-Induced Leakage Current in Power Diode with Semi-Insulating Polycrystalline Silicon Resistive Field Plate
Authors: Akihiro Yahata Akihiro Yahata , Masaki Atsuta Masaki Atsuta
Published: October 2002

Leakage current of a power diode was found to flow at a much lower voltage than that of avalanche breakdown under the conditions of high voltage rise rate ( dV/ dt) and low frequency, and this leakage current was characteristic of a semi-insulating polycrystalline silicon (SIPOS) resistive field plate (RFP). This current, which we call transient voltage-induced leakage current (TVIC), has not been reported previously. TVIC can be suppressed by optimizing the reduced surface field (RESURF) structure. The electric charge for TVIC increased as both the applied voltage and the pulse time interval increased, whereas it decreased as the temperature increased. A possible model to explain the TVIC mechanism was presented.
Critical Current Densities and Irreversibility Fields in Pb-Doped and Pb-Free Bi2Sr2Ca2Cu3Oy Superconductors
Authors: Shan Yu Shan Yu , Yuichi Okuda Yuichi Okuda , Eiji Takayama-Muromachi Eiji Takayama-Muromachi
Published: October 2002

From the hysteresis in DC magnetization loops, we evaluated critical current densities J
c and irreversibility fields B
irr of Pb-doped and Pb-free Bi-2223 superconductors which were prepared from nominal compositions Bi1.68Pb0.32Sr1.85Ca1.85Cu2.85B
x
O
y
(x=0, 0.01) and Bi2Sr1.6Ca2.4Cu3O10 by different heating processes. The intragrain J
c and B
irr for the Pb-doped samples were larger than those of the Pb-free one, although the superconducting volume fraction and superconducting characteristics of the three samples are almost the same. This result suggests that effective pinning centers are introduced by the partial substitution of Pb for Bi in Bi-2223.
Saturation Effects in Z-Scan Measurements
Authors: Oliveira Luimar C. , Tomaz Catunda Tomaz Catunda , Sérgio C. Zilio Sérgio C. Zilio
Published: October 2002

We investigate the behavior of the Z-scan technique in the case where the phase of the electric field departs from a Gaussian due to the saturation of the optical nonlinearity. The usual Gaussian decomposition theoretical approach cannot describe experimental results obtained with well-characterized chromium-doped saturable absorbers: ruby and alexandrite. This aim can be accomplished by extending the theory based on the Hankel transformation of the electric field through the inclusion of the phase saturation. As in the case of Kerr media, the nonlinear refractive index can be obtained from the measurement of the transmittance difference between peak and valley.
Hole Transport in Triphenylmethane Doped Polymers
Authors: Gruenbaum W. T. , E. H. Magin E. H. Magin , P. M. Borsenberger P. M. Borsenberger
Published: October 2002

Hole mobilities have been measured in poly(styrene) (PS) doped with a series of triphenylmethane (TPM) derivatives with different dipole moments. The results are described by a formalism based on disorder, due to Bässler and coworkers. The formalism is premised on the assumption that charge transport occurs by hopping through a manifold of localized states that are distributed in energy. A key parameter of the formalism is the energy width of the hopping site manifold. For TPM doped PS, the widths are between 0.106 and 0.117 eV, increasing with increasing dipole moment. The widths are described by a model based on dipolar disorder. The model is based on the assumption that the total width is comprised of a dipolar component and a van der Waals component. For TPM doped PS, the dipolar components are between 0.021 and 0.052 eV, while the van der Waals components are 0.105 eV. The van der Waals components are significantly larger than for PS doped with a wide range of triarylamine (TAA) molecules. The difference in the van der Waals component is described by a charge delocalization argument and is the principal reason for the difference in mobility of TPM and TAA doped polymers.
Simplex-Deep Level Transient Spectroscopy: A New Method of Transient Capacitance Signal Processing
Authors: Benzohra Mohammed , Hbib Nadia Medeghri-Rachedi
Published: October 2002

A new method of measuring the energy levels and capture cross sections of band gap traps has been developed. This method is based on deep level transient spectroscopy (DLTS) experimentation and simplex linear programming analysis; it concerns transient capacitance signal processing. This method can be performed on a pn junction or metal-insulator-semiconductor structure. Its advantage over conventional signal filtering, which is the double fast Fourier transform DLTS (FT-DLTS) method, is that it analyses directly, in the multiexponential mode, the transient capacitance signal. Comparing the two methods as applied to InP metal-insulator-semiconductor structures, the new method detects two close deep levels in the band gap where the FT-DLTS method detects only one.
Hole Transport in 1,1-Bis(di-4-tolylaminophenyl)cyclohexane-Doped Copolymers
Authors: Gruenbaum W. T. , Sorriero L. J. , Zumbulyadis P. M. Borsenberger
Published: October 2002

Hole mobilities have been measured in 1,1-bis(di-4-tolylaminophenyl)cyclohexane (TAPC) doped in a series of segmented thermoplastic copolymers. The mobilities are unexpectedly high, exceeding values obtained with TAPC-doped poly(styrene) by as much as 2 orders of magnitude. The results show that the enhancement in mobilities is due to an increase in the prefactor mobilities. The activation energies are not affected by changes in the polymer host. The enhancement is attributed to the preferential segregation of the TAPC into the styrene phase of the copolymers.
Sound Velocity Measurements of Molten Germanium
Authors: Yoshimoto Noriyuki , Shibata Hideki , Yoshizawa Masahito , Suzuki Kenjiro , Shigematsu Koji , Kimura Shigeyuki
Published: October 2002

The temperature dependence of the sound velocity of molten germanium was measured up to 1200° C using a newly developed high-temperature ultrasonic measurement system. The system is based on the phase-comparison method and provides highly precise sound-velocity measurement. The temperature dependence of sound velocity of molten germanium showed softening near the melting temperature during both heating and cooling processes. This could be attributed to microscopic structural changes in the liquid.
High Density Charge Storage Memory with Scanning Probe Microscopy
Authors: Fujiwara Ichiro , Sigeru Kojima Sigeru Kojima , Jun'etsu Seto Jun'etsu Seto
Published: October 2002

We demonstrate an ultrahigh density erasable charge storage memory with a scanning probe microscope in an oxide-nitride-oxide-silicon (ONOS) system of semiconductor nonvolatile memory media. It is found that by applying a voltage pulse between the tip and the silicon substrate, charge carriers can be made to be recorded and erased in the ONOS media. It is also found that the locally trapped charges cause local changes of the surface potential. The locally trapped charges ( recorded bits) can be read efficiently by detecting the change of the surface potential, without contacting the ONOS media, with the scanning Maxwell-stress microscope (SMM). A pattern of a 4 ×3 array of recorded bits could be successfully fabricated. The size of the smallest recorded bit is about 100 nm in diameter. This value corresponds to about 63 Gb/in2 in recording density. Furthermore, it is found that the recorded bits can be read at up to a frequency range as high as 10 MHz with heterodyne detected SMM.
Structural Change during Annealing of Amorphous Indium-Tin Oxide Films Deposited by Sputtering with H2O Addition
Authors: Nishimura Etsuko , Ando Masahiko , Onisawa Ken-ichi , Masaru Takabatake Masaru Takabatake , Tetsuroh Minemura Tetsuroh Minemura
Published: October 2002

This paper describes the effects of annealing on electric properties and structure of amorphous indium-tin oxide (ITO) films deposited by sputtering at room temperature and with H2O addition. The film resistivity was increased by annealing at 150–200° C; in this temperature range the growth of ITO crystallites dispersed in the amorphous ITO phase was observed. This increased resistivity was found to be due to decreases in both Hall mobility (µ H) and carrier density (n) of the films. Measurements of thermal desorption spectroscopy revealed that two different adsorption states, in terms of H2O molecules which are due to the hydrogen-bonded H2O and OH species, were formed in amorphous ITO films during film deposition and the subsequent annealing process. Factors in the decreases of µ H and n were discussed on the basis of the experimental results obtained.
Study of α-Sexithienyl Thin Film by Polarized Near Edge X-ray Absorption Fine Structure
Authors: Okajima Toshihiro , Narioka Satoru , Tanimura Sachiko , Hamano Kouji , Kurata Tetsuyuki , Uehara Yasushi , Araki Tohru , Ishii Hisao , Ouchi Yukio , Seki Kazuhiko , Nakahara Hiroo , Ogama Tetsuo , Koezuka Hiroshi
Published: October 2002

An ultrathin α-Sexithienyl (6T) film prepared by an organic molecular beam deposition method on a silver (Ag) film was studied by polarized near edge X-ray absorption fine structure (NEXAFS) spectroscopy using synchrotron radiation and IR-reflection absorption spectroscopy. The carbon K-edge NEXAFS spectrum of 6T was similar to those reported for poly-(3-methylthienylene) and thiophene. Polarized NEXAFS spectra of 6T exhibit strong angular dependence of 1 s→π* resonance intensity, showing that 6T molecules in the film deposited on the Ag film at room temperature had a highly oriented structure. To obtain quantitative information about molecular orientation, this dependence is analyzed by a comparison with theoretical calculation, indicating that the molecular axis is inclined by about 71° to the substrate surface. This angle is almost the same as that reported for 6T film on quartz.
Electron Phase Counting Micromagnetometry Using a Differential Phase Contrast/Interference Scanning Transmission Electron Microscope
Authors: Yajima Yusuke , Yoshio Takahashi Yoshio Takahashi , Katsuhiro Kuroda Katsuhiro Kuroda
Published: October 2002

A new method of micromagnetometry, electron phase counting (EPC), using a scanning transmission electron microscope with differential phase contrast and interference imaging modes has been proposed and tested. By counting the relative phase changes occurring in a pair of mutually coherent fine probes as they are moved from an observation point to a nearby reference point, integrated magnetic flux density at the observation point can be quantified without recourse to instrumental signal intensity calibration. Its feasibility for practical micromagnetometry has been confirmed by the successful application of two different EPC procedures to a NiFe alloy film.
Improvement of Signal-to-Noise Ratio in Microphone Photoacoustic Spectroscopy
Authors: Sakakura Naru , Sato Koji , Okamoto Yoichi , Jun Morimoto Jun Morimoto , Toru Miyakawa Toru Miyakawa
Published: October 2002

The signal-to-noise ratio (S/N) in gas-microphone photoacoustic spectroscopy (PAS) was improved by using a reflector which reflects back the scattered light in the PA cell. Compared with the conventional stainless steel cup for the sample container, a fused quartz cup with a reflector reduced the background noise to 1/4–1/5 that in conventional methods. This system permitted the detection of even 1% of CdSe powder diluted in 0.7 mg of KBr powder. Also the photoacoustic spectra of materials with small absorption coefficients were recorded to demonstrate the validity of this method.
Measurement of Cavitation Noise and Bubble Oscillation using Acoustooptic Detection Scheme
Authors: Sumio Takahashi Sumio Takahashi , Nobuaki Takahashi Nobuaki Takahashi
Published: October 2002

An optical method for detecting cavitation noise and bubble oscillation is presented. The acoustooptic effect of acoustic pressure and optical effect of bubble oscillation were utilized. In order to observe bubble oscillations, an attempt was made to separate the optical effect of bubble oscillations from the acoustooptic effect of acoustic pressure. A single sensing beam system detects both acoustic pressure and bubble oscillation, whereas a double sensing beam system cancels acoustooptic effect of acoustic pressure effectively allowing bubble oscillations to be detected separately. It has been demonstrated by experiment that the double sensing beam system decreases the acoustic pressure effect by more than 30 dB so that the frequency spectrum of bubble oscillation can be observed.
Dependence on Waveguide Width of Elastic Convolver Efficiency
Authors: Takao Ihara Takao Ihara , Yasuhiko Nakagawa Yasuhiko Nakagawa
Published: October 2002

Theoretical and experimental results are reported for the optimum width of a (Δv/v) waveguide which has high convolver efficiency. Instead of controlling the waveguide width in the micron range which is equivalent to varying the wave guide effect of a (Δv/v) waveguide, we applied an Al2O3 thin film to an Al waveguide in order to vary its waveguide effect by increasing the phase velocity of surface acoustic waves. The optimum width of the waveguide for convolver efficiency is close to one input wavelength.
Analysis of Piezoelectric Bending Accelerometer Using the Equivalent Circuit
Authors: Aoyagi Haruo Tanaka
Published: October 2002

To analyze the piezoelectric bending accelerometer using the equivalent circuit, a modified method must be used, because the differential equation of motion for the accelerometer includes a term for volume force due to acceleration. In this work, the piezoelectric bending accelerometer is divided into many short sections, and the volume force in each section is assumed to be the total force acting at the centroid of the section. Then, each short section can be represented by the equivalent circuit, and the total force acts as a constant voltage source at a terminal at the center of the section. A piezoelectric bending accelerometer has been analyzed using the modified equivalent circuit. The calculated voltage sensitivity of the accelerometer is in good agreement with the experimental value.
Characterization and Fabrication of Chimney-Shaped Metal Field Emitters
Authors: Cheng Huang-Chung , Wang Chih-Chong , Hsieh Tzu-Kun Ku
Published: October 2002

A novel fabrication technology has been successfully developed for chimney-shaped metal field emitters in order to improve the electrical characteristics of field-emission devices. This technology is based on anisotropic dry etching and sputtering deposition of metal film as well as wet etching of the attached silicon. It enables easy fabrication of chimney-shaped field emitters with excellent uniformity and high reproducibility. The anode current of the chimney-shaped Cr field emitter array (FEA) is 36.3 µA at the applied voltage of 1100 V and the threshold voltageVT, defined as that for which the anode currentIareaches 1 µA is 787 V. The chimney-shaped Cr FEA emits a current thirty times higher than that from the cone-shaped Cr-clad FEA at the applied voltage of 1100 V. This can be attributed to the presence of many sharp tips along the edge of the chimney-shaped emitter. The degradation phenomenon is not observed because compensation occurs between these many sharp tips. Another merit of this technique is that only one photolithography mask is needed during processing.
Quasi 3-D Quantitative Computerized Tomography for Reconstructing Sound Velocity Slices of a Weakly Scattering Object
Authors: Akira Yamada Akira Yamada
Published: October 2002

To obtain a quantitative sound velocity image using the technique of ultrasonic diffraction tomography, 3-D treatment is necessary. However, the amounts of data acquired and hardware resources used increase markedly when the conventional 3-D technique is applied. Furthermore, it is difficult to observe the waves over the full-aperture region around the 3-D object. In this paper, a quasi 3-D technique was proposed to reconstruct sound velocity slices of the object by transmitting and receiving acoustic waves over the cylindrical aperture around a single rotational axis. From the result of a simulation using the calculated scattered data from the spherical object, quantitative precision of the 3-D reconstructed sound velocity image was verified to satisfy the requirements for clinical applications.
Transducer Arrays for Rapid Data Acquisition of Ultrasonic Diffraction Tomography
Authors: Makoto Ohmaru Makoto Ohmaru , Tomoki Yokoyama Tomoki Yokoyama , Koichi Mizutani Koichi Mizutani , Keinosuke Nagai Keinosuke Nagai
Published: October 2002

We describe results of experiments and numerical simulations on transducer arrays and the apparatus used to drive them. Thses devices were fabricated for rapid data acquisition in ultrasonic diffraction tomography. The arrays are made by evaporation coating on piezoelectric ceramic substrates and the interval between the elements is using by the theory of acoustic holography. One of two similar arrays is used as the transmitter and the other is used as the receiver. In the experiment on a thin wire object it is proved that the interval is sufficient and that spline interpolation is effective, although the problem remains that the performance of each array element is different. The numerical simulation for the thick object shows, however, that the resolution of the reconstructed image is degraded. Because the element interval is inappropriate in this case.
Systematic Investigation of the Annealing Behavior of Magneto-optical Discs
Authors: Burkhard Friedrichs Burkhard Friedrichs , Michikazu Horie Michikazu Horie
Published: October 2002

A comprehensive study of the annealing behavior of magneto-optical disc substrates was performed, offering important insight into the origin of birefringence. The lateral birefringence is a result of the flow-induced molecular orientation in the skin layers generated in the mold filling stage, and the cooling-induced energy-elastic stresses generated inside and outside the mold. Cooling-induced energy-elastic birefringence relaxes quickly, and consequently the flow-induced birefringence with a radial dependence of decrease at the outer radius becomes predominant after annealing below the glass transition temperature. The annealing behavior of the vertical birefringence follows a Kohlrausch-Williams-Watts-type relaxation. The results serve as a predictive tool for similar substrates.
Liquid Streaming by High-Frequency Ultrasonic Waves
Authors: Guo-Qing Zhang Guo-Qing Zhang , Ken-ya Hashimoto Ken-ya Hashimoto , Masatsune Yamaguchi Masatsune Yamaguchi
Published: October 2002

Liquid streaming induced by ultrasonic waves in VHF range is discussed. Theoretical analysis shows that the radiation pressure and net body force caused by liquid streaming are proportional to the second and the fourth power of frequency, respectively. Experiments were performed using a ZnO-film/cover-glass composite transducer operated at 241 MHz. Strong liquid streaming was observed and the water surface above the transducer was lifted to 5 mm with the acoustic power of 40 mW. This value roughly agreed with the theoretical prediction.
Magnetooptical Signal Calculation with Simplified Substrate Birefringence Model
Authors: Shimano Takeshi , Mariko Umeda Mariko Umeda , Kazumi Kawamoto Kazumi Kawamoto
Published: October 2002

Uniform birefringence is introduced into a simple scalar magnetooptical signal simulation model for polycarbonate substrates. Several effects of vertical and lateral birefringence such as astigmatism, elliptical polarization distribution, reduction of the signal amplitude and DC offset, are discussed.
Optimum Operation Conditions of an Ultrasonic Motor Driving Fluid Directly
Authors: Ueha Junhui Hu
Published: October 2002

We proposed a new type of ultrasonic motor which consists of a fluid-filled ring stator and a rotor. The fluid is caused to flow in the circumferential direction by the ultrasonic vibration travelling along the ring stator. The operation mechanism was previously analyzed. In this paper, we present the results of experiments aimed at optimizing this motor. The acoustic streaming velocity of the motor can be increased by using the resonance of the fluid confined in the ring stator, employing a higher mode of stator vibration, and increasing the roughness of the stator wall. Also, it is clear that the nonlinearity of the acoustic field in the fluid is the main cause of the saturation of the acoustic streaming velocity, and that the saturated acoustic streaming velocity increases when the attenuation of the fluid acoustic field is increased.
Studies on Particle Separation by Acoustic Radiation Force and Electrostatic Force
Authors: Yasuda Kenji , Takeda Kazuo , Umemura Shin-ichiro
Published: October 2002

A method for separating particles in liquid by exploiting the competition between acoustic radiation force and electrostatic force has been investigated. To elucidate the size and charge dependence of the shift of the particles away from the sound pressure node, the effective charges of polystyrene spheres and alumina particles, which have opposite signs of electric charge on the surface, were measured for particles of various diameters. The shift of the particles from the pressure node due to the electrostatic force was also measured. Polystyrene spheres smaller than 10 µ m in diameter showed same mobility in a 1 Hz, 13.4 V
p
p
/mm alternating electric field, which indicates that the effective charge of the particle is directly proportional to the radius of the particle. Using 500 kHz ultrasound and a 0.5 V/mm electric field, 7 µ m polystyrene spheres and 10 µ m alumina particles were shifted in opposite directions, according to the sign of the effective charge on the particles.
Stress Property of SiGe Alloy Deposited by Very Low Pressure Chemical Vapor Deposition
Authors: Gu Shulin , Zheng Youdou , Zhang Rong , Han Ping , Shunming Zhu Shunming Zhu
Published: October 2002

We employed Raman scattering spectroscopy and stress measurements to study the stress property in SiGe alloys deposited by rapid thermal process, very low pressure chemical vapor deposition method. During deposition, strain existing in the film causes Ge atoms to distribute inhomogeneously. This effect can be suppressed by changing the reaction parameters, such as increasing substrate temperature or Ge composition. High hydrogen atom coverage on the growing surface or stress relaxation of the alloy will reduce this effect.
Novel Low-Cost Solid-State Heterojunction Solar Cell Based on TiO2 and Its Modification for Improved Efficiency
Authors: Mosaddeq-ur-Rahman Md. , Tetsuo Soga Tetsuo Soga , Takashi Jimbo Takashi Jimbo , Masayoshi Umeno Masayoshi Umeno
Published: October 2002

A theoretical study of a novel solid-state heterojunction solar cell based on low-cost material TiO2 (n-TiO2/p-CuInSe2) is made in order to determine its feasibility as a photovoltaic energy converter. A low theoretical efficiency limit of 1.51% has been achieved under ideal conditions. The high barrier height ΔE
C at the conduction band edge shows a deleterious effect on the cell performance. However, the cell can be modified by introducing a new oxide semiconductor PbxTi1-x
O2 instead of TiO2. Both the band gap of PbxTi1-x
O2 and the conduction band discontinuity ΔE
C at the PbxTi1-x
O2/CuInSe2 interface can be lowered by varying x. The theoretical efficiency limit of such a solar cell has also been calculated (18.78%) assuming ΔE
C=0, and no energy loss due to resistivity and bulk recombination.