bluuebunny/crossref_metadata_2025 huggingface dataset:
Hysteresis and Bifurcation for the Axisymmetric Waves in a Nonneutral Electron Plasma
Authors: Yamazawa Yohei , Michishita Toshinori
Published: October 2002

The hysteresis phenomena of the axisymmetric waves in a nonneutral electron plasma were observed by sweeping frequencies of the externally applied sinusoidal oscillations. The nonlinear response for the fundamental mode showed distinct hysteresis phenomenon with positive frequency shift. The response profile was obtained in the three-dimensional control space and compared with the theoretical stationary one. The bifurcation was also observed for the mode. The frequency shift changed its sign from positive to negative when the waves increased in the axial wavenumber. The observed responses for higher modes exhibited hysteresises with negative frequency shifts accompanied by sawtooth-like behavior due to the mode transitions. The mechanism was examined based on the ponderomotive force including the finite effect of the plasma column length.
Fast Method for Visualization of Temperature Distribution Using Acoustic Computerized Tomography
Authors: Ishikawa Eisuke , Mizutani Koichi , Nagai Keinosuke
Published: October 2002

Sound velocity is dependent on medium temperature and is estimated from the time of flight of sound. We propose a fast method for the visualization of temperature distribution using acoustic computerized tomography (A-CT). In this study, considering the property of a temperature gradient field, which is the visualization object and is approximated by a Gaussian function, the number of data points required by the CT is optimized and the speed of visualization is improved. As a result of noncontact measurements of the temperature distribution in the circular space of 100 mm radius which includes a high-temperature area of about 40 mm radius, sufficient spatial resolution is obtained by the data acquisition system which combines linear scanning of 11 measurement points and rotational scanning with a 22.5° angular step. In addition to the optimization of the data acquisition geometry, an aerial delay-line oscillator is used for the detection of sound velocity, in order to sensitize and simplify the system. Visualized results obtained by the A-CT agree well with the measurements taken by thermocouples. The fast visualization scheme proposed in this paper has an advantage over conventional methods in such applications as air conditioning, reactor monitoring and atmospheric monitoring among others.
Application of Microchip Fabricated of Photosensitive Glass for Thermal Lens Microscopy
Authors: Takeshi Ito Takeshi Ito , Kenji Uchiyama Kenji Uchiyama , Seishiro Ohya Seishiro Ohya , Takehiko Kitamori Takehiko Kitamori
Published: October 2002

Conventional wet chemical processes have not been successful in achieving a high aspect ratio channel on glass wafers because of isotropic etching of glass by hydrogen fluoride (HF). We fabricated a microchip of photosensitive glass in order to obtain a high aspect ratio channel (width:depth:aspect ratio = 150 µm:250 µm:1.67). The water glass bonding technique was applied to bond glass wafers at low temperature (40–80°C). The results of studying the characteristics of the water glass bonding technique for the micro total analysis system (µ-TAS) use show that dissolution of the material (sodium) from water glass layer was avoided by placing it in deionized water at 60°C for 4 h, and the bond strength was weakened by keeping it at high pH for a day. The microchip was available to analyze the amount of nitrite acid present by thermal lens microscopy as one method of optical chemical analysis. Although the etched glass surface had a roughness of about 1 µm, the calibration curve of thermal lens microscopy was similar to that of spectrophotometry.
Electrical and Electromechanical Properties of PbZrO3 Thin Films Prepared by Chemical Solution Deposition
Authors: Maiwa Hiroshi , Ichinose Noboru
Published: October 2002

Electrical and electromechanical properties of PbZrO3 (PZ) thin films deposited on Pt/Ti/SiO2/Si by chemical solution deposition were investigated. Precursor solutions with the Pb/Zr atomic ratio of 1.1 were used. The PZ thin films annealed at 650°C and 700°C for 1 h exhibited a double hysteresis loop, indicating that electric-field-induced antiferroelectric-to-ferroelectric phase transformation occurred at room temperature. The switching field diminished with increases in measurement temperature, and at 220°C, the polarization hysteresis loop became that of a ferroelectrics. A rectangular displacement hysteresis loop and maximum strains of 6.4–6.8×10-3 were observed.
Low-Temperature Fabrication of Ir/Pb(Zr,Ti)O3/Ir Capacitors Solely by Metalorganic Chemical Vapor Deposition
Authors: Fujisawa Hironori , Kita Kentaro , Shimizu Masaru , Niu Hirohiko
Published: October 2002

Ir/Pb(Zr, Ti)O3(PZT)/Ir capacitors were fabricated solely by metalorganic chemical vapor deposition (MOCVD). Both top and bottom Ir electrodes with mirror like surfaces were obtained at 300°C by MOCVD. Ferroelectric PZT thin films were successfully prepared at 395-540°C by MOCVD using (C2H5)3PbOCH2C(CH3)3 as a Pb precursor and PbTiO3 as a seed. Both Ir electrodes and PZT thin films showed good step coverage of 70–80%. PZT films prepared at 445–540°C exhibited well-saturated hysteresis loops with remanent polarization of 19–25 µC/cm2.
Preparation of Bi4Ti3O12/Bi2SiO5/Si Structures Derived by Metal Organic Decomposition Technique
Authors: Masaki Yamaguchi Masaki Yamaguchi , Takao Nagatomo Takao Nagatomo , Yoichiro Masuda Yoichiro Masuda
Published: October 2002

Bismuth titanate (Bi4Ti3O12) thin films were fabricated on a bismuth silicate (Bi2SiO5)-coated silicon substrate by the metal-organic decomposition (MOD) method. It was confirmed that the resultant films were single-phase Bi4Ti3O12 thin films with c-axis-dominant orientation. However, the fabricated films have a high leakage current density of approximately 104 A·cm-2. It is considered that this is mainly caused by the surface roughness due to the growth of plate-like grains. The growth of the Bi4Ti3O12 thin films using the MOD method is influenced by the substrate. Therefore, it is regarded that the addition of Bi2SiO5 thin film improves the crystallinity of Bi4Ti3O12 thin films.
Fabrication and Characterization of Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) Structures Using Ferroelectric (Bi, La)4Ti3O12 Films
Authors: Tokumitsu Eisuke , Isobe Takeaki , Kijima Takeshi , Ishiwara Hiroshi
Published: October 2002

We have fabricated and characterized Pt/(Bi, La)4Ti3O12(BLT)/Pt/Ti/SiO2/Si metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structures for ferroelectric-gate transistor applications. It is demonstrated that BLT films fabricated using the metalorganic decomposition (MOD) technique at 750°C have excellent electrical properties. Remanent polarization 2P
r as large as 30 µC/cm2 can be obtained. It is also shown that in the memory window increases with the area ratio S
F:S
M of the MFMIS structure and that a large memory window (3 V) can be obtained for a voltage sweep of ±5 V for MFMIS structures with an area ratio S
F:S
M of 1:15. In addition, it is demonstrated that MFMIS structures with an area ratio S
F:S
M of 1:15 have good data retention characteristics.
Local Epitaxial Growth of (103) One-Axis-Oriented SrBi2Ta2O9 Thin Films Prepared at Low Deposition Temperature by Metalorganic Chemical Vapor Deposition and Their Electrical Properties
Authors: Nukaga Norimasa , Mitsuya Masatoshi , Suzuki Toshimasa , Nishi Yuji , Fujimoto Masayuki , Funakubo Hiroshi
Published: October 2002

We compared a directly crystallized SrBi2Ta2O9 (SBT) film with one crystallized by solid-phase reaction from the fluorite phase prepared by metalorganic chemical vapor deposition (MOCVD). The region of the Bi/Ta mole ratio showing large remanent polarization (2Pr) was narrow for the film directly crystallized from the gas phase compared with that crystallized by solid-phase reaction. Moreover, the Bi/Ta mole ratio showing the maximum 2Pr value differed according to the preparation method used. The crystallinity and the orientation of the SBT phase directly crystallized from the gas phase were strongly influenced by those of the substrate; the (103)-oriented SBT grains directly crystallized from the gas phase grew hetero-epitaxially on (111)-oriented Pt grains. As a result, the direct crystallization of the film from the gas phase lowered the crystallization temperature of the SBT phase and resulted in a (103) one-axis-oriented film.
Poling Field Dependence of Ferroelectric Properties in Barium Titanate Ceramics
Authors: Ogawa Toshio
Published: October 2002

The domain switching and rotation in barium titanate ceramics were evaluated by investigating the poling field dependence of the ferroelectric properties. The effect of domain clamping on the planar coupling factor and dielectric constant at the coercive field was confirmed in barium titanate ceramics as well as in the cases of soft and hard tetragonal lead zirconate titanate ceramics and lead titanate ceramics. The frequency constant peaks due to domain clamping were also observed in barium titanate ceramics. Furthermore, it is considered that domain rotations occurred at the fields required to obtain the maximum dielectric constant and the minimum frequency constant.
Single Crystal Growth and Characterizations of A3BC3D2O14-Type Compounds for Piezoelectric Applications
Authors: Jung Il Hyoung , Kang Yong Ho , Shim Kwang Bo , Yoshikawa Akira , Fukuda Tsuguo , Auh Keun Ho
Published: October 2002

A3Nb1-x
Ga3+(5/3)x
Si2O14 (ANGS, A=Sr, Ca) compounds were investigated as a function of Nb and Ga mole ratios and grown using the micro pulling-down (µ-PD) technique after being prepared by the conventional solid-state reaction. On the basis of the µ-PD growth results, ANGS single crystals were grown by the Czochralski method. The grown Sr3NbGa3Si2O14 (SNGS) and Ca3NbGa3Si2O14 (CNGS) the single crystals showed that they were isostructural to that of A3BC3D2O14, which had the space group P321. The lattice parameters of SNGS and CNGS were calculated to be a=8.282, 8.087 and c=5.073, 4.980 Å, respectively. The defect distribution and piezoelectric properties of these crystals were measured.
Measurement of Moving Speed Using a Leaky Lamb Wave Device
Authors: Takeshi Fujita Takeshi Fujita , Kohji Toda Kohji Toda
Published: October 2002

A technique for measuring the moving speed of a tested object is described using a leaky Lamb wave device composed of two interdigital transducers (IDTs). The IDT on a thin piezoelectric ceramic plate radiates as an ultrasound beam into a liquid and also operates as a detector of the ultrasound signal reflected from a moving medium, at a liquid-solid interface. The delayed output has a frequency shift via a Doppler effect, corresponding to the moving speed of the reflection object. Basic performances of the leaky Lamb wave device and the measured results of the moving speed of a metal disk are presented.
Luminous Phenomenon of Silent Discharge Using a Piezoelectric Transformer
Authors: Teranishi Kenji , Suzuki Susumu , Haruo Itoh Haruo Itoh
Published: October 2002

Light emission is observed in the silent discharge that produced by a piezoelectric transformer (PT) in nitrogen. The spatial distribution of light emission is observed in the λ mode vibration of the PT and compared with the potential distribution on the PT surface. In the case of λ mode vibration, light patterns appear at four areas around the PT. The spatial emission and potential distributions match clearly, indicating that the intensity of light emission is related to the electric field intensity around the PT. It is observed that luminous patterns alternate around the PT by sinusoidal driving voltages, as induced by the piezoelectric effect of elastic vibration on the PT surface. The temporal variation of emission intensity follows the induced electric field on the PT.
Low-Temperature Sintering and Microwave Dielectric Properties of Ca(Li1/3Nb2/3)O3-δ Ceramics
Authors: Soo Kim Peng Liu , Hyun Yoon Ki
Published: October 2002

Effects of B2O3 and/or Bi2O3 on the sinterability and microwave dielectric properties of nonstoichiometric Ca(Li1/3Nb2/3)O3-δ(CLN) ceramics were investigated. With the addition of B2O3 from 0.5 wt% to 4.0 wt%, the dielectric constant (K) and Q·f value of CLN sintered at 990°C were as good as those of pure CLN sintered at 1150°C. These results are due to the enhancement of the apparent density of CLN at low temperature by liquid phase sintering with compositional modification of Ca(Li1/3Nb2/3)O3-δ. However, the dielectric properties of the specimens with 6.0 wt% B2O3 decreased significantly due to the formation of a secondary phase, Li2B4O7. The sintering temperature of CLN was further reduced by Bi2O3 at the expense of the Q·f value. Typically, K of 30.6, Q·f of 31000 GHz, and TCF of -17.5 ppm/°C were obtained for the specimens with 4.0 wt% B2O3 sintered at 1000°C.
Transverse Sound Velocity of the Ferroelectric Copolymer Film of Vinylidene Fluoride and Trifluoroethylene
Authors: Tajitsu Yoshiro , Kanbara Shintaro , Maeda Hidefumi , Ohigashi Hiroji , Date Munehiro , Fukada Eiichi
Published: October 2002

In order to investigate the intermolecular interaction between the individual chain molecules which causes the ferroelectric to paraelectric phase transition of ferrolectric polymers, we devised a new experimental system for measuring the transverse sound velocity for polymer films. Using the new system, we measured the transverse sound velocity v
55 which corresponds to the elastic stiffness tensor component C
55 which reflects the intermolecular interaction between the individual chain molecules (sliding motion between adjacent chain molecules) of the copolymer film of vinylidene fluoride and trifluoroethylene (P(VDF/TrFE)). The value of v
55 obtained here decreases significantly and then reaches a small constant nonzero value, in the temperature range from below the Curie point to the melting point. The results suggest that intermolecular interaction is strong in the ferroelectric phase and becomes very weak in the paraelectric phase, however, the intermolecular interaction between them does not disappear in the paraelectric phase.
Ferroelectric Properties and Structure Distortion in A-Site-Modified SrBi2Ta2O9
Authors: Noguchi Yuji , Shimizu Hiroyuki , Miyayama Masaru , Oikawa Kenichi , Kamiyama Takashi
Published: October 2002

The influence of Ca and Ba modification on the ferroelectric properties of SrBi2Ta2O9 (SBT) was investigated using dense ceramics, and their crystal structures were analyzed by the Rietveld method through high-resolution neutron powder diffraction. The 30% substitution of Sr by a larger Ba lowered the Curie temperature (T

C
) and decreased remanent polarization (2P
r). In contrast, an equal amount of smaller Ca modification resulted in a marked increase in T

C
and in a much higher coercive field, but did not improve 2P
r at an applied field lower than 200 kV/cm. Structure refinement revealed that spontaneous polarization (P
s) is determined by the average shift of perovskite blocks along the a axis, and that the Ca-modified SBT had almost the same P
s as SBT. The 30% Ca incorporation did not improve the intrinsic polarization, however enhanced TaO6 octahedral rotation in the a-b plane, which would lead to the higher T

C
.
Application of Brightness of Scanning Electron Microscope Images to Measuring Thickness of Nanometer-Thin SiO2 Layers on Si Substrates
Authors: Kita Yukihiro , Kasai Yuuki , Hashimoto Shoushin , Iiyama Kouichi , Takamiya Saburo
Published: October 2002

When a surface of a silicon wafer, on which a nanometer-thin SiO2 layer is selectively formed, is observed by a scanning electron microscope (SEM), the brightness of the SEM image at the SiO2 portion is stronger than that of the bare Si portion, and the brightness increases with the increasing thickness of the SiO2 layer. This paper reports experimental and theoretical studies relating to whether the brightness difference between the SiO2 and the bare Si portions is applicable to measuring the thickness of nanometer-thin SiO2 layers. The results suggest that the brightness of the SEM image monotonically increases with the SiO2 thickness and saturates when the thickness reaches 12 nm; thus, it is applicable to evaluate relative thickness in a range smaller than 4 nm (directly applicable) or 10 nm (with calibration based upon the theory).
Electron Paramagnetic Resonance and Photoluminescence Study of Defects in CuGaSe2Single Crystals Grown by the Traveling Heater Method
Authors: Nishi Takao , Medvedkin Gennadiy A. , Katsumata Yuji , Sato Katsuaki , Miyake Hideto
Published: October 2002

Electron paramagnetic resonance (EPR) atT= 4.2 K and photoluminescence (PL) spectra atT= 20 K have been employed to elucidate point defect features in CuGaSe2crystals grown by the traveling heater method. Isotropic and anisotropic paramagnetic centers have been found in crystals as-grown and annealed in various gas mediums. Three PL bands have been observed and the influence of H2, O2and Se2annealing has been studied. The presence of donor singlet VSe+has been evidenced in as-grown and H2annealed crystals. Complex study of EPR, PL spectra and defect physics models have allowed the addition of the point defect ensemble in CuGaSe2with defect pairs (2VCu-+ GaCu2+), VCuand other defect complexes, according to treatments used in this work.
Simulation and Experimental Study of the pH-Sensing Property for AlN Thin Films
Authors: Chiang Jung-Lung , Chen Ying-Chung , Chou Jung-Chuan
Published: October 2002

The aluminum nitride (AlN) thin film has been investigated for using in pH-ISFET (ion-sensitive field-effect transistor) devices. The AlN thin film was used as the sensitive membrane for simulating and analyzing the pH sensing properties. According to the simulation, we find that the AlN/SiO2 gate ISFET has high pH sensitivity and has a linear response for the current–voltage (I–V) and capacitance–voltage (C–V) curves. In the simulation, the pH sensitivity is about 52–59.8 mV/pH for adapting in all testing solutions (pH=1–14). In addition, in the experiment, the I–V and C–V curves of AlN/SiO2 gate ISFET were also measured and the pH-sensing property was discussed in the different buffer solutions.
Tunnel Junction for Long-Wavelength Vertical-Cavity Surface-Emitting Lasers
Authors: Sekiguchi Shigeaki , Kimura Tadayoshi , Okazaki Gen , Miyamoto Tomoyuki , Koyama Fumio , Iga Kenichi
Published: October 2002

To improve the performance of long-wavelength vertical-cavity surface-emitting lasers (VCSELs), we performed an extensive study of tunnel junctions for current injection and confinement. The introduction of a tunnel junction in long-wavelength VCSELs can substantially improve the current injection scheme, because an n-type material is utilized in the p-side region by inserting a tunnel junction. We fabricated long-wavelength lasers with a tunnel junction formed by metalorganic chemical vapor deposition (MOCVD) using tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBAs), and confirmed the current homogenization effect. We also proposed and fabricated a current confinement structure by means of a simple fabrication process using a tunnel junction, i.e., the automatically formed tunneling aperture (AFTA). The AFTA has a tunnel junction aperture and can be formed automatically during electrode thermal annealing. We investigated the formation condition of the AFTA by varying the annealing temperature and time. We performed secondary ion mass spectroscopy (SIMS) and tunneling electron microscopy (TEM) of an annealed tunnel junction in order to understand the formation of AFTA.
Numerical Study on Passive Q-Switching of Tunable Cr:LiCAF Laser with Cr:YSO Solid State Saturable Absorber
Authors: Yen-Kuang Kuo Yen-Kuang Kuo , Jih-Yuan Chang Jih-Yuan Chang
Published: October 2002

Passive Q-switching performance of the tunable Cr:LiCAF laser with the Cr:YSO solid state saturable absorber is numerically studied. The simulation results show that the Cr:YSO may be used as an effective saturable absorber Q switch for the tunable Cr:LiCAF laser over its entire tuning range from 725 nm to 840 nm.
Raman Scattering Study of InGaN Grown by Metalorganic Vapor Phase Epitaxy on (0001) Sapphire Substrates
Authors: Sugiura Touko , Kawaguchi Yasutoshi , Tsukamoto Takehiko , Andoh Hiroya , Yamaguchi Masahito , Hiramatsu Kazumasa , Sawaki Nobuhiko
Published: October 2002

We have studied the asymmetric broadening of the Raman spectra of In
x
Ga1-x
N grown on sapphire substrates with the aid of the spatial correlation model. The asymmetric broadening of the E2 phonon mode is enhanced in the region of immiscibility by increasing the indium molar fraction. The correlation length, which corresponds to the decay length of the E2 phonon mode, was estimated for the first time. It was on the order of 6–10 nm, which is on the same order of magnitude as the size of the columnar structure suggested by transmission electron microscope analyses.
Effects of Bottom Electrodes (Pt and IrO2) on Physical and Electrical Properties of Bi4-xLaxTi3O12 Thin Film
Authors: Yang Woo Seok , Kim Nam Kyeong , Yeom Seung Jin , Kweon Soon Yong , Choi Eun Seok , Roh Jae Sung
Published: October 2002

Negated
Bi3.35La0.85Ti3O12 (BLT) thin (90 nm) films were prepared on Pt (200 nm) and IrO2 (200 nm) electrodes by metalorganic decomposition (MOD) method, and crystallized by rapid thermal annealing (RTA) and the subsequent furnace annealing. BLT films were c-axis oriented on both electrodes irrespective of RTA temperature (600 and 700°C). However, the degree of c-axis orientation was much higher on IrO2 than on Pt, and significantly reduced only on Pt with decreasing RTA temperature. This result was related to the different stress of BLT film which is negligible on Pt, but 500 MPa (tensile) on IrO2 in the RTA temperature range of 600–700°C. The crystalline orientation of BLT film directly affected switching polarization (P
*-P
∧) which had much smaller value of 5 µC/cm2 on IrO2 than 12 µC/cm2 on Pt, and was increased to 16 µC/cm2 only on Pt with the decrease of RTA temperature. On the other hand, leakage characteristics were not changed with bottom electrode materials.
Novel Pretilt Angle Measurement Method for Twisted-Nematic Liquid-Crystal Cells by Apparent Retardation Measurement
Authors: Nishioka Takahiro , Kurata Tetsuyuki
Published: October 2002

We have proposed a novel pretilt angle measurement method for twisted-nematic (TN) liquid-crystal (LC) cells. In this method, the dependence of the apparent retardation of the TN cell on the cell rotation angle is analyzed by the simple mathematic equations derived here to determine the pretilt angle and the gap. This method can be applied to the TN LC display panel. The necessary range of the cell rotation angle is from -3° to 3°. This provides an advantage for both constructing a compact measurement system and measuring a small-size pixel.
Quantum Yield of Electron-Beam Induced Decomposition of SiO2 Overlay on Si in Nanolithography Using a Scanning Tunneling Microscope
Authors: Tetsuzo Ito Tetsuzo Ito , Masahide Gotoh Masahide Gotoh , Koichi Sudoh Koichi Sudoh , Hiroshi Iwasaki Hiroshi Iwasaki
Published: October 2002

We evaluate the quantum yield of SiO2 decomposition caused by electron-beam irradiation from the tip apex of a scanning tunneling microscope over an electron energy range of 10–180 eV and find onsets at 40 and 120 eV. These onsets are close to those found previously for electron-beam induced SiO2 dissociation by Auger electron spectroscopy and electron stimulated desorption. Based on the excitation function, we consider that the decomposition is activated by core level excitations like the Knotek–Feibelman mechanism.
Low-Temperature Formation of Thin-Gate SiO2 Films by the Ultrahigh-Vacuum Chemical Vapor Deposition with Reduced Subcutaneous Oxidation Using Remote-Plasma-Activated Oxygen and Si2H6
Authors: Kanamoto Kyozo , Yoshida Takashi , Oizumi Toru , Murai Akihiko , Kurabayashi Toru , Nishizawa Jun-ichi
Published: October 2002

We have investigated the growth condition dependence on the properties of SiO2 films by remote-plasma-enhanced chemical vapor deposition (RPECVD) in an ultrahigh vacuum system with remote-plasma-activated oxygen and Si2H6. During the RPECVD, subcutaneous oxidation of the Si substrate was not negligible, which degraded the controllability of the film thickness and the electrical properties. The amount of the active oxygen species that dominates the reactions of subcutaneous oxidation was considered to be significantly reduced with increasing O2 flow rate, while that of “pure” CVD remained unchanged. As a result, precise control of the RPECVD SiO2 thickness with reduced subcutaneous oxidation has been achieved by setting the O2 flow rate to the maximum and by using higher Si2H6 flow rates. The characteristics of the SiO2 films obtained using optimized RPECVD conditions at temperatures lower than 600°C without a postannealing process have been demonstrated to be comparable to those of thermally grown films.
Time-resolved Laser Scattering Spectroscopy of a Single Metallic Nanoparticle
Authors: Matsuo Yasutaka , Sasaki Keiji
Published: October 2002

A new technique is proposed for the transient absorption spectroscopy of a single metallic nanoparticle. This technique is based on a differential interference contrast (DIC) microscopy using pulsed laser light. A single nanoparticle is excited by a pumping laser beam, and the DIC signal of a probing light is measured to precisely determine the amplitude and phase of the forward-scattered light. The refractive index and the absorption coefficient of the excited particle can be estimated on the basis of the Rayleigh scattering theory. By changing the delay time between the pumping and probing pulses, absorption dynamics of a single nanoparticle can be observed on a femtosecond time scale. As a preliminary experiment, the electron dynamics of a 70 nm silver colloidal particle was analyzed with this technique.
Current Pulse Shaping in Electron Gun Using Ferroelectric Cathode
Authors: Hayashi Yasushi , Hotta Eiki , Flechtner Donald , Golkowski Czeslaw , Ivers Jim D.
Published: October 2002

We have operated an electron gun using a ferroelectric cathode at a diode voltage of 450 kV. The beam current and its waveform have been studied under various triggering conditions. Adjusting the amplitude and applied timing of the trigger pulse has led to a unique method of current pulse shaping for the ferroelectric diode. The method is convenient and the beam current with a reasonable pulse shape is achievable even with a relatively poor condition of the voltage pulse. Optimum conditions for applying the trigger pulse have been determined and the beam current with the required shape is obtained.
Temperature Rise of Extreme Ultraviolet Lithography Mask Substrate during Dry Etching Process
Authors: Chiba Akira , Hoshino Eiichi , Takahashi Masashi , Yamanashi Hiromasa , Ogawa Taro , Okazaki Shinji
Published: October 2002

Experiments and numerical calculations were performed to investigate the dry etching heating of mask substrate. Changes of the glass substrate temperature were observed by color changes of a heat-sensitive label pasted on the substrate. A simulation model based on a lumped heat capacity system was proposed to investigate the heat transfer mechanism at the contact interface between the mask and the stage or carrier. When thermal radiation dominates the heat transfer mechanism between the mask and the stage, a temperature rise of about 100°C was observed and predicted for an etching time of 60 s. The heating of mask substrate cooled by the stage indicated a temperature rise less than 43°C. The cause of mask substrate temperature rise was found to be insufficient adhesion between the mask and stage. Estimation of thermal response of a 150-mm square standard glass substrate with a thickness of 6.5 mm was attempted using the simulation model based on the experimental results. The dry etching of the mask substrates was found to be a practicable and safe thermal process if the etching time is within 60 s.
Correlation between Defect Concentration and Carrier Lifetime of GaAs Grown by Molecular Beam Epitaxy at Different Temperatures
Authors: Lin Gong-Ru , Liu Tze-An , Pan Ci-Ling
Published: October 2002

A pump-probe study of GaAs grown by molecular beam epitaxy at low temperatures (LT-GaAs) is performed. Ultrashort carrier lifetimes of the as-grown LT-GaAs increase from < 0.13 ps (measurement limitation) to 1.8±0.2 ps as the growth temperature is increased from 200°C to 320°C. The carrier lifetime was found to be approximately inversely proportional to the antisite defect concentration. This trend is found to be in reasonably good agreement with the Schokley–Read–Hall model. The decreasing trend in the amplitudes of continuous-wave and transient reflectivities (ΔR/R) as a function of the growth temperature for the LT-GaAs is explained as an induced absorption caused by dense arsenic antisite defects. The sign of the transient ΔR/R reversed for LT-GaAs grown at 200°C. This is tentatively attributed to the band gap renormalization effect.
Characterisation of Compact Discs using Time of Flight-Energy Elastic Recoil Detection Analysis
Authors: Zhang Yanwen , Possnert Göran , Jonsson Lars , Winzell Thomas , Whitlow Harry J.
Published: October 2002

The challenge of meeting the ever increasing demands for low-cost information storage media with greater information storage density and rapid access has prompted development of sophisticated optical technologies, e.g., compact disc (CD) and digital video disc (DVD) in read only memory (ROM), recordable (R), rewritable (RW) and random access memory (RAM). Here the suitability of time of flight-energy elastic recoil detection analysis (ToF-E ERDA) to characterise optical storage media film has been investigated. High-energy heavy ions (48 MeV 81Br8+ and 60 MeV 127I10+) from a tandem accelerator were used to analyse CD-ROM, CD-R and CD-RW structures. Up to 9 elements, H, C, O Al, P, Co, Cr, Ge, and Sb/Te could be distinguished simultaneously. The results demonstrate the unique power of the technique for characterising the composition and depth profile of the optical multi-layers as well as the ingress and influence of foreign species.
Morphology, Structure and Photoluminescence Properties of Zinc Oxide Films Prepared by Excimer Laser Irradiation of Sol–Gel-Derived Precursors
Authors: Nagase Toshimi , Ooie Toshihiko , Makita Yoji , Kasaishi Shuji , Nakatsuka Masahiro , Mizutani Nobuyasu
Published: October 2002

Morphology, structure and photoluminescence (PL) properties of zinc oxide (ZnO) films prepared by KrF-excimer-laser irradiation of sol–gel-derived precursors were studied. The precursors with a film thickness of 100 or 180 nm were irradiated by the laser at various energy fluences (Ef). Atomic force microscopy and transmission electron microscopy observations revealed that the laser irradiation at an Ef≥100 mJ/cm2 produced crystal growth of close-packed ZnO crystals in an upper layer. Laser irradiation at a high Ef (150 mJ/cm2) of the thinner precursor produced a remarkable crystallization throughout the film, resulting in larger grain size and smooth film surface. Our observation results suggest that the crystallization proceeds by sintering or solidification via melting. The films obtained at Ef≥100 mJ/cm2 showed green PL. The PL spectra were not significantly influenced by the excitation wavelength except for the thinner film irradiated at a high Ef (150 mJ/cm2); it showed a striking increase in the green PL intensity when excited at 275 nm instead of 325 nm. The unique excitation-wavelength dependence may be related to its characteristic threshold of electron excitation.
Titanium Nitride Membrane Application to Extended Gate Field Effect Transistor pH Sensor Using VLSI Technology
Authors: Chin Yuan-Lung , Chou Jung-Chuan , Lei Zhen-Ce , Sun Tai-Ping , Chung Wen-Yaw , Hsiung Shen-Kan
Published: October 2002

A new process for the fabrication of the extended gate field effect transistor (EGFET) together with complementary metal oxide semiconductor (CMOS) circuits on the same chip is reported. The sensing membrane of the EGFET is titanium nitride (TiN) conducting material and it is fabricated using the r.f. sputtering method. The chips are fabricated using the standard submicron 0.5 µm double poly double metal (DPDM) N-well CMOS IC process. No extra mask is used in the post-process. An instrument amplifier circuit is described that provides an output voltage dependent on the threshold-voltage variations in the sensing membrane. According to the experimental results, the high linear sensitivity approaches 57 mV/pH. The hysteresis voltage is 0.5 mV per cycle of buffer solutions of pH7→pH4→pH7→pH10→pH7. This structure is also insensitive to light. This EGFET is fabricated using the standard technology and no difficulty is experienced in realizing this multi species device. The EGFET and readout circuits are produced using VLSI technology, achieving reduced area and low cost. This device has the advantages of mass production.
Fabrication of 1 ×8 Multimode-Interference Optical Power Splitter based on InP Using CH4/H2 Reactive Ion Etching
Authors: Su Yu Jae , Yi Moon Jeong , Mun Choi Seok , Tak Lee Yong
Published: October 2002

1 ×8 multimode-interference (MMI) power splitters with a weakly guided ridge structure based on an InGaAsP/InP material for 1.55 µm operations were designed and fabricated. To determine the optimum etching condition of InP in CH4/H2 plasma for the formation of MMI power splitters, the effects of etching parameters, such as flow rates of constituent gases, rf power, and process pressure on the etch rate and surface morphology were investigated. The fabricated 3-µm-wide adjacent straight waveguides have propagation losses of 2.91 dB/cm at 1.55 µm for transverse electric (TE) polarization. The device performances in terms of the thickness of the upper cladding layer were theoretically and experimentally compared. The polarization dependence of the MMI power splitters was investigated. For TE [transverse magnetic (TM)] polarization, the excess loss of the devices at an operating wavelength of 1.55 µm was 1.02 dB (1.95 dB) and the splitting ratio was 0.68 dB (1.13 dB).
Characterization of Ferroelectric Property of C-Axis- and Non-C-Axis-Oriented Epitaxially Grown Bi2VO5.5 Thin Films
Authors: Sakai Tomohiro , Watanabe Takayuki , Cho Yasuo , Matsuura Kaori , Funakubo Hiroshi
Published: October 2002

Epitaxial Bi2VO5.5 films with c-axis- and non-c-axis-orientations were grown by metalorganic chemical vapor deposition. (001)-, (114)- and (102)-oriented Bi2VO5.5 films were epitaxialy grown on (100), (110) and (111)SrTiO3 substrates, respectively. Electrical properties of the (001)- and (114)-oriented films on (100)SrRuO3∥(100)SrTiO3 and (110)SrRuO3∥(110)SrTiO3 substrates were compared. The dielectric constant (ε
r) of the (001)-oriented film was smaller than that of the (114)-oriented one, suggesting that ε
r along the c-axis is smaller than that along other axes. Leakage current density of the (001)-oriented film was smaller than that of the (114)-oriented one. These results were in good agreement with those of the crystallographically equivalent oriented films of SrBi2Ta2O9 and Bi4Ti3O12. Ferroelectricity and domain structure were observed for both films by Polarization-Electric field measurements and scanning nonlinear dielectric microscopy, respectively. However, the large difference of remanent polarization depending on the film orientation observed for SrBi2Ta2O9 and Bi4Ti3O12 films was not observed for Bi2VO5.5 films.
Dielectric Morphology of Twin Domains in LaAlO3 Observed by a Scanning Microwave Microscope
Authors: Hyun Sangjin , Kim Ahram , Kwon Joonhyung , Char Kookrin
Published: October 2002

We investigated the twin domains of LaAlO3 (001) substrate using a scanning microwave microscope (SMM). Since the SMM can image the local dielectric constant of a sample quantitatively, we can observe the difference of the dielectric constant in the twin domains. Especially the (110) domains were observed more clearly than (100) domains, we attribute this to the difference of the strain in the ferroelastic LaAlO3.
Computer Simulation Study on Incident Fluence Dependence of Ion Reflection and Sputtering Processes from Layered and Mixed Materials
Authors: Kawakami Retsuo , Ohya Kaoru
Published: October 2002

The fluence dependence of D ion reflection and sputtering from C-layered W material, W-layered C material and W
x
C1-x
mixed material, has been demonstrated using the dynamic Monte Carlo program, EDDY. The fluence-dependent depth profile distributions explain such fluence dependence. For the layered materials, the fluence variations of reflection and sputtering are dependent on layer thickness. In particular, for the C layer thickness parallel to the mean ion range for the impact to pure C, the sputtering of the C layer is enhanced with increasing fluence by C emission due to the reflective scattering collisions of D with W near the surface. This is essentially due to the large target mass difference between W and C, which also brings about the fluence variations for the mixed material. The C sputtering is suppressed due to the dynamic behavior of C in the mixed material, whereas the reflection and W sputtering are enhanced.
Using NH3 Plasma Pretreatment to Improve the Characteristics of Organic Spin-on Low-k materials for Copper Metallization
Authors: Chang Kow-Ming , Tseng Ming-Hau , Deng I.-Chung , Tsai Yao-Pin , Yeh Sy-Jer
Published: October 2002

Organic low-k materials have got more attention for reducing integrated circuits RC delay time. A serious problem, in degradation of organic low-k materials is induced by ashing step. In this study, an NH3 plasma-treated spin-on low-k material was used as a dielectric layer for Cu metalization. After NH3 plasma treatment for 10 min, the low dielectric constant films can prevent ashing damage without changing their original dielectric constant. An extra advantage of blocking copper diffusion was achieved after NH3 plasma treatment. The improvement of low dielectric constant films was due to an oxynitride film formed on the surface of low dielectric constant film. This oxynitride film also prevents the Cu diffusion/migration into the underlying dielectric and plays a role of passive diffusion barriers.
Dielectric Properties of Erbium Doped Barium Titanate
Authors: Hwang Jin Hyun , Han Young Ho
Published: October 2002

The effect of Er ion incorporation into the stoichoimetric BaTiO3 on the dielectric properties and microstructural developement was studied. In the case of Er addition to the stoichoimetric BaTiO3 up to 2.0 mol%, there was no change in the Curie temperature. The presence of excess Er greater than 3.0 mol% led to an oxygen-deficient nonstoichiometry, resulting in a shift in the Curie point toward lower temperatures concurrent with the formation of the second phase, identified as Er2Ti2O7. The acceptor-doped behavior with the oxygen-deficient nonstoichiometry and the formation of the second phase are discussed in terms of the solubility and mode of incorporation of Er into BaTiO3.
Performance of Graphite Pastes Doped with Various Materials as Back Contact for CdS/CdTe Solar Cell
Authors: Hanafusa Akira , Aramoto Tetsuya , Morita Akikatsu
Published: October 2002

To date the problem of developing a suitable back contact for CdS/CdTe solar cells has yet to be resolved. The Cu-doped graphite paste that is widely used as a back contact is associated with degradation problems due to possible Cu diffusion across the CdS/CdTe junction. This study was designed to find ways to improve the graphite paste for superior electrical contacts. Mixtures of graphite paste with various material constituents and dopants consisting of silver-, lead-, nickel-, antimony-, bismuth-, or phosphor-based compounds, were studied. Results show that the performances of solar cells fabricated from these graphite pastes vary with the change in the composition. In the cases of Ag2Te and Ni2P, we studied their relationship with the solar cell characteristics with regard to dopant quantity, and furthermore in the case of Ag2Te, with regard to the sintering temperature of the graphite electrode. A fill factor (F.F.) of over 0.65 and efficiencies over 13% were obtained with Ag2Te, Ag3PO4, Ag2MoO4, and NiTe, and efficiencies over 12% were obtained with AgF, AgCl, Ni2P, and Ni3P.
Chemical Etching of {111} Surfaces of GaAs Crystals in H2SO4–H2O2–H2O System
Authors: Sugawara Shigeo , Saito Kaichi , Yamauchi Jin , Shoji Masako
Published: October 2002

The H2SO4–H2O2–H2O system, typically a solution with five parts H2SO4, one part H2O2 and one part H2O in volume ratio, is currently used for chemical polishing of a GaAs crystal to obtain microscopically smooth surfaces. However, the etching of the (111)Ga surface in this etchant leads to the formation of etch pits. In this study, the etching behavior of the (111)Ga surface in various compositions of the H2SO4–H2O2–H2O system at temperatures of 0–70°C is mainly re-examined. It is found that a microscopically smooth {111} surface can be obtained by etching in the solutions with 78+x parts H2SO4, two parts H2O2 and 20-x parts H2O (x=0–4) at 70°C. In contrast, dark and light pits are formed on the (111)Ga surface etched in a solution with two parts H2SO4, one part H2O2 and seven parts H2O at 0°C. Their origin is predicted on the basis of double-etching test results.
Preparation of Ultra thin SrBi2Ta2O9 Films Using Metalorganic Chemical Vapor Deposition Combined with a Modified Annealing Method
Authors: Hironaka Katsuyuki , Isobe Chiharu , Moon Bum-ki , Hishikawa Shinichi
Published: October 2002

We report a capacitor-preparation method using an ultra thin SrBi2Ta2O9 (SBT) film for application to low-voltage-operated ferroelectric random-access memories (FeRAMs). As the film thickness was reduced below 100 nm, the SBT capacitor reached dielectric breakdown at a much lower electric field. Atomic force microscopy (AFM) analysis revealed that the crystallization annealing roughened the interface between the electrode and SBT. We attributed the electrical breakdown to the localized electric field at the roughened interface. By modifying the annealing method for crystallization of SBT, the interface was maintained smooth and flat even after the crystallization annealing, resulting in good performance in terms of the leakage current vs. appled voltage (I–V) characteristics. Employing a 50 nm thick SBT film, by the modified annealing method, a low-voltage operation as well as highly insulating properties was realized; the remanent polarization (2P
r), coercive field (V
c) and leakage current density (J) at 1.5 V were 12.2 µC/cm2, 0.36 V and approximately 5×10-9 A/cm2, respectively.
Simultaneous Observation of Second-Harmonic Emission and Three-Photon Excited Photoluminescence from Hybrid Vapor Phase Epitaxy-Grown GaN Film
Authors: Lee Chao-Kuei , Kao Fu-Jen , Wang Shing Chung , Pan Ci-Ling
Published: October 2002

Nonlinear optical properties of the undoped hybrid vapor phase epitaxy-grown (GaN film sample) were investigated and analyzed using a tunable femtosecond laser as an excitation source. As the laser wavelength was tuned from 762–796 nm, the sample emitted signals corresponding to the second-harmonic wavelength from 381–398 nm with a quadratic power dependence. A strong three-photon-process-related signal at 367 nm with cubic power dependence was simultaneously observed for the first time.
Theoretical Analysis of Terahertz Harmonic Generation in Resonant Tunneling Diodes
Authors: Asada Masahiro
Published: October 2002

Frequency doubling and tripling due to photon-assisted tunneling in a resonant tunneling diode are theoretically analyzed in the terahertz range as an extension of the previously reported density-matrix model. The dependences of the second and third harmonics in the output current on input terahertz voltage, frequency, and applied bias voltage are calculated.
Quasi-Cw Ultraviolet Generation in a Dual-periodic LiTaO3 Superlattice by Frequency Tripling
Authors: Liu Z. W. , Zhu S. N. , Zhu Y. Y. , Qin Y. Q. , He J. L. , Zhang C. , Wang H. T. , Ming N. B. , Liang X. Y. , Xu Z. Y.
Published: October 2002

We propose a dual-periodically domain-inverted structure for realizing an efficient third-harmonic generation at an arbitrary fundamental wavelength. The structure allows to couple two separate optical parametric processes, frequency doubling and frequency adding, through a cascaded quasi-phase-matched interaction, therefore, generate third-harmonic directly from a superlattice sample. As an example, we designed and fabricated such a structure in a LiTaO3 crystal. Using a LD pumped 1.064 µm quasi-cw Nd:YVO4 laser as a fundamental source, considerable ultraviolet at 355 nm was generated from this superlattice by frequency tripling. And green at 532 nm was simultaneously obtained by frequency doubling.
Effect of RF Power and Substrate Temperature on Physical Properties of Zr0.8Sn0.2TiO4Films by RF Magnetron Sputtering
Authors: Hsu Cheng-Shing , Huang Cheng-Liang
Published: October 2002

Physical properties of rf-sputtered crystalline (Zr0.8Sn0.2)TiO4(ZST) thin films deposited on n-type Si(100) substrates at different rf powers and substrate temperatures have been investigated. The structural and morphological characteristics analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) were found to be sensitive to deposition conditions, such as rf power from 300 W to 400 W and substrate temperature (400°C, 450°C). Highly oriented ZST (111) and (002) perpendicular to the substrate surface were identified at a rf power of 400 W and a substrate temperature of 450°C. The selected-area diffraction pattern showed that the deposited films exhibited a polycrystalline microstructure. The grain size as well as the deposition rate of the film increased with the increase in both the rf power and the substrate temperature. The leakage current decreased with increasing rf power and substrate temperature. As rf power=400 W and substrate temperature=450°C, a leakage current of 7.2×10-11A was obtained at 1 V.
Au–Si Bonding on Si(111) Surfaces
Authors: Murayama Misao , Nakayama Takashi , Natori Akiko
Published: October 2002

To investigate the Au–Si bonding feature on Si(111) surfaces, surface energy calculations have been performed for 1 ×1- and √3 ×√3-Au/Si(111) systems by the first-principles method in a local density approximation. It was found that the Au overlayer considerably stabilizes the Si(111) surface. By analyzing the changes in the surface energy and the charge density at various Au positions on the surface, it was shown that the large electronegativity of Au produces covalent-like Au–Si bonds by either terminating dangling bonds of surface Si or inducing the charge transfer from Si–Si to Au–Si bonds, both of which promote surface stabilization and determine the Au overlayer height on Si(111) surfaces.
Partial Disorder of the Si(111)6×6-Au Surface Studied by Scanning Tunneling Microscopy
Authors: Higashiyama Kazuyuki , Egami Akihiro , Hosoi Shinya , Suzuki Kazushi
Published: October 2002

Scanning tunneling microscopy (STM) is used to investigate a 6×6 surface phase of the Au/Si(111) interface. Results show that no well-ordered structure is present on this surface. Instead, two ordered and one disordered 6×6 sublattices are observed to be formed in the distance scale of 500 Å. A kinematical calculation of the diffraction patterns is carried out taking into account the difference in sublattice order. The calculation reproduces the main features of the reported electron-diffraction patterns well. The comparison of these results with those of previous structural studies is discussed.
Comments on the Reflection/Excitation Properties of a Bipolar Potential Structure Used in Ion Wave Experiments
Authors: Raychaudhuri Santwana , Ichiki Ryuta , Kawai Yoshinobu , Lonngren Karl E
Published: October 2002

A series of experiments on the reflection of ion waves from a bipolar potential structure inserted in a double plasma machine is described. It was observed that the bipolar potential structure could also excite additional ion waves depending upon the bias voltages that were employed. The measured signals are interpreted to be pseudo-waves and ion acoustic waves.