bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Density Read-Only-Memory Disc Mastering Using Direct-Focus Laser Beam Recorder
Authors: Kondo Tetsuya , Nakagawa Eiji , Tsurukubo Takashi , Ohgo Takashi , Onizawa Takayuki , Saito Toshiya , Hasegawa Yuichi , Kai Masakatsu
Published: February 2005

The authors have developed a novel laser beam mastering apparatus using a deep-UV (DUV) laser for a high-density optical disc. A direct focusing mechanism, where the recording beam itself is also used for focusing, is applied in the laser beam recorder (LBR). The mechanism solves the focus depth issue and provides stable focusing. The evaluation results for the 23.3-Gbytes-capacity read-only-memory (ROM) disc revealed that uniform recording can be realized. Jitter variations in the tangential and radial directions were suppressed to less than 0.2% and 0.07%, respectively. A low residual tracking error signal was also attained. The measurement results for the 25-Gbyte-capacity disc show reasonable jitter not only for a resist/glass disc, but also for an injection-molded disc. The tilt margin of the disc confirmed that the disc was practical for application in the market. Furthermore, the evaluation of the 27 GByte disc indicated the possibility of higher density ROM disc mastering.
Dependency of Precipitation of Interstitial Oxygen on Its Crystal Nature in Czochralski Silicon Wafer
Authors: Lee Gon-Sub , Park Ki-Hoon , Furukawa Jun , Furuya Hisashi , Kwack Kae-Dal , Park Jea-Gun
Published: February 2005

The precipitate density of interstitial oxygen in CZ silicon after nucleation and precipitate growth heat treatment was determined by investigating its crystal nature. The oxygen precipitate density in the vacancy-dominant crystal region was approximately two orders higher than that in the interstitial-silicon-dominant region. In addition, the oxygen precipitate density strongly depended on the nucleation temperature. The maximum nucleation of oxygen precipitates occurred at ∼800°C for the vacancy-dominant region and at ∼700°C for the interstitial-silicon-dominant crystal region.
Thin Copper Seed Layers in Interconnect Metallization Using the Electroless Plating Process
Authors: Meen Teen-Hang , Chen Wen Ray , Huang Chien-Jung , Chiu Chih-Jen
Published: February 2005

In this paper, we present a process for growing a Cu seed layer on a Ta/SiO2/Si substrate using an electroless plating (ELP) process at an extremely low temperature (∼30°C). In this process, the activation treatment of the Ta/SiO2/Si substrate was carried out by immersion in a PdCl2/HCl solution prior to electroless Cu deposition. The optimum activation time for the substrate was clearly observed to be 7 min. The Cu seed layer was uniformly and smoothly deposited using a CuSO4 concentration of 30 mM for 80 s with an average roughness of 14 nm under a thin film of 50 nm thickness. The grain size of the Cu seed layer was 34 nm. After annealing in hydrogen ambience at 250–350°C, the average roughness of the Cu seed layer was reduced to 4 nm. A proposed mechanism for the ELP of Cu seed layers on Ta/SiO2/Si substrates is also presented.
Optical Properties of Zn1-xCdxSe Epilayers Grown on (100) GaAs b y Molecular Beam Epitaxy
Authors: Kuo Ming-Chin , Chiu Kuan-Cheng , Shih Tsai-Hsuai , Lai Yi-Jen , Yang Chu-Shou , Chen Wei-Kuo , Chuu Der-San , Lee Ming-Chih , Chou Wu-Ching , Jeng Syang-Ywan , Shih Yu-Tai , Lan Wen-Ho
Published: February 2005

Zn1-x
Cd
x
Se epilayers were grown on (100) GaAs substrates by molecular beam epitaxy. Lattice constants of the epilayers were measured by (004) rocking curve X-ray diffraction. A full width at half maximum of 475 to 2100 arcsec was obtained. The dependence of the energy gap on temperature, measured by the photoluminescence (PL) spectra, was fitted by Varshni's [Y. P. Varshni: Physica 34 149 (1967)] and O'Donnell's [R. P. O'Donnell and X. Chen: Appl. Phys. Lett. 58 2924 (1991)] models. The fitting parameters β (161 K to 368 K) and  (13 meV to 24 meV), related to phonon energy, were obtained from Varshni and O'Donnell fits, respectively. The activation energies calculated from the integrated PL intensity versus inverse temperature decrease as the Cd content increases. The broadening of the PL linewidth with temperature was fitted by Γ(T)=Γ0+Γa
T+ΓLO1/[exp
(\hbarωLO1/k
T)-1]+ΓLO2/[exp
(\hbarωLO2/k
T)-1]+Γiexp
(-<E
b>/k
T). The impurity binding energy, <E
b>, was found to decrease as the Cd composition increases.
Simulation and Fabrication of InGaP/Al0.98Ga0.02As/GaAs Oxide-Confined Collector-Up Heterojunction Bipolar Transistors
Authors: Chen Wen-Bin , Su Yan-Kuin , Lin Chun-Liang , Wang Hsin-Chuan , Yu Hsin-Chieh , Chen Shi-Ming , Su Juh-Yuh
Published: February 2005

Two-dimensional numerical simulations were performed to investigate the proposed oxide-confined collector-up heterojunction bipolar transistors (C-up HBTs). To achieve a high current gain, the effective base-emitter junction area should be decreased to be smaller than that of the base-collector junction. However, at the same time the offset voltage was increased by the decrease of the base-emitter junction area. A trade-off between the current gain and the offset voltage was observed for C-up HBTs. In the device fabrication, the current confinement of the partially oxidized Al0.98Ga0.02As layer was demonstrated by a simple current–voltage measurement applied to the base-emitter junction. With applying a 400°C oxidation process for 70 min, a current gain of 79 can be achieved with a low base sheet resistance of 203 Ω/sq. and an offset voltage of 160 mV. The relationship between the current gain and the offset voltage obtained from the experimental results shows the same trend as that observed in the simulations. The optimized condition of the oxidation depth is that in which the effective base-emitter junction area is slightly smaller than that of the base-collector junction.
Annealing Effect on Boron High-Energy-Ion-Implantation-Induced Defects in Si
Authors: Hsu Wei-Cheng , Liang Mong-Song , Chen Shih-Chang , Chen Mao-Chieh
Published: February 2005

In this work, we investigate the annealing effect on defects in Si induced by boron high-energy (1.5 MeV) ion implantation with respect to implantation dose (1.1×1013 and 5×1013 cm-2) as well as annealing scheme [rapid thermal annealing (RTA) and furnace annealing (FA)]. The higher dose implantation resulted in more serious degradation of the minority carrier generation lifetime in the implanted layers. Also, the degree of lifetime recovery by either RTA or FA was very limited with the higher dose implantation, presumably due to the presence of the implantation-induced dislocations. The degradation of the lifetime in the lower dose-implanted sample could be significantly recovered by the annealing process, particularly the RTA scheme; this is presumably because RTA has a better ability to reduce the implantation-induced interstitials.
Direct Observation of High-Frequency Chaos Signals from the Resonant Tunneling Chaos Generator
Authors: Maezawa Koichi , Kawano Yoichi , Ohno Yutaka , Kishimoto Shigeru , Mizutani Takashi
Published: February 2005

The direct observation of the chaos signal patterns in a microwave frequency range was demonstrated on the resonant tunneling chaos generator circuit. It is difficult to observe such high-frequency chaos because one must use a sampling oscilloscope. To overcome this problem, we devised a special circuit controlling the chaos to output identical signals repeatedly. This permits us to observe (seemingly)random patterns. This control scheme may lead to various applications.
Glass Transition Temperature Monitoring in Bilayer and Patterned Photoresist Films
Authors: Niakoula Dimitra , Raptis Ioannis , Goustouridis Dimitrios , Argitis Panagiotis
Published: February 2005

Monitoring of glass transition temperature in complex lithographic structures using an interferometry based methodology, is demonstrated. The method is applied in the case of bilayer photoresist structures, where the T
g
film values of both bottom and top polymeric layers are measured simultaneously. Furthermore, in the case of processed photoresist films the obtained signal provides the T
g
film value of resist areas exposed at different doses, enabling in situ measurements for material and process optimization studies.
Fabrication of Zn-Indiffused LiNbO3 Optical Waveguides by Diffusing Sol–Gel Spin-Coated ZnO Film at Low-Pressure Atmosphere
Authors: Selvan Jayaraman Senthil , Fujimura Masatoshi , Suhara Toshiaki
Published: February 2005

Planar and channel waveguides supporting both extraordinary and ordinary polarization modes were fabricated by diffusing sol–gel spin-coated ZnO film into Z-cut congruent LiNbO3 at low-pressure atmosphere. The waveguide showing propagation losses of 0.2 ±0.1 dB/cm for extraordinary and 0.7 ±0.2 dB/cm for ordinary polarization modes at 1.5 µm wavelength was fabricated by diffusing 330 nm ZnO film at 890°C for 4 h in a low-pressure of 1 Torr. The effect of spin-coated ZnO film thickness and diffusion conditions on the waveguiding properties are discussed.
Parametric Studies on Improved Laser Cutting Performance of Magnesium Alloy with Two Flow Nozzles
Authors: Fushimi Takashi , Kitazawa Masaya , Endo Masamori , Yamaguchi Shigeru , Nanri Kenzo , Fujioka Tomoo
Published: February 2005

We describe a newly proposed method of cutting a magnesium alloy using a high-energy CO2laser. Improved laser cutting was achieved when the movement of the molten metal in the kerf was controlled by supplying assist gas from two nozzles positioned above and below the cutting sample. In order to analyze the gas flow and the movement of the molten metal in detail, a flow visualization experiment that simulated the molten metal ejection was also performed using an acrylic work-piece and water as the operation fluid. The results of this simulation were then compared with those of a computational fluid dynamics calculation. Such comprehensive model analysis revealed that the well-balanced gas flows from the two nozzles could enable the desirable flow and fast velocity to be generated both in the kerf and underneath the workpiece, under the conditions where high-quality laser cutting is achieved.
Effect of Milling Process on the Electron Spin Resonance Center Formation in Pyrex Glass by Gamma-Ray Irradiation
Authors: Hirai Makoto , Ikeya Motoji
Published: February 2005

Ball-milled Pyrex glass (Corning 7740) was irradiated by gamma-rays to a dose of 30 kGy to investigate the milling effect on the formation of paramagnetic centers with ESR. The formation efficiency of E' centers was increased markedly while that of boron oxygen hole centers (BOHCs) was suppressed by 40%. An annealing experiment showed that the milling process makes BOHCs unstable, which may be the reason for the suppression. Reduction in the ESR intensity, after etching with hydrofluoric acid, clarified that both types of center are concentrated in the near-surface region in different ratios. The milling effect on E' center formation can be explained by the formation of oxygen vacancies in the near-surface region. A similar effect has already been observed in quartz. By contrast, the suppression of BOHC formation in the bulk region needs to be described by a new mechanism. We assume that internal elastic stress induced in the milled grains suppresses BOHC formation. Internal stress in the thermally tempered glass (TTG) was relieved by breaking it to submillimeter size. The observed dependence of the BOHC formation efficiency on grain size allowed us to estimate that the suppression rate per 1 MPa is more than 0.4%, which is consistent with the milling effect assuming a stress of 100 MPa.
Electro-Optical Bistability Associated With Stripe Formation in Highly Twisted Nematic Liquid Crystals
Authors: Yu Chang-Jae , Jeon Young Jae , Hong Sunkwang , Lee Sin-Doo
Published: February 2005

An electro-optical (EO) bistability associated with the stripe formation is studied in highly twisted nematic liquid crystals (NLCs) as a function of the ratio d/P
0 of the cell thickness d to the natural pitch P
0 in the presence of an applied voltage. For d/P
0≥0.6, it is found that the EO hysteresis appears in the π-twisted planar geometry. Particularly, for d/P
0≥0.75, a transition from the π-twisted state to the 2π-twisted state occurs together with the EO hysteresis. The origin of the EO bistability comes from the in-plane modulation of the molecular reorientation which leads to the formation of the stripe domains. The experimental data of the stripe period and the threshold for the appearance of the stripe domains are analyzed in terms of the periodicity of the in-plane modulation within the continuum theory.
Observation of Optical Interferometric Band Structure Representing Plastic Deformation Front under Cyclic Loading
Authors: Yoshida Sanichiro , Ishii Hideyuki , Ichinose Kensuke , Gomi Kenji , Taniuchi Kiyoshi
Published: February 2005

An interferometric band structure previously observed under monotonic tensile loading has been observed under cyclic loading as well. Like the previous monotonic loading case, the band structure is found to represent the plastic deformation front, indicating that it can be used for visualization of stress concentration. Observed correlation between the motions of the plastic deformation front and the test machine's crosshead indicates that the plastic deformation front moves in proportion to the strength of the displacement field induced by the test machine. This is consistent with a previous report that the propagation speed of the plastic deformation front varies in proportion to the monotonic loading speed.
Fabrication of Highly Dense Ru Thin Films by High-Temperature Metal-Organic Chemical Vapor Deposition with NH3 Gas as Ru Oxidation Suppressing Agent
Authors: Sun Ho-Jung , Kim Younsoo , Park Sung-Eon , Hong Kwon , Roh Jae-Sung , Sohn Hyun-chul
Published: February 2005

We attempted to fabricate highly dense Ru thin films by metal-organic chemical vapor deposition at an elevated temperature of 400°C, employing NH3 gas to suppress Ru oxidation. A solution of 0.2 mol/L tris(2,4-octanedionato)ruthenium [Ru(od)3, Ru(C8H13O2)3] dissolved in n-butylacetate was used as a Ru source and O2 as a reactant gas. It was revealed that NH3 gas effectively eliminated residual oxygen from the Ru films. However, at higher feeding rates of a metal-organic source, Ru films showed poor densities and high electrical resistivities mainly due to significant carbon incorporation. By optimizing Ru(od)3 flow rate to less than 0.3 g/min to reduce contaminating carbon supply, we successfully produced highly dense and conductive Ru films. The best Ru film had a density of 12.2 g/cm3 and a resistivity of 12.0 µΩ·cm, which were excellent values close to the bulk ones.
Breaking of Ice Using Pulsed Power
Authors: Ihara Satoshi , Yamabe Chobei
Published: February 2005

The breaking of ice using shock waves produced by a pulsed power generator is suggested as a new method for navigation of icebreakers in order to realize the safe and quick navigation in icebound sea. Shock waves can be produced by applying a voltage between electrodes in contact with an ice sample. The ice breaking by the pulsed power was demonstrated in tap water experimentally. During the experiments, the ice sample was artificially made from pure water. In the salt water with a salinity of 3.5%, the ice sample was not broken according to the results obtained using the cylindrical electrode with a flat tip. By using the conical electrode with the pointed tip, the above ice sample was broken. The shock waves caused by the ionized region formed at the tip of the conical electrode and the localized intense stress at the crack seem to be the important factors behind the ice breaking in the salt water.
Comments on “Cerenkov Instability due to Unmagnetized Electron Beam in Periodically Corrugated Waveguide” [Jpn. J. Appl. Phys. 42 (2003) 7095]
Authors: Shoucri Magdi M.
Published: February 2005

It is the purpose of the present comments to show that the boundary condition on the discontinuity of the wave electric field radial component at the interface of a relativistic electron beam with vacuum, used recently in Oguraet al.[Jpn. J. Appl. Phys. 42 (2003) 7095], as derived by Bobroff [IRE Trans. Electron Devices 6 (1959) 68] from the definition of an electric polarization, can be directly derived from Maxwell's equation. The equivalent boundary condition on the discontinuity of the wave magnetic field tangential component can also be directly derived from Maxwell's equations.
Nanofilms Based on Vapor Deposition of Polymerized Polypyrrole and its Characteristics
Authors: Kim Jinyeol , Kwon Sijoong , Han Sungwon , Min Youngkun
Published: February 2005

Nanofilms of polypyrrole (PPy) were prepared chemically by vapor deposition polymerization (VDP). It was found from the analysis of the morphological structure by atomic force microscopy that ultra thin films of PPy with thicknesses between 30 and 80 nm could be formed by VDP as well as by casting. These thin films showed surface features of highly ordered structural regularity. The surface resistance of PPy films more than 60 nm thick was enhanced up to 103 Ω/□ and light transmittance was increased up to 90% in the case of a film less than 40 nm thick. From the electronic absorption and Raman scattering spectra, it was found that the charged domains (chemical defects) dispersed in polymer chains of PPy nanofilms are due more to bipolarons than to polarons.
Optical Add/Drop Multiplexers Using Slanted Fiber Bragg Gratings
Authors: Endo Masaki , Miyakawa Hiroshi , Kawai Shigeru , Ohta Yoshinori
Published: February 2005

Novel optical add/drop multiplexers (OADMs) using slanted fiber Bragg gratings (S-FBGs) are proposed. The S-FBGs couple the guided mode to radiation modes, and they also couple specific radiation modes to the guided mode. A set of S-FBGs located near each other function as OADMs. Output light beams from an optical fiber couple to the other fiber by the slanted gratings. The proposed OADM does not require optical circulators that are components of conventional multiplexers using FBGs. Low-cost and small-size optical filters may be constructed. Calculation results successfully show the possibilities of OADMs.
UV-Induced Refractive Index Change of SiN Film and Its Application to Center Wavelength Trimming of Vertically Coupled Microring Resonator Filter
Authors: Naganawa Toshiki , Haeiwa Hirofumi , Kokubun Yasuo
Published: February 2005

In this study, to develop an accurate center wavelength trimming, we investigated the UV-induced refractive index change of the SiN film formed by plasma-enhanced chemical vapor deposition (PECVD) method using SiH4 gas and found that the refractive index of the SiN film was largely changed by -1.3×10-2 by the UV irradiation. Utilizing this phenomenon, we developed a novel center wavelength trimming using SiN as a ring core and irradiating UV laser beam. A wide range (-12.1 nm) of center wavelength was demonstrated and the shifted center wavelength was almost stable for more than 1200 h. A narrow channel spacing of filter array was realized by this technique.
Application of Arrayed-Waveguide Grating to Compact Spectroscopic Sensors
Authors: Komai Yuki , Nagano Hiroko , Kodate Kashiko , Okamoto Katsunari , Kamiya Takeshi
Published: February 2005

An arrayed-waveguide grating (AWG) fabricated using silica-based waveguides has good stability, good channel uniformity, high wavelength accuracy and low cost. The AWG is attractive not only for use in optical wavelength-division-multiplexed networks but also for potential applications to various spectroscopic measurements. We propose a compact spectroscopic sensor based on the AWG, and fabricated an AWG module for sensing. A liquid sample under test is poured into a groove in the first slab region of the AWG. The detector that is placed at the end face of the second slab region measures the spectral transmittance of the liquid. A preliminary experiment was carried out using the water solution of sodium acetate. We achieved the relative error in terms of the optical transmittance of 2.5%. Fundamental device characteristics and preliminary experimental results are reported.
A Three-Dimensional Micro-Electro-Mechanical System (MEMS) Optical Switch Module Using Low-Cost Highly Accurate Polymer Components
Authors: Yamamoto Tsuyoshi , Yamaguchi Johji , Takeuchi Nobuyuki , Shimizu Akira , Sawada Renshi , Higurashi Eiji , Uenishi Yuji
Published: February 2005

This paper describes a large-scale, compact three-dimensional (3D) micro-electro-mechanical system (MEMS) optical switch using two-axis tilt mirror arrays and free-space optics. This switch structure provides a practical solution for constructing a large-scale switching fabric due to its high density and low cost features. The MEMS mirrors are made of single-crystal silicon with integrated gimbal structures and are tilted two dimensionally by electrostatic force. In the mirrors, the driving electrode has a three-dimensional terrace structure and they effectively reduce the control voltage compared with conventional MEMS mirrors. The free-space optics consists of low-cost high-precision polymer components and is passively assembled in a series of simple steps. A prototype module with 100-channel optical fiber input/output has an overall hardware volume of approximately 170 cc (80×60×35 mm), and this exhibited a low coupling loss of 4.0 dB and a switching time of 3 msec.
Fabrication of Silica-Based Glass Optical Waveguide by UV Beam Scanning
Authors: Kashiwagi Ken , Yamashita Shinji
Published: February 2005

UV induced refractive index increase, the photosensitivity, in Ge-doped silica glass has been utilized for the fabrication of fiber Bragg gratings and long period fiber gratings. Recently, this phenomenon has also been applied to the fabrication of optical channel waveguides in order to achieve cost efficiency and fabrication flexibility. In this work, the fabrication of various optical waveguides by UV beam scanning is demonstrated. 10-mm-long straight optical waveguides and a Y-Branch waveguide with a branching ratio of nearly 50% are realized. We also propose and demonstrate a technique for the simultaneous fabrication of an optical waveguide and a Bragg grating by scanning UV beam through a phase mask.
Proposal and Analysis of a Semiconductor Klystron Device Using Two-Dimensional Electron Gas for Terahertz Amplification and Oscillation
Authors: Asada Masahiro
Published: February 2005

An amplifier device with two-dimensional electron gas, which has the possibility of operation in the THz range, is proposed and analyzed. In the operation principle, electrons traversing the input port emit and absorb THz photons, resulting in the splitting of the electron energy levels, and then, the beat of these splitting electron waves produces charge density modulation which emits an amplified output power at the output port. This operation principle is equivalent to that of the klystron tube in the low-frequency classical limit. Transconductance and power gain are analyzed quantum mechanically, taking into account the influence of electron scattering and electron energy distribution. Calculated results show that the transconductance has a peak in the sub-THz and THz ranges. An oscillator using this device integrated with a coplanar line and a slot antenna is proposed, and the possibility of THz oscillation is shown by analyzing the oscillation conditions.
Increase in Drive Current by Pt/W Protection on Short-Channel Schottky Source/Drain Metal–Oxide–Semiconductor Field-Effect Transistors with Metal Gate
Authors: Sato Hiroshi , Sato Hiroyuki , Iguchi Tsuyoshi , Asada Masahiro
Published: February 2005

Schottky source/drain metal–oxide–semiconductor field-effect transistors (MOSFETs) with 20–100-nm-long metal gates were fabricated. Using a Pt/W protection film on Er, the drive current of an n-type MOSFET was improved to be two orders of magnitude larger than that without the protection. The drain currents were 11 µA/µm for the n-type at V
DS = 1.5 V and V
GS = 2 V, and 16 µA/µm for the p-type at V
DS = -1.5 V and V
GS = -2 V. A CMOS inverter was fabricated by the same process and its clear switching characteristics were shown.
Iteration Exchanging Search Method for Designing a Wideband Antireflection Coating over the Visible Spectral Region
Authors: Liou Yeuh-Yeong
Published: February 2005

A simple straightforward method for achieving a wideband antireflection coating design over the visible spectral region was proposed. The design procedure utilized the tuning operation of the thickness of a two-material multilayer system first, and the exchanging operation of layers was applied afterward to refine the visible antireflection performance and simplify the design structure. An additional iteration process was used for the further improvement of the antireflection performance. It was shown that the two-material 30-layer iteration exchanging search for an antireflection coating design over the 400–750 nm spectral region was reduced to 16–20 layer structures, and their average visible spectral reflectivities were very good and reduced to approximately 0.032–0.033%.
Green Photoluminescence Suppression in ZnO Embedded in Porous Opal
Authors: Abrarov Sanjar M. , Yuldashev Shavkat U. , Lee Sergey B. , Kang Tae Won
Published: February 2005

The photoluminescence (PL) and transmittance characteristics of zinc oxide (ZnO) embedded in voids of silicon dioxide synthetic opal by the technologically simple sol–gel method are reported. The uniform formation of ZnO nanoparticles inside of the opal matrix can be obtained after its infiltration in an aqueous solution containing a zinc nitrite hexahydride precursor followed by thermal annealing. The green-PL suppression is observed due to the inhibition of spontaneous emission through oxygen vacancies in ZnO. The strong redshift of the transmittance characteristics signifies the essential filling of voids in the fcc packed structure. The infiltration of nanocrystals into synthetic opal may be used as an inexpensive method for the fabrication of polycrystalline ZnO with dominant ultraviolet-blue PL. This technology may also be promising for the fabrication of color light sources, such as RGB pixels in secondary-electron-emission or field-emission displays.
Effect of Annealing on the Tolerance of LiCaAlF6 Single Crystals against F2 Laser Irradiation
Authors: Kawaguchi Yoshizo , Narazaki Aiko , Sato Tadatake , Kurosaki Ryozo , Niino Hiroyuki , Sato Hiroki , Fukuda Tsuguo
Published: February 2005

The optical tolerance of annealed LiCaAlF6 single crystals against F2 laser irradiation was investigated. Annealed LiCaAlF6 (t=1.45 mm) shows an improved transmittance at 157 nm, 94.4% after the compensation of the surface reflection loss. Furthermore, after the initial increase by F2 laser cleaning, transmittance at 157 nm remains almost unchanged even after irradiation with a F2 laser beam up to 105 pulses at a fluence of approximately 160 mJ cm-2 pulse-1.
The role of Cation Vacancies on Microstructure and Piezoelectricity of Lanthanum-Substituted (Na1/2Bi1/2)TiO3 Ceramics
Authors: Yi Jae Yun , Lee Jung-Kun , Hong Kug Sun
Published: February 2005

The effects of incorporation of lanthanum (La3+) ions in Na1/2Bi1/2TiO3 (NBT) on microstructure and sintering characteristics were studied. As the content of incorporated La3+ increased in [(Na0.5Bi0.5)1-1.5x
V0.5x
La
x
]TiO3, the sintered density reached a maximum at x=0.05 and the grain size decreased as lanthanum ions increase from x=0 to x=0.05. Whereas, in [Na0.5Bi0.5-x
La
x
]TiO3, the incorporated lanthanum ions decreased the bulk density and increased the grain size. The effect of different La incorporation methods on the microstructure change suggested that the LaA
•–VA'' pairs played a critical role in suppressing the fast grain boundary movement and enhancing the densification of [(Na0.5Bi0.5)1-1.5x
V0.5x
La
x
]TiO3 ceramics. Lanthanum addition also changed the electrical properties of NBT. La ion incorporation with A-site cation vacancies modified the electrical property of NBT to satisfy the needs for the piezoelectric application.
High-Q Microwave Dielectric SrTiO3-Doped MgTiO3 Materials with Near-Zero Temperature Coefficient of Resonant Frequency
Authors: Cho Won Woo , Kakimoto Ken-ichi , Ohsato Hitoshi
Published: February 2005

The microwave dielectric properties of the (1-x)MgTiO3–xSrTiO3 system have been investigated. The objective of the present work is to compensate for the negative temperature coefficient of the resonant frequency (τf) of MgTiO3 by addition of SrTiO3. The variation in microwave properties of the system significantly depends on the amount of SrTiO3 present, and they can be matched using mixing rules. With increasing x, the dielectric constant (ε
r) increased and the quality factor (Q
f) decreased. A ceramic sample with x=0.036 of SrTiO3, sintered at 1270°C for 2 h, and having a near-zero temperature coefficient of resonant frequency (τf) of -1.3 ppm/°C can be obtained.
Influence of Frank Elastic Constant Anisotropy on Optical Pattern Formation Using Nematic Liquid Crystal Films
Authors: Hsu Hsu-Kuan , Lai Yinchieh , Chen Shu-Hsia
Published: February 2005

We investigate the influence of the Frank elastic constant anisotropy on optical pattern formation using nematic liquid crystal (NLC) films in one-feedback-mirror systems. The governing diffusion-like equation for the parallel planar-aligned and the vertical-aligned NLC films with an externally biasing quasi-static electric field under the hard boundary assumption is derived. The intrinsic Frank elastic constant anisotropy induces the anisotropy of the diffusion length, which results in the anisotropic distribution of the threshold intensity for optical pattern formation. The effects of the elastic constant anisotropy on optical pattern formation are studied for the first time and the obtained numerical results can reasonably explain the optical patterns that are formed.
Study of Mg ion Intercalation in Polycrystalline MoO3 Thin Films
Authors: Sian Tarsame. S. , Reddy Gade. B. , Shivaprasad Sonnada. M.
Published: February 2005

As-deposited amorphous MoO3 films were found to crystallize into a stable orthorhombic phase on annealing in air at 350°C. The feasibility of using Mg ions as intercalants, in polycrystalline MoO3 thin films has been investigated. These ions were intercalated galvanostatically at a constant current density of 166 µA/cm2. Structural studies carried out on intercalated films, show lattice expansion along b axis by 2.35% for x = 0.1 and 3.17% for x = 0.3. Partial restoration of b-axis is observed on deintecalation. The chemical status of Mo and O ions, before and after intercalation has been investigated using Photoemission Spectroscopy (core level spectra). Core level (CL) of Mo 3d levels indicate the presence of Mo+6 oxidation state only in unintercalated films, with a stoichiometry of MoO3. The intercalated ions are found to reduce Mo ions as revealed by the presence of Mo+5, Mo+4 and Mo+3 states in addition to Mo+6 state. Formation of Mg–O bonds is seen from the CL spectrum of O1s levels. From cyclic voltammetry experiments the estimated diffusion coefficient of Mg ions is found to be of the order of 10-19 cm2/s and the films are stable even after 300 cycles.
Orientation Control of Vanadylphthalocyanine Molecules Deposited on Pt (111) and Au (111) Surfaces
Authors: Jin Yonglong , Sawa Goro , Uchida Yoshiyuki , Kojima Kenzo , Ohashi Asao , Ochiai Shizuyasu , Mizutani Teruyoshi
Published: February 2005

Vanadylphthalocyanine (VOPc) thin films were prepared on Au (111) and Pt (111) substrates by molecular beam epitaxy. VOPc molecules deposited on the Au (111) substrate orientated parallel to the substrate surface, and grew epitaxially on the substrate surface whose temperature was maintained at 200°C. On the other hand, Phase III was formed on the Pt (111) substrate with a change in substrate temperature. This indicates that there are no VOPc trapping sites in the Pt (111) substrate.
Preparation of Sol–Gel Derived Titanium Oxide Thin Films Using Vacuum Ultraviolet Irradiation with a Xenon Excimer Lamp
Authors: Naganuma Yasuhiro , Tanaka Satomi , Kato Chihiro
Published: February 2005

Titanium oxide thin films are prepared by the sol–gel technique with 172 nm vacuum ultraviolet (VUV) irradiation using a Xe2
* excimer lamp. The effect of VUV irradiation on spin-coated films was investigated by UV-visible absorption, X-ray photoelectron, Fourier transform infrared and Raman spectroscopies. The results showed that VUV irradiation causes the removal of hydroxyl and organic functional groups from the transparent coating film without causing the reduction of titanium, so that the film begins to transform into an oxide from a hydroxide. It was found that VUV irradiation onto a dried coating film is effective in accelerating the formation of Ti–O networks and crystallization.
New Inductively Coupled Plasma System Using Divided Antenna for Photoresist Ashing
Authors: Terai Fujio , Kobayashi Hiroaki , Iyanagi Katsumi , Yamage Masashi , Nagatomo Takao , Homma Tetsuya
Published: February 2005

We have developed an inductively coupled plasma (ICP) system with a small chamber for 300-mm-diameter-wafer processes, and a good uniformity of ashing, and both low substrate temperature and low pressure were achieved. The features of this ICP system are substrate temperatures lower than 60°C in order to suppress chemical reactions, and low pressures of 3–5 Pa to suppress the both oxidation of Cu wiring and the degradation of low-k films. Furthermore, the antenna is divided plurally and capacitively coupled. This new antenna can achieve good uniformity in a small chamber because the capacitive coupling to the chamber through a quartz glass window can be easily controlled by reducing series impedance, even when the radio frequency (rf) power is very high. Moreover, the damage to the quartz glass window can be decreased by controlling the series impedance of the antenna, resulting in a long-lasting quartz window. The chamber structure was also optimized by performing an original plasma simulation to improve the uniformity of ashing rate. As results for 300-mm-diameter wafers in the 460-mm-diameter chamber, an average ashing rate of 848 nm/min with a uniformity of ±5.5% was obtained for photoresist films under the following conditions: an O2 gas flow rate of 200 sccm, a substrate temperature of 60°C, a gas pressure of 3 Pa and an rf power of 4 kW.
Measurement of the Hyperfine Structure and Zeeman Shift in Y I by High-Resolution Diode-Laser Spectroscopy
Authors: Nakada Haruaki , Jin Wei-Guo , Minowa Tatsuya , Katsuragawa Hidetsugu , Uematsu Haruko
Published: February 2005

High-resolution laser spectroscopy has been performed using a tunable diode laser to measure the hyperfine structure (hfs) and Zeeman shift of two transitions in Y I. The hfs constants A of 89Y were determined for the 4d5s
2
2
D
3/2 and 2
D
5/2 levels, and 4d5s5p
4
F
3/2 and 4
F
5/2 levels; the A values of the 4
F
3/2 and 4
F
5/2 were determined for the first time. Using circular polarizations, the Zeeman spectra were selectively measured and the g factors were determined for the 4d5s5p
4
F
3/2 and 4
F
5/2 levels.
Dielectric Properties of BaTiO3 Thin Films Derived from Clear Emulsion of Well-Dispersed Nanosized BaTiO3 Particles
Authors: Yamashita Yasuhisa , Yamamoto Hiroshi , Sakabe Yukio
Published: February 2005

The dielectric properties of thin films with microemulsion (ME)-routed nanocrystalline BaTiO3 particles were investigated in terms of the films' crystallinity and grain size. The ME method provided a clear emulsion of well-dispersed nanocrystalline BaTiO3 particles. BaTiO3 thin films were prepared by direct spin-coating of the clear emulsion on Si/SiO2/Al2O3/Pt substrates. By varying the postannealing temperature from 600°C to 1000°C, BaTiO3 thin films of different grain sizes were prepared. A fine BaTiO3 powder was removed from the clear emulsion by adding ammonia solution to cause flocculation, followed by centrifugation and washing. A transmission electron microscope (TEM) observation revealed that the powder generated many inner voids, but the thin films did not contain inner voids, thus resulting in high crystallinity. The dielectric properties of these films were measured as functions of temperature. Polarization as a function of voltage was measured, and a ferroelectric D-E hysteresis curve was observed in the sample with a mean grain size of 18 nm. The measurement of piezoelectric hysteresis using a scanning probe microscope (SPM) also revealed ferroelectricity in a small area just below the SPM probe. Direct use of the clear emulsion of well-dispersed nanocrystalline BaTiO3 particles in the ME method enables the fabrication of BaTiO3 thin films that consist of nanocrystalline BaTiO3 grains without inner voids, and the films exhibit great dielectric performance.
Ferroelectric Properties of Dysprosium-Substituted Lead Zirconate Titanate Thin Films Fabricated by Chemical Solution Deposition
Authors: Nakaki Hiroshi , Uchida Hiroshi , Yokoyama Shintaro , Funakubo Hiroshi , Koda Seiichiro
Published: February 2005

Dysprosium (Dy3+)-substituted lead zirconate titanate (PDZT) thin films were synthesized in order to improve the ferroelectric properties of lead zirconate titanate (PZT) films by crystal anisotropy enhancement. Thin films of Pb1.00-(3x/2)Dy
x
(Zr0.40Ti0.60)O3 (A-PDZT) and Pb1.00Dy
x
(Zr0.40Ti0.60)1-(3x/4)O3 (B-PDZT) were deposited on (111)Pt/Ti/SiO2/(100)Si substrates by chemical solution deposition (CSD). The ferroelectric properties of A- and B-PDZT thin films were compared with those of a non-substituted PZT film. Dy3+-substitution based on B-PDZT (x=0.02) enhanced the tetragonality of PZT film, which increased the P
r value of B-PDZT from 20 µC/cm2 up to 25 µC/cm2. On the other hand, both the c/a ratio and P
r value of the A-PDZT film decreased with increasing x continuously. These results suggest that the ferroelectric property was enhanced by the Dy3+-substitution for B-site in PZT crystal.
Fabrication and Properties of Ge-Doped (Bi,Nd)4Ti3O12 Thin Films by Chemical Solution Deposition
Authors: Sakamoto Wataru , Mizutani Yu-ki , Iizawa Naoya , Yogo Toshinobu , Hayashi Takashi , Hirano Shin-ichi
Published: February 2005

Nd- and Ge-codoped Bi4Ti3O12 thin films have been fabricated by chemical solution deposition. The effects of Ge doping in (Bi,Nd)4Ti3O12 on microstructural and ferroelectric properties were investigated for the development of low-temperature fabrication of ferroelectric Bi4Ti3O12-based thin films. Bi3.35Nd0.75Ti3-x
Ge
x
O12 [0≤x≤0.5] thin films were found to crystallize into the Bi4Ti3O12 phase above 600°C without forming any second phase. The crystal orientation and surface morphology of the synthesized films strongly depended on the Ge content of Bi3.35Nd0.75Ti3-x
Ge
x
O12. Among various compositions of Bi3.35Nd0.75Ti3-x
Ge
x
O12, Bi3.35Nd0.75Ti2.9Ge0.1O12 thin films showed excellent surface morphology and ferroelectricity regardless of the processing temperature. Furthermore, the doping of Ge below x=0.1 was found to be effective in improving the ferroelectric properties of the low-temperature-processed films. The P
r values of Bi3.35Nd0.75Ti3-x
Ge
x
O12 thin films with the optimum Ge content prepared at 600°C were above 15 µC/cm2 and equal to those of the films crystallized at 700°C.
Oxygen Vacancy Migration and Dispersive Photoconductivity in Bi4Ti3O12-d
Authors: Osada Minoru , Tada Masaru , Kakihana Masato , Noguchi Yuji , Miyayama Masaru
Published: February 2005

We investigated the influence of photoexcited nonequilibrium electrons in Bi4Ti3O12-d
which contains a high density of oxygen vacancies. With increasing oxygen deficiency, the photocurrent undergoes a rapid enhancement, accompanied by a marked change in kinetics. In heavily oxygen-deficient Bi4Ti3O12-d
(d=0.45), we observed a nonexponential relaxation of photogenerated carriers with an increasingly slow decay after termination of visible illumination with energy lower than the band gap. This phenomenon is similar to what has been reported for persistent photoconductivity effects in the layered perovskite YBa2Cu3O7-d
and Nd2Ti3O9, both of which resulted from the space charge field established by photoexcited electrons trapped at oxygen vacancies. We argue that oxygen vacancies acting as trapping centers for electrons are linked to dispersive diffusion in the perovskite blocks, which control carrier recombination.
Bonding of Lead Zirconate Titanate Ceramics to Si Single Crystals for Microdevices
Authors: Tanaka Katsuhiko , Konishi Takahiro , Kuze Wataru , Sugiyama Susumu
Published: February 2005

Bonding bulk lead zirconate titanate (PZT) ceramics having excellent piezoelectric properties to micromachinable Si single crystals could be used to produce microdevices that exploit piezoelectricity. The technique of bonding PZT ceramics to Si wafers using an intermediate gold layer was investigated. Well-bonded wafers with bonding strengths of more than 20 MPa were obtained by heating the wafers at 550°C for 2 h under the pressure of 0.8 MPa. A cantilever made of PZT-Au-Si-bonded wafer operated as a piezoelectric actuator, which exhibited a sufficient bonding strength.
Enhancement of Piezoelectric Properties of Low-Temperature-Fabricated Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 Ceramics with LiBiO2 Sintering Aid by Post-Annealing Process
Authors: Hayashi Takashi , Hasegawa Tomoyuki , Akiyama Yoshikazu
Published: February 2005

The improvement of the piezoelectric properties of low-temperature-fabricated 0.375Pb(Mg1/3Nb2/3)O3-0.25PbZrO3-0.375PbTiO3 (PMNZT) ceramics with a LiBiO2 sintering aid was investigated by adopting a post-annealing process. The sinterability of PMNZT powders was markedly enhanced by liquid phase sintering with the addition of LiBiO2, resulting in a decrease in the required sintering temperature from 1000 to 800°C and the formation of a grain boundary layer. And, it was confirmed by a transmission electron microscope-X-ray energy-dispersive spectrometry (TEM-EDS) that the secondary phase along grain boundaries, which deteriorated the piezoelectric properties, included Pb diffused from PMNZT grains as well as Bi from the LiBiO2 additive. The secondary phase along grain boundaries was significantly removed by annealing after sintering. The 0.75 wt% LiBiO2-added PMNZT ceramics sintered at 800°C for 2 h with post-annealing at 800°C for 10 h exhibited a higher electromechanical coupling factor (k
p) of 60.8% and a higher piezoelectric coefficient (d
33) of 504 pm/V (at 15 kV/cm), compared with those of the sintered specimens without post-annealing. Also, LiBiO2-added PMNZT multilayer ceramics with Ag internal electrodes were successfully sintered at 800°C. The post-annealed multilayer ceramics sintered at 800°C exhibited a higher d
33 value of 506 pm/V. Thus, a low-temperature sintering technique with post-annealing for the removal of the grain boundary layer without deteriorating piezoelectric properties was established.
Piezoelectric Properties of Ca3NbGa3Si2O14 Single Crystal
Authors: Karaki Tomoaki , Sato Ryoko , Adachi Masatoshi , Kushibiki Jun-ichi , Arakawa Mototaka
Published: February 2005

Langasite-type single crystal Ca3NbGa3Si2O14 (CNGS) was grown by the Czochralski technique. Dielectric, elastic and piezoelectric constants of CNGS were measured by the resonance-antiresonance method. At room temperature, dielectric constants ε11
T/ε0 and ε33
T/ε0 were 17.8 and 27.9, respectively. Electromechanical coupling coefficients k
12, k
25 and k
26 were also determined as 10.9, 17.3 and 11.9%, respectively. The measurements were carried out in a temperature range from -30 to 80°C. Temperature coefficients of the dielectric, elastic and piezoelectric constants were obtained. The line-focus-beam and plane-wave ultrasonic material characterization system was employed for measuring bulk acoustic velocities, and longitudinal and transverse wave velocities of 7408.4 m/s and 3136.2 m/s, respectively, in the c-direction uncoupled with piezoelectricity at 23°C were obtained. This was in good agreement with the results determined by the resonance-antiresonance method. The density of CNGS was 4125 kg/m3. All the parameters of the CNGS crystal for bulk and surface acoustic wave applications were determined in this research.
Ultrasonic Linear Motor with Two Independent Vibrations
Authors: Muneishi Takeshi , Tomikawa Yoshiro
Published: February 2005

We propose a new structure of an ultrasonic linear motor in order to solve the problems of high-power ultrasonic linear motors that drive the X
Y-stage for electron beam equipment and to expand the application fields of the motor. We pay special attention to the following three points: (1) the vibration in two directions of the ultrasonic linear motor should not influence mutually each other, (2) the vibration in two directions should be divided into the stage traveling direction and the pressing direction of the ultrasonic linear motor, and (3) the rigidity of the stage traveling direction of the ultrasonic linear motor should be increased. As a result, the supporting method of ultrasonic linear motors is simplified. The efficiency of the motor is improved and temperature rise is reduced. The stage position drift is also improved.
Dynamic Behavior of Helical Structure in Ferroelectric Liquid Crystals
Authors: Katayama Takashi , Uehara Hiroyuki , Furue Hirokazu , Hatano Jun
Published: February 2005

Ferroelectric liquid crystals (FLCs) take a helical structure which can be unwound by the application of an electric field. Although the static orientational process of FLC molecules is well known, the dynamic modification process of the helical structure is not clearly understood. We formulated equations for simulating the dynamic response in terms of the elastic free-energy density based on the continuum theory, and subsequently was solved the dynamic equations numerically. Furthermore, the conoscopic image was simulated by a 4×4 matrix method. We investigated the effect of spontaneous polarization and dielectric anisotropy on the dynamic behavior of the helical structure in FLC.
Distinctive Charge Density Distributions of Perovskite-Type Antiferroelectric Oxides PbZrO3and PbHfO3in Cubic Phase
Authors: Kuroiwa Yoshihiro , Fujiwara Hiroshi , Sawada Akikatsu , Aoyagi Shinobu , Nishibori Eiji , Sakata Makoto , Takata Masaki , Kawaji Hitoshi , Atake Tooru
Published: February 2005

The electron charge density distributions of simple perovskite oxides, PbBO3(B= Ti, Zr and Hf), in their cubic phase are investigated by analyzing high-energy synchrotron powder diffraction data by the maximum entropy method (MEM)/Rietveld method. Clear structural differences between the antiferroelectric and ferroelectric perovskites are revealed. In the cubic phase of PbZrO3and PbHfO3that undergo antiferroelectric phase transitions, the Pb atom is disordered around the special Wyckoff position. The thermal motion of the O atom is anisotropic, and the charge density distributions around the O atom are extended in the directions perpendicular to the Zr(Hf)-O covalent bond. None of these structural characteristics are observed in the cubic phase of PbTiO3that undergoes ferroelectric phase transition. The distinctive structural features observed in PbZrO3and PbHfO3should provide a clue to the mechanism of antiferroelectric phase transition.
Pump-Probe Study of E(TO) Polaritons in Zn-Doped LiNbO3
Authors: Lee C.-C. , Chia C.-T. , Chang Y.-M. , Sun M. L. , Hu M.-L.
Published: February 2005

Results of femtosecond pump-probe measurement of E(TO)-like polaritons in Zn-doped lithium niobate crystals are presented. The impulsive-stimulated-Raman-induced three delay-time oscillations, ω1, ω2 and ω3, are found and assigned to the linear combinations of three lowest E(TO)-like polaritons, ν1, ν2, and ν3, which are ω1=ν2-ν1, ω2=ν3-ν1 and ω3=2ν1. The obtained frequencies of ω1, ω2 and ω3 are well explained by dielectric dispersion calculation. The lifetimes of these oscillations induced by the electro optical effect are also deduced, and they are strongly correlated with the Raman lineshape of E(TO) phonons. Our results also imply that the vibrations of E(TO1) and E(TO2) are mainly attributed to the Nb and O atomic motions, while the vibration of E(TO3) is dominated by the defect structure.