bluuebunny/crossref_metadata_2025 huggingface dataset:
Competing Cluster Growth: The Cu/Sn/Si(111) System
Authors: Hu Qin , Zinke-Allmang M. , Mitchell I. V.
Published: October 2002

The phase separation competition of two thin film systems with a thermodynamic propensity toward clustering was studied. Copper and tin bilayers of approximately 40 monolayer total thickness were deposited on Si(111) surfaces, then annealed at temperatures between 300°C and 600°C. At intermediate ratios of Sn and Cu amounts deposited, two different shapes of clusters coexist on the Si(111) surface, while Sn covers the Cu bearing structures at higher amounts, leading to an apparent Sn Ostwald ripening growth dominated by a single characteristic length.
Flatness Deterioration of Silicon Epitaxial Film Formed Using Horizontal Single-Wafer Epitaxial Reactor
Authors: Habuka Hitoshi
Published: October 2002

This study theoretically clarifies, for the first time, the mechanism of the flatness deterioration of a silicon epitaxial film which is formed on a rotating silicon substrate in a SiHCl3–H2 system at atmospheric pressure using an industrially used horizontal single-wafer epitaxial reactor. The plate of the multi-inlet in the reactor generates the narrow region having a small SiHCl3 gas concentration, because this plate locally weakens the cold finger effect due to various changes in transport phenomena in the reactor. This nonuniform distribution of SiHCl3 gas concentration generated above the silicon substrate results in a nonuniform epitaxial growth rate distribution on the silicon substrate. The substrate rotation then results in a silicon epitaxial film having a concentrically reduced thickness profile, the radius of which corresponds to the position of the plate of the multi-inlet. Due to this mechanism, the multi-inlet design leads to the flatness deterioration of the silicon epitaxial wafer.
Indium-Based Interface Chemical Engineering by Electrochemistry and Atomic Layer Deposition for Copper Indium Diselenide Solar Cells
Authors: Guillemoles Jean-François , Canava Bruno , Yousfi El Bekkaye , Cowache Pierre , Galtayries Anouk , Asikainen Timo , Powalla Michael , Hariskos Dimitri , Schock Hans-Werner , Lincot Daniel
Published: October 2002

The key to achieve better Cu(In, Ga)Se2 (CIGS) cells is through the improvement of the CIGS/ZnO interface. In this work, we illustrate various approaches, wet and dry, to engineer that interface with processes that avoid the use of Cd containing compounds. Wet chemical treatments have been performed so as to test the possibility to improve that interface by surface doping of CIGS. X-ray photoelectron spectroscopy (XPS) and Kelvin probe studies show that such doping is not achieved in the conditions leading to best devices. Rather, the most desirable feature of the surface treatments appears to be surface passivation. We show that this can be achieved via CIGS surface reaction with In(III) ions, leading to 12.5% efficient devices. A well passivated interface can also be achieved directly, using an all dry process, by Atomic Layer Deposition (ALD) of In2S3 buffer layer, yielding to 13.5% efficient devices. The ALD growth of the buffer layers have been studied in situ with the help of a quartz crystal microgravimetry.
Surface Analysis for Selective SiO2 Etching by Reflectance Photoelastic Modulated Fourier Transform Infrared Spectroscopy
Authors: Doh Hyun-Ho , Chu Changwoong , Chi Kyeong-Koo , Moon Joo-Tae
Published: October 2002

Photoelastic modulated fourier transform infrared (PEM FTIR) spectroscopy has been used to study the bonding structure and compositions of fluorocarbon films generated during etching with CHF3/CO surface wave plasma (SWP). The C=C (stretching vibration mode at 1600 cm-1), C–C (940 cm-1), C–F (1032, 1164, 1260, 1291 cm-1), =C–H (780 cm-1) and C=O (1790 cm-1) peaks on the polymer films were identified using reflectance PEM FTIR. In addition to the peak assignment, the C–F spectra were fitted to three peaks–1280, 1250, 1200 cm-1, with Gaussian splitting, respectively. Comparing the etching results with the variation of FTIR spectra, it was found that the selectivity of SiO2 to poly-Si and photoresist with CO mixing ratio to CHF3 is correlated to the area ratio of [C=C]/[C–F] and [C=C]/[C=O]. The XPS result was also compared to reflectance PEM FTIR data to reveal the availability of reflectance PEM FTIR application. It was confirmed that there existed a good agreement between PEM FTIR and XPS data. When we integrated all the results from PEM FTIR, XPS and optical emission spectroscopy (OES), we found that the element of the C=C bond on the polymer surface played an important role as an etch inhibitor. The reflectance PEM FTIR measurement on the etched surface is considered to lead to an understanding the properties of polymer films generated during oxide etching.
Spatial Structure of Electronegative Ar/CF4 Plasmas in Capacitive RF Discharges
Authors: Kouji Kaga Kouji Kaga , Takashi Kimura Takashi Kimura , Takao Imaeda Takao Imaeda , Kazuyuki Ohe Kazuyuki Ohe
Published: October 2002

Spatial structures of charged particles in Ar/CF4 RF (13.56 MHz) capacitive discharges were investigated by changing the CF4 content up to 10% over the pressure range from 0.03 to 0.10 Torr, while keeping the discharge current at 250 mA. The ratio of negative ion to electron densities at the center was in the range from 2 to 12. The measured negative ions occupied the entire plasma region with a flat top profile at the center except at the pressure of 0.03 Torr and CF4 content lower than 5%, while the electron density distribution was uniform in the entire plasma region.
Anisotropic Molecule Dopant Method for Synthesizing a Zero-Birefringence Polymer
Authors: Tagaya Akihiro , Iwata Shuichi , Kawanami Eriko , Tsukahara Hisashi , Koike Yasuhiro
Published: October 2002

We have demonstrated the anisotropic molecule dopant method for synthesizing a zero-birefringence polymer that showed no orientational birefringence at any orientation degree of polymer chains. In this method, rod-like molecules such as trans-stilbene having opposite polarizability anisotropy to that of a host polymer were chosen to compensate orientational birefringence. Orientational birefringence of poly(methyl methacrylate) was completely compensated by doping with some types of anisotropic molecules. Compensation of orientational birefringence for drawn films of the zero-birefringence polymers was analyzed by the rotating parallel nicols method, and orientation functions for polymer main chains and the anisotropic molecules were determined by IR dichroism, which showed that both the polymer chains and the anisotropic molecules were oriented almost equivalently in the drawing process resulting in complete compensation at any draw ratio. Furthermore, the high transparency (37.2 dB/km) of the zero-birefringence polymer was confirmed by light scattering measurements.
Dynamics of a Magnetically Levitated Table with Hybrid Magnets
Authors: Chang Shun-Chang
Published: October 2002

In this paper, the detailed dynamic behaviors of a magnetic levitation vibration isolation table with hybrid magnetic actuators that integrate permanent magnets with controllable electromagnets are analyzed. The results reveal that, due to the realistic nonlinear characteristics of magnetic forces, the system exhibits codimension-two bifurcation in which a limit cycle and a pitchfork bifurcation are created. With special note of how feedback gains affect the behaviors of this magnetic levitation vibration isolation table, the regions of feedback gains suitable for stability are obtained. From the results of the analysis, it is evident that, due to the nonlinearity of magnetic forces, the feedback gains must be carefully selected to ensure the stability of this nonlinear system.
Particle Removal and Its Mechanism on Hydrophobic Silicon Wafer in Highly Diluted NH4OH Solutions with an Added Surfactant
Authors: Park Jin-Goo , Lee Sang-Ho , Kim Sang-Yong
Published: October 2002

Wafer cleaning in semiconductor processes is one of the most critical steps because of the rapid increase in the device integration density and its direct impact on device yield. Highly diluted NH4OH solutions to which a nonionic polyoxy-alkylene alkylphenyl ether surfactant was added were evaluated to measure their cleaning efficiency and to determine the particle removal mechanism. The particle removal experiment was performed in a 0.2 vol% NH4OH solution, which has a pH value equivalent to that of conventional SC1 (1:1:5, NH4OH:H2O2:H2O mixture) solution, as a function of solution temperature. A surfactant of critical micelle concentration of 50 ppm was added to NH4OH solution. The etch rate of silicon in 0.2 vol% NH4OH solution decreased to 2.4 Å/min from 92 Å/min at 80°C by the addition of the surfactant due to the adsorption of the surfactant on the surface. The particle removal efficiency increased as the temperature of the solutions increased. Particle removal of over 95% was observed when wafers were treated in surfactant-added NH4OH solution at 80°C. This can most likely be attributed to the slight increase of the etch rate and better passivation of the surfactant on the silicon surface at a higher temperature.
Oxidative Curing of Hydrogen Silsesquioxane Resin Films by Electron Beam Irradiation without Additional Heatings and Characterization of the Cured Films
Authors: Nakamura Takashi , Sasaki Motoshi , Kobayashi Akihiko , Sawa Kiyotaka , Mine Katsutoshi
Published: October 2002

We have developed a new curing process for hydrogen silsesquioxane (HSQ) films, which is applicable for interlayer dielectrics of LSI devices. In this process, an electron beam was used as a curing source. As a result, a practical curing speed was obtained without additional heat treatments at ambient pressure, since electron beams accelerate the oxidative curing reaction on HSQ. The cured films exhibited properties for practical use such as thermal stability, which are equivalent to films cured conventionally by heat treatment. The cracking resistance of the electron-beam-cured films is excellent. A film of 3.0 µm thickness did not show any cracks, whereas a thermally cured film with a thickness of 1.25 µm showed cracks. Furthermore, electron-beam-cured films with a thickness of 2.5 µm did not show any cracks even after nitrogen annealing at 400°C for 1 h. The mechanism of oxidative curing of HSQ by electron beam irradiation was also studied.
Influence of Nitrogen Doping on the Barrier Properties of Sputtered Tantalum Carbide Films for Copper Metallization
Authors: Wang Shui Jinn , Tsai Hao Yi , Sun Shi Chung , Shiao Ming Hua
Published: October 2002

The effect of nitrogen doping on the barrier properties of sputter-deposited tantalum carbide (Ta–C) films was investigated for the first time. With increasing nitrogen concentration, it was found that the resistivity of the barrier layer increases, while the growth rate decreases. In addition, the use of an optimum N2/Ar flow rate ratio of 2/24 during sputtering allows one to achieve tantalum carbon nitride (Ta–C–N) films with the highest thermal stability. According to I–V measurements on reverse-biased Cu/barrier/p+n diodes, the 600-Å-thick Ta–C–N barrier layer appeared to be effective in preventing Cu from reaching the Si substrate after 600°C annealing in N2 for 30 min, which is about 100°C higher than that in the case without nitrogen incorporation. The failure of the thermally annealed Ta–C–N film was attributed to the Cu diffusion through the local defects or grain boundaries of the layer into the Si substrate, which results in a significant increase in the diode leakage current.
The Role of an Overlayer in the Formation of Ni-based Transparent Ohmic Contacts to p-GaN
Authors: Kwak Joon Seop , Cho J. , Chae S. , Nam O. H. , Sone C. , Park Y.
Published: October 2002

The effect of an overlayer in the Ni-based ohmic contacts on contact resistivity, light transmittance and the performance of light emitting diodes (LEDs) has been investigated. The ohmic contact composed of an Au overlayer on Ni resulted in a low contact resistivity of 9×10-4 Ω·cm2 and a high transmittance of 92% after annealing at 500°C in O2 ambient. The LED with a Ni/Au contact showed a threshold voltage and an output power of 4.1 V and 1.7 mW at 20 mA, respectively. In the case of a Pt overlayer on Ni, the minimum contact resistivity was comparable to that of the Ni/Au contacts. However, the maximum transmittance was only 50%, which reduced the output power of the fabricated LED to 1.0 mW. For a Pd overlayer on Ni, the transmittance of 72% was obtained after annealing at 500°C in O2 ambient, while the contacts showed nonohmic behavior. The LED with the Ni/Pd contact resulted in a high threshold voltage of 7.5 V at 20 mA. These results were explained by the differences in the thermodynamic properties between the overlayer and Ni.
Influence of Growth Temperature and Thickness of AlGaN Caps on Electron Transport in AlGaN/GaN Heterostructures Grown by Plasma-assisted Molecular Beam Epitaxy
Authors: Elsass Christopher R. , Poblenz Christiane , Heying Ben , Fini Paul , Petroff Pierre M. , DenBaars Steven P. , Mishra Umesh K. , Speck James S. , Saxler Adam , Elhamrib Said , Mitchel William C.
Published: October 2002

The influence of Al0.05Ga0.95N cap thickness and growth temperature on the electrical properties of the Al0.05Ga0.95N/GaN two-dimensional electron gas (2DEG) was investigated. Varying the thickness of the Al0.05Ga0.95N barrier led to regions in which the dominant 2DEG scattering mechanisms were either Coulombic or interface roughness/alloy disorder scattering. The 2DEG sheet carrier concentration was found to increase with Al0.05Ga0.95N cap thickness and saturated at ∼ 25 nm. By increasing the growth temperature from 650°C to 750°C, the measured low temperature 2DEG sheet carrier concentration was found to decrease and the measured low temperature mobility was found to increase while the Al composition remained constant. Temperature dependent Hall measurements revealed that by increasing the growth temperature, the incorporation of impurities is decreased. A maximum 77 K mobility of ∼ 19,000 cm2/Vs was observed for films grown at 750°C with 20 nm thick Al0.05Ga0.95N caps.
Transport of Gas-Phase Species Stored in Stagnant Volumes under a GaN Metalorganic Vapor Phase Epitaxy Horizontal Reactor
Authors: Harafuji Kenji
Published: October 2002

Three-dimensional simulations of hydrodynamics and chemical reactions have been made for GaN metalorganic vapor phase epitaxy in a horizontal two-split-flow reactor. The time-dependent behavior of gas-phase species stored in various types of stagnant volumes such as return-flows and boundary layers has been elucidated both after turn-off and after turn-on of trimethylgallium (TMG) feed. As the gas flow rate increases, the size of the return-flow and relevant stagnant volumes becomes larger, and it takes more time to carry away stored species out of the reactor space after turn-off. When there are several spatially connected stagnant volumes from the upstream to downstream direction, the draining process from each stagnant volume is not an isolated and single phenomenon but is described as a cascade and interactive phenomenon among these stagnant volumes. That is, the time constant under the exponential decay phase in a stagnant volume is influenced by diffusion-dominated phenomena in the stagnant volume existing directly before. The mass fraction of the TMG and adduct after turn-on increases rapidly with a smaller time constant compared with that in the turn-off case.
Crystallization of 3C-SiC (111) Thin Films Grown on Si (111) Substrates by Post Thermal Annealing
Authors: Lee Hae Gwon , Kang Tae Won , Hong Sung Ui , Paek Mun Cheol , Kim Tae Whan
Published: October 2002

Thermal treatment of SiC thin films grown on p-Si (111) substrates by plasma enhanced chemical vapor deposition was performed to crystallize as-grown amorphous SiC layers. Nomarski optical microscopy and X-ray diffraction measurements showed that the as-grown SiC thin films on p-Si (111) substrates were amorphous and that the films annealed at 1100°C were crystallized with 3C-SiC (111) orientation. The results of X-ray photoelectron spectroscopy measurements showed that in the crystallized films, good stoichiometry was realized for the components of the SiC epilayer. These results indicate that SiC thin films grown on p-Si (111) substrates were crystallized by thermal treatment.
The Effect of the Interface Impurity in Fabrication of Spin Dependent Tunnel Junction
Authors: Lym Heung-Soon , Jeon Dong-Min , Baek Hyung-Ki , Yoon Seong-Yong , Lee Du-Hyun , Yoon Dae-Ho , Suh Su-Jeong
Published: October 2002

Ferromagnetic-insulator-ferromagnetic tunneling was measured in two types of Co/Al2O3/Co/NiFe junctions. For type 1 junction (two times of interface exposure to air), the maximum tunnel junction magnetoresistance (TMR) ratio was 16.5% at room temperature. Junctions with a relatively thicker Al layer showed a lower resistance and a higher TMR ratio. Whereas, junctions with a relatively thinner Al layer showed a fast increase of barrier width. The passivation effect of Al2O3 in oxidation process enhanced the TMR ratio. As the oxidation time is increased, the coercivity of Co bottom electrode is also increased. So the effect of CoO formation in the interface of the Co bottom electrode and the Al2O3 is discussed in three possible assumptions. For type 2 junction (just one time of interface exposure to air), the maximum TMR ratio was 21% at room temperature. And the TMR ratio was decreased to half at 550 mV. These junctions have potential use as low-power field sensors and memory elements.
Ni1-xCox–C Nanogranular Thin Films Prepared by a Co-Sputtering Method: Improvement in Magnetic Properties by Optimizing the Alloy Ratio
Authors: Satoshi Tomita Satoshi Tomita , Hiroaki Adachi Hiroaki Adachi , Minoru Fujii Minoru Fujii , Shinji Hayashi Shinji Hayashi
Published: October 2002

Nanogranular thin films consisting of Ni1-x
Cox alloy nanoparticles separated by graphitic matrices are fabricated by a co-sputtering method. The structure and magnetic properties of the films are studied. An improvement in their magnetic properties by optimizing the alloy ratio will be demonstrated. Transmission electron microscopic (TEM) observation shows nanoparticles with a small mean diameter (∼ 7 nm) and narrow size distribution (∼ 20% of mean diameter) at the Co/(Ni+Co) ratio (x) ranging from 0 to 0.83. In this region, the coercivity continuously increases with x and manifests a maximum value of 907 Oe at x=0.83. The increase can be explained in terms of alloy formation. With further increasing x up to x=1, the coercivity decreases. The decrease is caused by the existence of extremely large Co particles, which are revealed by TEM observation.
Spin Temperature Model for Distant Electron Nuclear Double Resonance Effect
Authors: Yamamoto Takamitsu
Published: October 2002

To clarify the mechanism of the distant electron nuclear double resonance effect, ruby Al2O3 (Cr3+) was studied by ENDOR technique in the V-band (50 GHz band). The most prominent ENDOR effect was observed at fields a little off the resonance field of electron spin resonance (ESR). To interpret this phenomenon, we propose the spin temperature model which deals with thermal equilibrium between the electron spin system and the nuclear spin system on the frame rotating at the Larmor frequency of the electron. Below the resonance field, the ENDOR effect caused by the energy flow from the nuclear spin system to the electron spin system is most prominent when the electron spin temperature is the lowest compared with the nuclear spin temperature. In the higher magnetic field than the resonance field where the electron spin temperature is negative, the ENDOR effect is caused by the electron spin deexcitation induced by the fluctuations of the effective field.
Coherent Hot-Electron Emitter
Authors: Machida Nobuya , Furuya Kazuhito
Published: October 2002

The structure and principle of an electron emitter ejecting electron waves with ultimate value of product of wavefront spread and current density in a solid-state condition is proposed. By introducing an additional electrode, the gate, to a double-barrier resonant-tunneling emitter, an electron flux with a single wavelength, a wide wavefront spread and high current density can be achieved. We justify the principle by electrostatic theory. This emitter might also be used for various types of solid-state spectroscopy.
Direct Observation of Femtosecond Pulse Buildup in a Self-Mode-Locked Laser Using an Intracavity Acoustooptic Modulator
Authors: Kinoshita Shuichi , Ito Eiichi , Omori Minoru , Ueki Shuji
Published: October 2002

A new method for observing the pulse buildup process using an intracavity acoustooptic modulator is developed. This method is applicable to most self-mode-locked lasers which require an extra initiation process and has the possibility to be extended to sub 10 fs lasers. Applying this method, we have successfully obtained the three-dimensional representation of the time variation of the autocorrelation trace using the combination of an intensity autocorrelator and a digital oscilloscope. With increasing magnitude of loss, the pulse is found to broaden and show an incoherent nature, indicating that the transition from coherent to incoherent oscillation takes place at a very early stage of the recovery process. We analyze the incoherent state by assuming that several frequency blocks with various phases are generated during the amplification process under an excess gain. The competition among these blocks is considered to result in the establishment of a solitary pulse.
A Model of Image Display in the Optimized Overdrive Method for Motion Picture Quality Improvements in Liquid Crystal Devices
Authors: Hajime Nakamura Hajime Nakamura
Published: October 2002

Motion picture images are related to device optical response by adopting a statistical distribution model, in which there are linear relationships in the mean and variance of two distributions with the motion velocity as the proportional constant, and the total optical intensity is conserved. This novel theory is applied to evaluate motion picture quality, as optimizing a well-known overdrive scheme. Insertion of a blanking period in each refresh cycle leads to less broadened and less shifted motion picture images, as demonstrated by a pi-cell device. Efficiently optimized overdrive scheme produces comparable improvement along with excellent intensity reproduction.
An Improved Fiber-Bundle-Coupler Array for End-Point Detection Process
Authors: Lin Gong-Ru
Published: October 2002

We demonstrated a new-designed plastic-optical-fiber-bundle (POFB) coupler array for dynamic monitoring and end-point detection of the photoresist development process. A better optical collecting efficiency is achieved by using a normal illumination/detection scheme and a POFB coupler with larger cross section. Time-resolved dissolution rate can be obtained by synchronous calculation of the reflected optical interference data with deviation of less than 1.5%. Experiment on in-situ mapping of transient thickness variation of photoresist film during development by using two-dimensional POFB coupler array is also reported. The POFB-based coupler exhibits relatively low coupling and insertion loss at visible light wavelength as compared with the silica-fiber-based one. The system is compatible for real-time/multi-port measurements of micro-lithographic and dielectric etching processes.
Polymer-Dispersed Liquid-Crystal Holographic Gratings Doped with a High-Dielectic-Anisotropy Dopant
Authors: Wu Shing-Trong , Mo Ting-Shan , Fuh Andy Ying-Guey , Wu Shin-Tson , Chien Liang-Chy
Published: October 2002

The first-order diffraction efficiency of holographic gratings formed in polymer-dispersed liquid-crystal (PDLC) films doped with a high-dielectric-anisotropy compound, HRL-410, were investigated. PDLC films doped with various HRL-410 concentrations were used to write gratings under different laser powers. By conducting a light-scattering study using a single Ar+ laser beam to excite the sample while probing with a He–Ne laser, we found that the dielectric material increases the rate of polymerization, which in turn affects the formation and the resultant morphology of the grating. The voltage required for switching the grating decreases significantly for the doped films. We propose a model to explain these experimental observations.
High Luminescence Polarization of InGaAs–AlGaAs Strained Layer Superlattice Fabricated as a Photocathode of Spin-Polarized Electron Source
Authors: Matsuyama Tetsuya , Mukai Masayasu , Horinaka Hiromichi , Wada Kenji , Nakanishi Tsutomu , Okumi Shoji , Togawa Kazuaki , Nishitani Tomohiro , Baba Toshio
Published: October 2002

High circular luminescence polarization of 65% was observed in the InGaAs–AlGaAs strained layer superlattice which was fabricated as a spin-polarized electron source. The dependence of photoluminescence polarization on the excitation photon energy was well explained by the calculated band structure of the sample. The spin relaxation time and the lifetime of photo-generated electrons in the conduction band were determined from the experimental results of the time-resolved photoluminescence measurement. The spin polarization of conduction band electrons at the instant of excitation was determined to be 94% from the photoluminescence polarization, the lifetime and the spin relaxation time.
Novel Method for Simulating Optical Properties of Reflective Cholesteric Liquid Crystal Displays
Authors: Li Qing , Bai Xiaole , Zhang Jian , Tong Linsu
Published: October 2002

In this study, a new method is used, which is much simpler than the layered numerical calculation method, to simulate the reflectivity of a multidomain reflective cholesteric liquid-crystal display (LCD). The theoretical calculation results are in good agreement with the experimental results. These simulations also show that the distribution of the helical axis of the liquid crystal has a pronounced effect on the viewing angle and colorimetric properties.
Investigation of Elastic Nonlinearities in Pb(Zn1/3Nb2/3)O3–PbTiO3 and Pb(Mg1/3Nb2/3)O3–PbTiO3 Single Crystals
Authors: Priya Shashank , Viehland Dwight , Ryu Jungho , Uchino Kenji , Yamashita Yohachi , Luo Haosu
Published: October 2002

The complex elastic and electromechanical properties of Pb(Zn1/3Nb2/3)O3–PbTiO3 (PZNT) and Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) single crystals under high power operational conditions have been determined using a new resonance method. In this method, rectangular specimens are piezoelectrically-driven into mechanical resonance and displacement of the transverse resonance mode is measured as a function of frequency (f) using an optical vibrometer method in conjunction with a frequency response analyzer. Under resonant high-power drive, it has been found that electromechanical nonlinearities are due to elastic ones, as the elastic and electromechanical properties were both found to scale with the square of the strain amplitude. The temperature (T) and ac electric field (E
ac) dependence of the mechanical quality factor Q
m was also determined and Iso-Q
m curves were constructed that can be used to predict performance criteria for high power applications.
Effect of Ni Doping on Improvement of the Tunability and Dielectric Loss of Ba0.5Sr0.5TiO3 Thin Films for Microwave Tunable Devices
Authors: Jeon Young-Ah , Seo Tae-Suck , Yoon Soon-Gil
Published: October 2002

The structural, microstructural, and surface morphological properties of Ba0.5Sr0.5TiO3 thin films were investigated as a function of Ni dopant concentration. The Ni-dopant concentration in BST films has a strong influence on the material properties including dielectric and tunable properties as well as film growth rate. Ni doped (≤3 mol%) BST films showed denser, smoother, and smaller grain sizes than those with 6 and 12 mol% Ni. Dielectric constant and loss of 3 mol% Ni-doped BST films were about 980 and 0.3%, respectively. In addition, tunability and figure of merit of 3 mol% doped BST films showed maximum values of approximately 39% and 108, respectively. Correlation of the material properties with dielectric and tunable properties suggests the the 3 mol% Ni-doped BST films are the optimal choice for tunable device applications.
Effects of A-Site (NaCe) Substitution with Na-Deficiency on Structures and Properties of CaBi4Ti4O15-Based High-Curie-Temperature Ceramics
Authors: Yan Haixue , Li Chengen , Zhou Jiaguang , Zhu Weimin , He Lianxin , Song Yuxin , Yu Youhua
Published: October 2002

Three kinds of bismuth-layer-structured ferroelectric (BLSF) ceramics, CaBi4Ti4O15 (CBT), Ca0.8(CeNa)0.1Bi4Ti4O15 (CNBT), and Na-deficient Ca0.8(Ce0.1Na0.05\Box0.05)Bi4Ti4O15 [CN\BoxBT] (where \Box represents vacancies) were prepared by a conventional ceramic technique. X-ray powder diffraction showed that their crystal structures are a single phase of BLSF with m=4. Sintering characteristics of the three ceramics were also discussed. Scanning electron microscope (SEM) micrographs of CN\BoxBT showed that the grain is platelike. The A-site (NaCe) substitution can improve the piezoelectric constant d
33 and high-temperature resistivity with decreasing Curie temperature. The modification by A-site (NaCe) substitution with Na-deficiency is more pronounced than CNBT, which not only leads to a very high piezoelectric constant d
33 and high-temperature resistivity but also increases the Curie temperature. The reason for the high T
c (T
c=866°C) of CN\BoxBT is considered to be internal stress. As a result, Na-deficient CN\BoxBT ceramic is found to be an excellent high-temperature piezoelectric material.
Liquid-Crystal Optical Rotator Using Weak Azimuthal Anchoring Surface
Authors: Yamaguchi Rumiko , Yamanaka Takuro , Sato Susumu
Published: October 2002

We propose a novel type of liquid-crystal (LC) micro-optical device to rotate the plane of polarization by an in-plane field switching technique. The LC optical rotator is designed to produce twisted LC orientation of various twist angles in the bulk, that is, LC molecules are fixed on one side of the substrate by rubbed strong anchoring and are rotated in plane on the counter substrate by nonrubbed weak anchoring. Optical properties of the LC rotators prepared using LC materials with positive or negative dielectric anisotropies are measured. In both types of LC rotators, the polarization direction can be controlled in the range of ±90° by applying the in-plane field on a very weak azimuthal anchoring surface, where the surface memory effect is hardly observed. In addition, the polarization switching property is independent of wavelength because the optical rotatory properties are similar to those of the conventional twisted nematic cell.
X-Ray Double-Crystal Diffractometry of Verneuil-Grown SrTiO3 Crystals
Authors: Yoshimura Jun-ichi , Sakamoto Takeshi , Yamanaka Junji
Published: October 2002

Using a double-crystal arrangement of nearly parallel setting, X-ray Bragg-case diffraction curves were measured for (100) and (110) surfaces of SrTiO3 crystals, grown by the Verneuil method and used widely as a substrate for fabricating electronic thin film devices. The peak height and half-width of rocking curves (200 and 220 reflections, Cu Kα1) measured from local areas of samples varied over a wide range with the samples and probed areas, presumably due to the effect of dislocations and other imperfections. A certain proportion of the measured curves was in fair agreement with the theoretical curve for a perfect crystal, being only 1–2 arcsec broader in half-width. The local-area rocking curve measurement provides like this useful information on the perfection characterization of SrTiO3 crystals. The measurement shows that mechanochemically polished surfaces of the sample crystals are significantly free of polishing strain in both the (100) and (110) samples, while the assessment of the bulk-crystal perfection by the experimental results needs a discussion. Rocking curves were also measured from the entire surface of the sample crystals to obtain an evaluation of overall misorientaion.
Confocal Multipath Laser Cavity to Enhance Compton Backscattering
Authors: Amano Sho , Mochizuki Takayasu
Published: October 2002

The design considerations of a confocal multipath laser cavity to enhance Compton backscattering are presented. Ray trace simulation results predicted that 29–14-fold enhancement of the laser field can be achieved at the confocal point by superposition of mode locked laser pulses. As a result, Compton backscattered X-rays, generated by interaction of an intense laser field with a relativistic electron beam, will be enhanced efficiently by a factor of more than 10.
Increase of Dielectric Constant of an Epitaxial (100) Yttria-Stabilized Zirconia Film on (100) Si Substrate Deposited by Reactive Sputtering in the Metallic Mode
Authors: Horita Susumu , Kuniya Takuji
Published: October 2002

A (100) heteroepitaxial yttria-stabilized zirconia (YSZ) film was prepared on a (100) Si substrate by dc magnetron sputtering with Ar+O2 gas. In this case, we used the metallic mode, in which the target is almost metallic due to the low O2 gas pressure and the sputtered metallic Zr and Y species around the substrate react with oxygen to be oxidized. The relative dielectric constant of the 10-nm-thick YSZ film deposited in the metallic mode was above 17, which is much larger than that obtained in the oxide mode, which is about 9. The oxide mode is normally used, in which the target surface is fully oxidized and the sputtering gas contains an excess amount of oxygen. The YSZ film deposited in the metallic mode was post-annealed at 300°C in N2 for 30 min. The equivalent silicon oxide thickness of the annealed YSZ film was estimated to be about 1.86 nm determined from the accumulation capacitance of the capacitance–voltage characteristics and its leakage current was less than 1 ×10-4 A/cm2 at 1 V.
Prevention against Oxidation of Mn Evaporant during Reactive Evaporation Process
Authors: Isai Masaaki , Fujiyasu Hiroshi
Published: October 2002

Manganese oxide films for lithium secondary batteries were prepared using a reactive evaporation method. The Mn metal in the crucible suffers severe oxidation during the reactive evaporation process, during which its deposition rate deteriorates with increasing deposition run. So it is difficult to maintain the stoichiometry of films from run to run. To prevent deteriorations, a quartz ampoule has been installed at the bottom of the Mn crucible, which isolated successfully the Mn evaporant from incoming oxygen atoms. It improved the reproducibility of film composition because of stabilizing of the deposition rate. The performance of quartz ampoule was compared with that of Mo separator and stainless steel (SUS) cell.
Substrate Bias Effect on Amorphous Hydrogenated Carbon Films Deposited by Filtered Cathodic Arc Deposition
Authors: Li Yan-Way , Chen Chia-Fu , Shue Yew-Bin , Yu Teng-Chien , Chang Jack Jyh-Kau
Published: October 2002

In the present study, we briefly describe the 45° angle magnetic filtered arc deposition (FAD) process and investigate the effect of substrate bias on the hardness of amorphous carbon (a-C) films. An attempt is made to correlate the microstructure, chemical composition and chemical bonding states with the hardness of the corresponding films. After deposition, the film properties were analyzed by Raman spectroscopy and nanoindentation system (NIS). It was found that amorphous carbon films possess highest hardness when deposited at substrate biases ranging from -50 V to -100 V. The hardness values do not show good correlation with Raman I(D)/I(G) ratio. Hydrogen additions to the system help prevent the nucleation of the graphite phase, and stabilize the sp3 bonding of amorphous hydrogenated carbon films. Hydrogen affected on the small graphitic crystalline growth. Films have higher hardness when they have higher fraction of sp3 content.
Investigation of the Conditions Required for the Formation of a Magnetic Neutral Loop Discharge Plasma
Authors: Sakoda Tatsuya , Okraku-Yirenkyi Yaw , Sung Youl-Moon , Otsubo Masahisa , Honda Chikahisa
Published: October 2002

In order to reveal the conditions required for the formation of a neutral loop discharge (NLD) plasma, distributions of excited atoms that are closely related to the distributions of the ionization rates were measured under various discharge conditions. Measurements of the distributions of these excited atoms were performed by laser induced fluorescence spectroscopy and optical emission spectroscopy. It was found that the results of these measurements were consistent with the theoretically predicted dependencies of electron heating on the magnetic field strength, the radio frequency (RF) electric field, and the frequency of the RF source. In addition, it was shown that the effects of electron-neutral collisions and of the finite size of the device set limitations on the formation of the NLD plasma.
Formation Mechanism of Strontium and Titanium Oxide Films by Metalorganic Chemical Vapor Deposition: An Isotopic Labeling Study Using 18O2
Authors: Nakamura Toshihiro , Momose Shun , Tachibana Kunihide
Published: October 2002

Isotopic labeling experiments using 18O2 were carried out to understand the decomposition and oxidation reactions of source molecules in the metalorganic chemical vapor deposition (MOCVD) of strontium and titanium oxide films. The isotopic ratios of oxygen incorporated in the deposited films were determined by time-of-flight secondary ion mass spectrometry (TOF-SIMS) in both positive and negative secondary ion detection modes. The obtained M18O+/M16O+ (M=Sr, Ti) ratios showed good agreement with the corresponding 18O-/16O- ratios. The oxygen incorporation from the oxidant gas (18O2) to the strontium oxide films is dominant under typical deposition conditions, while the majority of oxygen in the titanium oxide films originates from the ligands of the source molecules.
Dynamics of Optical Nonlinearity in Water-in-Oil Microemulsion
Authors: Vicari Luciano Rosario Maria
Published: October 2002

Strong optical nonlinearity is reported in water-in-oil microemulsion. Its time evolution is studied by self phase modulation of a Gaussian laser beam by an optically thin film. The material is WAD (water/AOT/decane, where AOT denotes sodium bis-diethylsulfosuccinate) far from critical points and near the percolative transition from electrically insulating to electrically conducting. A simple mathematical model is introduced for a quantitative description of the results. Time constants are shown to be too short to be due to the diffusion of spherical clusters. Electrostriction of rod-like clusters and their consequent diffusion could be involved in the development of the phenomenon.
Development of Miniature Diamond Anvil Cell for the Superconducting Quantum Interference Device Magnetometer
Authors: Mito Masaki , Hitaka Masako , Kawae Tatsuya , Takeda Kazuyoshi , Kitai Tetsuo , Toyoshima Noriaki
Published: October 2002

We have developed a novel miniature diamond anvil cell (mDAC) with a diameter of 8.5 mm and a length of 35 mm for a commercial superconducting quantum interference device (SQUID) magnetometer. In this mDAC, both X–Y and tilt adjustments of diamond anvil are possible. The SQUID magnetometer with this mDAC works under pressures higher than 1 GPa in a wide range of temperature and high magnetic field region. As for the test operation of this system, we first investigated the standard pressure effects of metallic superconductor Pb up to the pressure P = 3.8 GPa at the magnetic field H = 100 G and after that we investigated the pressure effect of an f-electron ferromagnetic compound GdZn2 up to P = 4.9 GPa for H ≤20000 G. The sensitivity of the present system is about 10-6 emu.
Experimental Study of Rayleigh–Taylor Instability in a Shock Tube Accompanying Cavity Formation
Authors: Wang Xiao-Liang , Itoh Motoyuki , Shi Hong-Hui , Kishimoto Masami
Published: October 2002

Rayleigh–Taylor instability at a gas-water interface has been investigated experimentally. Such instability was produced by accelerating a water column down a vertical circular tube employing shock wave impact. Accelerations from 50 to 100 times gravitational acceleration with fluid depths from 125 to 250 mm were studied. The resulting instability from small amplitude random perturbations was recorded and later analyzed using high-speed video images. Cavity formation was observed in the middle of the gas–water interface soon after the shock wave impact; bubbles and spikes then developed across the rest of the interfacial plane. Measurements of the growth coefficient of the bubbles and spikes show that they are nearly constant over different runs.
Epitaxial Nucleation of Protein Crystal on Poly-L-Lysine Modified Surface
Authors: Long Rong Long Rong , Hiroshi Komatsu Hiroshi Komatsu , Makoto Natsuisaka Makoto Natsuisaka , Shinichi Yoda Shinichi Yoda
Published: October 2002

The effects of microscope slides coated with poly-l-lysine (PLL) on the nucleation of tetragonal hen egg-white lysozyme (E.C. 3.2.1.17, HEWL) have been investigated using the batch method. It was found that the PLL-coated glass substrate selectively controlled the orientation of tetragonal lysozyme crystals to either {110} or {101} form depending on supersaturation. The total number of crystals retained on the coated glass substrate decreased by 20% compared to that of a normal glass substrate.
A New Silicon-on-Insulator Lateral Insulated-Gate Bipolar Transistor with Dual-Channel Structure
Authors: Young Sung Woo-Beom Choi
Published: October 2002

To improve the latch-up and forward voltage drop properties of the silicon-on-insulator (SOI) lateral insulated-gate bipolar transistor (LIGBT), a new SOI LIGBT structure is proposed and fabricated. The new device employs a dual-channel structure in order to enable more electrons to flow into the n-drift layer and to improve the latch-up characteristic.
Generalized Interconnect Delay Time and Crosstalk Models: I. Applications of Interconnect Optimization Design
Authors: Lee Trent Gwo-Yann , Tseng Tseung-Yuen , Wong Shyh-Chyi , Yang Cheng-Jer , Liang Mong Song , Cheng Huang-Chung
Published: October 2002

New analytical models for estimating the delay time of single line and coupled interconnect for ramp input waveform are derived. The accuracy of the signal delay time and crosstalk noise voltage models for various driver resistances, loading capacitances, and input-ramping rates has also been verified by simulation program with integrated circuit emphasis (SPICE) simulation. Based on the delay and crosstalk models, interconnect optimization design can be discussed thoroughly. The proposed guaranteed-performance interconnect design method is also discussed. These models are useful for performance estimation and layout optimization in VLSI synthesis as well as process optimization in technology development.
Generalized Interconnect Delay Time and Crosstalk Models: II. Crosstalk-Induced Delay Time Deterioration and Worst Crosstalk Models
Authors: Lee Trent Gwo-Yann , Tseng Tseung-Yuen , Wong Shyh-Chyi , Yang Cheng-Jer , Liang Mong Song , Cheng Huang-Chung
Published: October 2002

New analytical models for estimating crosstalk-induced delay time deterioration and the worst crosstalk models of a coupled interconnect for ramp input waveform are derived. The accuracy of these compact models at various driver resistances, loading capacitances, and input-ramping rates is verified by simulation program with integrated circuit emphasis (SPICE) simulation for the parallel interconnect system. The effects of crosstalk noise on the delay time at various ramp input rise times, for both simultaneous and non-simultaneous switching cases, are discussed here. In this study we show that crosstalk noise will be a limiting factor for future fast transition signals. The results reported herein are useful in the studies of delay time uncertainties due to noise and the interconnect worst-case design.
Formulation of a Viscoelastic Stress Problem Using Analytical Integration and Its Application to Viscoelastic Oxidation Simulation
Authors: Uchida Tetsuya , Nishi Kenji
Published: October 2002

Formulation of a viscoelastic stress problem adopting an analytical integration scheme, which was originally proposed by Peng and co-authors [Proc. Symp. Process Physics and Modeling in Semiconductor Technology, Manchester, 1991, p. 772; COMPEL 10 (1991) 341], is given in a complete form. This formulation includes the treatment of initial strain, an implicit solution method, and improvement of the solution by successive iteration. According to the formulation, a two-dimensional oxidation program is made. Through the calculations of oxidation of a simple test structure, it is reconfirmed that numerical instability can be improved by adopting the scheme of Peng and co-authors [Proc. Symp. Process Physics and Modeling in Semiconductor Technology, Manchester, 1991, p. 772; COMPEL 10 (1991) 341]. Other aspects of the behavior of the solution, including the dependence of the solution on the magnitude of time steps, are also shown.
High Electromechanical Coupling Factor and Electrostrictive Strain over Broad Frequency Range in Electrostrictive Poly(vinylidene fluoride-trifluoroethylene) Copolymer Films
Authors: Bharti Vivek , Xu T.-B. , Cheng Z.-Y. , Mai T. , Zhang Q. M. , Ramotowski Tom , Wright K. A.
Published: October 2002

Electromechanical coupling factor is one of the most important parameters for measuring the performance of materials for electromechanical transduction applications. In this paper, we will show that a transverse electromechanical coupling factor k
31 of more than 0.45 can be achieved in poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer under certain electron irradiation treatment conditions. In addition, the effective piezoelectric coefficients of the irradiated copolymer have been found to increase markedly in comparison to non-irradiated copolymers. Experimental evidences also indicate that the improved electrostrictive strains in irradiated copolymer films can be maintained over a broad frequency and temperature range.
Correlation of Photoreflectance Spectra with Performance of GaInP/GaAs Heterojunction Bipolar Transistors
Authors: Hsin Yue-Ming , Huang Ying-Sheng , Fan Chang-Chung , Wang Chen-Hao , Chen Hung-Ming , Li Nei-Yi
Published: October 2002

We have measured the photoreflectance (PR) spectra at 300 K and dc current gain for GaInP/GaAs heterojunction bipolar transistors (HBTs) grown by metalorganic chemical vapor deposition with different growth conditions. From the observed Franz–Keldysh oscillations, we have evaluated the built-in dc electric fields and associated band gaps in the GaInP emitter and GaAs collector regions. The observed increase in current gain with the low GaInP band gap is in agreement with band alignment between partially ordered GaInP and GaAs, but the observed current gain is not strongly dependent on electric field. For samples with comparable GaInP band gaps we have thereby detected a limiting factor, base bulk recombination, governing the current gain of HBTs from Gummel plots.
Effects of the Growth Temperature on the Properties of CdTe Thin Films for Solar Cell Applications
Authors: Jae-Hyeong Lee Jae-Hyeong Lee , Yong-Kwan Park Yong-Kwan Park , Kea-Joon Yang Kea-Joon Yang
Published: October 2002

CdTe films for solar cell application were prepared at various growth temperatures by a vacuum evaporation system having close spacing between the source and substrate. The CdTe thin films had a cubic structure highly oriented with the (111) direction perpendicular to the substrate surface, regardless of the growth temperature. The crystallites are of random shape and reach up to about 2 µm in size with increasing growth temperature. The higher growth temperature contributed to the reduction of dark resistivity from 6 ×107 Ω·cm at room temperature to 45.4 ×106 Ω·cm at 300°C. The photovoltaic properties of the CdS/CdTe solar cell were considerably improved with the increase in the growth temperature, which was caused by the increase of (111) texture and grain size in CdTe films.