bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Study on Shape Transformation of Silicon Trenches by High-Temperature Hydrogen Annealing
Authors: Sudoh Koichi , Iwasaki Hiroshi , Kuribayashi Hitoshi , Hiruta Reiko , Shimizu Ryosuke
Published: February 2005

We have studied shape transformation of micron-sized trenches on Si substrates during high temperature hydrogen annealing, performing numerical simulations based on Mullins' theory. We have considered evaporation-condensation and surface diffusion as mass transport mechanisms causing shape transformation. The simulation allowing only surface diffusion reproduces well the observed micron-scale aspects of shape transformation by hydrogen annealing at 1000–1150°C.
Improved Step-Graded-Channel Heterostructure Field-Effect Transistor
Authors: Yu Shu-Jenn , Hsu Wei-Chou , Li Yih-Juan , Chen Yeong-Jia
Published: February 2005

A heterostructure field-effect transistor with a step-graded channel has been successfully fabricated. The conduction electrons are distant from the AlGaAs/InGaAs interface; thus the Coulomb scattering is reduced, and consequently, electron mobility is increased. A high drain-current density and a large gate-voltage swing can be obtained. For a 1.2×100 µm2 gate, the maximum saturation drain-current density is 373 mA/mm and the maximum extrinsic transconductance is 148 mS/mm with a gate-voltage swing of 1.9 V.
Watt-Class High-Output-Power 365 nm Ultraviolet Light-Emitting Diodes
Authors: Morita Daisuke , Yamamoto Masashi , Akaishi Kazuyuki , Matoba Kousuke , Yasutomo Katsuhiro , Kasai Yoshio , Sano Masahiko , Nagahama Shin-ichi , Mukai Takashi
Published: February 2005

Ultraviolet (UV) light-emitting diode (LED) epilayers were grown on low dislocation density (1×108/cm2) GaN templates with sapphire substrates. Then, the GaN templates and sapphire substrates were removed using laser-induced lift-off and polishing techniques. Additionally, to enhance the extraction efficiency, this LED chip used a higher reflectance Ag p-type electrode, patterned surface, and silicone resin molding package. When this UV LED was operated at a forward-bias pulsed current of 1 A at room temperature, the peak wavelength, output power, forward voltage, and external quantum efficiency were 365 nm, 1.5 W, 4.4 V, and 44%, respectively.
Thermoelectric Properties of RF-Sputtered SiGe Thin Film for Hydrogen Gas Sensor
Authors: Tajima Kazuki , Qiu Fabin , Shin Woosuck , Sawaguchi Naoya , Izu Noriya , Matsubara Ichiro , Murayama Norimitsu
Published: February 2005

Phosphorus-doped Si0.8Ge0.2 thin films were deposited on the Si3N4/SiO2/Si substrate by the RF sputtering. Thermal annealing was carried out to crystallize as-deposited, amorphous-like SiGe thin films. With increasing annealing temperature and time, the crystallization of the SiGe thin films progressed, resulting in a high carrier mobility and a large absolute value of Seebeck coefficient. The SiGe thin film deposited on the Si3N4/SiO2/Si substrate and then annealed at 850°C for 5 h at an argon flow rate of 150 cc/min showed a Seebeck coefficient of -198 µV/K, a Hall mobility of 10.54 cm2/Vs, a carrier concentration of 1.1×1018 cm-3 at 100°C. The thermoelectric hydrogen sensor with the SiGe thin film annealed at 850°C for 5 h showed a voltage signal of 5.81 mV, a catalyst activity of 16.17°C and a response time, corresponding to 90% voltage signal of 50 s for 3% H2 in air. The sensor operating at 100°C detected hydrogen in air at concentrations from 0.01 to 3%, and showed a good linearity between voltage signal and gas concentration.
Thermal Stability of Cu/NiSi-Contacted p+n Shallow Junction
Authors: Wang Chao-Chun , Lin Hsin-Hung , Chen Mao-Chieh
Published: February 2005

The thermal stability of Cu/NiSi-contacted p+n shallow junction diodes was investigated with respect to their electrical characteristics and metallurgical reactions. The TaN/Cu/NiSi/p+n junction diode remained intact after 30 min thermal annealing at temperatures of up to 350°C. Upon annealing at 375°C, a marked increase in reverse bias leakage current occurred, and secondary ion mass spectrometry (SIMS) analysis indicated that Cu started to penetrate into the NiSi-contacted shallow junction region. After a higher temperature annealing at 425°C, a Cu3Si phase was formed. The failure of the TaN/Cu/NiSi/p+n junction diodes is attributed to the penetration of Cu through the NiSi layer into the junction region, leading to junction degradation by introducing deep-level trap states and the eventual formation of Cu3Si.
Correction of Critical Dimension Uniformity on a Wafer by Controlling Back-Surface Transmittance Distribution of a Photomask
Authors: Park Jong Rak , Kim Soon Ho , Park Jin-Hong , Lee Dong Gun , Kim Seong-Yoon , Cha Byung-Cheol , Choi Sung-Woon
Published: February 2005

We report on a new method for correcting the critical dimension (CD) uniformity on a wafer, using a transmittance-controlled photomask with phase patterns on the back. Theoretical analysis of changes in the illumination-pupil shape with respect to the variation of the size and density of the back-surface 180°-phase contact-hole patterns and experimental results using the transmittance-controlled photomask are presented. It is shown that pattern size on the back of the photomask must be made as small as possible in order to keep the illumination-pupil shape as close as possible to the original one and to achieve as large an illumination intensity drop as possible at the same pattern density. It is demonstrated that the method is very effective for correcting the CD nonuniformity on a wafer that is induced by both CD nonuniformity of the photomask and flare in the exposure tool.
Simulation of Photoresist Thermal Flow Process with Viscous Flow Model
Authors: Chung Won-Young , Kim Tai-Kyung , Lee Yero , Yoon Jin-Young , Kim Hyun-Woo , Park Young-Kwan , Kong Jeong-Taek
Published: February 2005

The photoresist (PR) thermal flow process is to enhance the resolution of lithography for the patterning of sub-200 nm-diameter contact holes as the required critical dimension (CD) approaches the physical limits of conventional lithography. It is difficult to predict the results of the application of this process, so we develop a new viscous PR flow model, which is verified to be applicable for various PRs from experimental results and is applied to the optimization of the layout design and process parameters. Using the model and simulation, we demonstrate the close agreement between the predicted and obtained results using with vertical scanning electron microscope (VSEM) to study the top corner rounding profile of a PR, and present a method for predicting the effect of changes in the dominant variables such as contact diameter, surrounding bulk density, and temperature. This model is also integrated with a lithography simulator. The layout design and process conditions for patterns with various contact diameters are optimized using our new methodology. The viscous flow model linked to the lithography simulator can be effectively used for predicting the contact patterning process and optimizing the layout, as well as, for analyzing defects.
Growth of Biaxially Textured CeO2/YSZ/CeO2 and SrTiO3 Buffer Layers on Textured Ni Substrates by Pulsed Laser Deposition
Authors: Chen Jun , Parilla Philip A. , Bhattacharya Raghu N. , Ren Zhifeng
Published: February 2005

Biaxially textured CeO2/YSZ/CeO2 and SrTiO3 buffer layers have been grown by pulsed laser deposition (PLD) on rolling assisted biaxially textured substrates (RABiTS) made of Ni. Full width at half maximum (FWHM) of the ω scan, φ scan of these buffer layers were comparable to the Ni substrates indicating good epitaxial growth on RABiTS. Atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements showed that these buffer layers were smooth and crack-free. CeO2/YSZ/CeO2/Ni and SrTiO3/Ni buffer layers prepared by this technique can be used as templates for the growth of high-T
c superconductors coated conductors. Unlike CeO2 seed layers, which could be easily epitaxially grown on RABiTS Ni substrates in forming gas, cube-on-cube epitaxial growth of SrTiO3 on RABiTS Ni substrates can be achieved only in a narrow window of deposition temperatures and forming gas pressure.
Spin-polarized Tunneling in Ultrasmall Vertical Ferromagnetic Tunnel Junctions
Authors: Haraichi Satoshi , Wada Toshimi , Ishii Kenichi , Hikosaka Kazunori
Published: February 2005

We have developed nanometer-scale vertical ferromagnetic tunnel junctions using a Si-based inorganic electron beam resist process, including barrier layer fabrication using metal evaporation in ozone atmosphere. The current–voltage (I–V) characteristics of Ni/NiO/Co multiple junctions with diameters of 20 nm have been measured in a magnetic field to investigate spin-polarized tunneling in the Coulomb blockade regime. The temperature dependence of the I–V curve indicates that Coulomb blockade phenomena occur at temperatures below 40 K, agreeing with the estimation of the single-electron charging energy from the device geometries. The magnetoresistance is strongly enhanced by magnetization reversal of Ni and Co, and the obtained MR ratio is greater than 100% in the Coulomb blockade regime at 15 K.
Experimental and Theoretical Investigation of Laser Medium in a Grid-Nozzle Multi-Kw Supersonic Chemical Oxygen Iodine Laser
Authors: Vyskubenko Oleg , Tei Kazuyoku , Sugimoto Daichi , Fujioka Tomoo
Published: February 2005

Laser medium parameters of a multi-kW grid-nozzle supersonic Chemical Oxygen Iodine Laser (COIL) were studied both experimentally and theoretically. Small signal gain (SSG) diagnostics were performed using a narrow line-width tunable laser by scanning a 1 GHz range around the (2P1/2)–(2P3/2) spin-orbit transition line of atomic iodine. Numerical simulation was employed to obtain the gain distribution along the optical axis, yield of singlet oxygen, iodine dissociation fraction and the temperature inside the laser cavity. Almost all the input parameters for the simulation were taken from the experimental data. The bulk of the singlet oxygen is found to be deactivated by the iodine jet, while the yield at the Nozzle Exit Plane (NEP) is found to be half of that in the subsonic area. Simulation also showed that 90% of molecular iodine is dissociated at the nozzle throat. Gain along the optical axis appeared to be non-uniform, and included absorption regions. The experimentally measured maximum gain value was found to be 0.26 m-1.
Improvement in Thermal Stability and Temperature Dependence of Diffractivity in Low-Tg Photorefractive Polymers Dispersed with Plasticizers
Authors: Tanaka Shin-ya , Kurihara Shun-ichiro , Nagayama Norio , Yokoyama Masaaki
Published: February 2005

In the study to solve on the thermal instability due to the crystallization of additives for poly-N-vinylcarbazole (PVK)-based low-T
g photorefractive polymers with ethylcarbazole (EtCz) as a plasticizer, it has been found that the addition of a dimeric analog of PVK, 1,3-biscarbazolyl propane (BisCzPro), is very effective, and the replacement of EtCz with BisCzPro or EtCz/BisCzPro mixtures enables us to control glass transition temperature (T
g) by changing the amount ratio of the additives and examine the temperature dependence of diffractivity while maintaining a transparent uniform film at high temperatures. As a result, we have clearly observed the existence of a specific temperature showing a maximum diffractivity, which is presumed to have resulted the decrease in the space field due to the detrapping and recombination of space charges by thermal agitation.
A Single to Multi-Wavelength Converter Using Fabry–Perot Laser Diode with Linear Optical Amplifier
Authors: Kang Jeung-Mo , Kim Yong Ook , Han Sang-Kook , Lee Seok
Published: February 2005

We propose and demonstrate a novel single to multi-wavelength converter using Fabry–Perot Laser Diode (FP-LD) with linear optical amplifier (LOA), which is based on cross-gain modulation (XGM) effect. This can convert an input signal to many wavelengths simultaneously for reconfigurable wavelength conversion in optical cross connect (OXC) and broadcasting in optical access network. Multi-modes of FP-LD were used for probe signals and LOA was used for cross gain modulation medium effect. The separation of FP-LD modes spacing is fixed as 0.8 nm to satisfy International Telecommunications Union (ITU) grid.
Analyses and Improvements of Whiteness of Reflective Liquid Crystal Displays
Authors: Huang Yi-Pai , Chu Liang-San , Shieh Han-Ping D.
Published: February 2005

A reflective liquid crystal display (R-LCD) has become an important component of a portable information device; however, its inadequate whiteness appearance is a major issue in achieving the potential of “electronic paper”. The factors causing inadequate whiteness were examined using a conventional R-LCD. Furthermore, a novel reflectance-profile-controlled component “random grating light control film” and a non dispersed LC mode with a high-cell-gap tolerance were presented to achieve the paper-white image of reflective LCDs.
Thermoluminescence of Laser-Irradiated Mg2SiO4:Tb
Authors: Miyoshi Tadaki , Kobayashi Takanobu , Shinohara Taketsugu , Okumura Koji , Kaneda Teruhisa
Published: February 2005

Thermoluminescence has been observed in laser-irradiated Mg2SiO4:Tb. Three glow peaks were observed at 130, 220 and 310°C. The glow peak observed at 220°C has not been previously reported for light-irradiated samples, and is similar to that observed in X-ray irradiated samples. The origin of these glow peaks was investigated.
Synthesis and Characterization of Sol–Gel-Derived (Pb1-xLax)Ti1-x/4O3 Thin Films
Authors: Chopra Sonalee , Sharma Seema , Goel Tara Chand , Mendiratta Raj Gopal
Published: February 2005

Ferroelectric lead lanthanum titanate (Pb1-x
La
x
Ti1-x/4O3) (PLTx) thin films (x=0.04, 0.08 and 0.12) have been prepared by sol–gel spin-coating process on ITO- coated 7059 Corning glass substrates. Investigations have been made on the crystal structure, surface morphology, dielectric and ferroelectric properties of the thin films. Characterization of these films by X-ray diffraction shows that the films annealed at 650°C exhibit tetragonal structure with perovskite phase. Replacement of lanthanum in lead titanate results in reduction of the tetragonal ratio (c/a), thereby resulting in better mechanical stability. Microstructural analyses of the films are carried out by obtaining atomic force microscope (AFM) images. AFM images are characterized by slight surface roughness with a uniform crack-free, densely packed structure. Dielectric, pyroelectric and ferroelectric studies carried out on these films have been reported. The dielectric constant increases with La concentration. The Curie temperature is found to decrease with the addition of lanthanum. The pyroelectric coefficient increases from 17 nC/cm2K to 31 nC/cm2K as La content increases from 4 to 12%. The pyroelectric figures of merit of the films have been calculated from these studies. These studies indicate that 8% lanthanum is the material best suited for infrared detectors owing to its high pyroelectric coefficient (∼29 nC/cm2K), high voltage responsivity (∼420 Vcm2/J), high detectivity (∼1.04×10-5 Pa-1/2) and low variation of pyrocoefficient with temperature.
Temperature Dependence of Physical Constants with Varied Molecular Length and Position of Fluorine Substituents in Phenyl-bicyclohexane Core Liquid Crystals
Authors: Ma Heng , Okada Hiroyuki , Sugimori Shigeru , Onnagawa Hiroyoshi , Toriyama Kazuhisa
Published: February 2005

The effects of a fluorinated substituent on physical properties of phenyl bicyclohexane liquid crystals (LCs) are reported. Temperature dependence of the physical properties for different terminals and extents of fluorine substituents were compared. Electro optic measurements suggest that the molecular length and position of fluorine strongly influence the threshold voltage and anisotropic dielectric constant. However, the resulting temperature dependences of refractive indices, order parameters and splay elastic constants indicate that the fluorine substituents cause minor differences. The effect of symmetric fluorine substituents on the benzene ring was also discussed.
Observation of Electric-Field-Driven Modulated Textures in Cholesteric Liquid Crystal Cells
Authors: Yao I-An , Wu Jin-Jei , Chen Shu-Hsia
Published: February 2005

We observed the modulated textures in a planar-aligned cholesteric liquid crystal cell by applying an electric field parallel to its helical axis. In this system, the twist favored by the chirality competes with the applied electric field. This competition causes the system to develop a series of ordered textures, in the sequence of striped texture-hexagonal texture-striped texture, with the increase of electric field. Of these textures, the hexagonal texture was experimentally observed for the first time.
Millimeter-Wave Annealing of SrBi2Ta2O9 Films Prepared by Sol–Gel Method
Authors: Matsumoto Takeshi , Saito Hidenori , Numata Ken , Miyake Shoji
Published: February 2005

SrBi2Ta2O9 (SBT) films were prepared on Pt/Ti/SiO2/Si substrates by the sol–gel method, and they were annealed by 28 GHz millimeter-wave (mm-wave) irradiation and electric furnace heating. The mm-wave absorption measurement for each component of the substrate materials and the film indicated a selective heating of the film by the mm-wave. Films annealed with mm-waves had larger grains and smaller amounts of non-ferroelectric pyrochlore than those annealed using an electric furnace. These differences brought about a higher remanent polarization for the mm-wave-annealed films. Leakage current, fatigue and retention properties of films treated by the two methods were comparable.
Deoxyribonucleic Acid Interaction with Silanized Surfaces
Authors: Yoda Sawako , Han Seung Pil , Kudo Hidetoshi , Kwak Kwang Joo , Fujihira Masamichi
Published: February 2005

We demonstrate here the observation of the interaction between DNA and silanized cover glass surfaces using a fluorescence microscope and an atomic force microscope (AFM). Two-component surface modification with one alkylsilane mixed with another silane derivative containing amino end groups enhanced the adsorption of negatively charged DNA molecules due to the electrostatic interaction with positive charges of protonated amino end groups. We investigated the electrostatic interaction of the DNA molecules with the mixed silanized surfaces as a function of the concentration of the amino end groups. In addition, interaction on molecular scales was demonstrated by a newly developed double combing method.
Self-Organization Process in Active-State Pitting-Instability of Active-State Pit Formation
Authors: Asanuma Miki , Yamada Akifumi , Aogaki Ryoichi
Published: February 2005

From the viewpoint of unstable growth of nonequilibrium fluctuations, the self-organization process of the pit in an active state was examined. At less-noble potentials, anodic dissolution of passive metal initially generates a specific pit, called the active-state pit, having a size similar to that of the conventional polishing-state pit formed at more-noble potentials. The inside of the active-state pit has a random irregular surface, sometimes as a result of crystalline micrograins. It was first concluded that the diameter of the pit in the active state as well as in the polishing state is determined by the same fluctuations arising from metal-ion formation due to the presence of specifically adsorbed anions on the metal surface. Then, the irregularity of the inside of the pit was attributed to the fluctuations arising from metal-complex formation following metal-ion formation; the aggressive anions autocatalytically bind with the metal ions, so that the fluctuations, unlike the fluctuations due to metal-ion formation, are randomly distributed. In active dissolution without passive film at much less-noble potentials, because of the high growth rates of the fluctuations due to metal-ion formation, the fluctuations of complex formation regulate the total reaction as the rate-determining step, so that the random irregularity characteristic of such fluctuations appears in the surface morphology. As the potential shifts toward the more-noble side, however, owing to the development of the concentration overpotential, the fluctuations of metal-ion formation are suppressed from growing, so that instead of the fluctuations of complex formation, the fluctuations of metal-ion formation control the total reaction of the formation of the active-state pit. Finally, after computer simulation of the self-organization process, the morphology of the active-state pit was compared with that of the polishing-state pit, and the morphological dependence on the passive film coverage and pitting time was examined.
Real-Time Growth Control of Ge–Sb–Te Multilayer Film as Optical Recording Media by In Situ Ellipsometry
Authors: An Sung Hyuck , Kim Jong Hyouk , Li Xuezhe , Kim Sang Jun , Kim Sang Youl
Published: February 2005

Using an in situ ellipsometer, we monitored the thin film growth curve of optical recording media in real time. Utilizing the complex refractive indices of Ge2Sb2Te5 and ZnS–SiO2 obtained from the analysis of spectroscopic ellipsometry data, we calculated the growth curves of ellipsometric constants vs thickness. By comparing the calculated growth curve of ellipsometric constants with the measured one, and by analyzing the effect of the density variation of the Ge2Sb2Te5 recording layer on ellipsometric constants, we precisely monitored the growth rate of Ge2Sb2Te5 and ZnS–SiO2 films, respectively, and eventually controlled the whole growth process of a multilayer sample made of Ge2Sb2Te5 and ZnS–SiO2 films. The accurate thickness control using in situ ellipsometry was verified through the analysis of the deposited multilayer sample using an ex situ spectroscopic ellipsometer.
Detailed Observation of Cell Junction in Anodic Porous Alumina with Square Cells
Authors: Asoh Hidetaka , Ono Sachiko , Hirose Tomohito , Takatori Ikuo , Masuda Hideki
Published: February 2005

The local structure of a cell junction in anodic porous alumina with square cells was studied by transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The initiation of a square lattice pattern, which is different from a normal hexagonal cell arrangement, induced the characteristic growth of a porous structure. The obtained oxide film was formed by a close-packed array of square cells following the initiation. The shape of the pores changed from circular to square corresponding to the transformation of the cell structure at the steady state. The incorporation of unoxidized aluminum into the oxide film and the generation of voids were observed at the fourfold point of the cell junction. The height of the protrusions of the aluminum substrate at the cell junction was considerably larger than that of protrusions formed in naturally occurring anodic porous alumina with hexagonal cells. These specific features were thought to be caused by the inhomogeneous distribution of current at the square pore base.
Surface Structure of Sc-O/W(100) System used as Schottky Emitter at High Temperature
Authors: Iida Shin-ichi , Nakanishi Yousuke , Nagatomi Takaharu , Takai Yoshizo
Published: February 2005

The surface characterization of the Sc–O/W(100) system was performed by low-energy electron diffraction, Auger electron spectroscopy and work function measurement at 1500 K, the operating temperature of the Sc–O/W(100) emitter. For this, a sample holder with a heater was newly developed. In addition, the differential measurement method was applied to low-energy electron diffraction. The present results reveal that the p(1×1)-Sc–O/W(100) surface having a work function of 3.2 eV is formed by heating at 1700 K.
Energy Transfer and X-Ray Radiation Characteristics of a Gas-Puff Z-Pinch
Authors: Takasugi Keiichi , Akiyama Hisashi
Published: February 2005

The characteristics of energy transfer and X-ray radiation from an Ar gas-puff z-pinch plasma have been investigated in the z-pinch discharge region. The input energy reached approximately 10% of the bank energy at maximum. The input energy had a little more than square dependence for the pinch current. The average energy distributed to each particle had a decreasing tendency with delay time. The electron temperature of hot spots was around 1 keV, and it increased slightly with delay time. The increase in the spectral intensity of He-like resonance line showed strong compression for large delay times. The hot spots are small in volume, but large amounts of energy are concentrated on them due to the local compression of the pinch column.
Study on the Absolute Density and Translational Temperature of Si Atoms in Very High Frequency Capacitively Coupled SiH4 Plasma with Ar, N2, and H2 Dilution Gases
Authors: Ohta Takayuki , Hori Masaru , Ishida Tetsuro , Goto Toshio , Ito Masafumi , Kawakami Satoru
Published: February 2005

The absolute densities and translational temperatures of Si atoms in very high frequency capacitively coupled SiH4 plasmas diluted with Ar, N2, and H2 gases were investigated by ultraviolet absorption spectroscopy with a ring dye laser and a hollow cathode lamp. It was found that the absolute density of Si atoms was of the order of 109–1010 cm-3 and the translational temperature of Si atoms ranged from 620 to 1130 K at a total pressure of 11 Pa, a dilution gas flow rate of 100 sccm, and a SiH4 flow rate of 0–15 sccm. The absolute densities and temperatures of Si atoms in plasma at an excitation frequency of 27 MHz were larger than those at 60 MHz under the conditions at the same electron density. Si atom heating was due to the energy of Si atoms released from the electron impact dissociation of SiH
x
(x=1–4). The translational temperatures of Si atoms in SiH4/Ar, SiH4/N2, and SiH4/H2 plasmas were evaluated to be 970, 1030, and 1130 K, respectively, at a frequency of 27 MHz, a SiH4 flow rate of 10 sccm, and a VHF power of 1500 W. The effect of Si atoms and SiH3 radicals on film deposition was investigated for SiH4/N2 in 27 MHz and 60 MHz plasmas. From the measurement using Fourier transform infrared absorption spectroscopy, the peak of the Si–H bond decreased and that of the N–H bond increased with increasing excitation frequency. Therefore, the film deposited at 60 MHz indicated a nitride-rich composition in comparison with that at 27 MHz. The contribution ratio of Si atoms to SiH3 radicals for film deposition in 27 MHz plasma was larger than that in 60 MHz plasma. These results are very important from the viewpoint of understanding neutral radical chemistries in the plasma and their related processing.
Organic Film Reactive Ion Etching Using 100 MHz rf Capacitive Coupled Plasma
Authors: Ohiwa Tokuhisa , Hayashi Hisataka , Sakai Itsuko , Kojima Akihiro , Shinomiya Eiichiro
Published: February 2005

A new reactive ion etching (RIE) process using a 100 MHz rf capacitive coupled plasma (CCP), where the wafer is placed on the cathode, has been studied. The electron densities obtained in the 100 MHz Ar plasma process were higher than those obtained in the 13.56 MHz Ar plasma process, and self-bias voltages (-Vdc) obtained in the 100 MHz plasma process were less than 1/3 of those obtained in the 13.56 MHz plasma process. The resist etch process in the 100 MHz plasma process using hydrogen-based gas chemistry showed high selectivity to SiO2 above 50. Also, the stacked mask process (S-MAP) in the 100 MHz plasma process showed a great improvement of the carbon film etch profile with less faceting of the spin-on-glass (SOG) mask, compared with that in the 13.56 MHz plasma process. Furthermore, the 100 MHz organic low-k film etch process using a SiO2 etch mask showed less erosion of the SiO2 mask edge and straight sidewall profile of the organic low-k film. The 100 MHz rf CCP process has a great advantage in organic film etching.
High-Efficiency Organic Electroluminescent Device with Multiple Emitting Units
Authors: Chang Chan-Ching , Hwang Shiao-Wen , Chen Chin H. , Chen Jenn-Fang
Published: February 2005

In this paper, we report on the fabrication of multilayer organic light emitting diodes (OLEDs) with high electroluminescent (EL) yield achieved by integrating two units of green-emissive devices in series. The architecture of the device used in the experiment is Indium–Tin–Oxid (ITO)/CuPc/NPB/C545T:Alq3/Alq3/Mg:Alq3/WO3/NPB/C545T:Alq3/Alq3/LiF/Al. We found the efficiency of the two-unit devices can be controllable by the thickness of WO3. The two-unit devices with 1-nm-thick WO3 produces the luminance efficiency of 49.2 cd/A at 20 mA/cm2, which is around four times that of the controlled single-unit device (ITO/CuPc/NPB/C545T:Alq3/Alq3/LiF/Al). Compared with reported research data, the “amplification effect” discovered in our device is a rather unexpected result. The external quantum efficiency of 12.6%, with near-saturated Commission Internationale d'Eclairage coordinates (CIEx=0.27, CIEy=0.68), is one of the best ever reported for a fluorescent dye-doped OLED. We also demonstrate that the electron injection layer of Mg:Alq3 is a necessary component for the enhancement of EL efficiency. These results may prove to be an effective method to enhance the efficiency as well as the lifetime of current OLEDs.
Coherent Optical Control of Molecular Motion Using Polarized Sequential Pulses
Authors: Itoh Kohichi , Toda Yasunori , Morita Ryuji , Yamashita Mikio
Published: February 2005

By using Raman-induced Kerr-effect spectroscopy, two-pulse excitations with different polarization combinations have been demonstrated for the selective coherent excitation of molecular vibrations in liquid CCl4. Anti correlated selective excitations as well as the suppressions of the two asymmetric vibrational motions were observed in the opposite configuration of polarization between the two-pump pulses. The measurements show that we can manipulate molecular motions by controlling the optical phase of sequential pulses through timing and polarization.
Production of Short-Pulse Synchrotron Radiation using a Head-Tail Bunch Oscillation in the Electron Storage Ring
Authors: Sakanaka Shogo
Published: February 2005

A means of producing short pulses of synchrotron radiation in the electron storage ring is proposed. By applying successive transverse kicks on a head and tail of an electron bunch in opposite directions, a head-tail oscillation can be excited. At certain moments with a regular period, the vertical slopes of the particles in the bunch are linearly correlated with their longitudinal positions. This correlation can be used to cut unwanted synchrotron radiation from the head and tail of the bunch, thereby providing short-pulse X-ray radiation, similarly to that proposed in previous papers.
Optimization of Spiral-Wobbler System for Heavy-Ion Radiotherapy
Authors: Komori Masataka , Furukawa Takuji , Kanai Tatsuaki , Noda Koji
Published: February 2005

We propose an amplitude modulation wobbler-scatterer system, a so-called spiral-wobbler system, to produce a large irradiation field in a relatively short irradiation port for heavy-ion radiation therapy. The wobbler parameters, such as the wobbler-radius-modulation function, the wobbler radial frequency and the rotational frequency, are optimized and the uniformity of the irradiation field is estimated as the function of irradiation time. By using a wobbler radial frequency of 23 Hz, and a wobbler rotational frequency of 59 Hz, an irradiation field with a uniformity of ±3% can be obtained for an irradiation duration of 1 s. The spiral-wobbler system is applicable to respiration-gated irradiation.
Fabrication of Optical Microelectromechanical-System Switches Having Multilevel Mirror-Drive Electrodes
Authors: Ishii Hiromu , Urano Masami , Tanabe Yasuyuki , Shimamura Toshishige , Yamaguchi Joji , Kamei Toshikazu , Kudou Kazuhisa , Yano Masaki , Uenishi Yuji , Machida Katsuyuki
Published: February 2005

This work describes a practical and high-yield method of fabricating optical microelectromechanical-system (MEMS) switches. The method features the use of thick-plated gold multilevel interconnections for the mirror-drive electrodes and polyimide coating to protect the fragile and easily-movable micromachined mirror. The multilevel electrode developed was over 80-µm high providing enough space for the tilting mirror placed above it. Open-short circuit yield was 100% on 6-inch wafers. All the processes for fabricating the electrodes were carried out at under 310°C, meaning the electrodes could be successively formed after mirror-control large-scale integrated circuits (LSIs) were fabricated on a wafer. The fragile mirrors are sealed in polyimide during the fabrication processes. As this method protects the mirrors against the shock and damage caused by factors such as the dicing process, it enables 3-dimensional MEMS structures that have moving portions to be handled through conventional fabrication processes without the need for any special care. The static and dynamic characteristics of the optical MEMS switches fabricated are shown.
Laser Pattern Profile Emitted through Optical Glass Fiber Bundle with Load
Authors: Yamauchi Toshihiko
Published: February 2005

The output pattern of a He–Ne laser that passes through an optical glass fiber bundle depends on the weight of load put on the fiber. The increment of the pattern radius exponentially increases with the load. It is considered that the bending of the fiber causes this increment. The estimated delay time also exponentially increases with the weight of the load, and the estimated delay time by the load and the bending is on the order of picosecond.
Dual Flat Flextensional Ultrasound Transducers for Enhancement of Transdermal Drug Delivery
Authors: Zhang Hong-Ye , Yeo Swee-Hock
Published: February 2005

The development of a lightweight, simple-structure and low-power-consumption sonophoresis device for drug delivery is required. For this purpose, a new sonophoresis device with dual flat flextensional ultrasound transducers was fabricated and investigated in this work. When both ultrasound transducers were operated at their fundamental resonance frequency (26.83 kHz), the radiated acoustic intensity (I
sptp) was about 2 to 4 times higher than that generated by a single ultrasound transducer in the proposed device. The proposed sonophoresis device has the capability to reduce the applied voltage at least twofold. Compared to the ultrasonic probe or converter from a commercial sonicator that weighs about one kilogram, the proposed sonophoresis device with double ultrasound transducers weighs only 73.3 g. All the results showed that the proposed sonophoresis device is feasible for use in practical applications.
Size Monitoring of Nanoparticles Growing in Low-Pressure Plasma using Laser-Induced Incandescence Technique
Authors: Eom Gyu Sub , Park Seongchong , Park Chul Woung , Choe Wonho , Shin Yong-Hyeon , Chung Kwang Hwa , Hahn Jae Won
Published: February 2005

To describe the temporal behavior of laser-induced incandescence (LII) signals emitted from nanoparticles in atmospheric flames or low-pressure processing plasmas, we derive two analytic formulae in detail from the energy balance equation of nanoparticles heated by laser pulses. We demonstrate quantitative size monitoring by observing Si nanoparticles growing in an argon plasma diluted with 5% SiH4 at a pressure of 20 mTorr, using the LII technique. In this experiment, it is found that the signal-to-noise ratio of the LII signal is sufficient to allow the identification of particles larger than 10 nm in diameter with a measurement uncertainty that is estimated to be less than 5%.
Single-Electron Tunneling Behavior of Organic-Molecule-Based Electronic Device
Authors: So Hye-Mi , Park Jong-Wan , Won Do-Jae , Yun Wan Soo , Kang Yongku , Lee Changjin , Kim Ju-Jin , Kim Jinhee
Published: February 2005

We fabricated electronic devices utilizing chemically synthesized organic molecules and Au nanoparticles and studied their electrical transport properties at low temperature. The Au/Ti electrodes separated by 10–60 nm were fabricated by electron-beam lithography and double-angle shadow evaporation. A self-assembled monolayer (SAM) of the organic molecules was formed on top of the electrodes, which was then bridged with Au nanoparticles trapped by electrostatic trapping. All the devices with SAM exhibited symmetric but nonlinear current-voltage characteristics along with the periodic gate modulation curves at low temperature. Our experimental data suggested that Coulomb blockade of single-electron tunneling is a dominant transport mechanism in our devices.
Grain Size Effect on Dielectric and Piezoelectric Properties of Alkoxy-Derived BaTiO3-Based Thin Films
Authors: Tanaka Kiyotaka , Suzuki Kazuyuki , Fu Desheng , Nishizawa Kaori , Miki Takeshi , Kato Kazumi
Published: February 2005

Lead- and bismuth-free Ba(Ti1-x
Zr
x
)O3 (BTZ) thin films were fabricated on Pt(111)/Ti/SiO2/Si(100) substrates by the chemical solution deposition (CSD) process. The BaTiO3 and BTZ005 thin films fabricated by the conventional process were observed to have a remarkable difference in grain size along the depth of the thin film. The microstructure of the BaTiO3 and BTZ005 thin films was improved by additional sintering process, and their grain sizes were increased to about 60 and 40 nm, respectively, by additional sintering at 800°C for 1 h. The dielectric constant ε
r and piezoelectric constant d
33 of the BaTiO3 thin film consisting of large grains by the additional sintering at 800°C for 1 h were found to be about 375 and 14.5 pm/V. But, ε
r and d
33 of the BTZ005 thin film changed negligibly with increasing of the grain size.
Effect of Back-Etching on Residual Stress in Lead Titanate Thin Films on Si Wafer
Authors: Ohno Tomoya , Suzuki Hisao , Masui Hirohisa , Ishikawa Kenji , Fujimoto Masayuki
Published: February 2005

This paper forcuses on the effect of back-etching on the residual stress in lead titanate (PT) thin film. The PT thin films were deposited by a chemical solution deposition (CSD) on a Pt/Ti/SiO2/Si substrate with different back-etching depth. The part of the Si substrates of 500 µm thickness was etched from back side (back-etching) with a wet etching process. The depth of the back-etching was controlled by changing the etching time in the range from 481.5 µm to 250 µm (residual Si; 18.5–250 µm). The residual stress in PT thin film was calculated from the phonon mode shift of raman scattering. In addition, the intrinsic dielectric constant for PT thin film was also calculated from the lattice mode frequencies. As a result, the residual stress in PT thin films abruptly increased with increasing depth of back-etching at around 300 µm (residual Si; 200 µm) and reached about 1.7 GPa.
Electrical Properties and Microstructure of Lead Zirconate Titanate Thin Film In Situ Grown by Hybrid Processing:Sol-Gel Method and Pulsed Laser Deposition
Authors: Wang Zhan Jie , Kokawa Hiroyuki , Maeda Ryutaro , Ichiki Masaaki
Published: February 2005

Highly oriented Pb(Zr
x
Ti1-x
)O3 (PZT) thin films were in situ grown on Pt/Ti/SiO2/Si substrates by a hybrid process combining the sol-gel method and pulsed-laser deposition (PLD). Crystalline phases and preferred orientation of the PZT films were investigated by X-ray diffraction analysis. Surface morphology and microstructure were observed by scanning electron microscopy and transmission electron microscopy, respectively. Electrical properties of the films were evaluated by measuring their P-E hysteresis loops and dielectric constants. The preferred orientation of the films deposited by hybrid processing can be controlled using the layer deposited by the sol-gel method. The deposition temperature required to obtain the perovskite phase in hybrid processing is 460°C, and is significantly lower than that in the case of direct film deposition by PLD on a Pt/Ti/SiO2/Si substrate. The dielectric constant and remanent polarization of the films in situ deposited at 460°C were approximately 900 and 15 µC/cm2, respectively.
Piezoresponse Force Microscopy Observations of Switching Behavior in Pb(Zr,Ti)O3 Capacitors
Authors: Fujisawa Hironori , Shimizu Masaru , Niu Hirohiko
Published: February 2005

We report on the polarization switching behavior in Pt/Pb(Zr,Ti)O3 (PZT)/SrRuO3/SrTiO3(111) capacitors observed by piezoresponse force microscopy (PFM). Through PFM observations of capacitors partially switched by applying switching pulses shorter than the switching time, the nucleation behavior and domain growth were investigated. Polarization switching preferentially originated from preexisting latent nuclei and consequently, switched domains appeared at the same positions for various pulses with the same polarity. On the other hand, switched domains were observed at different positions for voltage pulses with different polarities. On the basis of a comparison of domain patterns with topography, it is suggested that switched domains are roughly associated with PZT grains and that each grain has preferred polarization directions. Switching current measurements revealed that a voltage drop across the series resistance of the SrRuO3 bottom electrode and PFM system occurred in our measurements because the switching currents were more than 10 mA. Due to this voltage drop, the effective voltage applied to PZT thin film (V
PZT,eff) was almost constant at 2.8 V when external pulse voltages were changed from ±4 to ±10 V. For V
PZT,eff of 2.8 V, the density of latent nuclei and the velocity of sideward domain growth were estimated to be ∼1 µm-2 and 15 m/s, respectively.
Fabrications of Pb(Sc1/2Nb1/2)O3/xPbTiO3 Thin Films and Their Structural Characterizations
Authors: Asanuma Shutaro , Fukunaga Mamoru , Uesu Yoshiaki , Haumont Raphael , Dkhil Brahim , Malibert Charlotte , Kiat Jean-Michel
Published: February 2005

Highly oriented Pb(Sc1/2Nb1/2)O3 (PSN) and Pb(Sc1/2Nb1/2)O3/43%PbTiO3 (PSN/43%PT) thin films were fabricated on MgO and SrTiO3 (001) substrates by pulsed laser deposition (PLD) technique. La1/2Sr1/2CoO3 was deposited on the substrate as a bottom electrode layer for dielectric measurements. The orientation of the films was checked by X-ray diffraction method, and is found to be well oriented along the c-axis for PSN and PSN/PT. Film thickness was determined by the Laue oscillation of X-ray diffraction profile. This enables us to determine the number of pulses for stacking one layer of PSN and PSN/PT thin films. The temperature dependences of lattice constants of PSN and PSN/PT thin films were determined. They exhibit small but clear changes at almost the same temperature as that of the ferroelectric transition points of PSN and PSN/PT ceramics. The surface roughness of these films was observed using atomic force and scanning electron microscopes. Temperature change of dielectric constant ε and D-E hysteresis loop were determined for PSN and the real part of ε shows 850.
Phase Formations and Electrical Properties of Bi3.15La0.85Ti3O12 and Sm-Doped Bi3.073La0.85Sm0.077Ti3O12 Thin Films with Annealing Temperature
Authors: Ryu Sang-Ouk , Lee Nam-Yeal , Lee Won-Jae , Yoon Soon-Gil
Published: February 2005

The phase formation and electrical properties of (Bi,La)4Ti3O12 (BLT) thin film and Sm-doped BLT thin films prepared by the chemical solution deposition method on Pt/Ti/SiO2/Si substrates have been investigated. It was observed that the microstructure and electrical properties of BLT thin films dramatically varied with Sm-doping and annealing temperature. The crystallinity and grain size in both types of BLT films were definitely increased with annealing temperatures of BLT films but these films exhibited slightly different crystallographic orientation, which resulted in the different remanent polarization in BLT films. The remanent polarization (2P
r) of Sm-doped 130 nm-BLT films annealed at 750°C was about 26 µC/cm2. The Sm-doped BLT films also exhibited reduced leakage current density, compared to BLT films.
Pulsed-Laser-Deposited YMnO3 Epitaxial Films with Square Polarization-Electric Field Hysteresis Loop and Low-Temperature Growth
Authors: Shigemitsu Norimichi , Sakata Hironori , Ito Daisuke , Yoshimura Takeshi , Ashida Atsushi , Fujimura Norifumi
Published: February 2005

YMnO3 films were prepared by pulsed laser deposition (PLD) on epitaxial (111) Pt/(0001) sapphire substrates. A systematic study regarding the deposition conditions revealed that the composition of the YMnO3 epitaxial films changed depending on deposition temperature and period, due to the evaporation of Mn from the target and/or the film surface during the deposition. To overcome this issue, low-temperature growth, improvement in target density and the change in the substrate heating system were attempted. To enhance photonic ablation, the excimer laser for the ablation was changed from KrF (248 nm) to ArF (193 nm). Eventually, the ferroelectricity of the YMnO3 film deposited at 740°C was significantly improved. Furthermore, the YMnO3 film with almost identical ferroelectric property was successfully obtained even at 700°C.
Pulsed Laser Deposition of High-Quality (K,Na)NbO3 Thin Films on SrTiO3 Substrate Using High-Density Ceramic Targets
Authors: Saito Takehisa , Wada Takahiro , Adachi Hideaki , Kanno Isaku
Published: February 2005

High-quality (K,Na)NbO3 thin films were successfully deposited on a (100) SrTiO3 (STO) substrate by pulsed laser deposition. High-density KNbO3 (KN), (K0.5Na0.5)NbO3 (KNN) and NaNbO3 (NN) ceramic targets were prepared by spark plasma sintering (SPS). The crystallographic analyses of the film were performed by conventional X-ray diffraction (XRD) analysis and rocking curve measurement. The XRD reciprocal space map was also measured to determine the lattice constants of the film and analyze the crystallographic relationship between the grown film and the STO substrate. The fluctuation change in the orientation of crystals in the grown film decreased and the smoothness of the film surface improved with increasing sodium content of the film. For the NN films, the full width at half maximum (FWHM) of the rocking curve was as small as 0.12°. The XRD reciprocal space map measurements showed that the lattices of the KN and KNN films relaxed on the STO substrate but the NN film was restricted to it.
Investigation of Ru/TiN Bottom Electrodes Prepared by Chemical Vapor Deposition
Authors: Kang Sang Yeol , Kim Beom Seok , Hwang Cheol Seong , Kim Hyeong Joon , Kim Jin Yong , Lee Kwanghee , Lim Han-Jin , Yoo Cha-Young , Kim Sung-Tae
Published: February 2005

Ru thin films were prepared by metalorganic chemical vapor deposition (MOCVD) using cyclopentadienyl-propylcyclopentadienlylruthenium(II) [RuCp(i-PrCp)] and the nucleation behaviors of Ru films on Ta2O5, TiN, Si3N4, SiO2, TiO2 substrates were investigated. It appeared that the difference in nucleation behaviors on various substrates is due to the bonding type between atoms in substrate materials. The nucleation property of Ru films on TiN was successfully improved by plasma treatment of the TiN substrate using Ar before film deposition. It was found that the Ar plasma treatment selectively removes N ions from the surface, makes the TiN surface more metallic or ionic (due to the residual Ti-O bonding), and reduces the nucleation barrier. In addition, the oxidation resistance of Ru/TiN layers was improved by H2 annealing, which made the Ru films more dense.
Crystal-Oriented Bi4Ti3O12 Ceramics Fabricated by High-Magnetic-Field Method
Authors: Doshida Yutaka , Tsuzuku Koichiro , Kishi Hiroshi , Makiya Atsushi , Tanaka Satoshi , Uematsu Keizo , Kimura Tsunehisa
Published: February 2005

The effect of powder properties on the degree of crystal orientation of Bi4Ti3O12 (BIT) ceramics fabricated by a high-magnetic-field method was investigated. As expected, the degree of orientation of BIT ceramics exhibited little dependence on the crystallinity of the powder, and depended on the particle size of the powder. The degree of orientation increased up to 0.96 when the particle size increased from 0.5 to 1.2 µm. The particle size dependence of the degree of orientation was similar to the relationship between the order parameter and particle size, as derived from Langevin's theory on magnetic alignment. This suggests that the crystal orientation of ceramics fabricated by the high-magnetic-field method can be controlled by selecting the particle size of the powder used.