bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Possible Group-Velocity-Matched Broadband Second-Harmonic Generation in Various Periodically Poled Nonlinear Crystals
Authors: Lee Kwang-jo , Yoon Choon Sup , Rotermund Fabian
Published: July 2005

For the efficient second-harmonic generation of ultrashort pulses in wide spectral ranges, we theoretically studied all possible group velocity matched broadband frequency conversion processes in different periodically poled materials, using quasi-phase matching. Important parameters such as the poling period, type of interaction, spectral bandwidth and conversion efficiency are estimated in detail. The results show that some materials can be efficiently applied to the generation of sub-100 fs pulses near the wavelengths of a widely used Ti:sapphire laser.
Dual-Frequency Addressed Variable Optical Attenuator with Submillisecond Response Time
Authors: Liang Xiao , Lu Yan-Qing , Wu Yung-Hsun , Du Fang , Wang Hai-Ying , Wu Shin-Tson
Published: July 2005

We demonstrated a submillisecond response time and low-voltage variable optical attenuator (VOA) using a dual-frequency liquid crystal. The dynamic range of the VOA reaches 43 dB at a 1.55 µm wavelength. A normally on VOA with a flat wavelength response is obtained using a phase compensation cell. Fast rise and decay times are achieved using low-frequency overdrive and high-frequency undershoot voltages. Other approaches to further improve the VOA's performances are discussed.
Generation of SiOC films by the Thermal Induction
Authors: Oh Teresa
Published: July 2005

Hybrid type SiOC films have a blue and red shift according to the flow rate ratio and RF power by CVD. The reason of the chemical shift is due to the particular C–H bond effect such as condensation or elongation. It is generally known that a blue and red shift are clearly defined notwithstanding the small difference flow rate ratio. The physical properties due to the chemical shifts are also very difference, respectively. The flow rate ratio O2/BTMSM = 1.0 for SiOC films refers to the boundary changed from the blue shift to the red shift. This study deals with the generation of peculiar Si–O–C bond in as-deposited film and the C–O bond in annealed films with the flow rate ratio O2/BTMSM = 1.0 using the analysis of the X-ray photoelectron spectroscopy and Fourier transform infrared spectra. It is discussed the change of the bonding structure due to the nucleophilic and oxidation reaction by thermal induction.
Characteristics of Two-Dimensional Array-Type Barrier Microdischarges Operating at High Pressures of Inert Gases
Authors: Sakurai Takeki , Yoshida Shougo , Yoshikawa Hirohisa , Yoshizawa Shoutarou , Morimitu Akinobu
Published: July 2005

The characteristics of barrier microdischarges in a two-dimensional array have been investigated under pressures of inert gases less than 18 atm. A stable discharge is obtained and vacuum ultraviolet (VUV) light emissions radiating from excimers are detected in the entire range of pressures with various scales of microdischarge. VUV light intensity is linearly proportional to an externally applied voltage. The intensity also linearly increases with pressure less than apporoximately 5 atm and gradually decreases with increasing pressure. The pressure giving a maximum intensity, p
m, increases with decreasing microhole diameter of discharge. The ratio of VUV light intensity to electric input energy of discharge increases linearly with pressure up to p
m.
Emittance and Energy Measurements of Low-Energy Electron Beam Using Optical Transition Radiation Techniques
Authors: Sakamoto Fumito , Iijima Hokuto , Dobashi Katsuhiro , Imai Takayuki , Ueda Toru , Watanabe Takahiro , Uesaka Mitsuru
Published: July 2005

Emittance and energy of an electron beam in the range of 8 to 22 MeV were measured via optical transition radiation (OTR) techniques. The beam divergence effect on observations of the far-field OTR image at low energies was studied by means of numerical analysis. The numerical analysis indicates that if the beam divergence is under 1.5 mrad, a simultaneous single-shot measurement of emittance and energy is possible. The results of the single-shot experiment agree with independent measurements conducted using the quadrupole scan method and an electron spectrometer. The experiments were performed with an S-band linac at the Nuclear Engineering Research Laboratory, The University of Tokyo (UTNL).
Energy Quenching Effects on Dry-Etching Durability of Alicyclic-Aliphatic Copolymers and Polymer Blends Enhanced by Polymer-Chain Entanglement
Authors: Kushida Masahito , Kawamoto Kenryou , Harada Kieko , Saito Kyoichi , Sugita Kazuyuki
Published: July 2005

A correlation between the macromolecular structure and dry-etching durability is essential to design a resist of high performance. Ohnishi and ring parameters are known to be useful for estimating the durability, but some limitations are apparent, since the etching rate of a multicomponent matrix polymer is not only dependent on the composition. Previously, we have demonstrated that the etching rates of copolymers and polymer blends, which are composed of fragile aliphatic monomer and stable aromatic or alicyclic monomer units, are lower (the durabilities are higher) than the values calculated from those of the constituent homopolymers with the assumed wt% additivity. In this study, we prepared methyl methacrylate [MMA]/tricyclodecanyl methacrylate [TCDMA] copolymers of various compositions, and attempted to evaluate the dependence of etching rates on TCDMA content. The dependence was found to be inconsistent with those in the cases of α-methyl-styrene, 2-vinyl-naphthalene, and isobornyl methacrylate copolymers and polymer blends reported in the previous papers.
Making Monolayer of Inorganic Nanoparticles on Silicon Substrate
Authors: Yoshii Shigeo , Yamada Kiyohito , Matsukawa Nozomu , Yamashita Ichiro
Published: July 2005

A monolayer of inorganic nanoparticles (NPs) was fabricated on a silicon wafer using a cage-shaped protein, ferritin, which can sequester several kinds of inorganic NP in their cavities. Ferritins were bound electrostatically in aqueous condition to the silicon wafer which was modified with aminosilane molecules. The obtained sample was heat-treated at 500°C under oxygen gas, and the protein moiety and aminosilane were completely eliminated. The obtained NP monolayer showed no aggregation or sintering. This new method can be used to produce a dispersed inorganic NP monolayer on a silicon substrate as designed, which could be used as a nanodot array in floating nanodot gate memories.
Design and Fabrication of Multichannel Photonic Crystal Wavelength Filters to Suppress Crosstalk of Arrayed Waveguide Grating
Authors: Ohkubo Hiroyuki , Ohtera Yasuo , Kawakami Shojiro , Chiba Takafumi
Published: July 2005

Multichannel photonic crystal (PC) wavelength filters have three-dimensional (3D) PCs consisting of Ta2O5/SiO2 multilayer thin films fabricated by the autocloning method. The PC filters have the unique feature that their transmission wavelengths can be altered by changes not only in refractive indices or thicknesses of the constituent films but also in the in-plane lattice constants. In this study, we focused on connecting an array of PC filters to an arrayed waveguide grating (AWG) to suppress the crosstalk of the AWG. In this application, the transmission wavelength shift that depends on the in-plane lattice constants should be larger than about +40 nm, and the spectrum of the PC filters should be the flat-top type. To satisfy the former requirement, we improved the design of the PC filters and fabricated PC filters having a transmission wavelength shift of +36 nm. For the latter requirement, we applied a two-cavity PC filter and obtained the 3 dB bandwidth of 5.0 nm. Finally, we fabricated a module consisting of PC filters and an AWG. The crosstalk of the module was reduced to -20 dB lower than that of the AWG.
Low Temperature Synthesis of Extremely Dense and Vertically Aligned Single-Walled Carbon Nanotubes
Authors: Zhong Guofang , Iwasaki Takayuki , Honda Kotaro , Furukawa Yukio , Ohdomari Iwao , Kawarada Hiroshi
Published: July 2005

A novel point-arc microwave plasma chemical vapor deposition (CVD) apparatus was employed to grow single-walled carbon nanotubes (SWNTs) on Si substrates coated with a sandwich-like nano-layer structure of 0.7 nm Al2O3 (top)/0.5 nm Fe/5–70 nm Al2O3 by conventional high frequency sputtering. The growth of extremely dense and vertically aligned SWNTs with an almost constant growth rate of 270 µm/h within 40 min at a temperature as low as 600°C was demonstrated for the first time. The volume density of the as-grown SWNT films is as higher as 66 kg/m3.
Synthesis of Ni Nanowire-Encapsulated Carbon Nanotubes
Authors: Tanemura Masaki , Iwata Kazuki , Wakasugi Kazuki , Yamamoto Yoshiyuki , Fujimoto Yasutaka , Miao Lei , Tanemura Sakae , Morishima Ryuta
Published: July 2005

A novel method for synthesizing nanowire-encapsulated carbon nanotubes (CNTs) under a high-vacuum ambient is demonstrated. A mixture of acetylene (C2H2) and ammoniac (NH3) gases was effused through a molecular beam (MB)-nozzle onto a small area of a Ni mesh sample heated at 580°C using a newly developed MB-chemical vapor deposition (CVD) system. The densely distributed CNTs, which grew by the thermal decomposition of gases on the intensely gas-effused area, were almost identical in diameter (∼9 nm) despite a large difference in length (0.1–1 µm), and were almost completely filled with a single Ni nanowire of 6 nm in diameter. CNTs with discontinuous filling or those without filling were not observed. On the basis of the detailed transmission electron microscopy (TEM), the base growth mode accompanied by the diffusion of catalyst Ni atoms toward the growth sites was proposed to account for an extremely high rate of filling with nanowire into CNTs.
Protein Sensor Using Carbon Nanotube Field Effect Transistor
Authors: Kojima Atsuhiko , Hyon Chan Kyeong , Kamimura Takafumi , Maeda Masatoshi , Matsumoto Kazuhiko
Published: July 2005

The effect of the selective adsorption of pig serum albumin as an antigen on the electrical properties of a carbon nanotube channel field effect transistor on which anti-pig serum albumin was immobilized as an antibody by physisorption in phosphate buffer solution has been investigated. We have succeeded in real-time detection of the adsorption of pig serum albumin on anti-pig serum albumin as a decrease in the conductance of the carbon nanotube channel field effect transistor, by a label-free process.
Effects of Fabrication Process on Current–Voltage Characteristics of Carbon Nanotube Field Effect Transistors
Authors: Mizutani Takashi , Iwatsuki Shinya , Ohno Yutaka , Kishimoto Shigeru
Published: July 2005

The effects of the fabrication process on the current–voltage (I–V) characteristics of carbon nanotube field effect transistors (CNT-FETs) were studied in detail. A large hysteresis observed in the I–V characteristics of the CNT-FETs having no passivation film became small by passivating the device surface with a SiN
x
film. The conduction behaivior of the CNT-FETs changed from p-type to ambipolar characteristics by SiN
x
passivation. Ambipolar characteristics were also observed in the top-gate CNT-FETs with a gate-source spacing of 2 µm.
Nitrogen Doping of Single-Walled Carbon Nanotube by Using Mass-Separated Low-Energy Ion Beams
Authors: Yamamoto Kazuhiro , Kamimura Takafumi , Matsumoto Kazuhiko
Published: July 2005

Mass-separated nitrogen ions with the mass number of 14 were irradiated to the single-walled carbon nanotubes (SWCNTs) under an ultra high-vacuum pressure of 10-7 Pa for the purpose of achieving nitrogen doping in nanotubes. The incident angle of the ion beam was normal to the target nanotube, and the ion beam energy was 30 eV, which was close to the displacement energy of graphite. The dependence of the structure of SWCNTs on the ion dose was investigated. The ion dose ranged from 2.8×1014 to 2.2×1016 ions/cm2. The nitrogen ions are incorporated into graphite sheets of SWCNTs after irradiation at 2.8×1014 ions/cm2. The graphite structure is distorted and many defects are induced in the nanotube by the nitrogen incorporation. The structure is changed to amorphous after irradiation at 2.2×1016 ions/cm2. The nitrogen ions with the ion energy of 25 eV are irradiated to the field effect transistor device with the nanotube channel. The n-type characteristic appears upon ion irradiation, and the device exhibits ambipolar behavior.
Local Surface Potential Measurements of Carbon Nanotube FETs by Kelvin Probe Force Microscopy
Authors: Miyato Yuji , Kobayashi Kei , Matsushige Kazumi , Yamada Hirofumi
Published: July 2005

We fabricated carbon nanotube FETs (CN-FETs) by dielectrophoresis method. Two types of CN-FETs with either Au or Ti electrodes were prepared for the study of electrical junctions between metal electrodes and nanotubes. Local surface potential of the CN-FETs in working condition was mapped by Kelvin probe force microscopy (KFM). A large surface potential drop occurred at the interface between the Ti electrodes and the bundle of SWNTs, and this potential drop was changed by the applied gate voltage. This result suggests that the Schottky barrier at the drain edge is modulated by the gate bias.
Effect of Morphology on Field Emission Properties of Carbon Nanocoils and Carbon Nanotubes
Authors: Pan Lujun , Konishi Yasumoto , Tanaka Hiroyoshi , Suekane Osamu , Nosaka Toshikazu , Nakayama Yoshikazu
Published: July 2005

Helical carbon nanocoils exhibit excellent field emission properties, and are thus expected to be applicable as electron emitters in field emission displays. We have synthesized carbon nanocoils with different diameters by the catalytic thermal decomposition of acetylene using iron–indium–tin–oxide catalysts. It is found that the turn-on voltage is decreased by decreasing the average diameter of the grown carbon nanocoils. The turn-on voltage of as low as 30 V at the electrode gap of 130 µm was achieved when the coil diameter is decreased to 60 nm. The calculation for the concentration of the electric field on the coil surface has been performed using a finite element method. It is found that the strength of the electric field around the top ring of a coil is increased with the decrease of the tubular diameter of the coil and has a similar value as that at the tip of a carbon nanotube, suggesting that the efficiency of the field emission from nanocoils would be higher than that from nanotubes. These results can explain the high stability of field emission from carbon nanocoils.
Coulomb and Phonon Scattering Processes in Metal–Oxide–Semiconductor Inversion Layers: Beyond Matthiessen's Rule
Authors: Ishihara Takamitsu , Sano Nobuyuki
Published: July 2005

The separability of Coulomb and phonon scattering processes in inversion layers of metal–oxide–semiconductor field-effect-transistors (MOSFETs) was studied. The effect of finite collisional duration due to phonon scattering was considered in the evaluation of Coulomb scattering-limited mobility to investigate the relationship between the separability of Coulomb and phonon scattering processes and the long-range nature of Coulomb potential. It was found that the condition under which Coulomb scattering is separated from phonon scattering is determined by the relationship between the screening length due to free carriers in the inversion layers and the phonon mean free path. It was also found that the long-range component of the Coulomb potential is effectively cut off by phonon scattering.
Enhancing P-type Conductivity in Mg-doped GaN Using Oxygen and Nitrogen Plasma Activation
Authors: Hwang Jun-Dar , Lai Zhca-Yong , Wu Ching-Yuan , Chang Shoou-Jinn
Published: July 2005

Plasma-assisted activation (PAA) has been studied in detail to enhance the electrical and optical performance of Mg-doped GaN surface layers. The plasma-assisted activation technique was carried out in a plasma-enhanced chemical vapor deposition (PECVD) system with various ratios of N2 to O2 environments at 400 and 640°C. Plasma energy in our studies was used to decompose the Mg–H complex, and H atoms were absorbed by O2 gas to form H2O. On the other hand, N2 gas was introduced to compensate for nitrogen vacancies. A hole concentration higher than 2.44×1017 cm-3 was determined near the GaN surface and a specific contact resistance of 8.6×10-5 Ω·cm2 was achieved, this is better than that of conventional 700°C thermal annealing. A 400°C PAA sample exhibits the same specific contact resistance of 2.1×10-4 Ω·cm2 as that of a 700°C thermal annealed sample. Moreover, room temperature-photoluminescence (RT-PL) showed that the 400 and 640°C PAA samples had a stronger intensity compared to that of conventional samples. Peak intensities of RT-PL were centered at 438 nm for all samples. The best electrical and optical properties appeared at a N2 to O2 ratio of 5:3 in our study. A possible explanation is that a self-compensation mechanism is dominant in our plasma-assisted activation.
Generation of Optical Vortices by Converting Elegant Hermite Gaussian Beams
Authors: Okamoto Megumi , Sasada Hiroyuki
Published: July 2005

We have derived that an optical vortex of charge l can be generated in an arbitrary position over the transverse cross section of the light beam by converting a tailored elegant Hermite Gaussian beam of order l [J. Opt. Soc. Am. 63 (1973) 1093] using an astigmatic mode converter. We have indeed generated a quasi-elegant Hemite Gaussian beam of order 1 by superposing two Gaussian beams copropagating with a spatial separation, and converted it into a vortex beam. The vortex moves by varying the relative amplitude and phase of the Gaussian beams, which agrees well with the theoretical predictions.
Dislocation-Free InxGa1-xP1-yNy/GaP1-zNz Double-Heterostructure Light Emitting Diode on Si Substrate
Authors: Moon Soo Young , Yonezu Hiroo , Furukawa Yuzo , Kim Sung Man , Morita Yoshiro , Wakahara Akihiro
Published: July 2005

An In
x
Ga1-x
P1-y
N
y
/GaP0.982N0.018 double-heterostructure (DH) light-emitting diode (LED) was fabricated on a Si substrate using solid-source molecular beam epitaxy (SS-MBE) with an rf plasma nitrogen source. It was confirmed by high resolution X-ray diffraction (XRD) analysis that the structure of the LED had a small lattice mismatch to the Si substrate. A cross-sectional image obtained by transmission electron microscopy (TEM) revealed that there were no threading dislocations in the epitaxial layers. The electroluminescence (EL) properties were also evaluated. The EL peak wavelength of an In
x
Ga1-x
P1-y
N
y
/GaP0.982N0.018 DH LED was 665 nm at room temperature when the indium (x) and nitrogen contents (y) were 4.0% and 3.8%, respectively. A relatively wide EL spectrum was obtained. These specific features of EL spectra could be attributed to a long band tail formed by nitrogen in the In
x
Ga1-x
P1-y
N
y
active layer.
High-Peak-Power Ultrashort Pulse Generation Using All-Fiber Chirped Pulse Amplification System with Small Core Multimode Fiber
Authors: Takayanagi Jun , Nishizawa Norihiko , Nagai Hiroyuki , Yoshida Makoto , Goto Toshio
Published: July 2005

We present an all-fiber chirped pulse amplification system based on a normally dispersive single mode Er-doped fiber and a multimode fiber of 25 µm core diameter. The 260 fs sech2 transform-limited pulses generated in a passively mode-locked Er-doped fiber laser are stretched to 1 ps and amplified in an Er-doped fiber amplifier. Then the subsequent multimode fiber in which the pulses propagate only in the fundamental mode compresses the pulses to 80 fs. The pulse compression using the conventional multimode fiber as a large-core single-mode fiber is demonstrated for the first time. The peak power of the output pulses is increased to 44 kW.
Holographic Recording in Photoreactive Monomer/Polymer Composites
Authors: Ono Hiroshi , Tamoto Takashi , Emoto Akira , Kawatsuki Nobuhiro
Published: July 2005

We present the results of our experimental studies aimed at quantifying holographic recordings in photoreactive monomer/polymer composites. In addition to surface-relief gratings, index modulation gratings also appear during holographic recording, and the resulting dual gratings are characterized using the diffraction theory. The experimental results including the effects of the annealing temperature on the grating characteristics are explained on the basis of molecular migration.
Luminescence of Pulsed Laser Deposited Y2SiO5:Tb3+ Thin Film Phosphors on Flat and Corrugated Quartz Glass Substrates
Authors: Sohn Kee-Sun , Park Duk Hyun , Yoo Jeong Gon , Kim Ji Sik
Published: July 2005

Y2SiO5:Tb3+ thin film phosphors were deposited on flat and corrugated quartz glass plates by pulsed laser deposition (PLD) techniques in an attempt to use them in field emission displays (FED). As a preliminary step, cathodoluminescence and photoluminescence was monitored as a function of several processing parameters such as the oxygen partial pressure, the deposition time and the annealing conditions for films deposited on flat quartz glass plates. By adopting optimum processing conditions taken from the preliminary optimization process based on flat quartz glass substrates, Y2SiO5:Tb3+ thin films were also deposited on substrates on which a two-dimensional photonic crystal layer (2-D PCL) was developed, i.e., corrugated substrates. It was found that the Y2SiO5:Tb3+ thin film phosphor developed by PLD represents a promising candidate for use in field emission displays, and that the use of corrugated substrates enhanced the light extraction efficiency by a factor of 1.72.
Optical Head with Two Wavelengths in Single Path Using Holographic Optical Element
Authors: Shih Hsi-Fu
Published: July 2005

In this paper, we review a number of digital versatile disk (DVD) pickup designs and present a new structure with two wavelengths using a 780 nm integrated optical unit (IOU) and a 650 nm laser diode (LD) in a single optical path. The 780 nm IOU acts as a sensor for the 650 nm system. Two returned beams of different wavelengths are diffracted by a holographic optical element (HOE) to the same detector. With this construction, the number of components is reduced and alignment is effectively simplified.
Influences of Residual Argon Gas and Thermal Annealing on Ta2O5 Thin Films
Authors: Liu Wen-Jen , Chien Chia-Hung
Published: July 2005

Tantalum pentaoxide (Ta2O5) optical thin films were deposited on a quartz glass substrate by argon-ion-beam-assisted deposition (IBAD), and the influences of the residual argon gas and thermal annealing processes on the optical properties, stress and compositional and microstructural evolutions of Ta2O5 thin films were investigated in this study. Adopting oxygen thermal annealing treatment at the temperature of 425°C, the thin films not only reduced the residual argon gas and the surface roughness, but also provided sufficient stoichiometric ratio. Simultaneously, microstructural examination indicated few nano crystallized structures and voids existed in Ta2O5 thin films, and possessed a reasonable refractive index and a low extinction coefficient. We also suggested the use of IBAD system using a film compositional gas ion beam in replacing the argon ion beam for assisted deposition of optical films.
Comparison between Electron Beam and Near-Field Light on the Luminescence Excitation of GaAs/AlGaAs Semiconductor Quantum Dots
Authors: Mitsui Tadashi , Sekiguchi Takashi , Fujita Daisuke , Koguchi Nobuyuki
Published: July 2005

To precisely estimate electron beam excitation intensity and to understand exactly the electron beam excitation process in a semiconductor, we observed and compared the luminescence properties of GaAs/Al0.3Ga0.7As self-assembled quantum dots (QDs) by the cathodoluminescence (CL) and near-field scanning optical microscopy (NSOM) techniques. The actual excitation densities measured by the CL and NSOM techniques are nearly equal at the dose rates considered, except for a low dose rate in which the actual excitation density measured by the CL technique is slightly larger than that measured by NSOM technique. However, the difference between these excitation densities is extremely small relative to the expected value when electron–hole (e–h) pairs are temporarily densified as a result of a cascade process. Therefore, the spatially inhomogeneous distribution of e–h pairs in the generation and diffusion regions is considered to be the main cause of the small difference in excitation density in such a case.
Generation Behaviors of Optical Anisotropy Caused by Silver Nanoparticles Precipitated in Uniaxially Drawn Polyimide Films
Authors: Matsuda Sho-ichi , Ando Shinji
Published: July 2005

The optical anisotropy generated during thermal curing and simultaneous uniaxial drawing of poly(amic acid) (PAA) films dissolving silver nitrate was investigated. The PAA was converted to polyimide (PI) during thermal curing, and silver nanoparticles were precipitated in the oriented PI films. The anisotropy in optical transmittance, i.e., the polarization characteristic, of the films strongly depended on the holding time at the final curing temperature, and a large anisotropy in transmittance with a wide wavelength region (wide-range optical anisotropy) was observed only for a film cured for the optimal holding time. During heating at the final curing temperature, silver nanoparticles were anisotropically grown and aggregated along the drawing direction, generating a significant optical anisotropy. However, additional heating induces isotropic growth, aggregation, and fusion of silver nanoparticles, resulting in the reduction in anisotropy. A numerical analysis based on the Mie theory revealed that the wide-range optical anisotropy can be generated by the anisotropies in shape and the preferential aggregation and arrays of silver nanoparticles in the drawing direction as well as the large birefringence of PI films as dielectric media.
Linear Gray Level Adjustment for Ferroelectric Liquid Crystal Cell
Authors: Tzeng Shwu-Yun Tsay , Huang R. H. , Wu Jin-Jei , Wu Shune-Long
Published: July 2005

Thresholdless, hysteresis-free, “V-shaped” electrooptical switching in surface-stabilized ferroelectric liquid crystals, observed usually with a triangular voltage waveform was achieved using a combination of external capacitors and resistors at a driving characteristic frequency. The relationship between the external capacitors and the profile of the V-shape is discussed in terms of a voltage divider across the ferroelectric liquid crystal cell. An optimized circuit is demonstrated to alter the profile of the V-shaped electrooptical transmittance and raise the characteristic frequency so that the linear gray levels can be modulated in a wide range of applied voltage and operated at a driving frequency of 100 Hz.
Influence of Sr2+ Doping, Temperature and Frequency on Dielectric Constant, Dielectric Loss Factor and AC Conductivity of Ammonium Zinc Chloride Crystal
Authors: Gaffar Mohamed A. , El-Fadl Abdel Aziz Abu , Anooz Sand Bin
Published: July 2005

Ammonium zinc chloride (AZC) crystals doped with different strontium concentrations have been grown by the slow evaporation technique. Detailed temperature (300–450 K) and frequency (400–105 Hz) study of the dielectric constant (ε), loss factor (tan
δ) and the ac conductivity (σac) of the grown crystals has been carried out. Along the polar b-axis ε increased gradually with increasing temperature showing clear peaks at the phase transitions. Thermal recycling decreased ε, inhibited the peak height, decreased its broadening but without shifting the transition points. However, Sr2+-doping causes a shift of the transition temperature towards lower values and a decrease in the ε-peak broadening and height. Relation between 1/ε and T in the vicinity of the commensurate (C) to incommensurate (IC) phase transition revealed the validity of an equation similar to the Curie–Weiss law. Doping with Sr2+ in different concentrations causes a systematic change in the equation constants. Soliton pinning increased in the presence of Sr2+ leading to residual discommensurations (DC's) in the C-phase. The dielectric constant decreased continually with increasing frequency for the undoped and Sr2+-doped samples. Doping with 0.144 wt% Sr2+ destroyed 25% of the C-phase, which means the possibility of having AZC crystal with reduced C-phase. σac increased with increasing frequency following a power law of the form σ=σo
f
s. Conduction by hopping was found to be dominant in all phases of AZC and after doping with Sr2+ in different concentrations. Mechanism for DC formation and annihilation was also discussed.
Low-Temperature Deposition of Polycrystalline Titanium Oxide Thin Film on Si Substrate Using Supercritical Carbon Dioxide Fluid
Authors: Uchida Hiroshi , Otsubo Akiko , Itatani Kiyoshi , Koda Seiichiro
Published: July 2005

A novel technique for the deposition of oxide thin films using supercritical carbon dioxide (CO2) fluid was proposed for the large-scale circuit integration on a silicon (Si) substrate at a low temperature. Thin films of titanium oxide (TiO2) as a model material were fabricated from organometallic Ti(Oi-Pr)2(dpm)2 source on (100)Si substrates in supercritical CO2 fluid. The film deposition was accomplished using a flow-type supercritical fluid deposition apparatus designed on the basis of metal-organic chemical vapor deposition (MOCVD) systems. Flat films were fabricated on (100)Si substrates at a faster source delivery (fluid flow rate: 2.0–10.0 cm3/min), while granular deposits owing to homogeneous nucleation in the bulk supercritical CO2 fluid appeared on the substrates at a slower source delivery (fluid flow rate: 1.0 cm3/min). The amount of TiO2 deposited decreased gradually with increasing the temperature of CO2 fluid, which would be related to the change in the density of CO2 fluid. The crystalline TiO2 film was deposited on the (100)Si substrate at a substrate temperature of 80–120°C and fluid temperature/pressure of 40°C/8.0 MPa, at which the decomposition of organometallic Ti(Oi-Pr)2(dpm)2 source was accomplished. These results indicated that the supercritical CO2 deposition technique is suitable for the large-scale circuit integration on Si substrates.
Preparation and Characterization of Organic Thin Films on Substrates and Self-Supporting Films by RF Sputtering of Polyimide Films
Authors: Ren Yue , Baba Mamoru , Oishi Yoshiyuki
Published: July 2005

Organic thin films were prepared on substrates by a radio-frequency sputtering method using a polyimide film (Upilex-S) target, and some of them were successfully obtained as self-supporting thin films. It was found that these films were insoluble in an organic solvent, indicating that they were polymeric. The spectra of Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD) and optical absorption showed that the deposited films were amorphous but polyimide-like. The high durability of the films against heat and wear was also evaluated. Results suggested that these polymer-like films may be used as practical film materials for organic or hybrid electronic devices.
Determination of Nonlinear Resonance Parameters in Electron Storage Rings
Authors: Miyajima Tsukasa , Kobayashi Yukinori
Published: July 2005

The transverse betatron motions on and around the fourth- and third-order nonlinear parametric resonances of an electron storage ring at the Photon Factory were studied using a phase-space monitor system. The resonance parameters, consisting of a detuning parameter and a resonance strength, were determined through experiments as functions of a nonlinear magnetic field. In the experiments, among the nonlinear magnetic fields, only the octupole field strength was changed. As a result of the experiments, the detuning parameters were found to be linear functions of the octupole field strength for both resonances. Based on these detuning parameters, it was determined that the resonance strength of the fourth-order resonance, 4ν
y
=17, is a linear function, and the resonance strength of the third-order resonance, 3ν
y
=13, is a fourth-order polynomial. In addition, the origins of the resonances were deduced from the experimental results.
Technique for Preparing Defect-free Spray Coated Resist Film on Three-Dimensional Micro-Electromechanical Systems
Authors: Singh Vijay Kumar , Sasaki Minoru , Song Jong Hyeong , Hane Kazuhiro
Published: July 2005

Microstructures with high aspect ratio have been fabricated in micro-electromechanical systems (MEMS). The fundamental structures are relatively simple, since the fabrication process relies on planar photolithography. Spray coating of the photoresist is expected to become a new photolithography method for realizing real three-dimensional microstructures. However, as-deposited resist films have pinholes, particularly in the deep regions. This poses limitations to photolithography. Therefore, a new technique is introduced for removing pinholes by means of the migration of resist material on sample surfaces. Thinner vapor assists the migration of resist, generating the driving force of surface tension. The resist material accumulates in the regions with high pinhole density. Consequently, the pinholes are filled efficiently. This effect comes at the cost of thinning the resist coverage in convex corners of a cavity. The removal of pinholes and the decrease of resist film coverage at convex corners may be balanced.
The Features of DVD-RAM Stamper Studies via Laser Energy Adjustment
Authors: Wang Ming-Wen , Teng Kou-Hsin
Published: July 2005

To enhance the validity of signal and optical reflectivity on DVD-RAM, in this study we performed variable laser recording power experiments, and established the theoretical model for simulating the features that of the groove/land and header on a DVD-RAM stamper. This is the first work showing the features of the groove/land and header on a DVD-RAM stamper, that is, the geometry of a stamper, are mainly governed by laser recording power, recording speed, wavelength, photoresist film thickness, and photoresist properties. At a constant photoresist thickness, a difference in laser recording power is caused by the radius of the embossed area. The theoretically predicted results agree with the measurements of the features of the groove/land and header on a DVD-RAM stamper. At a fixed recording speed, recording power, when increased, can significantly increase the width of the groove/land and the length of the header.
Three-Modal Size Distribution of Self-assembled InAs Quantum Dots
Authors: Lee Chang-Myung , Choi Suk-Ho , Noh Sam-Kyu , Lee Joo In , Kim Jin-Soo , Han Il-Ki
Published: July 2005

We report a photoluminescence study of self-assembled InAs/GaAs quantum dots (QDs) in which excitation intensity and temperature were varied. The power-dependent photoluminescence spectra reveal three peaks associated with the ground-state transitions of QDs in three branches of different sizes. Thermal carrier redistribution among the three branches of QDs is observed and investigated in terms of the temperature dependence of their relative photoluminescence peak energy, linewidth and intensity. It is found that the optical properties are rather different and unexpected among the three branches of QDs with increasing temperature, which originate from the thermally activated carrier transfer from QDs in the smaller size group to those in the larger size group. We propose a model in which carrier transfer between QDs is facilitated by the wetting layer and which explains the unusual photoluminescence behavior.
Non Contact Atomic Force Microscope Electrical Manipulation of Carbon Nanotubes and Its Application to Fabrication of a Room Temperature Operating Single Electron Transistor
Authors: Hyon Chan Kyeong , Kojima Atsuhiko , Kamimura Takafumi , Maeda Masatoshi , Matsumoto Kazuhiko
Published: July 2005

We demonstrate that a non-contact atomic force microscope (AFM) can be used to cut and nick carbon nanotubes (CNTs) by applying negative bias to the metal-coated AFM tip when it is very close to the CNT. The voltage needed to cut the CNT completely varied from -8 to -15 V, while the nicking voltage ranged from -6 to -8 V. This technique was applied to make a nanoscale single CNT device. Unwanted CNTs were cut first to leave only one CNT connecting the electrodes. Finally, tunneling barriers defined by two small nicks were created on the CNT to fabricate a single electron transistor. The final device shows Coulomb oscillation and Coulomb diamond characteristics at room temperature.
Fabrication and Optical Properties of Low-Emissivity Coatings of Indium Tin Oxide or AlSiN and Ag-Alloy Multilayer Films on Glass
Authors: Chiba Kiyoshi , Kageyama Takashi , Iwata Tomoyuki , Fujimori Naoki , Oda Hironori
Published: July 2005

Transparent low-emissivity coatings comprising indium tin oxide (ITO) or AlSiN and Ag-alloy multilayer films were investigated. All films were prepared by dc magnetron sputtering. In ITO/AgCu-alloy/ITO/AgCu-alloy/ITO multilayer films, the spectral selectivity is influenced by the oxygen content of the gas mixture of Ar and O2 during ITO deposition. The visible light transmission (T
vis) of 76.2% and the shading coefficient of 0.51 were obtained for the multilayer films prepared with 1.76 vol.% O2 in the sputtering atmosphere. In AlSiN/AgCu-alloy/AlSiN/AgCu-alloy/AlSiN multilayer films, prepared by reactive sputtering of an AlSi-alloy target in the gas mixture of Ar and N2, the transmittance increased with increasing sputtering power during AlSiN deposition. The results of an Auger electron spectroscopy study suggest that this effect is likely attributed to the formation of AlSiON in the films at low power due to the influence of a residual gas. The emittance from 0.20 to 0.05 at 297 K was obtained for the AlSiN multilayer films with an AgCu-alloy layer of thickness in the range of 6 to 15 nm thick.
Reduced Hot-Carrier Induced Degradation of NMOS I/O Transistors with Sub-micron Source-Drain Diffusion Length for 0.11 µm Dual Gate Oxide CMOS Technology
Authors: See Kwang-Seng , Lau Wai-Shing , Toh Suey-Li , Liao Hong , Lee Jae Gon , Li Kun , Quek Elgin Kiok-Boone , Tee Kheng-Chok , Chan Lap-Hung
Published: July 2005

The effect of reduced source-drain diffusion length (Lov) on hot-carrier induced degradation of NMOS I/O transistors using 0.11 µm dual gate oxide (DGO) complementary metal oxide semiconductor (CMOS) technology will be reported. An understanding of hot-carrier induced degradation would be very important for modern DGO CMOS integrated circuits. And since hot carrier degradation is usually more serious in n-channel metal oxide semiconductor (NMOS) transistors, we will focus our discussion on the effect ofLovreduction on hot-carrier induced degradation in n-channel thick gate oxide I/O MOS transistors. It is discovered that asLovdecreases, which then gives rise to compressive strain in the channel region of the transistor, hot-carrier induced degradation in NMOS I/O transistors is reduced. Direct-current current-voltage (DCIV) spectrum suggests that no additional interface traps (ΔNit) generation or charge trapping was created when using shorterLovs.
Design and Analysis of On-Chip Tapered Transformers for Silicon Radio-Frequency Integrated Circuits
Authors: Cho Ming-Hsiang , Chen Kun-Ming , Huang Guo-Wei , Chiu Chia-Sung
Published: July 2005

In this paper, a tapered transformer structure based on a layout optimization technique is proposed, for the first time, for the design of silicon-based radio-frequency integrated circuits (RF ICs). Compared with a standard transformer structure, the proposed one showed improved quality factor (Q), coupling coefficient (k), and transmission coefficient. A three-dimensional electromagnetic simulation was performed to investigate the current crowding effects and coupling mechanism in transformers. We also developed a frequency-independent equivalent-circuit model to capture the transmission characteristics of the transformers. Good agreement between the simulation and measurement results was demonstrated from 0.1 GHz to 8.5 GHz.
Dependence of Analog and Digital Performances on Mechanical Film Stress of ILD Layers in Nanoscale CMOSFETs
Authors: Ji Hee-Hwan , Park Sung-Hyung , Kim Yong-Goo , Wang Jin-Suk , Lee Hi-Deok , Baek Seong-Hak , Kim Kyoung-Cheol , Song Byeung-Soo , Bae Hui-Kyoung , Lee Heui-Seung , Kang Young-Seok , Kim Dae-Byung , Park Jin-Won
Published: July 2005

In this study, film-stress-induced device performance variation is characterized in terms of digital and analog performances. Interlayer dielectric (ILD) layers such as PECVD Si3N4 and LPCVD SiON with different stress-affected saturation currents and off-state leakage currents are investigated extensively. To further analyze stress effects, the film stress of PECVD Si3N4 is varied from compressive stress to tensile stress. It is shown that tensile stress improved NMOS performance through the decrease of interface state density (D
it) and the increase of carrier mobility. In the case of PMOS with highly tensile stress, the mobility is decreased due to the increase of D
it. The oxide fixed charge Q
f of PMOS is also reduced evidently by the tensile stress film.
Deep Sub-Micron Device and Analog Circuit Parameter Sensitivity to Process Variations with Halo Doping and Its Effect on Circuit Linearity
Authors: Narasimhulu K. , Rao V. Ramgopal
Published: July 2005

Single halo (SH) and double halo (DH) metal oxide semiconductor field effect transistors (MOSFETs) have been reported to exhibit excellent short channel performance in the sub 100 nm regime. In this work, the effect of process variations such as gate oxide thickness, implantation parameters, channel length and temperature are systematically investigated on the device and analog circuit performance for all these technologies. Our simulation results on differential amplifiers and current mirrors show that, for an identical V
t mismatch in conventional (CON), DH, and SH devices, SH MOSFETs show a lower variation in the circuit parameters. It is found that, for a specified circuit parameter variation, almost a 25% higher V
t mismatch is tolerable with SH technologies as compared to the CON technologies. We also report in this work that, better saturation characteristics observed with SH devices improve the linearity of amplifiers when compared with the CON and DH devices, biased at identical voltage gains. However, one needs to account for the increased body bias induced non-linearity with SH technologies as demonstrated using circuit simulations for source follower and simple sample and hold circuits.
Fully Silicided NiSi Gate Electrodes on HfSiON Gate Dielectrics for Low-Power Applications
Authors: Manabe Kenzo , Takahashi Kensuke , Ikarashi Taeko , Morioka Ayuka , Watanabe Heiji , Yoshihara Takuya , Tatsumi Toru
Published: July 2005

The fully silicided (FUSI)-nickel monosilicide (NiSi) metal gate electrode on the HfSiON gate dielectric has been investigated for low-power metal-oxide-semiconductor field effect transistors (MOSFETs). We found that the FUSI-NiSi electrode on the HfSiON dielectric has a work function of 4.55 eV, which improved the threshold voltage shift of PMOSFETs by 0.15 V compared with that of the poly-Si/HfSiON MOSFETs. At the same time, full silicidation eliminated the gate depletion and thereby we achieved the capacitance equivalent thickness at inversion of 2.1 nm and a five-order-of-magnitude reduction in the gate leakage current compared with the poly-Si/SiO2 devices. Moreover, we obtained an excellent carrier mobility for the FUSI-NiSi/HfSiON transistors (PMOS: 100%, NMOS: 90% compared with the poly-Si/SiO2 reference transistors). These results show that the FUSI-NiSi/HfSiON gate stack is a promising candidate for next-generation low-power MOSFETs.
Improvement of Contact Resistance between Ru Electrode and TiN Barrier in Ru/Crystalline-Ta2O5/Ru Capacitor for 50 nm Dynamic Random Access Memory
Authors: Lim HanJin , Chung Suk-Jin , Lee Kwang Hee , Lee Jinil , Kim Jin Yong , Yoo Cha-Young , Kim Sung-Tae , Chung U-In , Moon Joo-Tae
Published: July 2005

The contact resistance (R
C) between a Ru electrode and a TiN plug in a crystalline Ta2O5 capacitor using Ru electrodes was evaluated. The TiN plug was oxidized in TiO
x
to increase the R
C to failure. Two origins of oxygen are determined by Auger electron spectroscopy (AES) analysis, namely, the seed step of Ru deposition and the initial step of Ta2O5 deposition. During Ta2O5 crystallization annealing at 700°C, the oxygen molecules from Ru diffused into the TiN plug, forming TiO
x
. Ru films with Ti exhibited a decreased R
C below 1 kΩ/contact and an increased leakage current of a Ru/Ta2O5/Ru capacitor according to the applied voltage, compared with Ru films without Ti. The atomic layer deposition (ALD) Ru process including a H2 plasma treatment decreased the R
C to 2.5 kΩ/contact on average. The fabrication scheme for the crystalline Ta2O5 capacitor using the Ru electrode for reducing RC between the Ru storage node and the TiN plug was proposed.
Formation of Nickel Self-Aligned Silicide by Using Cyclic Deposition Method
Authors: Terashima Koichi , Miura Yoshinao , Ikarashi Nobuyuki , Oshida Makiko , Manabe Kenzo , Yoshihara Takuya , Tanaka Masayasu , Wakabayashi Hitoshi
Published: July 2005

We have developed a novel nickel self-aligned silicide (salicide) process for future scaled metal-oxide-semiconductor field-effect transistors (MOS-FETs). Ni/Si multi-layered structures were fabricated by the cyclic deposition of Ni and Si. Nickel monosilicide (NiSi) films with a low resistivity, a uniform thickness, and a good morphology were obtained on Si(100) substrates after annealing at 400–600°C. Nickel silicide formed on SiO2 can be removed by wet etching if the total atomic number ratio of Ni to Si in the deposited layers is larger than unity. This shows that the nickel salicide process is possible by our method. We have fabricated MOS-FET structures with NiSi and confirmed that the consumption of Si in the substrate is much lower in our method than in the conventional method.
Suppression of Gate Depletion in p+-Polysilicon-Gated Sub-40 nm pMOSFETs by Laser Thermal Processing
Authors: Yamamoto Tomonari , Kubo Tomohiro , Okabe Ken-ichi , Sukegawa Takae , Wang Yun , Lin Tengshing , Talwar Somit , Kase Masataka
Published: July 2005

Laser thermal processing (LTP) was investigated as a gate pre-annealing technique and its advantages over rapid thermal annealing (RTA) with regard to both gate activation and suppression of boron penetration were confirmed by evaluating the electrical characteristics of sub-40 nm p-metal oxide semiconductor field effect transistors (pMOSFETs). Laser annealing transformed amorphous Si in which high doses of boron were implanted into poly-Si with highly activated boron profiles down to the gate/gate oxide interface. By suppressing gate depletion with suppressing boron penetration, LTP results in an on-current at I
off=70 [nA/µm] that is 4% greater than that in a device fabricated using conventional RTA. The off-state I
g current that flows mainly from the p+ poly-Si gate to the drain overlap region is smaller in devices fabricated using LTP because the reduced roughness of the poly-Si gate/gate oxide interface in these devices reduces the local electric field enhancement.
Electron Transport Model for Strained Silicon-Carbon Alloy
Authors: Chang Shu-Tong , Lin Chung-Yi
Published: July 2005

Electron mobility in strained Si1-xCx layers grown on a Si substrate is calculated as functions of carbon content, alloy scattering potential, and doping concentration at 300 K. Alloy scattering potential affects low-field mobility significantly. For a low alloy scattering potential (<0.6 eV), the strain effect is fully beneficial for in-plane transport in undoped Si1-xCx. For a high alloy scattering potential (>1 eV), the effects of alloy scattering override the strain-induced reduction in effective mass in undoped strained Si1-xCx. The electron transport model is validated by experimental data. In the doped strained Si1-xCx, both results from our model and experiments on electron transport indicate that the effects of alloy and impurity scattering prevail over the expected gain due to strain.