bluuebunny/crossref_metadata_2025 huggingface dataset:
Planar Multipass Ring Laser Cavity
Authors: Yi Jui-Yun , Huang Sheng-Lung
Published: July 2005

A planar multipass ring laser is demonstrated using a pair of spherical mirrors. The reentrant conditions of ring cavities are derived. The stabilities of laser cavities are also analyzed. A 3 atm.% Nd-doped YAG crystal of 1 mm thickness was used as the gain medium. The laser output is polarized even for cubic gain media. The polarization ellipticity is increased by a factor of 23.8 in a planar ring cavity compared with that in a nonplanar ring cavity.
Influence of Structure and C60 Composition on Properties of Blends and Bilayers of Organic Donor-Acceptor Polymer/C60 Photovoltaic Devices
Authors: Hayashi Yasuhiko , Yamada Ichiko , Takagi Shigeru , Takasu Akinori , Soga Tetsuo , Jimbo Takashi
Published: July 2005

We have fabricated both blended and bilayered organic photovoltaic cells (OPVCs) using C60 and poly[2-methoxy-5-(2'-ethylhexoxy)-1,4-phenylenevinylene] (MEH-PPV). Improvements in photovoltaic performance are seen in blended OPVCs when the C60 concentration is increased. It is believed that the optimized surface morphology of MEH-PPV/C60 composite and improved donor-acceptor proximity, leading to electron conductivity, contribute to the increase in power conversion efficiency E
ff. Two broad peaks were observed in the spectral response of the blended OPVCs, with maximum peaks at ∼490 nm (=I
BL1) and ∼350 nm (=I
BL2). The intensity ratio of I
BL1 to I
BL2 (I
BL1/I
BL2) decreases with an increase in the C60 concentration. Also, I
BL1 is blue-shifted by 25–30 nm with an increase in the C60 concentration. The significant improvement in the performance was observed in the bilayered OPVCs on the thermally induced interdiffusion of C60 into the MEH-PPV network, leading to the existence of C60 molecules within the exciton diffusion radius of the MEH-PPV network. The spectral response of bilayered OPVCs reveals two peaks at 535 nm and 345 nm. The former peak is red-shifted by 45 nm compared to that in blended OPVCs. We also investigate the effect of top electrode materials on the photovoltaic performances. To the best of our knowledge, we have obtained the best performances of blended and bilayered OPVCs fabricated with the Al and Mg electrodes, respectively. In both OPVC structures, the nanoscale composition control of the two materials, the choice of metal electrode, and the device processing techniques all play an important role in determining or enhancing the solar cell performance.
Impurity Levels in Layered Semiconductor GaS Doped with Cu
Authors: Shigetomi Shigeru , Sakai Kentaro , Ikari Tetsuo
Published: July 2005

The radiative recombination mechanisms of Cu-doped GaS have been investigated on the basis of photoluminescence (PL) measurements. The PL spectrum (at 77 K) related to the impurity level is dominated by a newly observed emission band at 1.97 eV. The temperature dependence of the full width at half-maximum and the shape of the PL spectrum are characterized by the recombination mechanism of the configurational coordinate model. It is found that the 1.97 eV emission band is related to the complex of vacancies and Cu atoms. In addition, it was found from optical absorption measurements that the acceptor level at approximately 0.4 eV above the valence band is formed by doping of Cu atoms.
Effects of Y2O3 on Temperature Stability of Acceptor-Doped BaTiO3
Authors: Song Young Hoon , Hwang Jin Hyun , Han Young Ho
Published: July 2005

Effects of Y2O3 on the temperature stability of acceptor-doped BaTiO3 dielectrics were studied. The sample doped with 1 mol% Y2O3 exhibited the highest dielectric constant. A substantial reduction in grain size was observed in the specimen with 1 mol% Y2O3 (∼0.6 µm), compared with the undoped specimen (∼1.5 µm). Each specimen with greater than 1 mol% Y2O3 showed a slight difference in grain size, compared with 1 mol% Y2O3. As the Y2O3 content was increased, the Curie point progressively moved to higher temperatures. The addition of Y2O3 improved the temperature dependence of the dielectric constants of the acceptor doped BaTiO3–Y2O3 system over the entire temperature range studied (-55–150°C) and the temperature coefficient of capacitance curves satisfied the X8R requirements above 3 mol% Y2O3.
Effect of Stacking Layers on the Microwave Dielectric Properties of (Li0.5Sm0.5)TiO3/CaTiO3 Thin Films
Authors: Lee Byoung Duk , Lee Hong Ryul , Yoon Ki Hyun , Kang Dong Heon
Published: July 2005

Effect of stacking layers on the microwave dielectric properties of the (Li0.5Sm0.5)TiO3/CaTiO3 (LSTO/CTO) thin films prepared by the metalorganic solution deposition technique (MOSD) was investigated. The dielectric constant (K), dielectric loss (tan
δ) and temperature coefficient of dielectric constant (TCK) of CaTiO3 films measured at 6 GHz were 160, 0.003 and -1340 ppm/°C, respectively. In contrast, the (Li0.5Sm0.5)TiO3 films showed K of 35, tan
δ of 0.001 and TCK of +320 ppm/°C. As the thickness of CTO layer in the LSTO/CTO films increased, K increased and TCK changed from positive values to negative values by dielectric mixing rule. Especially, LSTO(200 nm)/CTO(200 nm) films exhibited TCK of +10 ppm/°C, indicating temperature stability. The tan
δ of LSTO/CTO films increased with increasing the thickness of CTO layer. This result was attributed to the fact that the stresses were induced by the higher thermal-expansion coefficient of CTO than that of LSTO. Also, as compared with LSTO(200 nm)/CTO(200 nm) film, the K and TCK of LSTO(100 nm)/CTO(200 nm)/LSTO(100 nm) film were not changed, but the dielectric loss increased. This result indicated that the dielectric loss was affected by the number of interfaces between CTO and LSTO layers.
Detection of Continuous Sm C*–Sm A Phase Transition in Electroclinic Liquid Crystals by Dielectric Method
Authors: Thakur Anil K. , Biradar Ashok M. , Singh Surinder P. , Sharma Deepak K. , Bawa Sukhwant S.
Published: July 2005

The dielectric relaxation processes near the transition temperature (T
c) of Sm C*–Sm A phase transition in an electroclinic liquid crystal have been investigated in a homogeneously aligned cell of 2.5 µm thickness in the frequency range of 50 Hz to 10 MHz. No abrupt change in phase during the Sm C*–Sm A phase transition has been detected by the dielectic method; therefore no soft mode contribution to the dielectric permittivity near T
c in the Sm C* phase has been found. It has also been observed that the dielectric strength (Δε) near the transition temperature is very high. These two unusual behaviours of electroclinic liquid crystal material have been analyzed by means of theoretical calculations, taking into account the effect of the electric field in generalized Landau-type free energy densities (ΔF). The experimental results in this study agree well with theoretical predictions.
Synthesis of Y(P,V)O4:Eu3+ Red Phosphor by Spray Pyrolysis without Postheating
Authors: Shimomura Yasuo , Kurushima Tomoyuki , Olivia Risa , Kijima Naoto
Published: July 2005

We synthesized europium-activated yttrium phosphovanadate (Y(P,V)O4:Eu3+) red phosphor, which is expected to be applicable in plasma display panels, by spray pyrolysis. The effect of pyrolysis temperature on luminescence characteristics was clarified and the mechanism of this effect is discussed. A precursor solution containing sodium, which would act as a flux, was used in the first experiments. The obtained phosphor showed high luminance under UV excitation but the luminance under vacuum UV (VUV) excitation was very low. The luminance of the phosphor was improved using precursors without sodium. The phosphor synthesized at 1600°C had the same luminance as that synthesized by solid-state reaction under UV excitation. Its luminance under VUV excitation was 93% of the solid-state phosphor. Sodium ions accelerated the crystal growth of phosphor particles, but they decreased the luminance of the phosphor, particularly under VUV excitation.
Electron Emission from Indium Tin Oxide/Silicon Monoxide/Gold Structure
Authors: Mourad Magdy Hussein , Totsu Kentaro , Kumagai Shinya , Samukawa Seiji , Esashi Masayoshi
Published: July 2005

A field-emission cathode based upon the increase in the number of allowed conductive energy states in the silicon monoxide (SiO) forbidden gap as well as the increase in the number of interfacial states by indium tin oxide (ITO) ion diffusion into the SiO layer and silicon ion diffusion into the ITO layer while deposition is verified experimentally for the first time. This relatively low-cost electron emitter consists of an ITO layer sputtered on Pyrex glass, followed by an E-beam-evaporated silicon monoxide layer. The emitting layer is gold, deposited on the top of the silicon monoxide. Using ITO as a ground plate, instead of other previously published materials, a significant electron emission enhancement occurred.
Scanning-Tunneling Microscopy Observation of Monomethylsilane Adsorption on Si(111)-7×7
Authors: Sakai Masashi , Suemitsu Maki , Narita Yuzuru
Published: July 2005

Using scanning-tunneling microscopy, the initial adsorption of monomethylsilane (MMS) on the Si(111)-7×7 surface at room temperature is investigated. From results of the statistical analysis of the number of reacted sites, it is likely that MMS reacts with the surface using rest-atom/adatom pairs.
Rail Gap Switch Using Porous Metal as Electrode
Authors: Furuya Seizo , Tanaka Hiroaki , Takano Saburo , Irisawa Juichi
Published: July 2005

For multichannel gap switches, the shorter the formative and statistical time lags of each gap, the larger the number of arc channels. As we examined the breakdown characteristics of a sphere/plane gap using a mirror-finished brass plate and a porous metal as plane electrodes, we confirmed that formative and statistical time lags decrease when porous metals are used as a discharge electrode, so we expect that the number of arc channels increases when porous metal is used as one of the electrodes of a rail gap. We compared experimental results to confirm this. As a result, in the case of a gap length of 1 mm, the number of arc channels increases when porous metal is used as an electrode.
Post-treatment Method of Producing Ordered Array of Anodic Aluminum Oxide Using General Purity Commercial (99.7%) Aluminum
Authors: Chen Chien Chon , Chen Jung Husan , Chao Chuen Guang
Published: July 2005

A new and simplified method of fabricating anodic aluminum oxide has been developed. This new method uses anodization but follows a route different from the commonly known 1- or 2-step anodization. General-purity (99.7%) commercial aluminum is used instead of the high-purity aluminum required in conventional anodization. The disordered arrangements of pores that initially form on the surface of aluminum rearranged by self-diffusion inside the anodic aluminum oxide (AAO) layer via long-term heat treatment. The enlargement of the pores on AAO that crystallized to γ phase was achieved by pore widening. Uniformly distributed nanopores with a diameter of 75 nm and wall a thickness of 16 nm were formed on a 9 µm thick AAO film. These ordered nanochannels were obtained over an area of several square millimeters, with a density of 1.4×1010 pores per cm2.
Structural Modulation in Oxygen Deficient Epitaxial Bi2Sr2Ca1Cu2OX Observed by X-ray Reciprocal Space Mapping
Authors: Kaneko Satoru , Akiyama Kensuke , Shimizu Yoshitada , Hirabayashi Yasuo , Saito Keisuke , Kimura Takeshi , Funakubo Hiroshi , Yoshimoto Mamoru , Ohya Seishiro
Published: July 2005

X-ray reciprocal space mapping (XRSM) was employed to investigate the effect of oxygen deficiency on supercell (SC) modulation in an epitaxial Bi2Sr2Ca1Cu2O
x
(Bi-2212) single layer. Cross section XRSM (ω–2θ plane) was used to estimate both the lattice constants and SC periodicity in epitaxial Bi-2212, and plan view XRSM (ω–ψ plane) to verify the symmetry of an in-plane SC structure. The SC periodicity expanded along both the b- and c-axes on the Bi-2212 film post annealed in nitrogen atmosphere.
Vertical Growth of Individual Single-Walled Carbon Nanotubes on Silicon and SiO2 Substrates
Authors: Takagi Daisuke , Homma Yoshikazu , Suzuki Satoru , Kobayashi Yoshihiro
Published: July 2005

Individually isolated single-walled carbon nanotubes (SWNTs) have been successfully grown vertically on a substrate by chemical vapor deposition with methane and Fe or Co catalysts. Vertical growth is obtained when the growth temperature was high, 900–1000°C, and the tube diameter is large, 2–5 nm. Vertically grown SWNTs are short, ranging from several tens to 300 nm, which are useful for use as tips of a field emission or probe microscope. Fullerene encapsulation has been achieved directly in vertical SWNTs on a substrate.
Parametric Study on Growth of Carbon Nanocoil by Catalytic Chemical Vapor Deposition
Authors: Xu Guochun , Chen Beibei , Shiki Hajime , Katsumata Takashi , Takikawa Hirofumi , Sakakibara Tateki , Itoh Shigeo , Ina Takashi
Published: July 2005

Carbon nanocoils (CNCs) were synthesized by the catalytic pyrolysis of acetylene over a mixture of Fe and SnO2 particles in a chemical vapor deposition (CVD) apparatus. The effects of reaction temperature, the composition of Fe and SnO2 in the catalyst, and the ratio of acetylene (C2H2) to helium (He) gas were examined. An optimum output was obtained when the Fe/SnO2 ratio was 2/1, the flow rates of C2H2 and He gases were 150 and 700 sccm, respectively, and the reaction temperature was 700°C. Under these conditions, the CNCs were of 80% purity, with average coil diameters of 750 nm, fiber diameters of 300 nm and pitches of approximately 750 nm. The CNC yield weighed up to 60 times that of the catalyst in 10 min.
Electrical Heating Process for p-Type to n-Type Conversion of Carbon Nanotube Field Effect Transistors
Authors: Kamimura Takafumi , Matsumoto Kazuhiko
Published: July 2005

A new electrical heating process was proposed which converts carbon nanotubes from p-type to n-type by desorption of oxygen molecules around the carbon nanotubes. By applying a large voltage of ∼40 V between the source and drain electrodes in vacuum, a large drain current of ∼20 µA flows the carbon nanotube channel and heats it, which cause oxygen molecules to desorb from the surface of the carbon nanotube. After applying electrical heating, the carbon nanotube field effect transistors clearly showed n-type properties. Moreover, they recovered p-type properties when exposed to ambient air.
Raman Scattering of Single-Walled Carbon Nanotubes Implanted with Ultra-Low-Energy Oxygen Ions
Authors: Ohno Yasuhide , Inoue Koichi , Kamimura Takafumi , Maehashi Kenzo , Yamamoto Kazuhiro , Matsumoto Kazuhiko
Published: July 2005

Single-walled carbon nanotubes (SWNTs) implanted with ultra-low-energy oxygen (O+) ions have been studied by means of Raman scattering experiments. The relative intensities of the D-band related to some defects increase with the O+ dose in the Raman spectra of the implanted samples. Although no recognizable shift of phonon energies due to the ion implantation has been observed, the intensities of the Stokes and anti-Stokes lines originated from radial breathing modes of SWNTs which exhibit various behaviors due to degree of the implantation, indicating that the resonant energies are changed. To explain these findings, the structure and the electronic states of SWNTs with substitutional O impurities have been studied by applying theoretical calculations based on the first principle method and a tight-binding method. As a result, it has been suggested that the incorporation of oxygen atoms at carbon sites is plausible, and the experimental observation can thus be consistently explained on the basis of the O impurities in SWNTs.
Electrical Properties of Carbon Nanotube Bundles for Future Via Interconnects
Authors: Nihei Mizuhisa , Kawabata Akio , Kondo Daiyu , Horibe Masahiro , Sato Shintaro , Awano Yuji
Published: July 2005

We have developed carbon nanotube (CNT) vias consisting of about 1000 tubes using thermal chemical vapor deposition (CVD) at a growth temperature of 450°C with cobalt catalysts, titanium carbide ohmic contacts, and tantalum barrier layers on copper wiring. The lowest resistance obtained was about 5 Ω/via. The total resistance of the CNT via was three orders of magnitude lower than that of one CNT, indicating that the current flows in parallel through about 1000 tubes. No degradation was observed for 100 hours at via current densities of 2×106 A/cm2, which is favorably compared with Cu vias.
Molecular Dynamics Study of Double-Walled Carbon Nanotubes for Nano-Mechanical Manipulation
Authors: Kimoto Yoshihisa , Mori Hideki , Mikami Tomohito , Akita Seiji , Nakayama Yoshikazu , Higashi Kenji , Hirai Yoshihiko
Published: July 2005

Double-walled carbon nanotubes (DWNTs) are expected to be useful as elements in nano-mechanical systems such as nanobearings and nanosliders. A molecular dynamics simulation is carried out to estimate the relative motion between the inner and outer tubes. The force required to pull the inner tube out of the outer tube is evaluated quantitatively by pulling the inner tube under a constant velocity for DWNTs with various inter-tube spacings and chiralities. When the inner tube is pulled under smaller constant force, the inner tube vibrates inside the outer tube without being pulled out, and an energetics is applied to explain the critical force and vibrational amplitude. The constant force induces not only vibration along the tube axis but also rotation around the tube axis, which indicates the possibility of creating a slider crank mechanism using a DWNT.
Correlation between Field Electron Emission and Structural Properties in Randomly and Vertically Oriented Carbon Nanotube Films
Authors: Ikuno Takashi , Honda Shin-ichi , Furuta Hiroshi , Aoki Katsunori , Hirao Takashi , Oura  , Katayama Mitsuhiro
Published: July 2005

We investigated the influence of the structural properties of randomly oriented carbon nanotube (R-CNT) and vertically oriented carbon nanotube (V-CNT) films on their field electron emission properties. The R-CNT and V-CNT films were synthesized using FeNi catalysts by means of thermal and dual-RF plasma-enhanced chemical vapor depositions, respectively. The structural properties of the R-CNT and V-CNT films were dependent on the initial thickness of the FeNi catalyst. As the FeNi film thickness decreased, the diameters of both types of CNTs decreased. Although the field electron emission property of the V-CNT film was improved with increasing the aspect ratio of V-CNT, the field enhancement factor, β, obtained from the Fowler–Nordheim plot was found to be 100 times larger than that obtained from the geometric properties. R-CNTs exhibited a lower threshold field than V-CNTs. These results suggest that the field emission property is markedly influenced by the surface state rather than by the geometric factors of CNTs.
Resonance-free Millimeter-wave Coplanar Waveguide Si Microelectromechanical System Package using a Lightly-doped Silicon Chip Carrier
Authors: Song Yo-Tak , Lee Hai-Young , Esashi Masayoshi
Published: July 2005

A silicon (Si) microelectromechanical system (MEMS) package using a lightly-doped Si chip carrier for coplanar waveguide (CPW) microwave and millimeter-wave integrated circuits (MMICs) is proposed in order to reduce parasitic problems of leakage, coupling, and resonance. The proposed chip carrier scheme is verified by fabricating and measuring a GaAs CPW on two types of carriers (conductor-back metal and lightly-doped Si) in the frequency range 0.5 to 40 GHz. The proposed MEMS package using the lightly-doped (15 Ω·cm) Si chip carrier and the high resistivity silicon (HRS, 15 kΩ·cm) shows the low loss and resonance-free since the lightly-doped Si chip carrier effectively absorbs and suppresses the resonant leakage. The Si MEMS package for CPW MMICs has an insertion loss (S
21) of 2.0 dB, a reflection loss (S
11) of 10 dB, and a power loss (PL) of 7.5 dB at 40 GHz.
Low Effective SiO2 Thickness and Low Leakage Current Ta2O5 Capacitors Based on Tantalum Tetraethoxide Dimethylamino-Ethoxide Precursor
Authors: Yang Hsin-Chia , Cheng Yi-Chang
Published: July 2005

Tantalum pentoxide (Ta2O5) films have been chemically deposited at low pressure on heavily phosphorous doped poly silicon using oxygen and a metal organic precursor, tantalum tetraethoxide dimethylamino-ethoxide Ta(OC2H5)4(OC2H4N(CH3)2), (TATDMAE). Good conformality of Ta2O5 films was seen. Hydrocarbon contamination was reduced by way of the annealing processes. The capacitance and the leakage current of the patterned capacitors were measured. Continuous improvements based on the crystallization and the reduction of hydrocarbon contamination were achieved by reducing the effective SiO2 thickness (t
eff, or the equivalent SiO2 thickness), and t
eff∼30.6 Å on average was achieved for 100-Å-thick Ta2O5 films. Crystallization occurs at 800°C or above upon application of rapid thermal processing (RTP) in the N2 ambient. During crystallization, hydrocarbon contaminations are out-diffused, which leaves dangling bonds in the as-deposited Ta2O5 films. To reduce the dangling bonds, the films were continuously processed by means of RTP in an O2 or N2O ambient. The leakage current was measured and plotted. The I–V plot shows the non-symmetric structure, namely metal–insulator–silicon (MIS), and the leakage current at 1.0 V achieves 1.190×10-9 A/cm2.
Increase in Zero-Field Conductivity and Low-Field Magnetoresistance by Proton Irradiated Defects in La0.67Sr0.33MnO3 Films
Authors: Chou Hsiung , Tsai Min-Hsiung , Ou Min-Nan , Wu Mei-Fang , Hong Meng-Tsong , Sun Shih-Jye , Yu Yueh-Chung
Published: July 2005

The effects of uniform structure defects produced by irradiation with 1.7 and 3 MeV protons on the electrical conductivity and low-field magnetoresistance (LFMR) of La0.67Sr0.33MnO3 (00l) films were investigated. The irradiation of heavy ions, such as Ar+ ions, usually creates defects, resulting in a decrease in the conductivity by defect scattering and an increase in the magnetoresistance by spin distortion. In the present study, the irradiation of light ions, such as protons, created low density point defects, resulting in structural and spin disorders, and an increase in the magnetoresistance. In contrast to the heavy-ion irradiation experiment, the conductivity markedly increased by more than two orders of magnitude.
Stress on Junction-Down-Mounted Ridge-Waveguide Laser Diodes
Authors: Nomoto Etsuko , Nakahara Koji , Shimaoka Makoto
Published: July 2005

A novel way of evaluating thermal stress on junction-down-mounted ridge-waveguide laser diodes is proposed and demonstrated. Namely, spatially resolved electroluminescence and photoluminescence observations revealed that a localized stress of 2.2×107 Pa led to gradual degradation during aging.
Dependence of Terahertz Electric Fields on Electric Bias and Modulation Frequency in Pulsed Terahertz Emissions from Electrically-Modulated Photoconductive Antenna Detected with Free-Space Electro-Optic Sampling
Authors: Yasui Takeshi , Araki Tsutomu
Published: July 2005

We investigated the dependence of terahertz (THz) electric fields on electric bias and modulation frequency in the pulsed THz emissions from electrically modulated photoconductive antennas detected with free-space electro-optic sampling. The linear dependence of the THz electric field on the electric bias achieves distortion-free modulation of the THz pulse even for deep modulation. We confirmed that the signal-to-noise ratio in free-space electro-optic sampling of the THz pulse is strongly affected by the 1/f noise characteristics of the mode-locked laser, and is improved effectively by increasing the modulation frequency. The resulting signal-to-noise ratio was 4,900 in THz radiation power at 0.1 THz using an audio-frequency lock-in amplifier with a time constant of 1 ms and modulation frequency of 100 kHz. The proposed method will be a powerful tool for real-time or highly sensitive THz measurements.
Secure Information Display with Two Limited Viewing Zones Using Two Decoding Masks Based on Visual Secret Sharing Scheme
Authors: Yamamoto Hirotsugu , Hayasaki Yoshio , Nishida Nobuo
Published: July 2005

We propose a secure display technique using visual cryptography. The proposed technique ensures the security of visual information. Encrypted information is perceived when viewed through a mask pattern that is composed of dot patterns of a decoding key. In order to improve security of the decoding key, the proposed display technique employs two decoding masks. Without both decoding masks, the encrypted information presented on a display cannot be decoded. We have developed a set of encryption codes so that information of a secret image can be shared among two decoding masks and a displayed image. The pixel arrangements of the decoding masks and the displayed image are designed to provide two limited viewing zones. Each viewing zone is limited by the stacked decoding masks in front of the display so that only one person can view the information at each viewing zone.
Switching Current Study: Hysteresis Measurement of Ferroelectric Capacitors using Current–Voltage Measurement Method
Authors: Wang Ding-Yeong , Chang Chun-Yen
Published: July 2005

In this study, we utilize the current–voltage (I–V) measurement method for investigating the ferroelectric characteristics of ferroelectric capacitors, such as hysteresis loops, switching current characteristics, retention properties and depolarization characteristics. By applying triangular voltage wave forms without sweeping and measuring delay, the hysteresis switching current characteristic was determined and the polarization–voltage (P–V) loop could be obtained using an integral calculus. Additionally, two kinds of poling measurement were utilized to investigate the full-switching and nonswitching current characteristics. A strong agreement was found between nonvolatile polarization (ΔP) obtained from P–V loops and that obtained by poling measurements. Moreover, modified poling measurements were utilized to study the retention property of ferroelectric capacitors. A dynamic switching current characteristic was found in retention duration and an increased coercive voltage was also observed in its half-hysteresis loops as remaining time increased. Furthermore, another modified poling profile was utilized to investigate the depolarization characteristics of ferroelectric films.
Structure and Chemical Bonds of CNx Films Deposited by Alternating Irradiations of Mass-Separated Ion Beams of C+ and N+
Authors: Yamamoto Kazuhiro
Published: July 2005

Carbon nitride films were prepared on Si(100) wafers by alternating irradiations of mass-separated low-energy ion beams of C+ and N+ at an ultra-high vacuum pressure of 10-7 Pa. The dependences of the ion energy and transport ratios of carbon ions to nitrogen ions on the film structure and chemical bonds formed were investigated. The graphite-like film, which was prepared at an ion energy of 30 eV and a transport ratio of 1/1, has a highly preferential crystal orientation. The graphite basal plane is curved and interlinked, and the c-axis of the graphite basal plane is parallel to the film growth surface. This highly preferential crystal orientation changed to a random orientation with increasing ion energy up to 200 eV due to increasing number of sp2-hybridization C–N bonds. The ratio of the number of sp2 C–N to the number of sp3 C–N bonds also changed with ion transport ratio, and a new phase with a lattice spacing of 0.204 nm formed with increasing the sp3/sp2 number ratio.
Micropatterning of SrBi2Ta2O9 Ferroelectric Thin Films Using a Selective Deposition Technique Combined with Patterned Self-Assembled Monolayers and Liquid-Source Misted Chemical Deposition
Authors: Takakuwa Atsushi , Ishida Masaya , Shimoda Tatsuya
Published: July 2005

We demonstrated a novel patterning method using a selective deposition technique of ferroelectric thin films without etching. Self-assembled monolayers (SAMs) of 1H,1H,2H,2H-perfluorodecyltriethoxysilane [CF3(CF2)7CH2CH2Si(OC2H5)3; FAS] were patterned on Pt/SiO2/Si substrates. The patterned SAMs on these surfaces defined the selective area on which the liquid-source misted chemical deposition (LSMCD) of SrBi2Ta2O9 (SBT) was performed. Pt top electrodes were then sputter-deposited on the patterned SBT films by the liftoff method. The remanent polarization (P
r) of the obtained SBT films was 7.5 µC/cm2 with good squareness of the hysteresis loops for 50 µm×50 µm square capacitors. By this method, we succeeded in fabricating uniform lines of ferroelectric thin films of 0.5 µm width. These results show that a selective deposition technique is promising for realizing high-density ferroelectric random access memories (FeRAMs).
Synthesis of Well-Aligned Carbon Nanotubes Using a High-Density RF Inductive Coupling Plasma
Authors: Shirai Hajime , Kikuchi Tomoyuki , Kobayashi Tomohiro
Published: July 2005

Growth of vertically well-aligned carbon nanotubes was demonstrated utilizing high-density rf inductive coupling plasma-enhanced chemical vapor deposition of methane. A sufficient supply of CH4-related precursors as well as a rapid large number of dangling bonds at the top surface due to a negative substrate dc bias are essential for promoting the deposition rate of vertically well-aligned carbon nanotubes. Rapid deposition at 60 Å/s of vertically well-aligned multi-walled carbon nanotubes was achieved using pure methane (50 sccm) by adjusting the plasma conditions.
One Consideration on Infiltration Property of Oxide Particles
Authors: Ishii Katsunori , Kihara Yoshiyuki , Fujii Kan-ichi
Published: July 2005

A vibration-based sphere-pack technology employing large and small particles is discussed on the basis of a simulation of the fabrication of an atomic fuel pin, by employing four types of model particle. The infiltration property is almost free from the material and mass density. From this result, the feasibility of mixing with the heavy metallic uranium as the getter of absorbing oxygen, thereby preventing the oxidization of the fuel pin, is suggested.
A High S/N Ratio Object Extraction CMOS Image Sensor with Column Parallel Signal Processing
Authors: Tate Tomoyasu , Sugawa Shigetoshi , Chiba Koji , Kotani Koji , Ohmi Tadahiro
Published: July 2005

A new complementary metal oxide semiconductor (CMOS) image sensor with a capability for noise reduction, column-parallel analog to digital (A/D) converters, a capacity for signal processing for object extraction every approximately 1 ms and a high-quality frame signal output every 1/60 s has been developed. The sensor pixel circuit is composed of a photodiode, a signal readout circuit with noise reduction and sample-hold functions. The sensor is equipped with column-parallel A/D converters and arithmetic logic units (ALU). Three feature values for object extraction, such as color difference, color intensity and texture, are first calculated, and motion is detected using the inter frame differences of these feature values. The calculations of these feature values are simplified so as to be implemented by compact ALU. The size of pixel, A/D converter and ALU are small enough to be able to incorporate them into practical sensor chip.
Horizontal Switching of Half-Wave Liquid Crystal Cell for Transflective Display
Authors: Park Kyoung-Ho , Kim Jae Chang , Yoon Tae-Hoon
Published: July 2005

We propose optical configurations of a horizontal-switching liquid crystal cell for a transflective display. Optimum configurations can be obtained by using a half-wave liquid crystal cell and three retardation layers. The phase compensation method or the mirror imaging method can be used to achieve the perfect dark state in the transmissive part. We demonstrated excellent optical performance of the proposed transflective configurations.
Analog Edge-Filtering Processor Employing Only-Nearest-Neighbor Interconnects
Authors: Nakashita Yusuke , Mita Yoshio , Shibata Tadashi
Published: July 2005

The hardware edge detection system is becoming important for real-time perception applications such as object recognition. However, the hardware edge detecting system realized by massively-parallel processing element architecture has a critical problem called “interconnection explosion.” In this study, a new “Only-Nearest-Neighbor Interconnects” architecture has been developed, in which a processing element communicates with only four adjacent cells, realizing a very simple interconnection. Furthermore, the arithmetic operations used in the new architecture involve only two types of calculation: addition and subtraction. These simple calculations have been achieved easily using floating-gate metal-oxide semiconductor (MOS) technology. A test chip was designed and fabricated using 0.35 µm double-poly, triple-metal complementary MOS (CMOS) technology. The experimental results of the edge detection from grayscale images are presented using the core processing elements.
Re-Examination of Impact of Intrinsic Dopant Fluctuations on Static RAM (SRAM) Static Noise Margin
Authors: Tachibana Fumihiko , Hiramoto Toshiro
Published: July 2005

The impacts of intrinsic threshold voltage (V
th) fluctuations in metal oxide semiconductor field effect transistors (MOSFETs) on the static random access memory (SRAM) static noise margin (SNM) are re-examined in the 90 nm to 45 nm technology generations on the basis of the 2003 International Technology Roadmap for Semiconductors (ITRS). The V
th fluctuations due to random dopant fluctuations are calculated using the cube model and the deviations in SNM are derived using two-dimensional device simulations and SPICE simulations. It is found that five sigma of SNM deviations is ensured at gate length L
g=53 nm in the 90 nm node at β=1.5. It is also demonstrated that, although four sigma of SNM deviations exceeds the average SNM in the 65 nm (L
g=32 nm) and 45 nm (L
g=22 nm) nodes, four sigma of SNM deviations is ensured by adjusting L
g, the power supply voltage (V
dd), V
th and the drain-induced barrier lowering (DIBL) without using improved MOSFET structures.
Scaling of Three-Dimensional Integral Imaging
Authors: Park Jae-Hyeung , Choi Heejin , Kim Yunhee , Kim Joohwan , Lee Byoungho
Published: July 2005

Integral imaging, which used to be called integral photography, has recently been attracting attention because of its potential for dynamic color autostereoscopy with full parallax and without the use of special glasses. For its practical use, the scaling of integral imaging is of high importance because different systems have different lens characteristics such as lens size and focal length in general. In this paper, we discuss the guiding rules in the scaling of integral imaging. Generalized analysis on scaling is presented and ratio-conserving scaling for distortion-free reconstruction is proposed. Experimental results are also presented for the verification of our analysis.
Evaluations of Scaling Properties for Ge on Insulator MOSFETs in Nano-Scale
Authors: Du Gang , Liu Xiao Yan , Xia Zhi Liang , Wang Ya Ke , Hou Dan Qiong , Kang Jin Feng , Han Ru Qi
Published: July 2005

Germanium metal-oxide-semiconductor field-effect transistors (MOSFETs) have attracted tremendous attention due to the high carrier mobility especially in the low-field. Compared to Si, in bulk germanium the velocity would saturate at a lower field with a lower saturation velocity. Thus the scaling behavior of germanium MOSFET with gate length in nano-scale is very important. In this work, characteristics of both n- and p-channel germanium on Insulator (GOI) MOSFETs with channel length (L
ch) ranging from 20 nm to 130 nm are simulated by 2D self-consistent full-band Monte Carlo device simulator to investigate the scaling properties. The results indicate that both for n and p channel GOI MOSFETs have favorable scaling properties in nano-scale due to the non-stationary transport near source side especially for p channel device. But the surface roughness scattering is a critical issue that might suppress the non-stationary transport. Short channel effect (SCE) is serious in GOI devices and much thinner Germanium layer have to use to optimize the performance.
Mobility and Number Fluctuations in MOS Structures
Authors: Hamayoshi Shinichi , Nakamoto Takayuki , Wada Masanori , Ohkura Kensaku , Tabei Tetsuo , Ikeda Mitsuhisa , Higuchi Katsuhiko
Published: July 2005

It is demonstrated that the mobility and number fluctuations in an n-channel metal oxide semiconductor field effect transistor (n-MOSFET), which has a shallow-doped channel, can be separately measured. The mobility fluctuation becomes the dominant source of noise in the case where a negative gate voltage is applied. This is because carriers are not near the Si/SiO interface. If a positive gate voltage is applied to the MOSFET, carriers exist near the Si/SiO interface, so that noise due to the number fluctuation becomes dominant.
Temperature Effects of Constant Bias Stress on n-Channel FETs with Hf-based Gate Dielectric
Authors: Choi Rino , Lee Byoung Hun , Young Chadwin D. , Sim Jang Hoan , Bersuker Gennadi
Published: July 2005

Temperature dependence of degradation and breakdown behavior of hafnium silicate gate dielectrics in n-channel field-effect transistors (NFET) with polysilicon and TiN gate electrodes has been investigated. At elevated temperatures under positive gate bias, devices with polysilicon gate electrodes exhibit a so-called V
th turn around phenomenon (a change of the direction of the V
th shift from positive to negative), accompanied by decreasing transconductance and increasing gate leakage current. Hot-holes generation in the poly-Si gate by the injected electrons and a subsequent hole diffusion and trapping near the high-k/Si-substrate interface is proposed to contribute to the turn around behavior. No V
th turn around phenomenon was observed in devices with the TiN gate electrode. This hole induced degradation of the high-k/poly-Si gate stack may further complicate integration of the polysilicon gate electrode with high-k dielectrics.
High-Mobility Dual Metal Gate MOS Transistors with High-k Gate Dielectrics
Authors: Takahashi Kensuke , Manabe Kenzo , Morioka Ayuka , Ikarashi Taeko , Yoshihara Takuya , Watanabe Heiji , Tatsumi Toru
Published: July 2005

Dual metal gate transistors with high-k gate dielectrics have been investigated for low-power metal oxide semiconductor (MOS) devices in 45 nm nodes and beyond. Using high-quality HfSiO gate dielectrics, using TiN and Ta for the gate electrode, and minimizing process damage, we have succeeded in markedly improving device performance. Effective work functions of 4.9 eV for TiN and 4.3 eV for Ta on HfSiO were obtained for the first time. Symmetrical threshold voltages of ±0.5 V were realized for these work functions. Small hysteresis and low interface trap densities for both TiN and Ta were obtained, which are almost the same as those of poly-Si/HfSiON transistors. No degradation in electron mobility was achieved for the first time for Ta-NMOS transistors at an effective field of 1.0 MV/cm. The gate leakage current at an equivalent electrical oxide thickness in an inversion of 1.7 nm was suppressed to 1 mA/cm-2 at a gate bias of Vth+0.6 V.
Degradation of Nitride/W/WNx/Poly-Si Gate Stack by Post-Thermal Processes
Authors: Cho Heung-Jae , Jang Se-Aug , Kim Yong Soo , Lim Kwan-Yong , Oh Jae-Geun , Lee Jung-Ho , Park Tae-Su , Back Tae-Sun , Yang Jun-Mo , Yang Hong-Seon , Sohn Hyun-Chul , Kim Jin-Woong
Published: July 2005

We investigated the effect of post-thermal processing on the gate oxide reliability in nitride/W/WNx/polycrystalline-Si (poly-Si) gated metal-oxide-semiconductor (MOS) capacitors. As the thermal processing became severer, grater development of mechanical stress and degradation of the gate oxide were observed. Microvoids were also found at the triple point between the gate oxide and two poly-Si grains. The wide variation in mechanical stress during post-thermal processing is believed to create the microvoids and generate additional dangling and strained bonds in the oxide and at the SiO2/Si interface, resulting in the degradation of the gate oxide.
Effects of Post-Deposition Annealing on the Electrical Properties of HfSiO Films Grown by Atomic Layer Deposition
Authors: Cho Hag-Ju , Lee Hye Lan , Park Hong Bae , Jeon Taek Soo , Park Seong Geon , Jin Beom Jun , Kang Sang Bom , Shin Yu Gyun , Chung U-In , Moon Joo Tae
Published: July 2005

Post-deposition annealing was investigated for hafnium silicate films deposited on Si substrates by atomic layer deposition. Annealing in NH3 at 750°C incorporated 13 At.% nitrogen in hafnium silicate, and hysteresis significantly depended on film thickness. In contrast, annealing in N2 at 950°C suppressed hysteresis and its dependence on the film thickness. In addition, effective mobility and positive bias temperature instability were improved by N2 annealing of as-deposited hafnium silicate films. Finally, additional N2 annealing following NH3 annealing was effective to obtain highly dense hafnium silicate films with good mobility and optimized nitrogen incorporation.
Application of Arsenic Plasma Doping in Three-Dimensional MOS Transistors and the Doping Profile Evaluation
Authors: Kobayashi Kei , Eto Takanori , Okuyama Kiyoshi , Shibahara Kentaro , Sunami Hideo
Published: July 2005

The application of plasma doping in three-dimensional (3-D) metal oxide semiconductor (MOS) transistors is proposed. One of the key steps in for fabricating 3-D MOS transistors with high-aspect-ratio channels is 3-D doping. Thus, plasma doping is analyzed and its profile is evaluated. Since conventional evaluation methods are not very effective for impurity concentration profiling along the sidewall of a vertical structure, a new method utilizing impurity-enhanced oxidation is proposed. By this method, an arsenic-doped layer of approximately 1×1020 cm-3 in concentration has been formed uniformly for a beam of 1 µm height and 0.2-1 µm width.
Tight-Binding Quantum Chemical Molecular Dynamics Study on Depth Profile Prediction in Low Energy Boron Implantation Process
Authors: Tsuboi Hideyuki , Sagawa Ai , Iga Hideki , Sasata Katsumi , Masuda Tsuyoshi , Koyama Michihisa , Kubo Momoji , Broclawik Ewa , Yabuhara Hidehiko , Miyamoto Akira
Published: July 2005

Creation of shallow junction for the future generation LSI is a crucial step in semiconductor industry and low-energy boron implantation process is considered to be a key technology. In this study, we have statistically investigated the effects of orientation of implantation on the dynamic behavior of boron implantation process into hydrogen-terminated Si(001) 2×1 surface by using our original tight-binding quantum chemical molecular dynamics method, which is over 5,000 times faster than conventional first-principle molecular dynamics method. It was found that depth profile of boron implantation can be controlled by orientation of boron implantation and the shallowest implantation depth was obtained in the case of tilt angle equal to 7° among the investigated tilt angles of 0°, 7°, 15°, 22.5°, 30° and 45° at the initial boron energy of 100 eV. At the boron implantation process of over 1 keV energy the tilt angle of 7° has been employed experimentally and the same tilt angle was predicted to be the best even at low-energy region of 100 eV. Furthermore, we investigated the effect of rotation angle on the depth profile and at all the investigated tilt angles the average implantation depth becomes shallower for rotation angle of 45° that is along <011> direction, than for rotation angle of 0° that is along <001>. Hence, the shallowest depth profile was obtained in the case of tilt angle of 7° and rotation angle of 45°, where the distribution of intruded boron atom was more concentrated than for the same tilt angle but rotation angle of 0°. The effect of tilt and rotation angles on the boron implantation process has not been clarified experimentally at low-energy boron implantation process of less than 1 keV and hence we concluded that theoretical optimization of low-energy boron implantation process has been succeeded by means of our original tight-binding quantum chemical molecular dynamics method.
New Strained Silicon-on-Insulator Fabricated by Laser-Annealing Technology
Authors: Mishima Yasuyoshi , Ochimizu Hirohisa , Mimura Atsushi
Published: July 2005

A new low temperature process that can be used to fabricate a strained silicon-on insulator (SOI) using an excimer-laser-irradiated relaxation technique is proposed. An excimer laser is used to relax the stress of a SiGe layer on a SOI substrate. The results of Raman spectra show that changing the laser power density on the SiGe layer controls the stress of a Si layer on the SiGe layer. We confirm that increasing the laser power density enhances the electron mobility of strained Si on a relaxed SiGe/SOI structures. This electron mobility increases to 630 cm2/Vs, which is an increase of approximately 180%, compared with that of the unstrained Si on a strained SiGe/SOI structure.
Width Effect on Hot-Carrier-Induced Degradation for 90 nm Partially Depleted SOI CMOSFETs
Authors: Lai Chieh-Ming , Fang Yean-Kuen , Pan Shing-Tai , Yeh Wen-Kuan
Published: July 2005

The hot-carrier-induced degradation of partially depleted silicon-on-insulator complementary metal-oxide-semiconductor field-effect transistors (CMOSFETs) at various applied voltages was investigated using 90 nm body-contact silicon-on-insulator (BC-SOI) devices with 1.6 nm gate oxides and various gate widths. In this work, a small gate-width device with a large drain current density was observed to suffer from serious hot-carrier-induced degradation. By inspecting the gate current (I
G) degradation, the quality of gate oxide was observed to decay apparently after hot-carrier stressing. For a 90 nm BC-SOI nMOSFET of 1.2 µm narrow gate width, the tolerance of 1.6 nm ultra thin gate oxide layer was very low particularly around the channel edge region; thus, device reliability is very critical and easily degraded because of device gate oxide breakdown after hot-carrier stressing.
Bi-Directional Hybrid Optical Fiber Amplifier for C or C-plus-L Band
Authors: Yeh Chien-Hung , Lee Chien-Chung , Chi Sien
Published: July 2005

We have proposed and experimentally demonstrated a bi-directional hybrid optical fiber amplifier, which operates in the ranges of the C and C-plus-L bands simultaneously, based on two erbium-doped fiber amplifiers (EDFAs) and an semiconductor optical amplifier (SOA). The proposed amplifier also provides C or C-plus-L band amplified spontaneous emission (ASE) light source for fiber sensor and detection applications.
Ultrashallow Junction Formation Using Novel Plasma Doping Technology beyond 50 nm MOS Devices
Authors: Im Kiju , Cho Won-ju , Ahn Chang-Geun , Yang Jong-Heon , Baek In-Bok , Lee Seongjae , Baek Sungkweon , Hwang Hyunsang
Published: July 2005

In this paper, we demonstrate a novel plasma ion-shower doping (PLAD) technique for fabricating a nanoscale silicon-on-insulator metal-oxide-semiconductor field effect transistors (SOI MOSFETs). The source drain (S/D) extensions of the SOI n-MOSFETs were formed by elevated-temperature (ET) PLAD. Even though activation annealing after PLAD was excluded to minimize the diffusion of dopants, which resulted in laterally abrupt S/D junction, we obtained a low sheet resistance of 920 Ω/□ by the ET PLAD at 230°C. The fabricated SOI n-MOSFET with a gate length of 50 nm adopted in the proposed junction formation technique showed suppressed short-channel effects. The successful operation of a MOSFET with a high-κ gate dielectric and metal gate revealed that the proposed junction formation technique is compatible with devices made of low-thermal-budget material.