bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Sol–Gel-Derived and Crystallized HfO2 Thin Films Dependent on Sol Solution
Authors: Shimizu Hirofumi , Nemoto Daiki , Ikeda Masanori , Nishide Toshikazu
Published: January 2011

We investigated sol–gel-derived hafnium dioxide (HfO2) films on silicon substrates fired in air at 350, 450, 550, and 700 °C for 30 min using either formic acid (HCOOH) or nitric acid (HNO3) solutions as a catalyst. At less than 450 °C, both films are amorphous and approximately 8–10 nm thick. Crystallization into the monoclinic structure (111) was found to occur at 560 °C in the HCOOH sol. In the HNO3 sol, the crystallization into the monoclinic structures (111) and (111) occurs at 470 °C. The temperature-programmed desorption curves of the sol–gel-derived HfO2 thin films using each sol solution are separated into five distinct H2O desorption components caused by physically adsorbed H2O, chemically adsorbed OH, and/or Hf–OH bonds in the HfO2 film. On the basis of these components, a model is proposed to explain the H2O desorption mechanism. The dielectric constant (relative permittivity: ε
HfO2) of the sol–gel-derived HfO2 film was calculated to be 11 and the EOT was estimated to be 2.1 nm, which need to be improved. As an alternative gate insulator in advanced integrated complementary metal–oxide–semiconductor (CMOS) devices, the amorphous state of the sol–gel-derived HfO2 film is promising for both sol solutions, if H2O desorption can be accomplished and other defects eliminated.
Study of Carrier Behavior in Pentacene in a Au/Pentacene/Ferroelectric Poly(vinylidene fluoride–trifluoroethylene)/Indium Tin Oxide Structure by Electric-Field-Induced Second-Harmonic Generation Measurement
Authors: Li Jun , Zhang Le , Ou-Yang Wei , Taguchi Dai , Manaka Takaaki , Iwamoto Mitsumasa
Published: January 2011

Through electric-field-induced second-harmonic generation (EFISHG) measurement, we studied carrier injection and accumulation in a pentacene layer under the effect of dipole reversal in a ferroelectric poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] layer. The change in the electric field in the pentacene layer due to polarization reversal in the P(VDF–TrFE) layer was determined by direct probing. Using the value of remnant polarization of P(VDF–TrFE) obtained from displacement current measurement (DCM), we showed that the EFISHG response closely reflected the hole injection and accumulation at the pentacene/P(VDF–TrFE) interface induced by spontaneous polarization in P(VDF–TrFE).
Thermal Diffusivities of Tris(8-hydroxyquinoline)aluminum and N,N'-Di(1-naphthyl)-N,N'-diphenylbenzidine Thin Films with Sub-Hundred Nanometer Thicknesses
Authors: Oka Nobuto , Kato Kazuki , Yagi Takashi , Taketoshi Naoyuki , Baba Tetsuya , Ito Norihiro , Shigesato Yuzo
Published: January 2011

The thermal diffusivities of tris(8-hydroxyquinoline)aluminum (Alq3) and N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) films have been characterized quantitatively using a “rear heating/front detection-type” nanosecond thermoreflectance system. Alq3 or α-NPD films sandwiched by Al films, Al/(Alq3 or α-NPD)/Al three-layered films, were prepared by vacuum evaporation. Al acted as a reflective layer for pulse lasers in the thermoreflectance system. The nominal thicknesses of Alq3 and α-NPD layers varied roughly from 30 to 100 nm. The thermal diffusivities of Alq3 and α-NPD films were found to be (1.4–1.7)×10-7 and 1.4×10-7 m2 s-1, respectively.
Unusual Formation of Switchable Hexagonal Columnar Phase by Bent-Shaped Molecules with Low Bent-Angle Naphthalene Central Core and Alkylthio Tail
Authors: Li Xiaodong , Kang Sungmin , Lee Seng Kue , Tokita Masatoshi , Watanabe Junji
Published: January 2011

The low-angle bent-shaped molecules with 1,7-naphthalene central core and alkylthio tails can form a novel hexagonal columnar phase and a dark B4 phase. The columnar phase has a large two-dimensional hexagonal lattice with edges of 65–75 Å and exhibits polar switching with spontaneous polarization along the column axis. Calculated from the density (∼1 g·cm-3) and unit volume, the number of molecules that are necessary to fill a 4.6-Å stratum of each column were found to be ∼11. Such a large number of molecules can be accommodated only in the tube-like assembly, which may be the first example as formed by the usual bent-shaped molecule with a single alkylthio tail.
Homogeneous Alignment of Liquid Crystals on an Ion-Beam-Exposed Indium–Tin-Oxide Surface without Coating Alignment Layer
Authors: Hwang Soowon , Jin Hye-Jung , Yoon Tae-Hoon , Kim Jae Chang
Published: January 2011

We propose a liquid crystal (LC) alignment method that can align LC molecules homogeneously on ion-beam-exposed indium–tin-oxide (IB-ITO) surface without coating alignment layer. To achieve high quality alignment conditions, the ion beam exposure energy and time have been found to be in the range from 50 to 1500 eV and from 1 to 300 s, respectively. On the IB-ITO surface treated under these conditions, a groove pattern is formed to be parallel to the ion beam exposure direction and optical anisotropy is induced to be parallel to the groove pattern, which causes the LC molecules to align. Moreover, thermal stability is ensured by baking the IB-ITO surface, due to effects such as an increase in polar anchoring energy. According to this method, the coating process of alignment layer is eliminated as well as alignment material is saved, which reduce fabrication cost.
Anomalies in the Temperature Dependence of the Photoelectrical Response of GaAs/InGaP Superlattices
Authors: Parisini Antonella , Ghezzi Carlo , Tarricone Luciano , Vantaggio Salvatore , Baldini Michele , Gombia Enos
Published: January 2011

Photoelectrical measurements were taken on InGaP (p+)-GaAs/InGaP-InGaP (n+) multilayers structures, formed by a sequence of nominally undoped InGaP/GaAs quantum wells, interposed between two p+ and n+ InGaP cladding layers. The heterostructures were grown through Low Pressure Metal Organic Vapour Phase Epitaxy, with liquid precursors for the III–V elements and growth conditions optimized for obtaining sharp interfaces and negligible ordering effects in InGaP. The experimental temperature dependence of the photoelectrical signal intensity exhibited peculiarities and anomalies which could lead to erroneous analysis of the perpendicular transport mechanisms, so that they are here critically discussed in the light of a partial depletion of the nominally intrinsic superlattice region of the p–i–n structure.
Modeling of Self-Sustained Pulsation Based on Two-Section Distributed Feedback Lasers with Shift-Layer
Authors: Chen Jer-Shien , Lee San-Liang , Kung Hong-Chang , Tsao Hen-Wai
Published: January 2011

We propose a numerical model to estimate the self-sustained pulsation frequency (SSP frequency) for a two-section distributed feedback laser (TS-DFB). A modulation transfer function is derived from the rate equations for carriers and photons. The SSP frequency can be obtained from the singularity condition of the transfer function. A useful but simple systematic design procedure is proposed for investigating the effects of various structural parameters on the SSP condition. The device parameters varied in the analysis include carrier density, section length ratio, grating coupling coefficient, and the refractive index change caused by adding a shift-layer. The device structure used for the SSP experiments and analysis is a TS-DFB laser with a shift-layer. This type of lasers can have stable lasing mode with large side-mode suppression ratio such that the inherent mode instability in a conventional index-guide DFB laser can be eliminated in this structure. This can simplify the operation of the SSP laser. The analysis model can also be applied to other laser structures. The results of numerical analysis match well with the experimental data.
InGaN-Based Resonant-Cavity Light-Emitting Diodes with a ZrO2/SiO2 Distributed Bragg Reflector and Metal Reflector
Authors: Kim Jae-Hun , Lee Seung-Jae , Park Si-Hyun
Published: January 2011

We fabricated InGaN-based resonant-cavity light-emitting diodes (RC-LEDs) in which one of the reflectors forming the cavity was made of Ag metal and the other was a ZrO2/SiO2 dielectric distributed Bragg reflector (DBR). Ag metal was deposited onto an InGaN epitaxial layer grown on a sapphire substrate. A ZrO2/SiO2 DBR was deposited onto n-GaN after a Ag/InGaN/sapphire sample was bonded to a silicon substrate using Au bonding metal and the sapphire substrate was removed by a laser lift-off process. Multiple emission modes with a narrowed spectrum were observed with corresponding dips in the reflectance of the resonant cavity, which was examined by microreflectance measurements. The output intensity of the RC-LED was higher than that of a conventional LED and the turn-on voltage increased with a slight decrease in series resistance. The output power of the RC-LED in a 1 ×1 mm2 chip increased linearly with the injection of current up to a 500 mA.
Fabrication and Characterization of Evanescent Semiconductor Optical Isolators with Small Gain Saturation Effect
Authors: Shimizu Hiromasa , Goto Syunsuke
Published: January 2011

We report the fabrication and characterization of an evanescent semiconductor optical isolator. The fabricated device exhibited 7.4 dB/mm optical isolation and improved gain saturation characteristics. The effect of the gain saturation on the semiconductor optical isolator was clarified by experimental results and comparison with previously reported propagation characteristics. The demonstrated device is appropriate for monolithically integrated semiconductor optical isolators, which will be useful for all-optical signal processing.
Efficiency Improvement of Single-Junction In0.5Ga0.5P Solar Cell with Compositional Grading p-Emitter/Window Capping Configuration
Authors: Chang Yi-An , Kuo Hao-Chung , Lu Tien-Chang , Lai Fang-I , Kuo Shou-Yi , Laih Li-Wen , Laih Li-Hong , Wang Shing-Chung
Published: January 2011

In this study a novel p-emitter/window capping configuration design applied to a p+–n In0.5Ga0.5P solar cell is developed. By grading the Ga and Al compositions in the interface between the p-In0.5Ga0.5P emitter and p-In0.5Al0.5P window layers, the output characteristics of the p+–n In0.5Ga0.5P solar cell are improved. It is found that the photoluminescence (PL) intensity is increased and the minority carrier lifetime obtained from room-temperature time-resolved (TR) PL measurement can be increased from 5.3 ns of the typical design to 7.0 ns, indicating that the application of compositional grading can improve crystal quality and the interface becomes smoother, thus reducing the nonradiative recombination losses. Both the short-circuit current and open-circuit voltage are increased correspondingly and the conversion efficiency is improved from 14.57% of the typical design to 15.32% of the new p-emitter/window configuration under one-sun air-mass 1.5 global illumination.
Formation of Porous Titanium Film and Its Application to Counter Electrode for Dye-Sensitized Solar Cell
Authors: Rahman Mohammad Maksudur , Kojima Ryota , Fihry Mehdi El Fassy , Kimura Yasuo , Niwano Michio
Published: January 2011

It is important to reduce the series resistance of a dye-sensitized solar cell (DSC) to improve its conversion efficiency. Here, a porous titanium (Ti)/dense Ti/aluminum (Al)/glass composite counter electrode for a DSC was fabricated. A porous and a dense Ti layer were deposited by a DC magnetron sputtering process. The dense Ti film was used as a protective layer against corrosion of the Al layer, which reduces the sheet resistance of the counter electrode. The solution treatment furthermore roughened the surface of the porous Ti layer. The composite counter electrode increased the fill factor and short-circuit current, resulting in the improvement of the conversion efficiency of the DSC. Our results indicate that it is important to introduce a porous material to the counter electrode of the DSC to improve the performance of the DSC and that the porous Ti film with rough surfaces is a promising material.
Generation and Homodyne Detection of Continuous Terahertz Waves Using Single Photoconductive Antenna
Authors: Murasawa Kengo , Hidaka Takehiko
Published: January 2011

The generation and homodyne detection of continuous terahertz (THz) waves using a single photoconductive antenna excited by dual-wavelength continuous-wave laser light have been carried out. The THz waves emitted from the photoconductive antenna are returned and focused onto the same photoconductive antenna via a mirror. Sinusoidal variation of the homodyne current corresponding to the mirror displacement was observed. The homodyne current is caused by THz waves with the frequency of 1028 ±5 GHz. The homodyne current amplitude of 0.5–1.5 nA with a signal-to-noise ratio of 10–25 is obtained with the incident laser power of 4 mW and bias voltage of 10–30 V applied to the photoconductive antenna. The homodyne current amplitude is proportional to the square of the incident laser power up to 2 mW, which can be explained by considering the dependences of the dc photocurrent and dc photoconductance on the irradiating laser power.
Broadband Single-Polarization Single-Mode Operation in Highly Birefringent Photonic Crystal Fiber with a Depressed-Index Core
Authors: Lee Sun-Goo , Lim Sun Do , Lee Kwanil , Lee Sang Bae
Published: January 2011

A novel design for a broadband single-polarization single-mode photonic crystal fibers is proposed and numerically analyzed by using a finite-element method. It is shown that the single-polarization single-mode operation spectral region of a highly birefringent photonic crystal fiber can be strongly enhanced by introducing a suitably down-doped silica rod inside the fiber core. In the proposed design, the single-polarization single-mode guidance can be realized in the wavelength range from 1.0 to 1.8 µm with the confinement loss less than 0.12 dB/km.
Slot Waveguide by Using Double High-Mesa Structure for Optical Absorption Sensing
Authors: Alam Intekhab , Hamamoto Kiichi
Published: January 2011

Slot waveguide, of which the optical field profiles mainly in the slot region, is attractive for sensing application by optical absorption because it has a high portion of optical field inside the slot region. A slot waveguide itself can be structured by utilizing buried hetero, ridge, rib, strip, and high-mesa structures. Among them, slot waveguide by using double high-mesa structure is attractive because it offers higher portion of optical field profile inside the slot region compared to the others. One critical issue is its propagation condition, as the slot waveguide structure may allow “directional-coupler” mode, which prevents proper utilization especially to the sensing application. To get rid of the directional-coupler mode propagation, here we propose a scheme by utilizing leaky mode for each high-mesa part. Under the condition of leaky mode for each high-mesa part, it is successfully confirmed that there is a propagation condition of which optical field mainly profiles in the slot region. Based on this propagation condition, more than 85% of the optical field profile can be achieved in the slot region. Moreover, under this condition, it is also confirmed that a very small radius of curvature of 10 µm is available, which is useful for long length integration into a compact area. We have also discussed about a mode-size converter to inject optical field into this double high-mesa slot waveguide from regular single high-mesa waveguide. Only 1.08 dB excess loss has been reported at mode-size converter.
Design of Rectangular Transmission Gratings Fabricated in LiNbO3 for High-Power Terahertz-Wave Generation
Authors: Nagashima Keisuke , Kosuge Atsushi
Published: January 2011

Precise parameters are investigated for rectangular transmission gratings fabricated in a LiNbO3 substrate for high-power terahertz-wave generation. Here, a simple setup is considered, where the pumping laser is injected into the grating surface from air or fused silica. The maximum diffraction efficiencies are 0.4 for air and 0.9 for fused silica. The designed gratings have deep grooves with a depth of about 0.5 µm and a width of 0.12–0.14 µm. It was found that the diffraction efficiency is much less sensitive to the groove depth than to the groove width.
New Violet Phosphor Sr7Al12O25:Eu2+ Synthesized from Sr–Al–O:Eu Powder Mounted on Polycrystalline Alumina
Authors: Akasaka Hiroki , Tada Hiromi , Ooki Tomoharu , Nakamura Atsushi , Komatsu Keiji , Tsuchida Shinya , Ohshio Shigeo , Nambu Nobuyoshi , Saitoh Hidetoshi
Published: January 2011

A new violet phosphor was synthesized by sintering under the reduction condition from the Sr–Al–O:Eu powder oxidized from an ethylenediaminetetraacetic (EDTA) complex on a polycrystalline alumina plate. The crystalline phase of violet phosphor was determined to be Sr7Al12O25 by the change in the crystallinity of the product with a change in the composition of the raw material. The emission wavelength of the phosphor was 410 nm for Sr7Al12O25:Eu2+. For the composition of Sr:Al:Eu = 6.86:8:0.14 in the EDTA complex with sintering at 1400 °C, Sr7Al12O25:Eu2+ was obtained only in the crystalline phase of Sr7Al12O25 and exhibited the highest emission intensity of 410 nm in our experiment. The sintering temperature at sintering and composition of metals in the EDTA complex affected the emission wavelength change from 410 to 460 nm because of change in crystallinity. These changes indicate that the emission color in the range from violet to green is controlled by composition change or sintering temperature.
Systematic Study on Ce:LuLiF4 as a Fast Scintillator Using Storage Ring Free-Electron Lasers
Authors: Nakazato Tomoharu , Furukawa Yusuke , Cadatal-Raduban Marilou , Pham Minh , Tatsumi Toshihiro , Saiki Ayumi , Arikawa Yasunobu , Sarukura Nobuhiko , Nishimura Hiroaki , Azechi Hiroshi , Mima Kunioki , Fukuda Tsuguo , Hosaka Masahito , Katoh Masahiro , Kosugi Nobuhiro
Published: January 2011

Ce:LuLiF4 is evaluated as a fast scintillator using a storage ring free-electron laser operating in the deep-ultraviolet region. The relatively flat spectral response across its absorption bands makes this material an attractive scintillator for various excitation sources. Its decay time is acceptable for ignition timing in fast-ignition, inertial confinement nuclear fusion using laser. This report is the first systematic study on Ce:LuLiF4 as a scintillator, wherein the storage ring free-electron laser is also shown as a powerful tool for material survey.
Macroscopic Differential Phase Shift Quantum Key Distribution Using an Optically Pre-Amplified Receiver
Authors: Kukita Tatsuya , Takada Hiroshi , Inoue Kyo
Published: January 2011

Since it was noted that quantum computers could break public key cryptosystems based on number theory, extensive studies have been undertaken on quantum cryptography, which offers unconditionally secure communication based on quantum mechanics. We investigate a quantum key distribution (QKD) scheme using macroscopic coherent light with optically pre-amplified direct differential detection. A transmitter “Alice” sends a series of two macroscopic nonorthogonal coherent states that partially overlap due to quantum noise. A receiver “Bob” amplifies and receives it with direct differential detection followed by a thresholding process. To avoid difficulties in detection, our scheme uses conventional direct differential photodetection, not single-photon detection or homodyne detection as in previous QKD protocols. System performance assuming some eavesdropping is evaluated, the results of which suggest that our scheme is usable for short or medium distance.
Accidental Coincidence Counts Observed in Mandel Dip Measurement Using Independently Produced Photon Pairs at 1550 nm
Authors: Yoshizawa Akio , Xue Yinghong , Tsuchida Hidemi
Published: January 2011

Mandel dip measurement was performed at 1550 nm using photon pairs created via spontaneous parametric down conversion in two separately located periodically poled lithium niobate waveguides. A visibility of 77.6% was obtained in fourfold coincidence counting. We experimentally clarified that the simultaneous generation of three pairs (one pair created in one waveguide and two pairs created in another waveguide) is the main source of accidental coincidence counts. Propagation loss before mixing two photons at a beamsplitter for observing photon bunching plays an important role in the determination of visibility. A large loss improves visibility, but also reduces the number of fourfold coincidence counts.
Relationship between Thin-Film Transistor Characteristics and Crystallographic Orientation in Excimer-Laser-Processed Pseudo-Single-Crystal-Silicon Films
Authors: Mitani Masahiro , Endo Takahiko , Tsuboi Shinzo , Okada Takashi , Kawachi Genshiro , Matsumura Masakiyo
Published: January 2011

The characteristics of thin-film transistors (TFTs) fabricated on pseudo-single-crystal (PSX)-Si thin films were examined. The variations of mobility were more than the theoretical values derived from the crystallographic orientation dependence of a bulk Si metal–oxide–semiconductor (MOS) transistor. To clarify the origin of this discrepancy, the relationships between the TFT characteristics and the crystallographic orientation of Si films in the channel region were investigated by using an electron backscattering pattern (EBSP) method. It was found that the surface orientation dependence for the PSX-Si TFT was different from that for a bulk Si MOS transistor, especially for the p-channel mode. A group of TFTs having a nearly {100}-oriented nucleus had a mobility close to those of simultaneously processed silicon-on-insulator (SOI) devices in the p-channel mode as well as in the n-channel mode. In contrast, a group of TFTs having a nearly {110}-oriented nucleus had a low and widely scattered mobility. The reason for these results is that twin boundaries with dislocations are easily generated in a grain grown from a {110}-oriented nucleus in order to compensate for the difference of the growth rates in different directions.
Effect of Electron Flow Direction and Via Number on Electromigration Mechanism for Copper Dual Damascene Interconnects
Authors: Cheng Yi-Lung , Shiau Ming-Kai , Chung Wei-Yuan , Wang Ying-Lang
Published: January 2011

In this study, the effects of the via number and the current direction on electromigration characteristics in the dual-damascene Cu lines have been investigated. The results reveal an interesting difference in electromigration behavior of electron up- and down-flow directions on the multi-via structures. Increasing the via number results in a higher electromigration failure time and then reaches saturation for electron up-flow case. As for electron down-flow direction, the failure time is independent of the via number. Moreover, the failure time of Cu lines with via structure is lower than that without via structure. A higher current density at the triple junction site in the inner via is the possible mechanism, resulting in a shorter failure time and via-number independent. These observed effects are specific to Cu dual-damascene structures and can provide great technological implications in electromigration improvement.
Fabrication of Nanosilicon Ink and Two-Dimensional Array of Nanocrystalline Silicon Quantum Dots
Authors: Ishikawa Tetsuya , Nikaido Hiroki , Usami Koichi , Uchida Ken , Oda Shunri
Published: January 2011

An assembly of nanoparticles using a colloidal solution is promising for the fabrication of future highly integrated electron and photoelectronic devices because of low manufacturing cost, flexible substrates, and alternative methods that can overcome the limitation of top-down technology. We have successfully prepared two-dimensional arrays of nanocrystalline silicon (nc-Si) quantum dots with a uniform size of 10 nm. However, the area of two-dimensional arrays has been limited because of the problems of dissolution in water and agglomeration of nc-Si due to a high surface reactivity. The key issue is the surface modification of nc-Si particles. In this study, we have demonstrated the evaluation of surface modification states of nc-Si QDs by zeta potential and particle size distribution measurements. As a result of the optimization of the surface modification process, we have successfully obtained a well-dispersed nc-Si QD solution, namely, nanosilicon ink. Furthermore, we have successfully fabricated a two-dimensional array of nc-Si QDs using the Langmuir-Blodgett film method in the entire 1 ×1 cm2 silicon substrate.
Doping Effect of Single-Wall Carbon Nanotubes on the Microwave Absorption Properties of Nanocrystalline Barium Ferrite
Authors: He Keqiang , Yu Liming , Sheng Leimei , An Kang , Ando Yoshinori , Zhao Xinluo
Published: January 2011

The microwave absorption properties of single-wall carbon nanotubes (SWNCTs) and barium ferrite nanocrystalline (SWCNT/BaFe12O19) composites with different doping ratios are investigated in the frequency region of 2–18 GHz. The transmission line theory is used to calculate the reflection loss properties, and microwave absorptive mechanism of the SWCNT/BaFe12O19composites is discussed. The experiment results reveal that the microwave absorption properties of composite are very sensitive to the volume percentage of SWCNTs. Owing to the multiple absorptive mechanisms, the microwave absorption properties of composite are evidently improved. When SWCNTs are doped with 6 vol % of the sample volume, the maximum reflection loss of the SWCNT/BaFe12O19composite with a 3 mm thickness reaches 30.79 dB at 10.5 GHz, and the range of resonance absorption peak below -10 dB is about 6 GHz.
Laser-Induced Thermal Effect on Sensitivity of Scanning Near-Field Optical Microscope Probe
Authors: Lee Haw-Long , Yang Yu-Ching , Chang Win-Jin
Published: January 2011

In this study, the laser-induced thermal effect on the sensitivity of a scanning near-field optical microscope (SNOM) tapered probe is analyzed. In the analysis, the thermal effect can be considered as an axial force and is dependent on the temperature distribution of the probe. The Rayleigh–Ritz method is used to determine the sensitivity of the probe. According to the analysis, the sensitivity of the first three vibration modes increases when the thermal effect is taken into account. When the contact stiffness is low, the thermal effect on the sensitivity of mode 1 is particularly significant. The sensitivity of mode 1 increases with increasing taper angle and coating thickness of the probe. In addition, the effect of a SNOM probe with three different coating materials, Al, Au, and Ag, on the sensitivity of mode 1 is studied. The result shows that the highest sensitivity is obtained for the probe with an Al coating, whereas it is the lowest with a Au coating.
Influences of Surface Topography on the Flying Performances of a Sub-3 nm Air Bearing Slider
Authors: Hua Wei , Liu Bo , Yu Shengkai , Zhu Weidong
Published: January 2011

This paper studies the influences of the surface roughness and waviness on the static and dynamic flying performances of a thermal protrusion slider with flying height under 3 nm. Simulations show that the air bearing force and the contact force are proportional to the average roughness values of the surfaces, while the intermolecular force or the electrostatic force are the smallest for the smoothest surfaces when the minimum flying height is above a certain value. As a result, the total force on the slider is the largest on the smoothest surfaces in a certain minimum flying height region. When the minimum flying height is designed in this region, the flying ability of the slider is maximized. The energy analysis method is introduced to study the influences of the surface waviness on the dynamic performances of the slider. It is observed that the surface waviness may excite the slider to the bouncing state. The kinetic energy for maintaining the slider in the bouncing state comes mainly from the intermolecular force, while the air bearing force plays an important role in stabilizing the slider. The contributions of other forces, such as the friction force and the contact force, are also evaluated quantitatively. In order to improve the flying stabilities of the slider, the intermolecular force, the friction force and the electrostatic force should be reduced as much as possible.
Solid Composition Control of MgxZn1-xO in Halide Vapor Phase Epitaxy
Authors: Fujii Tetsuo , Yoshii Naoki , Kumagai Yoshinao , Koukitu Akinori
Published: January 2011

Using thermodynamic analysis, the solid compositions of Mg in Mg
x
Zn1-x
O grown by halide vapor phase epitaxy (HVPE) are calculated in terms of the various input partial pressures of the gaseous species. It is revealed that the Mg composition shows temperature stability up to 1200 °C, while there is a strong dependence on the input VI/II ratio and the input H2 partial pressure at high temperatures. Based on the thermodynamic calculations, the epitaxial growth of Mg
x
Zn1-x
O layers with different Mg compositions has been demonstrated. The thermodynamic model is found to accurately describe the experimentally observed dependence of Mg compositions on the input VI/II ratio that is used in the growth of Mg
x
Zn1-x
O.
Electrodeposition of SnO2 Thin Films from Aqueous Tin Sulfate Solutions
Authors: Vequizo Junie Jhon M. , Wang Jun , Ichimura Masaya
Published: January 2011

Tin oxide (SnO2) thin films were successfully electrodeposited on indium tin oxide (ITO) coated glass substrate from an acidic aqueous solution containing SnSO4 at room temperature. Oxygen bubbling was employed so that dissolved oxygen serves as oxygen precursor. With O2 bubbling and short deposition time, transparent films were obtained. The composition ratios of the films were measured by Auger electron spectroscopy. The n-type conductivity and the photosensitivity of the films were confirmed from photoelectrochemical measurement.
Dependences of Initial Nucleation on Growth Conditions of InAs on Si by Micro-Channel Selective-Area Metal–Organic Vapor Phase Epitaxy
Authors: Kondo Yoshiyuki , Deura Momoko , Takenaka Mitsuru , Takagi Shinichi , Nakano Yoshiaki , Sugiyama Masakazu
Published: January 2011

In order to improve the uniformity of InGaAs lateral islands on Si grown by micro-channel selective area growth, we have investigated the dependences of initial InAs nucleation on the partial pressures of trimethylindium (P
TMIn) and tertiary butylarsine (P
TBAs) using the in situ monitoring of surface reflectivity. The high P
TMIn resulted in a short incubation period, a high density of nuclei, and vertical growth, suggesting that a high P
TMIn is suitable for obtaining single nuclei in each growth area, which is vital for the growth of single-domain crystals on Si. Laterally grown InAs nuclei, which are preferable for the lateral growth of InGaAs crystals that succeeds the initial nucleation of InAs, were obtained using either a low P
TMIn or a high P
TBAs, however, the effect of the latter was not significant. P
TBAs did not affect the incubation period. The density, uniformity, and shape of InAs nuclei can be controlled effectively by adjusting P
TMIn, but the uniformity and lateral shape could not be obtained simultaneously. We, therefore, devised a flow-modulated sequence and obtained InAs islands that grew in the lateral direction and almost filled the growth area with a single-crystal domain.
Dynamic Behavior Analysis of Crystal with Magnetic Anisotropy under Imposition of Rotating Magnetic Field
Authors: Iwai Kazuhiko
Published: January 2011

The alignment behavior of a crystal with a magnetic anisotropy of χc< χaunder the imposition of a rotating magnetic field has been investigated by numerical calculation. The promotion of the crystal alignment when the projection of the magnetically hard axis on the magnetic field rotating plane is parallel to the magnetic field direction and its suppression when the magnetically hard axis is perpendicular to the magnetic field direction can be explained by the fact that the direction of the driving torque acting on the crystal minimizes the magnetic energy. Non dimensional alignment time normalized by the alignment time under the imposition of a static field is constant in the out-of-step region where the crystal cannot follow the magnetic field rotation during its alignment. The initial phase difference between the projection of the magnetically hard axis on the magnetic field rotating plane and its direction hardly affects the alignment time in the out-of-step region but strongly affects that in the synchronous region where the crystal rotation synchronous with the magnetic field rotation. A crystal aligns quickly if the initial phase difference is between 0 and 90° in the synchronous region. The minimum alignment time is the same as that under the imposition of a static field.
Characteristics of SrTiO3Field-Effect Transistors with DyScO3Gate Insulators
Authors: Nishio Kazunori , Abe Takuya , Takahashi Ryota , Lippmaa Mikk
Published: January 2011

We have developed a top-gate type of field-effect transistor with a single-crystal SrTiO3channel and a DyScO3gate insulator stack consisting of an epitaxial interface layer and an amorphous breakdown barrier layer. We show that the zero-bias conductivity of the transistor channel is strongly affected by the presence of charged traps in the amorphous gate insulator. Low off-state current could only be achieved in devices that were fabricated at an oxygen ambient pressure of 10 mTorr. At lower pressures, metallic channel interfaces were obtained, even after post-annealing in air. When both epitaxial and amorphous DyScO3films were grown at 10 mTorr of oxygen, the on/off ratio of the field-effect transistors (FETs) reached 106. We argue that when designing oxide FETs, it is necessary to consider not only breakdown characteristics, but also the charged trap density in wide-gap oxide insulators.
Simple Model to Inclusively Understand a Radiated Wave Field in Slot-Excited Microwave Plasmas
Authors: Tsuji Akihiro , Yasaka Yasuyoshi
Published: January 2011

A simple model to inclusively understand radiated wave fields in slot-excited microwave plasmas has been developed. It is shown that the result of the simple model has a good agreement with that of a full wave model from the viewpoint of the mode spectra. The calculation cost of the simple model is considerably lower than that of a commonly used full wave model. In addition, it is also shown that the mode spectra exist in the broad region in the case of a few slots and in the narrow region in the case of many slots. The comparison with the experimental results supports that the physical phenomena such as mode jumps and hysteresis behavior observed in experiments are understood in terms of the mode spectra. Therefore, the simple model is useful to inclusively understand the antenna system and to design an antenna system with the complex slot geometry.
Development of Wide Ion Beam Profile Measurement Method for a Period-by-Period Extreme Ultraviolet Multilayer Milling System
Authors: Tosaka Aki , Sakai Yu , Tsuru Toshihide , Yamamoto Masaki
Published: January 2011

To develop an ion milling system for multilayer mirrors in the extreme ultraviolet (EUV) wavelength region, the current density profile of a φ100-mm-ion beam has been measured by plural methods. The profile has been measured indirectly via milling thickness by an optical surface profiler (WYKO TOPO-2D) and an X-ray diffractometer. Direct current detection by a commercial Faraday cup and a newly developed array electrode sensor was also performed. These methods were compared and evaluated in terms of their experimental results. It was demonstrated that our array electrode sensor is useful for observing a wide ion beam profile with reasonable accuracy.
Evaluation of Electrophoretic Migration of Submicron Particles in a Microgap by Optical and Current Responses
Authors: Sugita Tatsuya , Ohshima Tetsuya
Published: January 2011

We studied the electrophoretic migrations of submicron particles in nonpolar inks sealed in narrow gap cells of 5.3 µm by using optical and current responses. We evaluated the mobility of particles by using the optical responses of the total reflection at interfaces between electrodes and the solvent in addition to simultaneously measuring current, from which the concentrations of ions and charged particles were analyzed. The mobility of the particles in the narrow gap was similar to that of the bulk ink, except for the case with no charge director and less dependence on the charge director concentration. We also analyzed how the mobility was distributed and how the particles interacted with the interface by using the optical responses.
Effect of Flexural Rigidity of Tool on Machining Accuracy during Microgrooving by Ultrasonic Vibration Cutting Method
Authors: Furusawa Toshiaki
Published: January 2011

It is necessary to form fine holes and grooves by machining in the manufacture of equipment in the medical or information field and the establishment of such a machining technology is required. In micromachining, the use of the ultrasonic vibration cutting method is expected and examined. In this study, I experimentally form microgrooves in stainless steel SUS304 by the ultrasonic vibration cutting method and examine the effects of the shape and material of the tool on the machining accuracy. As a result, the following are clarified. The evaluation of the machining accuracy of the straightness of the finished surface revealed that there is an optimal rake angle of the tools related to the increase in cutting resistance as a result of increases in work hardening and the cutting area. The straightness is improved by using a tool with low flexural rigidity. In particular, Young's modulus more significantly affects the cutting accuracy than the shape of the tool.
Analysis of Change in Motional Capacitance of the Electrical Equivalent Circuit of Quartz-Crystal Tuning-Fork Tactile Sensor at Resonance by Combining Analytical Models for Elastic Foundation and L-Shaped Bar with Torsion Spring
Authors: Itoh Hideaki , Hatakeyama Naoki
Published: January 2011

We derived the analytical formula of the motional capacitance C

a
of a quartz-crystal tuning-fork tactile sensor by use of the conservation law of energy that the electrostatic energy in C

a
is equal to the sum of the strain energy of its arm and the elastic energy of the material in contact with its base. In this analysis, the strain energy of the arm and the elastic energy of the material in contact with its base were obtained by applying the torsion spring model to the joint of the arm and the base, which were depicted as an L-shaped bar, and the elastic foundation to the materials in contact with its base, and the electrostatic energy of the arm was derived by applying the bimorph flexural model to the arm treated as a piezoelectric material. As a result of calculation, we found that the calculated value of the change in reciprocal motional capacitance Δ(1/C

a
) of the quartz-crystal tuning-fork tactile sensor by our model is closer to the measured one for plastics than that given by the theoretical formula of motional capacitance of only one arm and Δ(1/C

a
) is affected by the Young's moduli of materials in contact with the sensor's base.
Photocurrent Response of Photoreceptive Devices Using a Retinoid Immobilized in a Chitosan Gel Film
Authors: Tsuchida Yosuke , Hidaka Akira , Mitachi Seiko
Published: January 2011

In order to realize a biophotonic device with biomimetic functions, we focus on the retinal in human eyes. A photoreceptive device was prepared using all-trans retinal immobilized in a gel film chitosan. This device was prepared with either indium tin oxide (ITO)-coated glass and gold-coated glass electrodes (ITO–Au), or using ITO electrodes for both ends (ITO–ITO). Each device was irradiated with 365 nm ultraviolet light for 20 s intervals at an applied voltage of 4 V. The photocurrent response was synchronized to the ON–OFF states of the ultraviolet light and was about 16 times higher for an ITO–ITO device than for an ITO–Au device. We searched for the optimum applied voltage because the ITO–ITO devices deteriorated on the second day at 4 V and found that 3 V produced a photocurrent response in both pre- and post-regenerated devices. Further ITO–ITO devices using three kinds of retinoids (all-trans retinal, all-trans retinoic acid, and all-trans retinol) were prepared. Photocurrent responses measured by a similar method persisted for 331 days using retinal, 313 days using retinoic acid, and 59 days using retinol. Furthermore, the photocurrent response was also observed in post-regenerated gel films of these ITO–ITO devices. These photoreceptive devices could be applied to bio-functional optical sensing or to future visual information processing devices.
Fabricating Super-hydrophobic Polydimethylsiloxane Surfaces by a Simple Filler-Dissolved Process
Authors: Lin Yung-Tsan , Chou Jung-Hua
Published: January 2011

The self-cleaning effect of super-hydrophobic surfaces has attracted the attention of researchers. Typical ways of manufacturing super-hydrophobic surfaces include the use of either dedicated equipment or a complex chemical process. In this study, a simple innovative filler-dissolved method is developed using mainly powder salt and rinsing to form hydrophobic surfaces. This method can produce large super-hydrophobic surfaces with porous and micro rib surface structures. It can also be applied to curved surfaces, including flexible membranes. The contact angle of the manufactured artificial hydrophobic surface is about 160°. Furthermore, water droplets roll off the surface readily at a sliding angle of less than 5°, resembling the nonwetting lotus like effect.
High-Frequency Single-Cell Isolation of Bacteria Using Microenclosure Array with Multipillar Structure
Authors: Matsutani Akihiro , Takada Ayako
Published: January 2011

We proposed and demonstrated the single-cell isolation of bacteria using a microenclosure array with a structure composed of many micropillars. We fabricated the microenclosure array on a semiconductor wafer by electron beam lithography and the dry etching technique. The capturing frequency for single cells of Escherichia coli was approximately 50% using a 4-µm-width microenclosure array. We think that the proposed novel technique is very simple and useful for the single-cell isolation of many kinds of bacteria using a microenclosure array of optimum size.
Influence of Polarization on the Efficiency of InxGa1-xN/GaN p–i–n Solar Cells
Authors: Jeng Ming-Jer
Published: January 2011

The net polarization charge and induced internal electric field can positively or negatively affect the performance of InGaN-based optoelectronic devices, depending on the formation of the polarization charge. While positive polarization charges at the InGaN/n-GaN interface are supposed to affect solar efficiency positively by increasing the electric field, negative polarization charges at the InGaN/n-GaN interface negatively affect efficiency by forming an energy barrier. However, the solar performance is not improved in a beneficial case when the polarization charge reaches 1020 cm-3. In the detrimental case, the efficiency of p-GaN/i-In0.1Ga0.9N/n-GaN solar cells is seriously degraded from 2.75 to 0.49% as the polarization charge increases from 0 to 2.5×1018 cm-3. The insertion of graded layers with a slowly increasing In content is proposed to relax the polarization, and shown to improve solar efficiency.
Fabrication Method of Sub-100 nm Metal–Oxide–Semiconductor Field-Effect Transistor with Thick Gate Oxide
Authors: Singh Vipul , Inokawa Hiroshi , Endoh Tetsuo , Satoh Hiroaki
Published: January 2011

Based on the standard large-scale integrated circuit (LSI) process, sub-100 nm gate metal–oxide–semiconductor field-effect transistor (MOSFET) with thick gate oxide was fabricated. This was realized only by the modification of layout design, and no customization of the fabrication process was necessary. This unique designing technique is of great use in obtaining low-input-leakage MOSFET by advanced LSI process for high-performance analog applications.
Fabrication of ZnO Nanopillars and Their Application to Organic Photovoltaic Cells Based on Conducting Polymer and Fullerene
Authors: Moritou Hiroki , Hori Tetsuro , Ojima Masayoshi , Fukuoka Naoki , Kubo Hitoshi , Fujii Akihiko , Ju Xiaohui , Feng Wei , Ozaki Masanori
Published: January 2011

The fabrication of ZnO nanopillars by electrodeposition and their application to an organic photovoltaic cell have been studied. The growth of ZnO nanopillars on indium-tin-oxide coated quartz substrates strongly depends on the conditions of electrodeposition. The use of a ZnO nanopillar in organic photovoltaic cells with a C60/poly(3-hexylthiophene) interpenetrating interface resulted in improved performance.
Thermal Nanoimprinting on Prealigned Photoreactive Polymer Liquid Crystal for Molecular Reorientation
Authors: Okada Makoto , Manabe Sayaka , Kurita Mami , Kondo Mizuho , Haruyama Yuichi , Kanda Kazuhiro , Emoto Akira , Ono Hiroshi , Kawatsuki Nobuhiro , Matsui Shinji
Published: January 2011

Molecular orientation in a photo-crosslinkable liquid crystalline polymer (PLCP) film was explored by a thermal nanoinprinting technique using a SiO2/Si mold with a line-and-space (L&S) pattern. A molecular oriented structure was confirmed by polarization optical microscopy and diffraction efficiency measurements, at which the reoriented direction was parallel to the mold lines. We demonstrated thermal nanoimprinting on prealigned PLCP films by linearly polarized UV (LPUV) and evaluated the optical characteristics of imprinted PLCP films. As a result, the prealigned PLCP films were reoriented by thermal nanoimprinting.
Sorafenib Therapy in Patients with Advanced Hepatocellular Carcinoma in Advanced Liver Cirrhosis
Authors: Schütte Kerstin , Zimmermann Lars , Bornschein Jan , Csepregi Antal , Rühl Ricarda , Ricke Jens , Malfertheiner Peter
Published: January 2011

Background and Aim: Sorafenib has become the treatment standard for patients with advanced hepatocellular carcinoma (HCC). It is not clear whether patients with advanced liver function impairment (Child B) and patients undergoing additional locoregional therapy may tolerate treatment with sorafenib and benefit. We aimed to evaluate the tolerability and efficiency of sorafenib in patients with advanced HCC and different stages of liver cirrhosis, and in combination with locoregional therapy. Methods: In 50 patients with advanced HCC treated with sorafenib tolerability and efficiency of the therapy with respect to stage of liver cirrhosis, existence of extrahepatic tumor spread, and additional locoregional therapy were evaluated. Results: Fifty patients with advanced HCC were treated with sorafenib, and 13 received additional locoregional therapy. Tolerability of the systemic treatment was moderate in all patients, with no significant differences between the subgroups, while the median survival was better in patients with Child A than Child B cirrhosis. Conclusion: Tolerability and toxicity of a systemic treatment with sorafenib are moderate in patients with liver cirrhosis in Child A or B. Prospective randomized studies are required to evaluate the efficacy and tolerability of combined systemic and locoregional treatment approaches in patients with advanced HCC.