Improvement in Ferroelectric Fatigue Endurance of Poly(methyl metacrylate)-Blended Poly(vinylidene fluoride–trifluoroethylene)

Joo-Won Yoon, Sung-Min Yoon, Hiroshi Ishiwara — 2010-03-05T10:00:00+09:00

Authors: Joo-Won Yoon, Sung-Min Yoon, Hiroshi Ishiwara
Ferroelectric poly(vinylidene fluoride–trifluoroethylene) [P(VDF–TrFE)] and poly(methyl metacrylate) (PMMA)-blended P(VDF–TrFE) thin films are deposited by spin coating on Pt/TiO_{2}/SiO_{2}/Si, and their fatigue endurance is investigated by forming metal–ferroelectrics–metla (MFM) capacitors. It has been found that fatigue endurance is significantly improved by blending PMMA into P(VDF–TrFE). Under the tested conditions, the best endurance for alternating voltage pulses is obtained in the 4 wt % PMMA blended P(VDF–TrFE) film.

LiF/Al Base Electrodes in Vertical Metal-Base Organic Transistors for Heat-Treatment-Free Process

Fumito Suzuki, Ken-ichi Nakayama, Yong-Jin Pu, Masaaki Yokoyama, Junji Kido — 2010-03-05T10:00:00+09:00

Authors: Fumito Suzuki, Ken-ichi Nakayama, Yong-Jin Pu, Masaaki Yokoyama, Junji Kido
Clear current modulation and current amplification were observed in vertical metal-base organic transistors (MBOTs) without heat treatment in air that was previously essential. The devices, which use a LiF/Al base electrode and a C_{60} layer under it, were prepared without heat treatment and showed a large current modulation exceeding 114.5 mA cm^{-2} and a current amplification factor of 51.7 at a collector voltage of 5 V and a base voltage of 3 V. The LiF/Al base electrode and the C_{60} layer under it were found to contribute to the increase in on current and to the decrease in off current, respectively.

Low-Voltage Pentacene Field-Effect Transistors Fabricated on High-Dielectric-Constant Strontium Titanate Insulator

Hu Yan, Toshihiko Jo, Hidenori Okuzaki — 2010-03-05T10:00:00+09:00

Authors: Hu Yan, Toshihiko Jo, Hidenori Okuzaki
A strontium titanate (SrTiO_{3}) thin film on a heavily doped n-type silicon wafer prepared by sputtering was characterized by various means. The result indicated that the thin film mainly consisted of an 87-nm-thick amorphous SrTiO_{3} with a Sr:Ti:O ratio of 1:1.3:4.7, a dielectric constant of ε_{r}=12.1, and a leakage current density of 0.2 nA/cm^{2} at an electric field of 1 MV/cm. Pentacene field-effect transistors fabricated using the SrTiO_{3} thin film as an insulator, showed well-saturated output characteristics at low driving voltages (V_{D}=-3 V), and a hole mobility of 0.08 cm^{2} V^{-1} s^{-1}, an on/off current ratio of 10^{4}, and threshold voltage of -0.7 V.

A Proposal of a Novel Gain Profile Model of Multi-Quantum-Well Semiconductor Optical Amplifiers

Satoshi Shimizu, Hiroyuki Uenohara — 2010-03-05T10:00:00+09:00

Authors: Satoshi Shimizu, Hiroyuki Uenohara
We introduce a novel model of the gain profile of multi-quantum-well semiconductor optical amplifiers (MQW-SOAs) that takes the variation of the gain spectrum with carrier density into detailed account. In this model, the gain spectrum is approximated by a cubic function and its peak gain, peak-gain wavelength, and polynomial coefficients are expressed by hyperbolic functions of carrier density. By using the proposed model, we calculated the static gain characteristics and dynamic response of cross gain modulation (XGM) of an SOA and compared them with the experimental results. Under both operation conditions, very good agreement with the experimental results was obtained.

Optimization of Active Layer Thickness in Planar Organic Solar Cells via Optical Simulation Methods

Patrick Boland, Gon Namkoong — 2010-03-05T10:00:00+09:00

Authors: Patrick Boland, Gon Namkoong
A thin-film optical simulation modeling has been used to determine ideal active layer thicknesses for regioregular poly(3-hexylthiophene) and phenyl-C_{61}/C_{71}-butyric acid methyl ester (P3HT:PC_{61}BM and P3HT:PC_{71}BM) organic blends used as photoactive components in polymer solar cells. Solar cells are simulated based on their optical properties after varying such factors as active layer thickness, electron and hole mobilities, and the Langevin recombination efficiency. Our results indicate that optimizing device efficiency is strongly dependent on the simultaneous control of active layer thickness and the charge carrier mobilities.

LiNbO_{3} Waveguide Quasi-Phase-Matched Highly Nondegenerate Twin Photon Generation Device for Heralded Single Photon Source

Shozo Kajita, Masatoshi Fujimura, Toshiaki Suhara — 2010-03-05T10:00:00+09:00

Authors: Shozo Kajita, Masatoshi Fujimura, Toshiaki Suhara
We designed, fabricated, and characterized a LiNbO_{3} waveguide quasi-phase-matched highly nondegenerate twin photon generation device for a heralded single photon source. The power of the generated photon was nearly proportional to the pump power, as theoretically predicted. The temporal correlation of the generated twin photon was demonstrated by a photon coincidence counting experiment.

Development of a Total Reflection Zone Plate for Hard X-ray Focusing

2010-03-05T10:00:00+09:00

Authors: Takuya Tsuji, Hidekazu Takano, Takahisa Koyama, Yoshiyuki Tsusaka, Yasushi Kagoshima
A total reflection zone plate (TRZP) was developed and fabricated as a hard X-ray focusing device. It consists of a Au zone pattern drawn on a flat SiO_{2} substrate. The reflection only from the zone pattern can be extracted by operating the TRZP with a grazing incident angle between critical angles of Au and SiO_{2}. The effective zone size is fully reduced to the drawn zone size with a small reduction ratio below 1/100. A focusing test using 10 keV X-rays was performed at the “Hyogo-ID” beamline (BL24XU) of SPring-8, and a focusing beam with diffraction-limited size was achieved.

New Approach to Enhance Contrast Ratio at Normal Incidence by Controlling the Retardation of Optical Compensation Film in Vertically Aligned Liquid Crystal Displays

Makoto Ishiguro, Megumi Sekiguchi, Yukito Saitoh — 2010-03-05T10:00:00+09:00

Authors: Makoto Ishiguro, Megumi Sekiguchi, Yukito Saitoh
We found that the light leakage at normal incidence of a vertically aligned liquid crystal display (VA-LCD) in black state is strongly affected by the polarization states of obliquely incident light. Experimental results were explained by a light scattering model of substrates on both sides of a liquid crystal layer. Applying this model, we found that the contrast ratio at normal incidence can be highly enhanced by controlling the retardation value of retardation films. This is a new, effective approach to enhancement of the contrast ratio in LCDs, different from the conventional approach of simply decreasing the depolarization of the scattering media.

Fast Eight-Domain Patterned Vertical Alignment Mode with Reactive Mesogen for a Single-Transistor-Driving

You-Jin Lee, Soo In Jo, Jae-Hoon Kim, Chang-Jae Yu — 2010-03-05T10:00:00+09:00

Authors: You-Jin Lee, Soo In Jo, Jae-Hoon Kim, Chang-Jae Yu
We proposed a wide-viewing patterned vertical alignment (PVA) mode with eight-domains driven by a single transistor. The eight-domain PVA mode was fabricated by introducing two different pretilt angles in a pixel using polymerized reactive mesogens (RMs) within alignment layer. The pretilt angles are simply controlled by an applied voltage during illumination of ultraviolet light for polymerization of the RMs. In addition, the polymerized RMs give rise to defect-free transition in our advanced PVA mode and thus fast response can be achieved over whole grey level.

Optoelectronic Characteristics of HgSe Nanoparticle Films Spin-Coated on Flexible Plastic Substrates

Jaewon Jang, Kyoungah Cho, Kwangsub Byun, Wan-Shick Hong, Sangsig Kim — 2010-03-05T10:00:00+09:00

Authors: Jaewon Jang, Kyoungah Cho, Kwangsub Byun, Wan-Shick Hong, Sangsig Kim
The optoelectronic characteristics of HgSe nanoparticle films spin-coated on plastic substrates are investigated in this work. The photocurrent of a representative HgSe nanoparticle film under the illumination of 633-nm wavelength light is 10 times larger than the dark current in air at room temperature. In addition, the effects of bending on the optoelectronic characteristics of the HgSe nanoparticle film are examined by applying tensile and compressive strains to the plastic substrate.

Highly Stacked and High-Quality Quantum Dots Fabricated by Intermittent Deposition of InGaAs

Takeyoshi Sugaya, Takeru Amano, Masahiko Mori, Shigeru Niki, Michio Kondo — 2010-03-05T10:00:00+09:00

Authors: Takeyoshi Sugaya, Takeru Amano, Masahiko Mori, Shigeru Niki, Michio Kondo
We report the successful fabrication of a highly stacked and well-aligned InGaAs quantum dot (QD) structure of over 50 layers without using a strain compensation technique by the intermittent deposition of InGaAs layers and an As_{2} source, resulting in no degradation in crystal quality. Intermittent deposition of InGaAs layers at relatively high temperature accounts for the formation of InGaAs QDs despite their small lattice mismatch with GaAs. The photoluminescence measurements indicate that the 50-stack InGaAs QD structures have high crystal quality, whereas the crystal quality of multistacked InAs QDs becomes much worse even with four-stack structures.

Stability and Indium Incorporation Processes on In_{0.25}Ga_{0.75}N Surfaces under Growth Conditions: First-Principles Calculations

Toru Akiyama, Tomoki Yamashita, Kohji Nakamura, Tomonori Ito — 2010-03-05T10:00:00+09:00

Authors: Toru Akiyama, Tomoki Yamashita, Kohji Nakamura, Tomonori Ito
The structural stability and indium incorporation on In_{0.25}Ga_{0.75}N surfaces for various orientations are studied on the basis of first-principles total-energy calculations. The calculated surface phase diagrams as functions of temperature and pressure demonstrate that the (0001) and (2-201) surfaces with bulk In concentration of 25% are stabilized for low temperature growth conditions. In contrast, the (1-100) surface forms topmost Ga–N dimers over the wide range of growth conditions, and Ga atoms are preferentially adsorbed on the (1-100) surfaces. These results imply that InGaN with In concentrations of ∼25% can be grown on c-plane and semipolar (2-201) orientations.

Characteristics of Internal Inductively Coupled Plasma Source for Ultralarge-Area Plasma Processing

2010-03-05T10:00:00+09:00

Authors: Jong Hyeuk Lim, Gwang Ho Gweon, Seung Pyo Hong, Kyong Nam Kim, Yi Yeon Kim, Geun Young Yeom
The capacitive–inductive (E–H) mode transition characteristics of an ultralarge-area (2,750×2,350 mm^{2}) inductively coupled plasma (ICP) system with multiple internal U-type antennas have been investigated. When the electrical characteristics of the ICP antenna such as power transfer efficiency and ICP source impedance, were measured as a function of ICP power, a distinctive change from E to H mode was identified at an rf power of approximately 3 kW. When the power transfer mode was changed from capacitive to inductive for the multiple U-type antenna configuration, better plasma uniformity was obtained owing to the more uniform power deposition along the antenna line.

Recent articles in Jpn. J. Appl. Phys.

Improvement in Ferroelectric Fatigue Endurance of Poly(methyl metacrylate)-Blended Poly(vinylidene fluoride–trifluoroethylene)

LiF/Al Base Electrodes in Vertical Metal-Base Organic Transistors for Heat-Treatment-Free Process

Low-Voltage Pentacene Field-Effect Transistors Fabricated on High-Dielectric-Constant Strontium Titanate Insulator

A Proposal of a Novel Gain Profile Model of Multi-Quantum-Well Semiconductor Optical Amplifiers

Optimization of Active Layer Thickness in Planar Organic Solar Cells via Optical Simulation Methods

LiNbO_{3} Waveguide Quasi-Phase-Matched Highly Nondegenerate Twin Photon Generation Device for Heralded Single Photon Source

Development of a Total Reflection Zone Plate for Hard X-ray Focusing

New Approach to Enhance Contrast Ratio at Normal Incidence by Controlling the Retardation of Optical Compensation Film in Vertically Aligned Liquid Crystal Displays

Fast Eight-Domain Patterned Vertical Alignment Mode with Reactive Mesogen for a Single-Transistor-Driving

Optoelectronic Characteristics of HgSe Nanoparticle Films Spin-Coated on Flexible Plastic Substrates

Highly Stacked and High-Quality Quantum Dots Fabricated by Intermittent Deposition of InGaAs

Stability and Indium Incorporation Processes on In_{0.25}Ga_{0.75}N Surfaces under Growth Conditions: First-Principles Calculations

Characteristics of Internal Inductively Coupled Plasma Source for Ultralarge-Area Plasma Processing