bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study of Floating-Gate-Type Metal–Oxide–Semiconductor Capacitors with Nanosize Triangular Cross-Sectional Tunnel Areas for Low Operating Voltage Flash Memory Application
Authors: Liu Yongxun , Guo Ruofeng , Kamei Takahiro , Matsukawa Takashi , Endo Kazuhiko , O'uchi Shinichi , Tsukada Junichi , Yamauchi Hiromi , Ishikawa Yuki , Hayashida Tetsuro , Sakamoto Kunihiro , Ogura Atsushi , Masahara Meishoku
Published: June 2012

The floating-gate (FG)-type metal–oxide–semiconductor (MOS) capacitors with planar (planar-MOS) and three-dimensional (3D) nanosize triangular cross-sectional tunnel areas (3D-MOS) have successfully been fabricated by introducing rapid thermal oxidation (RTO) and postdeposition annealing (PDA), and their electrical characteristics between the control gate (CG) and FG have been systematically compared. It was experimentally found in both planar- and 3D-MOS capacitors that the uniform and higher breakdown voltages are obtained by introducing RTO owing to the high-quality thermal oxide formation on the surface and etched edge regions of the n+ polycrystalline silicon (poly-Si) FG, and the leakage current is highly suppressed after PDA owing to the improved quality of the tetraethylorthosilicate (TEOS) silicon dioxide (SiO2) between CG and FG. Moreover, a lower breakdown voltage between CG and FG was obtained in the fabricated 3D-MOS capacitors as compared with that of planar-MOS capacitors thanks to the enhanced local electric field at the tips of triangular tunnel areas. The developed nanosize triangular cross-sectional tunnel area is useful for the fabrication of low operating voltage flash memories.
Microfabrication of Si-Based High-Index-Contrast-Grating Structure by Thermal Nanoimprint Lithography and Cl2/Xe-Inductively Coupled Plasma Etching
Authors: Matsutani Akihiro , Hashidume Yuuki , Ohtsuki Hideo , Koyama Fumio
Published: June 2012

We demonstrated the fabrication of a Si-based high-index-contrast-grating (HCG) structure by thermal nanoimprint lithography and Cl2/Xe-inductively coupled plasma (ICP) etching. A vertical etching profile and a smooth etched surface, which satisfy the requirements for optical device application, were obtained. We believe that this proposed process is useful for the microfabrication of Si-based optical devices, such as the HCG structure, photonic crystals, narrow optical waveguides, and micro-electro-mechanical systems (MEMS).
Pattern Transfer Characterization after Double-Level Lithography for a Fabrication of the Three-Dimensional Aluminum Titanium Carbide Air Bearing Surface of the Hard Disk Slider
Authors: Pholprasit Patama , Atthi Nithi , Thammabut Thawat , Jeamsaksiri Wutthinan , Hruanun Charndet , Poyai Amporn , Silapunt Rardchawadee
Published: June 2012

The transfer characteristics of the three-dimensional (3D) photoresist (PR) pattern to the aluminum titanium carbide (AlTiC) layer made for an air bearing surface (ABS) using the double-level lithography process and reactive ion etching (RIE) is investigated. The simulated process windows for single-level (conventional) and double-level lithography provide the process conditions to obtain desired PR thicknesses. The PR pattern with the underneath AlTiC layer is then etched with the designed recipe that consists of three consecutive etchings using CF4, O2, and CF4, respectively. The triple-step pattern is successfully formed on the AlTiC layer. The nonlinear relationship of the cumulative exposure and the PR thickness is believed to contribute to a decrease in etch selectivity of PR:AlTiC on the double-exposure area with the cumulative exposure.
Simple Fabrication of Nickel Micropatterning under Ambient Condition: Use of Pen-Type Nanolithography and Electroless Plating
Authors: Onoue Miki , Ushijima Hirobumi
Published: June 2012

Recently, the research and development of printed electronics has been expanded. Patterning of various materials is required to fabricate many electronic devices by the printing technique. Nickel patterning, for instance, is the subject matter of condensers. In this study, we demonstrated (1) catalytic Pd patterning by fountain-pen nanolithography (FPN) and (2) the preparation of Ni micropatterns by Ni electroless plating. The FPN is one of the pen-type nanolithography techniques and it can yield microsize patterns.
Fabrication of 5-nm-Sized Nanodots Using Self-Assembly of Polystyrene–Poly(dimethylsiloxane)
Authors: Huda Miftakhul , Liu Jing , Yin You , Hosaka Sumio
Published: June 2012

In this work, we studied the self-assembly development of a polystyrene–poly(dimethylsiloxane) (PS–PDMS) block copolymer with molecular weight of 7,000–1,500, which has potential to form nanodots with size of several nanometers. Annealing time and temperature were intensively investigated. Distinct nanodots with a size of 6 nm and a pitch of 13 nm were obtained at a low annealing temperature of 130 °C, and nanodots with a size of 5 nm and a pitch of 12 nm were obtained at an annealing temperature of 170 °C. It was found that nanodots were formed when annealing time was reduced to as short as 6 h. This technique implies the possible high-throughput and low-cost fabrication of magnetic recording media with a density of up to 5.17 Tbit/in.2.
Alignment and Use of Self-Assembled Peptide Nanotubes as Dry-Etching Mask
Authors: Andersen Karsten B. , Castillo-León Jaime , Bakmand Tanya , Svendsen Winnie E.
Published: June 2012

Self-assembled diphenylalanine peptide nanotubes provide a means of achieving nanostructured materials in a very simple and fast way. Recent discoveries have shown that this unique material, in addition to remaining stable under dry conditions, rapidly dissolves in water making it a promising candidate for controlled nanofabrication without organic solvents. The present work demonstrates how this unique structure can be aligned, manipulated and used as both an etching mask in a dry etching procedure and as a lift-off material. As a further demonstration of the potential of this technique, the peptide nanotubes were utilized to fabricate silicon nanowire devices and gold nanoslits in a rapid manner.
Molecular Dynamics Study on Enhanced Cu Coverage of Trench Filling with Low-Index Ta Surfaces
Authors: Hong Rong-Tai , Yang Jaw-Yen
Published: June 2012

The Cu coverage of trench filling enhanced by different low-index surfaces of tantalum in physical vapor deposition is studied by molecular dynamics simulation with the embedded atom method (EAM) as the interaction potential for the present alloy metal system. The deposition morphologies and bottom step coverage enhancement of trenches with three different aspect ratios are examined. It is found that the Cu adatom on Ta(110) with uniform and low surface diffusion barrier energy and that on Ta(111) with high surface energy lead to the improvement of the surface diffusion of Cu adatoms. The shadowing effect is inhibited on Ta(110) and Ta(111) such that the bottom step coverage of the trench is enhanced markedly at an early stage and the final coverage of trench filling is improved significantly. Also, the texture of deposition on the trench with Ta(110) has a uniform structure owing to the low surface energy, while that with Ta(111) has a nonuniform structure owing to the high surface energy on the sidewall.
Influence of Rapid Thermal Annealing and Substrate Terrace Width on Self-Organizing Formation of Periodic Straight Nanogroove Array on NiO(111) Epitaxial Thin Film
Authors: Yamauchi Ryosuke , Tan Geng , Shiojiri Daishi , Koyama Koji , Kaneko Satoru , Matsuda Akifumi , Yoshimoto Mamoru
Published: June 2012

Room-temperature-grown NiO(111) epitaxial thin films on atomically stepped sapphire (0001) substrates by pulsed laser deposition have straight atomic steps. For a terrace width of about 50 nm, a periodic straight nanogroove array with a depth of about 6 nm was formed over the film surface after rapid thermal annealing. When using a substrate with a terrace width of about 250 nm, it is observed that two types of 180°-rotated triangular crystalline domain are alternately grown on each film terrace divided by the nanogrooves.
Characterization of ZnO Tetrapods Prepared by a Simple Oxidation of Zn Plate in Air Atmosphere
Authors: Bae Du-han , Lee Geun-Hyoung
Published: June 2012

ZnO tetrapods were synthesized by a simple evaporation and oxidation of Zn plate in air atmosphere. The Zn plate was placed in an alumina crucible and the crucible was simply inserted into a furnace at 930 °C without any additives. The oxidation time was changed in the range of 30 to 120 min to investigate the effect of oxidation time on the morphology and optical property of ZnO tetrapods. The X-ray diffraction (XRD) results showed the ZnO tetrapods had wurtzite structure. The field emission scanning electron microscopy (SEM) images revealed that the shape of the tetrapod legs changed from needle to hexagonal shape, and then to cylindrical shape with the increase in oxidation time. On the other hand, the highest UV/green emission ratio was observed for the ZnO tetrapods which consisted of legs with hexagonal shape. In addition, the dead spots in cathodoluminescence (CL) images were observed at the center of the tetrapods.
Photodissolution Suppression and Photocatalytic Activity Improvement through Crystallinity Improvement of ZnO Nanocrystalline Thin Films
Authors: Kasahara Rei , Harako Susumu , Komuro Shuji , Zhao Xinwei
Published: June 2012

Zinc oxide (ZnO) is an attractive candidate for semiconductor photocatalysis studies because of its strong oxdizability and wide bandgap. However, ZnO has the problem of photodissolution in the aqueous phase and photocatalytic activity decrease due to dissolution. In this paper, we report the photocatalytic property of nanocrystalline ZnO thin films fabricated by laser ablation. The films grown at different annealing temperatures and times have been characterized using X-ray diffraction and a scanning electron microscope. The photocatalytic activity of ZnO thin films was determined by the decoloration of azo dye OrangeII solution and hydrogen generation. It was shown that the photocatalytic activity of ZnO thin films depends on the annealing temperature and time, and photodissolution of the sample can be inhibited by increasing the crystallinity of ZnO. It was also shown that the ZnO thin layer with high crystallinity generates hydrogen from NaOH solution without applying bias voltage.
Hydrothermal Synthesis of Silicon-Based Hollow Nanostructures
Authors: Sonae Satoru , Ara Masato , Tada Hirokazu
Published: June 2012

Silicon-based hollow structures with a diameter on the order of 300 nm were prepared from silicon monoxide by hydrothermal synthesis without any catalytic materials. Structural analysis of the products revealed that the shell of hollow structures was composed of amorphous SiO
x
. It was expected that nanoscale bubbles act as cores on which thin SiO
x
shells grew. Since the nanobubbles are generated in water under high pressure at the nuclei formation stage, the dimension of capsules can be controlled by adjusting the pressure.
Utilization of Size-Controlled Squid Ink Particles as Enhancer for the Porosity of Titania Electrode in Dye-Sensitized Solar Cell
Authors: Matsuura Toshihiko , Kato Takamine , Minato Ken-ichi , Ueno Takashi
Published: June 2012

TiO2 films were prepared using a paste mixture of titania and size-controlled squid ink particles that was used to manufacture macroporous electrodes in a dye-sensitized solar cell (DSSC). The sintering procedure at 450 °C decomposed the ink particles, thereby increasing the porosity of the structure in the films. An increase in the proportion of ink particles in the paste formulation increased the surface roughness of the films. The ink particles in the paste consequently enhanced the film porosity. The TiO2 films prepared using a paste mixture consisting of 30% ink particles had the roughest surface, but its DSSC had the lowest photoelectric conversion efficiency. Thus, this study revealed the effects of the paste composition on the TiO2 film morphology and DSSC performance.
Effect of Solvent on the Dielectric Properties of Nanocomposite Poly(methyl methacrylate)-Doped Titanium Dioxide Dielectric Films
Authors: Ismail Lyly Nyl , Mohamad Nik Noor Hafizah Nik , Shamsudin Muhamad Salleh , Zulkefle Habibah , Abdullah Mohd Hanapiah , Herman Sukreen Hana , Rusop Mohamad
Published: June 2012

A poly(methyl methacrylate)-doped titanium dioxide (PMMA:TiO2) nanocomposite film was obtained by spin coating the nanocomposite solution onto a silicon substrate. The nanocomposite solutions were prepared by dissolving the PMMA and TiO2nanopowder in three different types of organic solvent, namely, toluene, tetrahydrofuran (THF), and acetone. We found that the dielectric properties of the PMMA:TiO2nanocomposite are dependent on the type of solvent used. The dielectric properties measured at a frequency of 1 kHz showed that acetone gives the highest dielectric constant and capacitance compared with toluene and THF. Toluene gives the lowest dielectric loss among the three. The topography and roughness of the PMMA:TiO2nanocomposite indicate that a particular solvent results in a different kind of surface morphology.
Simple Fabrication of Two-Dimensional Self-Assemblies Consisting of Gold and Silver Nanoparticles at an Air/Toluene Interface and Their Surface-Enhanced Raman Scattering Activity
Authors: Sugawa Kosuke , Tanoue Yoshimasa
Published: June 2012

A methodology for fabricating two-dimensional assemblies consisting of octadecylamine-stabilized gold, silver, and mixed gold and silver nanoparticles at an air/toluene droplet interface is reported. After evaporation of the toluene solvent, the structure and optical properties of the resulting high-density nanoparticle assemblies were evaluated by transmission absorption spectroscopy and scanning electron microscopy (SEM). In addition, an investigation of the surface-enhanced Raman scattering (SERS) activity of para-mercaptoaniline molecules adsorbed on these assemblies revealed that by increasing the mixing ratio of silver nanoparticles to gold nanoparticles, SERS signals were significantly enhanced due to an adjustment in the excitation wavelength of surface plasmon resonance and an enhancement of the local electromagnetic field.
Fast Formation of Conductive Material by Simultaneous Chemical Process for Infilling Through-Silicon Via
Authors: Kawakita Jin , Chikyow Toyohiro
Published: June 2012

It is necessary to develop a fast and inexpensive fabrication process of vertical electric wiring by through-silicon via (TSV) technology for advanced three-dimensional semiconductor devices. In this research, a fast-forming conductive composite was successfully developed by simultaneous deposition of conductive organic polymer (polypyrrole) and metal (silver) from the liquid phase, accelerated by photoirradiation. The growth rate of the composite was 38 nm·s-1, which is more than 10 times higher than that of copper by conventional plating. The electric conductivity of the composite was 2.1×104 Ω-1·cm-1, which is on the same level as general metal conductors. In addition, the effects of reaction conditions on the growth rate and the conductivity of the composites were revealed. From these results, the infilling time of the TSV was expected to shorten from the present 2–10 h to 5–10 m.
Effect of Potassium Chloride Concentration on the Structural and Optical Properties of ZnO Nanorods Grown on Glass Substrates Coated with Indium Tin Oxide Film
Authors: Yang Hee Yeon , No Young Soo , Kim Jin Young , Kim Tae Whan
Published: June 2012

ZnO nanorods were grown on glass substrates coated with an indium tin oxide film by electrochemical deposition. X-ray photoelectron spectroscopy spectra of the ZnO samples included Zn 2p3/2, Zn 2p1/2, and O 1s peaks, indicative of the formation of ZnO nanorods. Scanning electron microscopy images showed that the density of the ZnO nanorods decreased with increasing potassium chloride (KCl) concentration. No spurious phase was observed in X-ray diffraction patterns, regardless of the KCl concentration. A strong UV peak between 382 and 385 nm in the PL spectra was related to the near band-edge emissions of ZnO nanorods.
Imprinted Pattern Profile-Dependent Optical Properties of Metal Nanostructures
Authors: Choi Jun-Hyuk , Park Seong-Je , Lee Ji-Hye , Kim Chul-Hyun , Jeong Jun-Ho , Choi Dae-Geun , Lee Eung-Sug , Jeong Jong-Ryul
Published: June 2012

As-imprinted right-edged pillar structures were reconfigured into a tapered sidewall profile by CHF3-based reactive ion etch. The transmittance spectra improved as the sidewall became more tapered for longer etch times. The effect was most distinctive (28.4%) in the transmittance trench zone at wavelengths from 460 to 470 nm owing to the reduced diffraction scattering loss. The transmittance enhancement for silver-coated corrugated nanostructures was even greater (57.0%) for a tapered sidewall structure, in close agreement with the predictions of simulations. The infrared transmittance was notably reduced compared with that in the UV–visible zone, suggesting the possible applications of the structures in heat-insulated windows.
Silica/Ultraviolet-Cured Resin Nanocomposites for Replica Molds in Ultraviolet Nanoimprinting
Authors: Yun Cheol Min , Kudo Shimpei , Nagase Koichi , Kubo Shoichi , Nakagawa Masaru
Published: June 2012

Fluid UV-curable composite resins made with methacrylate-modified silica nanoparticles (NPs), a diacrylate monomer, and a photoinitiator without nonreactive solvents were prepared to develop composite replica molds in UV nanoimprinting. 1,4-Bis(acryloyloxy)butane was compatible with NPs up to an inorganic silica component of 60 wt %, and its cured composite films showed a high transmittance of >89% at an i-line wavelength of 365 nm. The fluorinated antisticking layer obtained from an antisticking reagent was formed effectively on a composite surface at which bare silica surfaces of NPs appeared by photooxidation of the composite film surface. Composite replica molds could be fabricated by putting a droplet of the composite resin on a silica substrate modified with a reactive adhesion layer, filling cavities of a fluorinated master mold with the resin under a pentafluoropropane (PFP) atmosphere, curing the molded resin by exposure to UV light, and treating the surface of the cured resin with the antisticking reagent after demolding. It was confirmed that the composite replica molds were available for step-and-repeat UV nanoimprinting using an acrylate-type UV-curable resin in PFP. The composite replica molds showed remarkably smaller release energies than the replica mold without NPs.
Morphological Changes in Ultraviolet-Nanoimprinted Resin Patterns Caused by Ultraviolet-Curable Resins Absorbing Pentafluoropropane
Authors: Kaneko Shu , Kobayashi Kei , Tsukidate Yoshitaka , Hiroshima Hiroshi , Matsui Shinji , Nakagawa Masaru
Published: June 2012

In this article, we revealed the maximum values of pentafluoropropane (PFP) absorbed by acrylate-type monomers and UV-curable resins causing radical photopolymerization and measured the viscosities in a state saturated with PFP. We described the influences of PFP condensable gas effectively used in UV nanoimprinting on the morphologies of resin patterns fabricated by UV nanoimprinting. The weights of the resins and monomers were increased by exposure to a PFP atmosphere, while the viscosities were reduced markedly. The absorption of PFP depended on the chemical structures of the monomers. The solubility parameter calculated by the Hoy method clearly suggested that the monomer with a solubility parameter of 20 (J cm-3)1/2absorbed the most PFP. The UV-curable resin composed of the monomer absorbing a large amount of PFP resulted in morphological changes in nanoimprinted resin patterns where the height was lowered and the outermost surface became rough. The UV-curable resins having hydroxyl groups play an important role in preserving the size fidelity of UV-nanoimprinted resin patterns.
Effective Linewidth Measurement of 45-nm-Half-Pitch Ultraviolet Nanoimprint Lithography Patterns by Scanning Electron Microscope Inspection and Extremely Shallow Si Etching
Authors: Suzuki Kenta , Youn Sung-Won , Wang Qing , Hiroshima Hiroshi , Nishioka Yasushiro
Published: June 2012

Resist pattern shrinkage during a scanning electron microscope (SEM) inspection is a critical issue in the measurement of the linewidth or critical dimension (CD) of sub-100 nm polymer patterns. For example, the pattern shrinkages were set to 2.3–4.4 nm for half-pitch (hp) 45–90 nm line and space (L/S) PAK-01 patterns fabricated by UV nanoimprint under SEM conditions to diminish pattern shrinkage. We propose an evaluation method of actual CDs of UV nanoimprint lithography (UV-NIL) patterns by extremely shallow Si etching combined with residual layer removal etching. The method was used to conduct stable measurement without any shrinkage problem by transferring patterns fabricated by UV nanoimprint to the Si substrate. Although the linewidth slightly decreased with etching time, we estimated the linewidths just after the residual layer removal for nominal 45, 65, and 90 nm L/S patterns to be 40.3, 55.1, and 72.1 nm, respectively, by combining the widths determined by SEM with the depths determined by AFM. The method enables us to evaluate linewidth more precisely for finer patterns.
Improvement of Electrical Stimulation Protocol for Simultaneous Measurement of Extracellular Potential with On-Chip Multi-Electrode Array System
Authors: Kaneko Tomoyuki , Nomura Fumimasa , Hattori Akihiro , Yasuda Kenji
Published: June 2012

Cardiotoxicity testing with a multi-electrode array (MEA) system requires the stable beating of cardiomyocytes for the measurement of the field potential duration (FPD), because different spontaneous beating rates cause different responses of FPD prolongation induced by drugs, and the beating rate change effected by drugs complicates the FPD prolongation assessment. We have developed an on-chip MEA system with electrical stimulation for the measurement of the FPD during the stable beating of human embryonic stem (ES) cell-derived cardiomyocyte clusters. Using a conventional bipolar stimulation protocol, we observed such large artifacts in electrical stimulation that we could not estimate the FPD quantitatively. Therefore, we improved the stimulation protocol by using sequential rectangular pulses in which the positive and negative stimulation voltages and number of pulses could be changed flexibly. The balanced voltages and number of pulses for sequential rectangular pulses enabled the recording of small negative artifacts only, which hardly affected the FPD measurement of human-ES-cell-derived cardiomyocyte clusters. These conditions of electrical stimulation are expected to find applications for the control of constant beating for cardiotoxicity testing.
Effect of Microscale Surface Geometry of Electrodes on Performance of Microbial Fuel Cells
Authors: Kano Tomonori , Suito Eiichi , Hishida Koichi , Miki Norihisa
Published: June 2012

In this study, we experimentally revealed that the microscale surface geometry of anodes strongly affects the performance of microbial fuel cells (MFCs). MFCs have much need to be improved in their power. The power generated by an MFC is considered to be strongly affected by the interaction between the organic bacteria and the inorganic electrode surfaces. In prior work, the nanoscale surface roughness of the anode was discussed; however, we consider that the microscale surface geometry may play a crucial role given the bacteria size of micrometer order. We used a two-chamber MFC and the direct electron transfer bacteria Shewanella putrefaciens. We prepared seven types of anode electrodes with different microscale surface geometries and experimentally found that the MFC performance depended on the contact area between the bacteria and the anode. The MFC generated the maximum power when the contact area between the anode and bacteria was the largest.
Extended Depth of Field Optics for Precise Image Analysis in Microfluidic Flow Cytometry
Authors: Hattori Akihiro , Yasuda Kenji
Published: June 2012

We have examined a method to address the defocusing problem on target samples in a microfluidic pathway by an optical approach and report our experiment. An imaging optics has been constructed for extension of the depth of focused field. This system consists of four parts: (1) a low numerical aperture (NA; i.e., large depth of field) objective lens; (2) a zoom lens; (3) a light-emitting diode (LED) illumination source; and (4) a charge-coupled device (CCD) camera. As a low NA objective lens contributes to the extension of the depth of field and a zoom lens contributes to the optimization of pixel resolution on an image sensor of a camera, the same resolution as that of a 40× objective lens was acquired by the combination of a 10× objective lens and a 4× zoom lens as the spatial resolution of the latter combination was within the size of pixels of the CCD camera. As a result, improved depth of field was obtained at any magnification from 10× to 40×, and it was indicated that an extended depth of field optics for image-based microfluidic pathways such as in flow cytometry can be constructed using a low NA objective lens and a zoom lens.
Quantitative Evaluation of Closed-Loop-Shaped Cardiomyocyte Network by Using Ring-Shaped Electrode
Authors: Nomura Fumimasa , Kaneko Tomoyuki , Hamada Tomoyo , Hattori Akihiro , Yasuda Kenji
Published: June 2012

Re-entry of excitation in the heart is one of the abnormal phenomena that causes lethal arrhythmia and is thought to be induced by the looped structure of the excitation conduction pathway. To evaluate the geometrical pattern dependence of electrophysiological results, we fabricated three models of cardiomyocyte networks and compared their beating frequencies (BFs), amplitudes of a depolarization peak, and field potential durations (FPDs). The set of different closed-loop-shaped network models from 3 to 8 mm in length showed the same BFs, amplitudes, and FPDs independent of their loop lengths, whereas the BFs and FPDs of 60 µm small clusters, and the FPDs of the 2 mm open-line-shaped network model were different from those of a closed-loop-shaped network model. These results indicate that the mm order larger size of clusters might create lower BFs, and the closed-loop-shaped model may generate longer FPDs. They also suggest the importance of spatial arrangement control of the cardoimyocyte community for reproducible measurement of electrophysiological properties of cardiomyocytes, especially control of the closed-loop formation, which might change the waveforms of FPDs depending on the difference in the geometry and conduction pathway of the cell network.
Photochemically Induced Crystallization of Proteins Accelerated on Two-Dimensional Gold Gratings
Authors: Tawa Keiko , Haruta Susumu , Okutsu Tetsuo , Nishii Junji
Published: June 2012

The photochemically induced crystallization of lysozyme was studied on a two-dimensional surface relief grating coated with a thin gold film (2D-plasmonic chip), a flat thin gold film, and a flat UV-curable resin. The lysozyme solution prepared in a metastable compositional region was dropped on each surface. After an exposure to visible light from a filtered Hg lamp (500 and 800 nm in wavelength, 1.5 W/cm2) for 30 min followed by 18 h keeping in the dark, the crystal particles were observed in the droplets. Under a microscope, the numbers of crystalline particles were counted to be 1280, 258, and 180 on the 2D-plasmonic chip, the flat gold film, and the flat UV-curable resin, respectively. It was suggested that the crystallization tendency of lysozyme was effectively accelerated by the enhanced electric field caused by the coupling of incident light with surface plasmon polaritons on the 2D-plasmonic chip.
New Laser-Scan Exposure System for Delineating Precise Helical Patterns onto Sub-50-µm Wires
Authors: Horiuchi Toshiyuki , Sasaki Ryosuke
Published: June 2012

A new laser-scan exposure system for patterning onto fine wires and pipes with diameters as small as 40 µm was developed. New schemes for vertically holding specimens were adopted, and improved optics of imaging and in situ observation were used. In addition, specially contrived half-vacuum support guides were attached, and a short-wavelength violet laser with a wavelength of 408 nm was also attached. Because the laser beam spot was kept steady at a constant size by the improved half-vacuum support guide with triple narrow slits, patterns with homogeneous widths of approximately 20 µm were constantly delineated suppressing the width fluctuations to less than ±2 µm. In addition, owing to the short-wavelength laser, exposure time was greatly decreased to approximately 1/10 compared with the previous system. The new exposure system will be applicable to development of fine microcomponents such as microcoils useful for very fine probe pins of semiconductor device testers.
Transparent Solar Concentrator for Flat Panel Display
Authors: Yeh Chia-Hung , Chang Fuh-Yu , Young Hong-Tsu , Hsieh Tsung-Yen , Chang Chia-Hsiung
Published: June 2012

A new concept of the transparent solar concentrator for flat panel display is experimentally demonstrated without adversely affecting the visual effects. The solar concentrator is based on a solar light-guide plate with micro prisms, not only increasing the absorption area of solar energy but also enhancing the conversion efficiency. The incident light is guided by the designed solar light-guide plate according to the total internal reflection (TIR), and converted into electrical power by photovoltaic solar cells. The designed transparent solar concentrator was made and measured with high transparency, namely 94.8%. The developed solar energy system for display can store energy and supply the bias voltage to light on two light-emitting diodes (LEDs) successfully.
Electrowetting Lens Employing Hemispherical Cavity Formed by Hydrofluoric Acid, Nitric Acid, and Acetic Acid Etching of Silicon
Authors: Lee June Kyoo , Choi Ju Chan , Jang Won Ick , Kim Hak-Rin , Kong Seong Ho
Published: June 2012

We demonstrate the design of an electrowetting lens employing a high-aspect-ratio hemispherical lens cavity and its micro-electro-mechanical-system (MEMS) fabrication process in this study. Our preliminary simulation results showed that the physical and electrical durability of the lens can be improved by the mitigation of stresses on the insulator at the hemispherical cavity. High-aspect-ratio hemispherical cavities with various diameters and very smooth sidewall surfaces were uniformly fabricated on a silicon wafer by a sophisticated isotropic wet etching technique. Moreover, we experimentally investigated the optical properties of the MEMS-based electrowetting lens with the proposed cavity. Two immiscible liquids in the proposed lens cavity were electrostatically controlled with negligible optical distortion and low focal-length hysteresis due to the fully axis-symmetrical geometry and smooth sidewall of the cavity.
Lamé-Mode Octagonal Microelectromechanical System Resonator Utilizing Slanting Shape of Sliding Driving Electrodes
Authors: Okamoto Tadashi , Tanigawa Hiroshi , Suzuki Kenichiro
Published: June 2012

For high-resonant-frequency microelectromechanical system (MEMS) resonators, the reduction of the gap between the driving electrode (DE) and the resonant plate is very important, because the electromechanical coupling coefficient greatly increases to compensate for the output signal decrease. In this paper, we describe a new technique for forming a submicron narrowed gap by sliding a DE with a slanting shape. The slant gap helps to avoid the pattern size dependence in the fabrication, because each gap length is the same. By adapting the sliding DE, a Lamé-mode octagonal MEMS resonator was investigated. The fabricated resonator has the Lamé-mode resonance at 12.48 MHz. After narrowing the gap, the mechanical displacement amplitude was directly measured using a laser-Doppler vibrometer. The results show that the narrowed gap yields a great improvement (92 times) in the amplitude, compared with that before narrowing the gap. A large decrease in the absolute impedance and a large phase transition around the resonant frequency have also been observed. The influence of the experimentally obtained gap length asymmetry on the degradation of the resonators is also discussed.
Thermal–Photovoltaic Hybrid Solar Generator Using Thin-Film Thermoelectric Modules
Authors: Mizoshiri Mizue , Mikami Masashi , Ozaki Kimihiro
Published: June 2012

We fabricated thin-film thermoelectric modules for thermal–photovoltaic hybrid solar generator. Bi0.5Sb1.5Te3(p-type) and Bi2Te2.7Se0.3(n-type) thermoelectric thin films were deposited by radio-frequency magnetron sputtering method and patterned to form plane-type thermoelectric modules using lift-off technique. The hybrid module consisted of the thin-film thermoelectric module, a photovoltaic module, a hot mirror, and a near-infrared (NIR) focusing lens. NIR light, which does not contribute to photovoltaic conversion, was separated from solar light using the hot mirror. When the NIR light was focused onto the hot side of the thermoelectric module by the lens, the open voltage generated by the thin-film thermoelectric generator was 78 mV. The total open voltage of the thermal–photovoltaic hybrid generator increased by 1.3% compared to that of the photovoltaic module alone.
Micro-Electro-Mechanical-Systems-Based Micro-Ro-Boat Utilizing Steam as Propulsion Power
Authors: Choi Ju Chan , Choi Young Chan , Lee June Kyoo , Kong Seong Ho
Published: June 2012

We report the design and fabrication of a micro-electro-mechanical-systems (MEMS)-based microactuator, that floats on the surface of water and is driven by steam. We named the actuator “micro-Ro-boat”, a compound word created from the words “robot” and “boat”. The MEMS-based micro-Ro-boat utilizes steam as the propulsion power, giving it a high speed and long lifetime. A hydrophobic surface has been utilized for the wing of the actuator to enhance the buoyancy. Instead of using gas or fuel, the proposed micro-Ro-boat utilizes steam form electrically heated water. The velocity of the micro-Ro-boat is in the range of 0.5–2 cm/s and the maximum loading capability for a device size of 10 ×10 mm2is 0.4 g.
Miniaturized Dual-Axis Electrolytic Tilt Sensor
Authors: Choi Ju Chan , Choi Young Chan , Lee June Kyoo , Kong Seong Ho
Published: June 2012

The electrolytic tilt sensor operates by measuring the change of conductance between detecting electrodes immersed in an electrolyte. Previously reported electrolytic tilt sensors detect an inclination only on one axis owing to the structural limit for symmetric formation of the detecting electrodes with a fiducial electrode as the reference on the same substrate. In this paper, we report the design and fabrication of a micro-electro-mechanical-system (MEMS)-based dual-axis electrolytic tilt sensor. The proposed tilt sensor has overcome its structural limit by placing the fiducial common electrode at the bottom of the electrolyte cavity for contact with the electrolyte through a via-hole. The proposed tilt sensor shows approximately 50 mV of change in the output voltage per degree of inclination angle in an operating angle range of ±70°.
Simple Atmospheric-Pressure Nonthermal Plasma-Jet System for Poly(dimethylsiloxane) Bonding Process
Authors: Kim Kangil , Kim Geunyoung , Oh Yeongtaek , Park Tae-Gyu , Han Dong Chul , Yang Sang Sik
Published: June 2012

In this paper, we propose a simple nonthermal plasma-jet system operated at atmospheric pressure. To evaluate the capability of surface modification, we performed an experimental study on the surface modification of poly(dimethylsiloxane) (PDMS) using Ar, He, and N2 plasma jets. The contact angles of a water droplet were measured after the surface modification by the proposed system. Among the three types of plasma used, the nitrogen plasma is the most efficient for surface modification. The N2 plasma-jet treatment for 60 s decreased the contact angle of PDMS to about 30°. The hydrophilic property of the modified surface lasted for at least 3 days. The PDMS modified with the nitrogen plasma is bonded well with glass. The bonding strength is equivalent to the yield strength of PDMS.
Fabrication of Three-Dimensional Metalized Movable Microstructures by the Combination of Two-Photon Microfabrication and Electroless Plating
Authors: Ikegami Takashi , Stocker Michael P. , Monaco Kathleen , Fourkas John T. , Maruo Shoji
Published: June 2012

We propose a method to fabricate three-dimensional (3D) metallic movable microparts by the combination of two-photon microfabrication and electroless plating. In this method, polymeric movable microparts with anchors made by two-photon microfabrication are metalized by electroless plating, and then the anchors are removed by laser ablation using a femtosecond pulsed laser. As a result, a metalized freely movable micropart whose motion is restricted to a shaft can be produced. We succeeded in fabricating sophisticated 3D metallic microrotors by adjusting the experimental conditions of both electroless copper plating and laser ablation.
Square-Patterned Narrow-Band Infrared Emitter for Filter Less Infrared Gas Sensor
Authors: Song Jun Tae , Park Joong Hee , Lee June Kyoo , Choi Ju Chan , Kong Seong Ho
Published: June 2012

In this study, we proposed a square-patterned narrow-band infrared (IR) emitter for a filterless IR gas sensor. As a new method of infrared gas sensing compared with previous research, it is proposed that a narrow-band IR emitter fabricated by micro-electro-mechanical-systems (MEMS) technology be applied to analyze dimethyl ether [(CH3)2O] gas. The proposed IR emitter consists of a TiN/SiO2/TiN trilayer, where the top TiN layer is square-patterned. The IR emitter radiates emissions at wavelengths of 7.68 and 7.88 µm in accordance with the type of sample. The wavelength can be adjusted by changing the period of the surface pattern. The proposed IR emitter shows a narrow peak width (Δλ/λ) of 0.16–0.23. The apparatus for gas detection consists of the proposed IR emitter, a gas cell and a bolometric IR sensor based on amorphous SiGe:H. The change in electrical resistance of the gas detector during inflow of (CH3)2O gas, which has a fingerprint wavelength in the range of 7.6–10 µm, was much smaller than that during inflow of CO2 gas, because (CH3)2O absorbed its corresponding wavelength in the range of 7.6–10 µm. Because of the concentrated radiation of the IR emitter at the wavelength of 7.88 µm, (CH3)2O absorbs relatively large amounts of infrared energy. The electrical resistance of the gas detector changed linearly as the concentration of (CH3)2O gas increased in the range of 0 to 500 ppm.
Effects of Specimen Dimensions on Adhesive Shear Strength between a Microsized SU-8 Column and a Silicon Substrate
Authors: Ishiyama Chiemi , Tasaki Toshikazu , Chan Tso-Fu Mark , Sone Masato
Published: June 2012

The adhesive shear strength between a microsized SU-8 columnar specimen and a Si substrate has been evaluated, especially focusing on the effects of the bonded specimen dimensions using Weibull analysis. The adhesive shear strength complicatedly changed with changing dimensions of the SU-8 column. Themvalue for the adhesive shear strength is much smaller in SU-8 specimens with smaller columnar lengths, because the effective factor on the delamination, such as natural defects at the interface, should be widely scattered at the smaller columnar length. In contrast, themvalue is much larger in the longest columns, which suggests that the dispersion of the natural defect should less affect the adhesive strength. This may be because that the longest SU-8 column should be softer than the others owing to the lower degree of cross-linking. All the results show that the adhesive shear stress is strongly affected by the bonded film thickness, because the effects of natural defects and/or mechanical properties of bonded SU-8 may change by the thickness.
Electrical Conductive Corundum-Structured α-Ga2O3 Thin Films on Sapphire with Tin-Doping Grown by Spray-Assisted Mist Chemical Vapor Deposition
Authors: Akaiwa Kazuaki , Fujita Shizuo
Published: June 2012

We report the fabrication of electrical conductive tin-doped α-Ga2O3 thin films on c-plane sapphire substrates. The mist chemical vapor deposition method brought tin-doped α-Ga2O3 thin films with high crystallinity without noticeable other phases, as highlighted by the full-width of X-ray diffraction ω-scan rocking curves as small as 40 arcsec, for the tin atomic density in the film upto ∼1020 cm-3. The resistivity decreased by more doping of tin, and the α-Ga2O3 thin film with minimum resistivity exhibited n-type conductivity with the Hall mobility of 2.8 cm2 V-1 s-1 and the carrier density of 2.7 ×1019 cm-3.
Enhanced Hole Transport in Mg-Doped AlxGa1-xN/GaN Superlattices by Strain and Period Modulations
Authors: Liu Ningyang , Li Ding , Wang Lei , Liu Lei , Yang Wei , Li Lei , Cao Wenyu , Lu Cimang , Wan Chenghao , Chen Weihua , Hu Xiaodong
Published: June 2012

This is a report on parallel and perpendicular hole transport characteristics of Mg-doped Al
x
Ga1-x
N/GaN superlattices (SLs). For parallel transport, the sheet resistance of SLs was dramatically decreased by a factor of 7, from 15.2 to 2.20 kΩ/□, when an AlN interlayer was inserted to reduce tensile strains. By optimizing the periods of SLs, we have further achieved a better value of 1.68 kΩ/□. For perpendicular transport, the vertical conductivity of SLs was also improved from 1.91×10-5 to 3.76×10-4 Ω-1 cm-1 by reducing the tensile strains. However, this vertical conductivity improvement deteriorated, when the periods outside optimum or medium boundaries as illustrated in the experimental results. These results indicate that strain and period modulations can have a great impact on the conductive properties of SLs. Meantime, less tensile strains or medium periods can favor the enhancement of hole transports in SLs.
Effect of Alkaline pH on Polishing and Etching of Single and Polycrystalline Silicon
Authors: Venkatesh R. Prasanna , Prasad Y. Nagendra , Kwon Tae-Young , Kang Young-Jae , Park Jin-Goo
Published: June 2012

In this paper, the polishing and etching behavior of single and polycrystalline silicon were studied. Prior to chemical mechanical polishing (CMP) process, the surfaces were treated with dilute hydrofluoric acid (DHF) to remove native oxides. The surface analysis shows that the poly contains trace amount of oxygen even after DHF treatment. The static and dynamic etch rates, and removal rates were measured as a function of slurry pH. The single silicon showed a higher static etch rate than the poly. After static etch rate measurements, poly showed higher surface roughness and more hydrophilic which indicates that the surface of poly is different from single crystal silicon. The friction force between pad and substrate and pad temperature was also measured as a function of pH during polishing in order to get more understanding of polishing process. At all the pH values being investigated, poly showed lower dynamic and removal rates, higher friction force and higher temperature. This indicates that the removal of poly in CMP is predominantly by mechanical actions. Also, these results, suggest a mechanism in which the oxygen present in the poly grain boundaries strongly influences the etching and removal mechanism.
Role of InGaN Insertion Layer on Nitride-Based Light-Emitting Diodes
Authors: Zheng Zhiyuan , Chen Zimin , Xian Yulun , Fan Bingfeng , Huang Shanjin , Jia Weiqing , Wu Zhisheng , Wang Gang , Jiang Hao
Published: June 2012

In this study, we systematically investigate the effect of InGaN insertion layer (IL) on nitride-based light-emitting diodes. First, a series of samples with different InGaN ILs (Si doping level, thickness) were fabricated and investigated. An optimized condition of the IL was obtained based on current–voltage and electroluminescence measurements. Furthermore, in order to investigate the dominant mechanism for the improved performance of the samples with IL, the optimized sample and a control sample without InGaN IL were compared by means of X-ray diffraction, atomic force microscopy, photoluminescence, injection-current-dependent electroluminescence measurements and infrared camera images. Based on the discussion of these measurement results, we conclude that the performance improvements of samples with InGaN IL are due to both the effects of strain relaxation and better current spreading.
Low Voltage and High Transmittance Polymer-Stabilized Blue-Phase Liquid Crystal Device by Combined In-Plane and Oblique Electric Field along the Horizontal Direction
Authors: Bae Kwang-Soo , Lee You-Jin , Yu Chang-Jae , Lee Hyeokjin , Park Jae-Hong , Kim Jae-Hoon
Published: June 2012

We propose a polymer-stabilized blue-phase liquid crystal (PS-BPLC) device with high transmittance and low driving voltage by designing the electrode structure. The electrodes are comprised with two interdigitated bottom pixel electrodes with opposite polarities and a top common electrode with 0 V, which is placed in the middle of the two bottom electrodes. Since these electrode structures could generate a strong horizontal electric field and induce a high Kerr effect, we could realize a lower driving voltage (30 V) and higher transmittance characteristics (20%) than those of conventional PS-BPLC cells with an in-plane switching electrode structure.
Active Mode-Locking of an Erbium-Doped Fiber Laser Using an Ultrafast Silicon-Based Variable Optical Attenuator
Authors: Chang You Min , Lee Junsu , Lee Ju Han
Published: June 2012

This paper presents the use of an ultrafast Si-based variable optical attenuator (VOA) in the active mode-locking of an erbium-doped fiber (EDF) laser. The Si VOA is a low-cost, commercially-available telecommunication component based on a p–i–n diode integrated with a ridge waveguide. The feasibility of using this compact and ultrafast Si-based VOA for the fiber laser mode-locking has been investigated. Using the weak beam modulation within an EDF ring cavity through the use of a 1.94-V driven Si-based VOA, a fundamental mode-locking at ∼14.1 MHz was successfully achieved. The temporal width and optical power of the output pulses were ∼169 ps and ∼-6 dBm, respectively.
Microscopic and Spectroscopic Studies of Light-Induced Magnetization Switching of GdFeCo Facilitated by Photoemission Electron Microscopy
Authors: Ohkochi Takuo , Fujiwara Hidenori , Kotsugi Masato , Tsukamoto Arata , Arai Kuniaki , Isogami Shinji , Sekiyama Akira , Yamaguchi Jun'ichi , Fukushima Kazuaki , Adam Roman , Schneider Claus M. , Nakamura Tetsuya , Kodama Kenji , Tsunoda Masakiyo , Kinoshita Toyohiko , Suga Shigemasa
Published: June 2012

By means of soft X-ray photoemission electron microscopy (PEEM), we have for the first time observed spatially and temporally resolved element-specific magnetization switching driven by circularly polarized femtosecond laser pulses. We have confirmed that the magnetization switching depending on the helicity of the circularly polarized laser occurs in the region where the spin temperature is raised appropriately. It is also found that the electronic states in the irradiated region remain unchanged even after millions magnetization reversal cycles.
Mid Wavelength Type II InAs/GaSb Superlattice Photodetector Using SiOxNy Passivation
Authors: Huang Jianliang , Ma Wenquan , Cao Yulian , Wei Yang , Zhang Yanhua , Cui Kai , Deng Gongrong , Shi Yanli
Published: June 2012

We report on a mid wavelength (MW) type II InAs/GaSb superlattice (SL) photodetector structure using SiO
x
N
y
as the passivation material. The 50% cutoff wavelength of the photoresponse is 4.8 µm at 77 K. R
0
A, the resistance-and-area product at zero bias, is 2.1×103 Ω·cm2 for the device with the SiO
x
N
y
passivation, which is about 13 times larger than that without the passivation. Our result indicates SiO
x
N
y
passivation is an effective way to reduce the shunt current for MW InAs/GaSb SL photodetector.