bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluorination of Graphene by Reactive Ion Etching System Using Ar/F2 Plasma
Authors: Matsutani Akihiro , Tahara Kousuke , Iwasaki Takayuki , Hatano Mutsuko
Published: June 2013

We demonstrated a novel fluorination process of graphene using Ar/F2 plasma. We carried out characterization of the plasma-processed graphene with Raman spectroscopy. In addition, it was found that the proposed “face-down” technique using Ar/F2 plasma was a low-damage fluorination process. We believe that the proposed technique using Ar/F2 plasma is very useful for the fluorination of graphene films by optimizing the process conditions for electronic and optical device applications.
1.3-µm Quantum Dot Distributed Feedback Laser with Half-Etched Mesa Vertical Grating Fabricated by Cl2 Dry Etching
Authors: Goshima Keishiro , Tsuda Norio , Yamada Jun , Sugaya Takeyoshi , Komori Kazuhiro , Amano Takeru
Published: June 2013

We propose a quantum dot (QD) laser with the half-etched mesa distributed feedback (HEM DFB) structure fabricated by single-step dry etching. The HEM DFB structure provides several advantages, such as low scattering loss and wavelength stability. In this study, we demonstrated a low threshold current of 23 mA and a high thermal stability of 0.077 nm/K for 1.3 µm ground state emission. We also improved the performance of the slope efficiency of HEM DFB lasers by using Cl2 dry etching.
Enhancement of Radiative Recombination by Different Indium Composition of Multiple Quantum Barriers in GaN-Based Light-Emitting Diodes
Authors: Park Euyhwan , Kim Garam , Kim Wandong , Kim Janghyun , Kang Donghoon , Son Joong-Kon , Park Byung-Gook
Published: June 2013

In this study, the characteristics of the nitride-based blue light emitting diodes (LEDs) having different indium contents multiple quantum barriers were analyzed numerically. The carrier concentrations in the quantum wells (QWs), energy band diagrams, radiative recombinations were investigated. InxGa1-xN with different indium-composition multiple quantum barriers (QBs) instead of GaN QBs were designed to improve hole transport and radiative recombination. The simulation results indicate that LEDs have a better hole transport in the active regions and uniformity of hole concentration over the conventional LED with GaN QBs. Consequently, the luminescence power of proposed structure was enhanced about 60 times at 3.0 V.
Comparative Study of Device Performance and Reliability in Amorphous InGaZnO Thin-Film Transistors with Various High-k Gate Dielectrics
Authors: Lee In-Kyu , Lee Se-Won , Gu Ja-gyeong , Kim Kwan-Su , Cho Won-Ju
Published: June 2013

A comparative study of the electrical characteristics and device instabilities in InGaZnO thin-film transistors (IGZO-TFTs) with four different high-k gate dielectrics (Al2O3, HfO2, Ta2O5, and ZrO2) has been conducted. High-k gate dielectrics have a sufficiently low leakage current for the gate insulator of IGZO-TFTs and ZrO2 has the highest dielectric constant, followed by Ta2O5, HfO2, and Al2O3. However, the charge trapping in high-k gate dielectrics induced the bias stress instability and degradation of IGZO-TFTs over time. In particular, the positive bias stress (PBS) and positive bias temperature stress (PBTS) caused a large positive threshold voltage (V
th) variation due to electron trapping, while the negative bias stress (NBS) and negative bias temperature stress (NBTS) brought about a much smaller V
th shift. In particular, the Al2O3 and HfO2 gate insulators have significant threshold voltage shifts for the PBS and PBTS measurements. Among the four different high-k gate dielectrics, ZrO2 is the most promising high-k gate dielectric for the IGZO-TFTs because of its high dielectric constant, low subthreshold swing, high mobility, large drive current, small hysteresis, and high on/off current ratio.
Characterization of GaAs-Based Three-Branch Nanowire Junction Devices by Light-Induced Local Conductance Modulation Method
Authors: Sato Masaki , Kasai Seiya
Published: June 2013

Nonlinear voltage transfer characteristics in GaAs-based three-branch nanowire junction (TBJ) devices were investigated by a light-induced local conductance modulation method. In this measurement system, the conductance in the device was locally increased by focused laser light irradiation. The nonlinear transfer curve was greatly changed when the laser light was irradiated on the positively biased branch. The conductance domain was found to exist at the end of the positively biased branch of the TBJ by scanning the light position. When a SiNxthin layer was deposited on the nanowire surface, the surface potential was increased and the nonlinearity in the transfer curve was reinforced simultaneously. The obtained results suggest that the asymmetric channel depletion model is appropriate for the observed nonlinearity mechanism in the GaAs TBJ at room temperature.
Temperature Dependence of Resistance of Conductive Filament Formed by Dielectric Breakdown
Authors: Otsuka Shintaro , Kato Takashi , Kyomi Takuya , Hamada Yoshifumi , Tada Yoshihiro , Shimizu Tomohiro , Shingubara Shoso
Published: June 2013

An investigation of current–voltage (I–V) characteristics and the temperature dependence of resistance in a resistive switching (RS) memory with a Cu/SiO2/Au device was performed. Moreover, conductive spots were observed by scanning electron microscopy (SEM) and cross-sectional transmission electron microscopy (TEM). Both unipolar and bipolar operation modes were obtained. From the temperature dependence of resistance, it is suggested that the conduction mechanism of the low resistance state (LRS) is metallic conduction and that of the high resistance state (HRS) is variable-range hopping (VRH) conduction. The results of observing the device support this suggestion. We propose the switching mechanism in the Cu/SiO2/Au device from these results.
Characterization of Metal–Insulator–Semiconductor Capacitor with Poly(methyl methacrylate):Titanium Dioxide as Insulator
Authors: Ismail Lyly Nyl , Zulkefle Habibah , Sauki Nur Sa'adah Mohd , Zain Aznilinda , Herman Sukreen Hana , Mahmood Mohamad Rusop
Published: June 2013

The electrical characteristics of metal–insulator–semiconductor (MIS) capacitor employing nanocomposite poly(methyl methacrylate):titanium dioxide (PMMA:TiO2) as insulator and zinc oxide (ZnO) as the semiconductor were discussed. The capacitance of the MIS devices was found to be 0.42 and 0.29 nF at frequency of 1 kHz and 1 MHz respectively. Meanwhile, the dielectric loss values are constant (∼60×10-3) in the frequency range from 100 Hz to 100 kHz. Current–voltage (I–V) results for MIS are much higher than MIM is due to there is a trapped holes/electron located at the semiconductor–insulator interface which contributes to high leakage current in the MIS device. We conclude, although interposing the PMMA:TiO2nanocomposite insulator layer between the semiconductor and Al electrodes degrades the MIS device performance, nevertheless, they remain sufficiently good for use in organic electronic devices.
Growth of Aligned Single-Crystalline TiO2 Nanorod Arrays on Transparent Conducting Oxide Coated Glass
Authors: Tsai Jung-Che , Hon Min-Hsiung , Leu Ing-Chi
Published: June 2013

In this work, we report a simple hydrothermal method for growth of aligned TiO2 nanorod arrays directly on SnO2:F (FTO) coated glass substrates without any seed layer. The rectangular nanorod is single crystalline with a tetragonal rutile structure. The diameter, length and density of the nanorods are determined by the synthesis temperature. When synthesis temperature increases from 110 to 190 °C, the diameter increases from 53 to 249 nm, and the length increases from to 324 to 1904 nm. However, the highest density is obtained at 150 °C due to nuclei coalescence at the high synthesis temperature. The activation energy for formation of TiO2 nanorod arrays is 102 kJ/mol obtained by using an Arrhenius equation.
Welding Thin Pt Wires with Dissimilar Diameters by Joule Heating
Authors: Fujimori Masato , Tohmyoh Hironori
Published: June 2013

In this paper, the Joule heat welding of thin Pt wires with different diameters was performed and the current required for successful welding was investigated. The diameter of one wire was 800 nm and the others had various diameters of 1, 2, and 5 µm. Various combinations of wire lengths were used in the welding experiments. The minimum and maximum currents for successful welding were found to be highly dependent on the length of the 800 nm diameter wire. From these experimental results, it was inferred that the highest temperature in the system during welding occurred in some part of the 800 nm diameter wire and that the temperature in the larger diameter wire with sufficient heat capacity were almost unchanged. It was also found that the conditions for successfully welding wires of different diameter can be described by a parameter previously proposed for classifying the successful conditions for welding two 800 nm diameter wires.
Resolution Limits of Nanoimprinted Patterns by Fluorescence Microscopy
Authors: Kubo Shoichi , Tomioka Tatsuya , Nakagawa Masaru
Published: June 2013

The authors investigated optical resolution limits to identify minimum distances between convex lines of fluorescent dye-doped nanoimprinted resist patterns by fluorescence microscopy. Fluorescent ultraviolet (UV)-curable resin and thermoplastic resin films were transformed into line-and-space patterns by UV nanoimprinting and thermal nanoimprinting, respectively. Fluorescence immersion observation needed an immersion medium immiscible to the resist films, and an ionic liquid of triisobutyl methylphosphonium tosylate was appropriate for soluble thermoplastic polystyrene patterns. Observation with various numerical aperture (NA) values and two detection wavelength ranges showed that the resolution limits were smaller than the values estimated by the Sparrow criterion. The space width to identify line patterns became narrower as the line width increased. The space width of 100 nm was demonstrated to be sufficient to resolve 300-nm-wide lines in the detection wavelength range of 575–625 nm using an objective lens of NA= 1.40.
Uniform Thermal Nanoimprinting at Low Pressure by Improved Heat Transfer Using Hydrofluoroethers
Authors: Mekaru Harutaka , Hiroshima Hiroshi
Published: June 2013

We propose a low-pressure process of thermal nanoimprinting by improved heat transfer. In poly(ethylene terephthalate) (PET;Tg=75 °C), poly(methyl methacrylate) (PMMA;Tg=105 °C), and polycarbonate (PC;Tg=150 °C), in which fine pattern transfer can be performed at 12.9 MPa, if the imprinting pressure is reduced to one-third, poor transfer occurs at the edges of the patterned area, and the uniformity of the entire patterned area degrades. However, it turned out that moldability can be improved significantly by introducing hydrofluoroether (HFE) between the mold and the surface of thermoplastic sheets. A dispensing method using a pipette was chosen to introduce HFE, and three types of HFE liquid, namely, Novec 7100 (bp=61 °C), Novec 7200 (bp=76 °C), and Novec 7300 (bp=98 °C), were tested. It was confirmed that the uniformity was greatly improved by combinations of PET and Novec 7100, PMMA and Novec 7200, and PC and Novec 7300. The heat of the mold spread efficiently onto the surface of thermoplastics via the HFE liquid, and it seems to result in the same effect as a preliminary heating process before the mold comes into contact with the thermoplastic sheet.
Study of Demolding Characteristics in Step-and-Repeat Ultraviolet Nanoimprinting
Authors: Iyoshi Shuso , Okada Makoto , Katase Tetsuya , Tone Katsuhiko , Kobayashi Kei , Kaneko Shu , Haruyama Yuichi , Nakagawa Masaru , Hiroshima Hiroshi , Matsui Shinji
Published: June 2013

Ultraviolet (UV) nanoimprinting includes a contact process necessary for transferring nanoscale features from a mold to a UV-curable resist coated on a substrate. The demolding that comes with the contact process is a source of defects, and an obstacle to be overcome for nanodevice fabrications. In this study, we aim to execute more than 10000 times of step-and-repeat UV nanoimprinting with a single mold, tracing demolding forces and water contact angles of the mold surface as the indication of mold-resist/substrate interface and mold degradation. A condensable gas, a UV-curable resist, and a fluorosurfactant were considered in this study. It was revealed that 1,1,1,3,3-pentafluoropropane (PFP) or HFC-245fa, which is the common industrial name, as a condensable gas and a type of fluorosurfactant played an important role in minimizing the demolding impact and thus helped in increasing mold lifetime. The surfactant-added resists performed 6500 imprinting steps in PFP.
Study of Organic Thin Film Transistors on Ultraviolet-Curable Dielectrics with Periodic Patterns Fabricated by Nano Imprint Technology
Authors: Chen Henry J. H. , Chen Jun-Yu
Published: June 2013

In this work, the organic thin film transistors (OTFTs) on UV-curable dielectrics with periodic patterns fabricated by nano imprint technology were investigated. The surface morphologies of pentacene and device performances with respect to line/space ratio of periodic patterns were studied. The anisotropic electrical characteristics of OTFTs were also investigated. This technique will be suitable for the future low-cost and flexible electronics applications.
Enhanced Sensing Properties by Dual-Gate Ion-Sensitive Field-Effect Transistor Using the Solution-Processed Al2O3Sensing Membranes
Authors: Bae Tae-Eon , Jang Hyun-June , Lee Se-Won , Cho Won-Ju
Published: June 2013

The sensitivity of conventional ion-sensitive field-effect transistors (ISFETs) is limited to 59 mV/pH, which is the maximum value in electrochemical potential according to the Nernst equation. Here, the silicon-on-insulator (SOI) based dual-gate (DG) ISFETs with SiO2/Al2O3(OA) using solution based process was evaluated to obtain higher pH sensitivity. The device exhibited a significantly enhanced pH sensitivity of 407.3 mV/pH for the DG operation by capacitive coupling between top and bottom gate oxide. Therefore, the SOI-based ISFETs using solution process and the DG monitoring method are very promising to biological sensors application in terms of high performance and large process area.
Simultaneous Synthesis and Biotinylation of Proteins Using Puromycin-Based Labeling Technology for Fabrication of Protein Array Chip
Authors: Kumal Subhashini Raj , Biyani Manish , Ueno Shingo , Akagi Takanori , Ichiki Takanori
Published: June 2013

Protein arrays represent a class of devices that are of growing importance in the field of proteomics. These arrays enable screening of a large amount of proteins in a short time and at a lower cost. Here we present a method to fabricate protein array using biotin-conjugated puromycin to simultaneously synthesize and label proteins followed by immobilization onto streptavidin-functionalized surface based on the noncovalent biotin-streptavidin interaction. This method demonstrates the fabrication of protein array based on cell-free transcription/translation system using unmodified DNA as a starting genetic material. As a consequence, the procedure of protein arraying has been greatly simplified over the conventional approaches that require tedious and multi-step reactions. Further, an integrated approach of micro reactor array technology makes this method very simple and robust for achieving high-density protein arrays.
Fabrication of a Wrinkled Surface on Poly(dimethylsiloxane) Using a Thermal Curing Process
Authors: Lee Dong Guk , Jeong Ok Chan
Published: June 2013

We describe the fabrication of a spontaneous wrinkled surface on poly(dimethylsiloxane) (PDMS). The wrinkled surface on an elastic PDMS substrate was fabricated by thermally shrinking liquid PDMS coated on a cured PDMS layer during a simple thermal curing process. Optical and atomic force microscopy, deflections of PDMS cantilever beams on the wrinkled surface, and contact angles of water droplets on the wrinkled surface were used to quantitatively investigate the wrinkled patterns on the PDMS layer. The morphology of cells seeded on the fabricated wrinkled surface was observed.
Optofluidic Devices with Surface-Enhanced Raman Scattering Active Three-Dimensional Gold Nanostructure
Authors: Takahashi Ryo , Fukuoka Takao , Utsumi Yuichi , Yamaguchi Akinobu
Published: June 2013

Rapid and sensitive chemical sensing using a microfluidic device equipped with a sterically bulky three-dimensional gold nanostructure (Au3D) was demonstrated. Au3D was expected as a surface-enhanced Raman scattering (SERS) active structure. Au3D was fabricated by convective self-assembly, known as a “coffee-ring”, of the mixed solution of gold colloidal nanoparticles and polystyrene latex particles. SERS measurements of a trace amount of 4,4'-bipyridine (4bpy) in aqueous solution were performed using Au3D in batch and flow format, and typical spectra of 4bpy with enhanced peaks were immediately observed after dropping (batch) or injecting (flow). While the detection limit was about the 10 nM 4bpy in batch measurement, the detection of a further enhanced spectrum of 1 nM 4bpy was accomplished in flow measurement. We confirmed that Au3D was available for convenient SERS optofluidic measurement.
Pinned Square Lens Arrays and Their Application to Integral Photography
Authors: Yasuda Shin , Shimizu Keishi
Published: June 2013

A fabrication method for square lens arrays together with their application to integral photography is presented. Our square lens arrays are fabricated by a technique similar to the fabrication of cylindrical lens arrays that was reported in Opt. Rev. 19 (2012) 287. This technique features the easy control of the pitch and radius of curvature of the lens arrays. The lens pitches in both transverse and longitudinal directions are controlled by adjusting the interval of partition walls created by scratching a polymeric substrate with a sharp edge. The radius of curvature is controlled by adjusting the volume of the ultra-violet curable polymer deposited into square apertures formed by the partition walls. The vertices of the partition walls prevent the spreading of the polymer owing to the pinning effect. It is also demonstrated that our square lens array succeeded in realizing three-dimensional integral printing.
p-Type Sb2Te3and n-Type Bi2Te3Films for Thermoelectric Modules Deposited by Thermally Assisted Sputtering Method
Authors: Mizoshiri Mizue , Mikami Masashi , Ozaki Kimihiro
Published: June 2013

We developed a thermally assisted sputtering method (TASM) based on direct current magnetron sputtering to increase the rates of deposition of Sb2Te3and Bi2Te3films. The sputtering target was heated with the thermal energy of Ar plasma without any additional heating systems. The stoichiometric Sb2Te3(p-type) and Bi2Te3(n-type) films were obtained by TASM. The maximum deposition rate of the films was approximately 1.6 µm/min, which is large for a sputtering method. The differences in the composition ratio between the sputtering target and the deposited films were as small as 3.6 (p-type) and 1.5% (n-type). TASM was applied to the fabrication of a flexible thermoelectric film module. The generation properties of the film module coincided with the values that were estimated on the basis of the thermoelectric properties of films deposited on a SiO2glass substrate. These results indicate that TASM is useful for fabricating thermoelectric film modules.
Electrolytic Tilt Sensor with Domed Cap for Improved Performance
Authors: Choi Ju Chan , Choi Young Chan , Lee June Kyoo , Kong Seong Ho
Published: June 2013

In recent years, some efforts have been made in our laboratory to improve the performance of previously reported electrolyte-based tilt sensors. Even though the previously reported electrolytic tilt sensors have merits of low cost and a simple fabrication process, they show several undesirable performances such as inconsistent response time and slow reversion when it returns to the initial position (inclination angle of 0°) from an arbitrary tilted position. The irregular performances are caused by the flat upper cover. In this paper, we report the design and fabrication of an electrolytic tilt sensor with a domed cap for improving the response time and instant reversion. For a fast and regular reversion, the cavities on the cap substrate have been designed to be a domed shape. The measured reversion time with the proposed tilt sensor from 10° to the initial state was approximately 0.3 s, which is more than 6 times faster than the previously reported one.
Variable Resonance Frequency Selection for Fishbone-Shaped Microelectromechanical System Resonator Based on Multi-Physics Simulation
Authors: Kuroda Shinjiro , Suzuki Naoya , Tanigawa Hiroshi , Suzuki Kenichiro
Published: June 2013

In this paper, we present and demonstrate the principle of variable resonance frequency selection by using a fishbone-shaped microelectromechanical system (MEMS) resonator. To analyze resonator displacement caused by an electrostatic force, a multi-physics simulation, which links the applied voltage load to the mechanical domain, is carried out. The simulation clearly shows that resonators are operated by three kinds of electrostatic force exerted on the beam. A new frequency selection algorithm that selects only one among various resonant modes is also presented. The conversion matrix that transforms the voltages applied to each driving electrode into the resonant beam displacement at each resonant mode is first derived by experimental measurements. Following this, the matrix is used to calculate a set of voltages for maximizing the rejection ratio in each resonant mode. This frequency selection method is applied in a fishbone-shaped MEMS resonator with five driving electrodes and the frequency selection among the 1st resonant mode to the 5th resonant mode is successfully demonstrated. From a fine adjustment of the voltage set, a 42 dB rejection ratio is obtained.
A Compact 1×3 Silicon Photonic Waveguide Switch Based on Precise Investigation of Coupling Characteristics of Variable-Gap Coupler
Authors: Munemasa Yasushi , Hane Kazuhiro
Published: June 2013

A variable-gap silicon nanowire waveguide coupler was fabricated and its characteristics were measured for comparison with those determined by a rigorous electromagnetic simulation. The three-dimensional model of the coupler was simulated by the finite-difference time-domain method. On the basis of the results obtained, a compact 1×3 silicon nanowire coupler switch was designed and fabricated. The 1×3 switch was composed of two couplers with parallel silicon nanowire waveguides of 400 nm width and 260 nm thickness and comb-drive electrostatic actuators. The output isolation and extinction ratio of the variable coupler were measured to be 12.9 and 18.6 dB, respectively. The loss of the variable coupler was 0.21 dB. The measured coupling coefficient was explained quantitatively by the simulation. The proposed 1×3 switch was demonstrated by showing the infrared images of the switch outputs. The port isolation of the 1×3 switch was better than 11.3 dB.
Directional Difference of Patterns Printed by Scan-Projection Lithography Using a Gradient Index Lens Array
Authors: Horiuchi Toshiyuki , Suzuki Takeru , Kobayashi Hiroshi
Published: June 2013

Peculiar patterning characteristics of scan projection lithography using a gradient index lens array were investigated. When a lens array with two-line lenses was used, pattern widths of line-and-space patterns differed according to the pattern directions. Parts of the light rays diffracted in the direction perpendicular to the lens line are lost without passing through the lenses, because only two lenses are available in that direction. As a result, the resolution of patterns parallel to the lens line slightly degrades. On the other hand, light rays parallel to the lens line are sufficiently used for imaging. For this reason, the widths of line patterns printed in a positive resist slightly decrease. However, if the two-line lens array was replaced by a four-line lens array, the peculiar patterning characteristics were almost lost, and patterns were printed almost without directional differences. This is because the lens array width becomes sufficient.
Fabrication of Silicon Microdisk Resonators with Movable Waveguides for Control of Power Coupling Ratio
Authors: Kanamori Yoshiaki , Sato Yuichi , Hane Kazuhiro
Published: June 2013

Silicon microdisk resonators with monolithically integrated comb-drive microactuators were fabricated for optical switches. Each of the resonators mainly consisted of a microdisk, a movable waveguide, a fixed waveguide, and a comb-drive microactuator. The gap distance between the movable waveguide and the microdisk could be controlled with the microactuator. Therefore, the power coupling ratios of the resonators were varied. Using the comb-drive microactuator, the resonator could be driven at low voltage of 21 V which had been difficult to drive the resonator using a parallel plate electrostatic microactuator ever. We fabricated the microdisk with a diameter of 10 µm. At a resonant wavelength of 1553.3 nm and a voltage of 21 V applied to the microactuator, it was obtained that the light propagating into a through port was switched to the microdisk with an extinction ratio of 8.8 dB, a FWHM of 0.17 nm, and a quality factor of 9137.
Ultrasonication: An Efficient Agitation for Accelerating the Supersaturation-Limited Amyloid Fibrillation of Proteins
Authors: Yoshimura Yuichi , So Masatomo , Yagi Hisashi , Goto Yuji
Published: June 2013

Amyloid fibrils are self-assemblies of proteins with an ordered cross-β architecture. Because they are associated with serious disorders, understanding their structure and mechanism of fibrillation is important. Irradiation with ultrasonication leads to fragmentation of amyloid fibrils, useful for seeding experiments. Recently, ultrasonication has been found to trigger the spontaneous formation of fibrils in solutions of monomeric amyloidogenic proteins. The results indicate that amyloid fibrillation is similar to the crystallization of solutes from a supersaturated solution. The accelerating effects of ultrasonication on amyloid fibrillation suggest that cavitation microbubbles play a key role in effectively converting the metastable state of supersaturation to the labile state, leading to spontaneous fibrillation. Moreover, ultrasonic irradiation would be promising for a high-throughput screening assay of amyloid fibrillation, advancing the study of supersaturation-limited amyloidogenesis.
Piezoelectric Properties of CuO-Doped (K,Na)NbO3Lead-Free Ceramics Synthesized with Hydrothermal Powders
Authors: Yokouchi Yuriko , Maeda Takafumi , Bornmann Peter , Hemsel Tobias , Morita Takeshi
Published: June 2013

We report the piezoelectric properties of CuO-doped hydrothermal (K,Na)NbO3ceramics that can be applied as hard-type lead-free piezoelectric ceramics. To date, we have succeeded in synthesizing high-quality KNbO3and NaNbO3powders by the hydrothermal method, which is based on an ionic reaction at high temperature (around 210 °C) and pressure. Increasing both the piezoelectric constantdand the mechanical quality factor (Qm) is important for resonance-type piezoelectric devices, such as ultrasonic motors and transformers. CuO doping into hydrothermal (K,Na)NbO3ceramics was examined to realize hard-type lead-free piezoelectric ceramics. By doping with 1.2 mol % CuO,Qmwas increased and the dielectric loss (tan δ) was decreased to 0.5%. The grain size was also influenced by the amount of CuO doping, which indicates thatQmis related to the density. To achieve a higherQmvalue, the grain size is required to be less than 5 µm; however, excessive CuO doping leads to anomalous grain growth. Optimal piezoelectric properties were obtained for 1.2 mol % CuO-doped (K,Na)NbO3;k31= 0.32,d31= -44 pC/N,Qm(radial) = 959, and tan δ= 0.5%. These characteristics showed that CuO doping with hydrothermal powders is effective for obtaining hard-type ceramics, and the mechanical quality factor is more than ten times higher than that of nondoped hydrothermal (K,Na)NbO3ceramics. Therefore, compared with the conventional solid-state method, we could succeed in obtaining hard-type ceramics by a simple and short process.
Lamb Wave Characteristics of Composite Plates Including a Diamond Layer with Distinct Electrode Arrangements
Authors: Chen Yung-Yu
Published: June 2013

Diamond films have been utilized to develop surface acoustic wave filters and micromechanical resonators because of the highest acoustic wave velocity and largest product of frequency and quality factor (f·Q) of diamond among all materials. A theoretical analysis of Lamb wave characteristics in multilayer piezoelectric plates including a diamond layer is presented in this paper. Formulae for effective permittivity are derived using the transfer matrix method and are further employed to calculate Lamb wave phase velocity dispersions. The electromechanical coupling coefficients (ECCs) are also calculated exactly by Green's function method. Detailed calculations are carried out for ZnO/diamond and AlN/diamond composite plates with four distinct electrode arrangements. Results show that the ZnO/diamond structure yields a phase velocity of 6420 m/s and a large ECC of 7.41%, which makes it suitable for high-frequency wideband filter applications. Moreover, in the AlN/diamond structure, the S0mode exhibits a large phase velocity of up to 10.3 km/s and a moderate ECC of 1.97%. Such favorable characteristics are expected to contribute to the development of AlN/diamond Lamb wave oscillators operating at approximately 5–10 GHz without the need for a sub-micrometer-resolution lithographic process. Therefore, both ZnO/diamond and AlN/diamond Lamb wave devices are highly promising candidates for RF devices in modern communication systems with advantages over conventional surface acoustic wave devices.
Effect of Heat Generation of Ultrasound Transducer on Ultrasonic Power Measured by Calorimetric Method
Authors: Uchida Takeyoshi , Kikuchi Tsuneo
Published: June 2013

Ultrasonic power is one of the key quantities closely related to the safety of medical ultrasonic equipment. An ultrasonic power standard is required for establishment of safety. Generally, an ultrasonic power standard below approximately 20 W is established by the radiation force balance (RFB) method as the most accurate measurement method. However, RFB is not suitable for high ultrasonic power because of thermal damage to the absorbing target. Consequently, an alternative method to RFB is required. We have been developing a measurement technique for high ultrasonic power by the calorimetric method. In this study, we examined the effect of heat generation of an ultrasound transducer on ultrasonic power measured by the calorimetric method. As a result, an excessively high ultrasonic power was measured owing to the effect of heat generation from internal loss in the transducer. A reference ultrasound transducer with low heat generation is required for a high ultrasonic power standard established by the calorimetric method.
Subharmonic Wave Generation at Interfaces of a Thin Layer between Metal Blocks
Authors: Hayashi Takahiro , Biwa Shiro
Published: June 2013

Subharmonic waves were significantly generated at the interfaces of aluminum blocks and an aluminum foil subjected to a 6 MHz burst incident wave. Although the fundamental wave amplitude was linearly varied with input voltage, the subharmonic waves generated at the interfaces indicated strong nonlinearity. Analyzing the relationship of the subharmonic wave generation, the applied contact pressure, and the stress of the ultrasonic wave has revealed that subharmonic components can be generated when the incident ultrasonic wave has sufficiently large stress to separate the contacting interfaces. At rough surfaces, the subharmonic peak could not be observed because a large true contact pressure prevented the interfaces from separating.
Study on Water Distribution Imaging in the Sand Using Propagation Velocity of Sound with Scanning Laser Doppler Vibrometer
Authors: Sugimoto Tsuneyoshi , Nakagawa Yutaka , Shirakawa Takashi , Sano Motoaki , Ohaba Motoyoshi , Shibusawa Sakae
Published: June 2013

We propose a method for the monitoring and imaging of the water distribution in the rooting zone of plants using sound vibration. In this study, the water distribution measurement in the horizontal and vertical directions in the soil layer was examined to confirm whether a temporal change in the volume water content of the soil could be estimated from a temporal changes in propagation velocity. A scanning laser Doppler vibrometer (SLDV) is used for measurement of the vibration velocity of the soil surface, because the highly precise vibration velocity measurement of several many points can be carried out automatically. Sand with a uniform particle size distribution is used for the soil, as it has high plasticity; that is, the sand can return to a dry state easily even if it is soaked with water. A giant magnetostriction vibrator or a flat speaker is used as a sound source. Also, a soil moisture sensor, which measures the water content of the soil using the electric permittivity, is installed in the sand. From the experimental results of the vibration measurement and soil moisture sensors, we can confirm that the temporal changes of the water distribution in sand using the negative pressure irrigation system in both the horizontal and vertical directions can be estimated using the propagation velocity of sound. Therefore, in the future, we plan to develop an insertion-type sound source and receiver using the acceleration sensors, and we intend to examine whether our method can be applied even in commercial soil with growing plants.
S0 Mode Lamb Wave Resonators Using LiNbO3 Thin Plate on Acoustic Multilayer Reflector
Authors: Kimura Tetsuya , Daimon Katsuya , Ogami Takashi , Kadota Michio
Published: June 2013

Lamb wave modes can be classified as a fundamental anti-symmetric mode (A0), a symmetric mode (S0), and their higher order modes. Membrane-type A1 mode Lamb wave resonators have been reported by the authors for future mobile communication systems. Although the reports show promising results, it is difficult to fabricate the resonators because they have a large dispersion of phase velocity and electromechanical coupling factor, and also are fragile. In this study, the authors suggest a solidly mounted resonator (SMR)-type S0 mode Lamb wave resonator, which can solve the above-mentioned difficulty. An SMR-type S0 mode Lamb wave resonator was successfully realized for the first time. The resonator exhibits a 1.5 times faster phase velocity and a 1/3 smaller temperature coefficient of frequency than the commonly used surface acoustic wave (SAW) devices composed of an Al electrode and a 36–48°YX-LiTaO3 substrate.
A Configuration of Widely Tunable Surface Acoustic Wave Filter
Authors: Inaba Masahiro , Omori Tatsuya , Hashimoto Ken-ya
Published: June 2013

This paper proposes a configuration of the radio frequency surface acoustic wave (SAW) filter with wide tunability for both the passband width and the center frequency. At first, it is shown how the center frequency and the passband width are adjustable with the VC setting. It is also shown that a flat passband and steep transition bands are realizable when multiple stages are cascaded with mirror inversion. Then, influence ofQfactors is discussed. Finally, two types of tunable filters are designed, and applicability of this filter topology is demonstrated.
Evaluation of Piezoelectric Ta2O5 Thin Films Deposited on Sapphire Substrates
Authors: Iwamoto Shunsuke , Saigusa Ryosuke , Kakio Shoji
Published: June 2013

X-axis-oriented tantalum pentoxide (Ta2O5) piezoelectric thin films were deposited on sapphire (Al2O3) substrates, from which single crystallization due to epitaxial growth can be expected, using an RF magnetron sputtering system. The crystallinity and Rayleigh-type surface acoustic wave (R-SAW) propagation properties of the thin films were evaluated. From the measured diffraction (X-ray diffraction) patterns and the spotted pattern in the measured pole figures, in which poles were arranged to form the vertices of a hexagon, the possibility of the crystallization of hexagonal Ta2O5 with a (203)-plane oriented in the c-Al2O3 substrate plane due to epitaxial growth was shown. For the first mode of the R-SAW on the Ta2O5/R-plane Al2O3 sample, a coupling factor of 1.65% and a phase velocity of 5,120 m/s were obtained for a normalized thickness of 0.175. Unfortunately, no increase in coupling factor and no major improvement in propagation loss were observed upon the crystallization of hexagonal Ta2O5.
Demonstration of Noncontact Ultrasonic Mixing of Droplets
Authors: Nakamura Ryohei , Mizuno Yosuke , Nakamura Kentaro
Published: June 2013

The noncontact ultrasonic mixing of two droplets is demonstrated, for the first time, by controlling the acoustic field using the following two methods: (1) by changing the distance between the vibrator and the reflector and (2) by modulating the driving voltage amplitude applied to the vibrator. The operating principle is confirmed by measuring the acoustic pressure distribution and the temporal change in the acoustic pressure near the mixing position. We also show that the stable mixing of droplets with high repeatability is feasible by method (2), which does not involve the use of mechanically moving parts.
Single-Phase Drive Ultrasonic Linear Motor Using a Linked Twin Square Plate Vibrator
Authors: Yokoyama Keiji , Tamura Hideki , Masuda Kentaro , Takano Takehiro
Published: June 2013

A novel linear motion ultrasonic motor, which uses a single resonance mode driven by a single phase and has the same motor characteristics for operation in reverse directions, is developed. An in-plane breathing mode in the square plate is strongly driven by the transverse effect of a piezoelectric ceramic. A stator resonator consists of twin square plates linked by V-shaped beams. Only one side of the square plate can be excited by the resonance of the breathing mode, when the other passive side plate is electrically opened so that the effective elasticities and the resonant frequencies between both plates are different; as a result, the friction edge of the resonator vibrates in a slant locus to move a load slider. The reverse operation is easily obtained by switching the driving side of the square plates. We designed the stator resonator by FEM analysis and fabricated a prototype for our experiment. The prototype motor showed good characteristics, for example, a moving slider velocity of 100 mm/s, a thrust force of 3.5 N, and an efficiency of 30% when the preload was 10 N, the input effective voltage was 5 V, and the input power was 1.2 W.
Resonant-Type Smooth Impact Drive Mechanism Actuator Operating at Lower Input Voltages
Authors: Morita Takeshi , Nishimura Takuma , Yoshida Ryuichi , Hosaka Hiroshi
Published: June 2013

We report on the design and fabrication of a resonant-type smooth impact drive mechanism (SIDM) actuator based on a multilayered piezoelectric ceramic transducer. Conventional SIDMs use off-resonant sawtooth-shaped displacement in developing stick–slip motion of a slider, but require large input voltages for high-speed operation. In contrast, in resonant-type SIDMs, a quasi-sawtooth-shaped displacement is obtained by combining two resonant vibrational modes. This driving principle enables low input voltage operations. In combining the modes, their frequency ratio must be 1:2. To design and optimize the stator transducer to generate sawtooth-shaped displacements, a transfer matrix method was adopted. With a preload of 270 mN, the no-load speed was 40 mm/s under a driving voltage of 1.6 V (peak to peak). This input voltage was one-sixth that of previous SIDMs for the same performance. Concurrently, heat generation was significantly reduced because dielectric losses were suppressed under the lower input voltage operation.
Relationship between Quality Value and Temperature Ratio for Step-Shape Thermoacoustic System
Authors: Shibata Kenji , Sakamoto Shin-ichi , Nakano Yosuke , Watanabe Yoshiaki
Published: June 2013

Miniaturized thermoacoustic systems are examined in this study for application to electronic equipment. Our previous studies revealed that stable oscillation can be achieved in miniature step-shape thermoacoustic closed-tube systems. However, closed-tube systems present problems: the temperature ratio of the stack cannot be formed to raise the temperature in the system. Moreover, the stack is thin. Miniature thermoacoustic systems have high loss because of the high frequency necessary to shorten the total length. Despite these problems, miniature step-shape thermoacoustic systems can achieve oscillation conditions. This paper concerns a step-shape thermoacoustic system, focusing on the temperature ratio and the quality value as parameters to estimate the loss in a system. Consequently, results show that the efficiency of the thermoacoustic system is improved by adopting a step-shape in the system, with the step-shape system being driven at low temperature.
Increasing Bandwidth of Ultrasound Radio Frequency Echoes Using Wiener Filter for Improvement of Accuracy in Measurement of Intima–Media Thickness
Authors: Kageyama Sho , Hasegawa Hideyuki , Kanai Hiroshi
Published: June 2013

It is very important to make early diagnoses of atherosclerosis for the prevention of lifestyle-related diseases. The intima–media thickness (IMT) is used as a diagnostic index of cerebrovascular diseases and atherosclerosis throughout the body including the coronary artery. In the field of the medical diagnostics, ultrasonic equipment using a pulse–echo method is widely used. In conventional ultrasonic diagnostic equipment, ultrasonic images are obtained by receiving ultrasonic echoes and converting their amplitudes into brightness. In general, ultrasonic B-mode images are degraded by the narrow-band characteristics of the ultrasonic transducer. In the present study, a method was proposed for shortening the lengths of the received ultrasonic pulses from an object of interest using a Wiener filter. As a result, the lengths of ultrasonic pulses were shortened and the visibility of interfaces of the intima–media complex of the carotid arterial wall was improved by the proposed method, which realizes accurate measurement of the IMT.
Trial of Human Bone Cross-Sectional Imaging In vivo, Using Ultrasonic Echo Waves
Authors: Mano Isao , Horii Kaoru , Matsukawa Mami , Otani Takahiko
Published: June 2013

We have tried in vivo imaging of the distal forearm bone using ultrasonic echo waves. The obtained ultrasonic echo images were compared with X-ray computed tomography (CT) images. In the case of vertical incidence of an ultrasonic wave to the cortical bone surface, not only the outer and inner boundaries of the near side of the cortical bone but also the inner and outer boundaries of the far side of the cortical bone were identified. The thicknesses of the cortical bone and cancellous bone calculated using the echo waves approximately agreed with those determined from X-ray CT images.
Effectiveness of Convolutional Code in Multipath Underwater Acoustic Channel
Authors: Park Jihyun , Seo Chulwon , Park Kyu-Chil , Yoon Jong Rak
Published: June 2013

The forward error correction (FEC) is achieved by increasing redundancy of information. Convolutional coding with Viterbi decoding is a typical FEC technique in channel corrupted by additive white gaussian noise. But the FEC effectiveness of convolutional code is questioned in multipath frequency selective fading channel. In this paper, how convolutional code works in multipath channel in underwater, is examined. Bit error rates (BER) with and without 1/2 convolutional code are analyzed based on channel bandwidth which is frequency selectivity parameter. It is found that convolution code performance is well matched in non selective channel and also effective in selective channel.
Surface Transitions During InGaN Growth on GaN(0001) in Metal–Organic Vapor Phase Epitaxy
Authors: Pristovsek Markus , Kadir Abdul , Kneissl Michael
Published: June 2013

Using in-situ ellipsometry measurements we observed three different surfaces during growth of InGaN(0001) in metal–organic vapor phase epitaxy, which is similar to reports for GaN(0001) or In on GaN in molecular beam epitaxy. Among these surfaces one is identical to the pre-growth GaN surface (for less than 10% In), the second contains about 1 monolayer (ML) of metal (for In between 10 and 35%), and finally a surface with ≤2 ML of metal (for 45% In). Exceeding an In/(Ga+In) input ratio of 80% in the gas phase leads to the formation of In droplets.
Investigation of Strain-Relaxation Characteristics of Nitrides Grown on Si(110) by Metalorganic Chemical Vapor Deposition Using X-ray Diffraction
Authors: Jiang Quanzhong , Lewins Christopher J. , Allsopp Duncan W. E. , Bowen Chris R. , Wang Wang N.
Published: June 2013

This paper describes the effect of an interfacial biaxial stress field on the dislocation formation dynamics during epitaxial growth of nitrides on Si(110). The anisotropic mismatch stress between a 2-fold symmetry Si(110) atomic plane and the AlN basal plane of 6-fold symmetry may be relaxed through the creation of additional characteristic dislocations, as proposed by Ruiz-Zepeda et al. with Burgers vectors: b= 1/2[2̄110] and b= [12̄10], ±60° from [112̄0]. The dislocations generated under such a biaxial stress field appear annihilating more efficiently with increasing thickness, leading to high-quality nitride epilayers on Si(110) for improved quantum efficiency of InGaN/GaN quantum wells.
Growth of GaN Columns and Microstructures on (111) Si by Using Ge Layer via Metal Organic Chemical Vapor Deposition
Authors: Park Jinsub , Shin Keun Wook , Kim Jong Hak , Yoon Euijoon
Published: June 2013

We demonstrate the successful growth of GaN columnar and microdisk structures on a (111) Ge/Si substrate via metal organic chemical vapor deposition. X-ray diffraction and energy disperse spectroscopy results reveal that the well aligned GaN nanocolumnar structures are grown on a Si substrate by using the Ge layer. The relatively higher growth temperature induces a change in surface morphology of GaN from columnar to microdisk structures. The possible growth mechanism of columnar structured GaN was considered from the Ga-metal/Ge eutectic materials system.
GaN-Based Metal–Insulator–Semiconductor Ultraviolet Sensors with CsF Insulating Layer
Authors: Chen Chin-Hsiang , Tsai Chia-Ming , Yang Ming-Han , Lin Wei-Chi , Liu Shih-Kun
Published: June 2013

Nitride-based metal–insulator–semiconductor (MIS) ultraviolet (UV) photodetectors (PDs) with a CsF insulating layer were proposed and fabricated. The dark current was considerably reduced and the UV-to-visible contrast ratio was enhanced by inserting the CsF insulating layer. The noise-equivalent powers (NEPs) were 9.05×10-10, 1.27×10-9, and 2.4×10-9W, and the normalized detectivity (D*) values were 7.5×107, 5.35×107, and 2.83×107cm Hz0.5W-1for the PD with a 5-nm-thick CsF layer, the PD with a 50-nm-thick CsF layer, and the PD with a 100-nm-thick CsF, respectively, when biased at 1 V.