bluuebunny/crossref_metadata_2025 huggingface dataset:
Conductive Atomic Force Microscopy Analysis for Local Electrical Characteristics in Stressed SiO2 Gate Films
Authors: Watanabe Yukihiko , Seko Akiyoshi , Kondo Hiroki , Sakai Akira , Zaima Shigeaki , Yasuda Yukio
Published: February 2005

We have investigated microscopically the current leakage characteristics of SiO2 gate films in metal-oxide-semiconductor structure capacitors subjected to the Fowler-Nordheim (FN) constant current stress using a conductive atomic force microscope (C-AFM). Current images of C-AFM clearly reveal the leakage current spots in the samples in which the stress induced leakage current was confirmed by the macroscopic current-voltage (I-V) measurement. On the other hand, in the sample after the repeated macroscopic I-V measurement, there is a shift in threshold voltage for the appearance of current spots and its value directly corresponds to the voltage shift observed in the macroscopic capacitance-voltage measurements for this sample. The total number of current spots observable in the C-AFM scanned area critically depends on the substrate voltage: the spot number initially increases with the voltage to a certain value then decreases. The visibility of the current spot is well explained by the holes trapped locally at defect sites created in the stressed SiO2.
Simultaneous Formation of Multiwall Carbon Nanotubes and their End-Bonded Ohmic Contacts to Ti Electrodes for Future ULSI Interconnects
Authors: Nihei Mizuhisa , Horibe Masahiro , Kawabata Akio , Awano Yuji
Published: February 2005

We have succeeded in growing multiwall carbon nanotubes (MWNTs) with low-resistance ohmic contacts to titanium electrodes by hot-filament chemical vapor deposition (HF-CVD) using a nickel catalyst layer on a titanium electrode. The contact resistance of the sample with nickel/titanium electrodes was two orders of magnitude smaller than that of the sample with nickel catalyst electrodes without titanium. We assumed that the low-resistance ohmic contact was achieved by forming titanium carbide (TiC) during the growth at the MWNT/titanium electrode interface. Moreover, we have demonstrated the growth of vertically aligned bundles of MWNTs, which were end-bonded to the lower titanium electrodes, selectively in via holes. We believe this is the first report of such simultaneous formation of MWNTs and their end-bonded low-resistance ohmic contacts, and its first trial application to carbon nanotube (CNT) vias for future ULSI interconnects.
Improvement of AlGaInP Multiple-Quantum-Well Light-Emitting Diodes by Modification of Ohmic Contact Layer
Authors: Wang Hsin-Chuan , Su Yan-Kuin , Lin Chun-Liang , Chen Wen-Ben , Chen Shi-Ming , Li Wen-Liang
Published: February 2005

A meshed contact layer was proposed to enhance the current-spreading ability of AlInGaP light-emitting diodes (LEDs). Via the modification of the contact layer, the luminous intensity was increased by a factor of 1.16 compared with that of the conventional LEDs at a wavelength of 570 nm. Moreover, the brightness reliability of such a new structure was found to be superior to that of conventional structures.
InGaN/GaN Multi-Quantum Well Metal-Insulator Semiconductor Photodetectors with Photo-CVD SiO2 Layers
Authors: Chang Ping-Chuan , Chen Chin-Hsiang , Chang Shoou-Jinn , Su Yan-Kuin , Chen Po-Chang , Jhou Yi-De , Liu Chun-Hsing , Hung Hung , Wang Shih-Ming
Published: February 2005

InGaN/GaN multiple-quantum well (MQW) structure was epitaxial growth by metal-organic chemical vapor deposition (MOCVD). Their MIS photodiodes with SiO2 interlayer were fabricated successfully using photochemical vapor deposition. The normal undoped-GaN metal-semiconductor-metal (MSM) potodiodes were also prepared to compare with them. It was found that the minimum dark current of InGaN/GaN MQW photodiodes was 4.2×10-13 A with 88 nm-thick SiO2 layer under 5 V reverse bias voltage. Furthermore, it was found that we can significantly reduce the dark current of this photodiodes by inserting a thin SiO2 interlayer in between metal electrode and the underneath InGaN/GaN MQW. With a 53 nm-thick SiO2 interlayer, it was also found that we could achieve a high 1.53×103 photo current to dark current contrast.
Optical Properties of Acrylate-Based Negative-Type Photoresist and Its Application to Optical Waveguide Fabrication
Authors: Gustafik Pavol , Sugihara Okihiro , Okamoto Naomichi
Published: February 2005

In this article, we present some of the optical properties of a polymeric acrylate-based photoresist material called PNME, by its principal components, which are pentaerythritol triacrylate, n-methyldiethanolamine, and eosin. The refractive index and absorption spectra were measured. Because of the low absorption of PNME in the datacom and telecom regions, PNME was studied with respect to its suitability for the fabrication of a channel waveguide and/or an optical fiber. A multimode optical waveguide was fabricated using a cold UV stamping fabrication method, and propagation losses at 1.3 µm were measured. An optical fiber core was fabricated using a light-induced self-writing fabrication method. In our study, it was found that optical waveguides made from PNME have low propagation losses due to smooth sidewalls and the low absorption of PNME. An optical waveguide with a corrugated core was also fabricated.
Monte Carlo Simulation of Single-Electron Nanocrystal Memories
Authors: Sim Jae Sung , Kong Jihye , Lee Jong Duk , Park Byung-Gook
Published: February 2005

We present a Monte Carlo simulation method for single-electron nanocrystal memories including the nanocrystal interdot effect, and show the simulation results obtained. A nanocrystal memory was modeled as a network of modified single-tunnel junctions for its program operation and as a network of channel resistances for simulating drain current to extract its threshold voltage. The results show that, in programming characteristics, device parameters have mutual trade-off relationships in the clearness of steplike single-charging features and in the magnitude of threshold voltage shifts. The presented method will be helpful for the design of single-electron nanocrystal memories.
Active Pixel Sensor Using a 1×16 Nano-Wire Photodetector Array for Complementary Metal Oxide Semiconductor Imagers
Authors: Park Jae-Hyoun , Seo Sang-Ho , Wang In-Soo , Yoon Hyung-June , Shin Jang-Kyoo , Choi Pyung , Jo Young-Chang , Kim Hoon
Published: February 2005

In this paper, a novel photodetector using an N-channel metal oxide semiconductor field effect transistor (NMOSFET) with a 30 nm-wide silicon nano-wire is described. The photodetector was fabricated on silicon-on-insulator (SOI) substrate and its wire was patterned by optical lithography, electron beam lithography and thermal oxidation. At room temperature, the device has similar I
DS-V
DS characteristics to a general NMOSFET when incident light is supplied instead of the gate voltage. A maximum responsivity of higher than 1×102 A/W and optical transient time of 80 µs have been obtained. Additionally, for the purpose of demonstrating the feasibility of the new device application, a 1×16 complementary metal oxide semiconductor (CMOS) active pixel sensor (APS) connected with the novel photodetector array was also designed and fabricated using 1-poly and 2-metal 1.5 µm CMOS technology. It is confirmed that this photodetector with high sensitivity as well as nano-scaled area could be applied to an image acquisition system for low illumination level.
Electronic and Structural Properties of Interdiffused Self-Assembled Quantum Dots from Magneto-Photoluminescence
Authors: Awirothananon Sunida , Sheng Wei Dong , Babinski Adam , Studenikin Sergei , Raymond Sylvain , Sachrajda Andrew , Potemski Marek , Fafard Simon , Ortner Gerhand , Bayer Manfred
Published: February 2005

A set of self-assembled InAs/GaAs quantum dot (QD) samples annealed at various temperatures for 30 s was studied using magneto-photoluminescence up to 28 T. Blueshifts increasing with annealing temperature, due to Ga-As interchange at the QD-barrier interface, are correlated with a reduction in inhomogeneous broadening and a reduction in inter-sublevel spacing. These new sample properties allow us to obtain clear crossing patterns closely matched with Fock-Darwin diagrams where the field applied perpendicular to the QD plane lifts the state degeneracies. In the limit that in-plane electron and hole wavefunction extension is the same, the splitting of the p-shell with magnetic field is inversely proportional to the in-plane exciton reduced mass. We use this to obtain the evolution of the latter with intermixing, and compare with predictions of single-particle k*p calculations.
Magnetization Reversal Process of Submicrometer-Scale Hall Bars of Ferromagnetic Semiconductor p-In0.97Mn0.03As
Authors: Sekine Yoshiaki , Nitta Junsaku , Koga Takaaki , Oiwa Akira , Yanagi Satoshi , Slupinski Tomasz , Munekata Hiroo
Published: February 2005

The magnetization reversal process of submicrometer-scale Hall bars of the ferromagnetic semiconductor p-In0.97Mn0.03As has been investigated by measuring the Hall resistivity with changing the direction of the applied magnetic field. The angle dependence of the coercive force indicates that the magnetization reversal process is more likely governed by the magnetic domain wall displacement. Furthermore, observation of several Barkhausen jumps on a 0.7-µm-wide Hall bar makes it clear that p-In0.97Mn0.03As has a small-domain-sized multidomain structure near the coercive force. It is also shown that p-In0.97Mn0.03As has an ideal uniaxial magnetic easy axis perpendicular to the plane. The magnetization reversal process of p-In0.97Mn0.03As is distinct from that of a similar ferromagnetic semiconductor p-Ga1-x
Mn
x
As.
Retention and Read Endurance Characteristics of a Ferroelectric Gate Field Effect Transistor Memory with an Intermediate Electrode
Authors: Khoa Tran Dang , Horita Susumu
Published: February 2005

Fundamental characteristics such as retention and read endurance of a ferroelectric gate field effect transistor (F-FET) memory with an intermediate electrode were investigated and reported. It was verified that the retention time of the new F-FET was longer than 98 h. By taking into account the leakage currents of both the ferroelectric capacitor C
f and the MOSFET used for data writing (W-FET), we found that, for positive reading voltage, the leakage currents of the ferroelectric capacitor and the W-FET are unfavorable for the P
r
+ state and the P
r
- state, respectively, in terms of read endurance. The overall read endurance is determined by a competition between the leakage currents of the C
f and the W-FET. The drain-connected configuration (DCC) was effective to minimize the unexpected influence of the leakage current of the W-FET.
Characteristics of Si Integrated Antenna for Inter-Chip Wireless Interconnection
Authors: Rashid A. B. M. Harun-ur , Watanabe Shinji , Kikkawa Takamaro
Published: February 2005

The characteristics of a small-size integrated dipole antenna on Si have been evaluated for use in inter-chip wireless interconnections and the measured characteristics are compared with the results obtained by 3D finite element simulation. The measured inter-chip transmission coefficients for a 0.02 mm2 dipole antenna pair manually separated by 10.5 mm each other in the horizontal plane and in a omit plane where the receiver chip is 2.6 mm higher than the transmitter chip were -42.7 dB and -57.5 dB at 20 GHz when the antennas were fabricated on a high-resistivity Si substrate and on standard Si substrate, respectively. This shows the feasibility of using integrated dipole antennas for wireless clock distribution and data transmission in future 3D ICs or in stacked chip scale packaging.
Electrostatic Discharge Protection under Pad Design for Copper-Low-K VLSI Circuits
Authors: Lee Jam Wem , Li Yiming , Chao Alice , Tang Howard
Published: February 2005

An electrostatic discharge (ESD) under pad structure is proposed and demonstrated for the novel copper-low-K circuit design. By using this approach, the density of both devices and pads could be markedly improved; in a rough estimation, approximately five to twenty percent of the chip area could be saved. Moreover, tests of ESD, latch-up, and bond yield are performed and are found to be better than those of the conventional ones. The designed structure could be considered as a very effective achievement, and this is particularly true for the sub-0.1 µm circuit with copper-low-K interconnections.
Effects of Different Materials Used for Internal Floating Electrode on the Photovoltaic Properties of Tandem Type Organic Solar Cell
Authors: Triyana Kuwat , Yasuda Takeshi , Fujita Katsuhiko , Tsutsui Tetsuo
Published: February 2005

Three thin heterojunctions sandwiched between indium tin oxide (ITO) and the top electrode as triple-heterojunction organic solar cells have been fabricated. Each heterojunction cell consists of CuPc as a donor layer and perilene tetracrboxylic-bis-benzimidazole (PTCBI) as an acceptor layer. Ultra thin (1 nm average thickness) layers of Ag or Au have been inserted between two heterojunctions as an internal electrode. Ag and Au were chosen as materials both for internal floating and top electrodes. Influences of different deposition sequences of the organic layer in each heterojunction cell and different electrode materials were also investigated. The optimum devices were obtained when the same material was used both as an internal electrode and a top electrode. When the deposition sequence of the heterojunction is PTCBI/CuPc, the most suitable electrode is Au and the ITO is negative relative to the top electrode. Meanwhile, Ag is suitable for an electrode when the deposition sequence is CuPc/PTCBI. In this second deposition sequence, the ITO is positive relative to the top electrode. The open circuit voltage (V
oc) of both optimum devices is on the order of 1.35–1.5 V. These values are approximately three times higher than that in single-heterojunction organic solar cells.
Thin Film Transistors with Oriented Copper Phthalocyanine Crystals Fabricated by Physical Vapor Deposition under DC Electric Field
Authors: Sakai Masatoshi , Iizuka Masaaki , Nakamura Masakazu , Kudo Kazuhiro
Published: February 2005

Crystalline copper phthalocyanine (CuPc) films have been fabricated by physical vapor deposition using a cylindrical furnace. Field effect transistors (FETs) of the crystalline CuPc film are fabricated by optimizing the deposition conditions. Crystal orientation along the electric field is enhanced by an application of a DC electric field during crystal growth. The electric-field-assisted orientation is effective in a submillimeter area. The degree of crystal orientation improves with increasing electric field strength. High current and a remarkable threshold for the drain voltage are observed in the FET characteristics of the oriented crystalline film.
Effect of Surface States on Piezoelectric Photothermal Specta of Silicon Single Crystals
Authors: Memon Aftab A. , Malinski Miroslaw , Fukuyama Atsuhiko , Ikari Tetsuo
Published: February 2005

The effect of surface states on the piezoelectric photothermal (PPT) spectra of p- and n-type, <100> oriented, single crystal silicon was investigated. We showed that a PPT signal bearing a lower energy edge around 1.04 eV at room temperature was due to the bulk effect. This bulk signal was greatly affected by another signal bearing a broad peak around 1.18±0.01 eV. The broad peaked signal was found to be due to the surface states. The variation in amplitude and phase of the 1.18±0.01 eV signal revealed that the surface states were affected by the ambient illumination and low-temperature thermal annealing at 350 K. The results also indicated that a very low absorption coefficient in indirect semiconductors can be effectively observed by using the proposed PPTS technique.
Method for Detecting Defects in Silicon-On-Insulator Using Capacitance Transient Spectroscopy
Authors: Nakashima Hiroshi , Wang Dong , Noguchi Takashi , Itani Kousuke , Wang Junli , Zhao Liwei
Published: February 2005

A method for detecting defects such as interface states and a deep trap in Si-on-insulator (SOI) has been proposed, which is based on deep-level transient spectroscopy (DLTS) analysis of the metal-oxide semiconductor (MOS) structure. It is shown, for a bonded p-type SOI wafer consisting of 5 µm top-Si (T-Si) and 1 µm buried oxide (BOX) layers, that the interface state densities between T-Si/BOX and BOX/back-Si (B-Si) can be measured. Furthermore, the validity of this DLTS technique for the detection of a discrete deep level has been confirmed by using a Fe-doped SOI wafer. It is shown that the Fe concentration in B-Si is consistent with that of bulk Si, while the Fe concentration in T-Si shows significant enhancement. Through these investigations of SOI wafers, the validity of this DLTS method has been demonstrated.
Dependence of Hot Electron Transport on Base Layer Thickness of Magnetic Tunnel Transistor
Authors: Hirose Takakazu , Fujiwara Yuji , Jimbo Mutsuko , Kobayashi Tadashi , Shiomi Shigeru , Masuda Morio
Published: February 2005

The hot electron transport phenomenon has been investigated in magnetic tunnel transistors with various base layer thicknesses. In terms of Au layer thickness, the magneto-current and the transfer ratio were at a maximum when the Au layer thickness was approximately 8.0 nm. For the magnetic layer thickness, the transfer ratio decreased monotonically with increasing magnetic layer thickness. The magneto-current increased with increasing magnetic layer thickness up to 3.0 nm, and a maximum increase of approximately 370% was observed at 77 K.
Wide Acceptance Angle of Second-Harmonic Green Generation by Periodically Poled Potassium Niobate
Authors: Shichijyo Shiro , Hirohashi Junji , Kamio Hiroyuki , Yamada Kazuhiro
Published: February 2005

Periodically poled KNbO3 (PPKN) with a period of 40 µm were prepared to demonstrate the second-harmonic generation of green (532 nm). The propagation direction was set to be the b axis in order to use large nonlinear coefficient d
31, and the embryonic nucleation method was applied to form a spatially uniform domain inversion. The conversion efficiency and angle tolerance of PPKN were compared with those of conventional critical phase-matched KN (CPMKN). The angle θ on the b–c plane) acceptance of PPKN was 0.96 deg·cm, which was 38 times higher than that of CPMKN (0.025 deg·cm), and wide-angle tolerance was demonstrated. Its conversion efficiency was approximately 2 times higher than that of CPMKN.
Characterization of Large-Area AlGaInP/Mirror/Si Light-Emitting Diodes Fabricated by Wafer Bonding
Authors: Horng Ray-Hua , Huang Shao-Hua , Wuu Dong-Sing , Jiang Yann-Zyh
Published: February 2005

High-brightness AlGaInP/mirror/barrier/Si light-emitting diodes (LEDs) with vertical electrodes were fabricated using a wafer bonding technique. The high-thermal-conductivity Si substrate provides a better heat sink (compared with GaP or GaAs), which is a particularly important characteristic for high-power, large-area emitter applications. It allows for saturation of the small-area LED (300×300 µm2) after 150 mA injection and for the large-area LED (1200×1200 µm2) to increase output power even at 300 mA injection. The light output of the large-area vertical-conducting LED is mainly affected by the top-side (i.e., n-AlGaInP cladding) electrode design, where an interdigitated-finger electrode provides the better current spreading performance and prevents the current crowding problem. The extent of junction heating on LED samples (300×300–1200×1200 µm2) can also be evaluated from the corresponding electroluminescence spectra and emission-peak-wavelength driven by different injection current values. Finally, using a natural lithography technique, the mirror-substrate (MS) LEDs with textured surfaces present a brightness of 10 cd, which is about 4 cd brighter than that of the MS LED without a textured surface. With a combination of the MS wafer bonding and surface texturing techniques, thermal management in packaging becomes the key factor in further enhancing the external quantum efficiency of large-area LEDs under high flux operation.
Laser-Induced Bulk Damage of Various Types of Silica Glasses at 532 and 355 nm
Authors: Kuzuu Nobu , Yoshida Kunio , Ochi Kanyoshi , Tsuboi Yoshitaka , Kamimura Tomosumi , Yoshida Hidetsugu , Namba Yoshiharu
Published: February 2005

Laser-induced bulk-damage threshold (LIDT) of various types of silica glasses at 532 and 355 nm caused by lasers with pulse widths of ≈5 ns (refered as nanosecond laser [NSL]) and 30 ps (refered as picosecond laser [PSL]) were observed. The LIDTs of fused quartzes (FQs) produced by melting natural quartz powder were less than those of synthetic fused silicas (SFSs) at both wavelengths. At 355 nm, the LIDT of SFS containing 1000 ppm of Cl was almost the same as that of FQ at 1 pulse, and that at 12000 pulses was between those of SFSs and FQs. The variation of LIDT among samples for PSL is less than that for NSL.
Changes in Optical Absorptions in Natural Quartz Irradiated by γ-Rays and Its Isochronal Annealing
Authors: Aoki Takashi
Published: February 2005

The clear natural Brazilian quartz used in this experiment had a weak optical absorption at the A1-band (1.85–2.0 eV) before γ-ray irradiation. By irradiating the sample, a strong A2-band absorption (2.65–2.75 eV) was produced, while the A1-band absorption increased only very slightly, although both the A1- and A2-bands are related to an aluminum impurity. The thermal activation process of the A2-band absorption was investigated by isochronal annealing to evaluate the activation energy. When possible losses were taken into consideration, an activation energy E=0.32 eV was obtained, where the losses are light transmission losses originating from multiple scattering, absorption by surface damage, and scattering in random directions by the surface roughness of a specularly polished quartz plate. When an ideal state was assumed, in which the transmission losses did not exist, an activation energy E=0.28 eV was obtained. From these results, the activation energy for this color center is evaluated to be 0.3±0.2 eV.
Effects of High-Temperature Metal-Organic Chemical Vapor Deposition of Pb(Zr,Ti)O3 Thin Films on Structural Stabilities of Hybrid Pt/IrO2/Ir Stack and Single-Layer Ir Bottom Electrodes
Authors: Sun Ho-Jung , Choi Eun Seok , Lee Tae Kwon , Hong Tae Eun , Yang Jun-Mo , Kweon Soon Yong , Kim Nam Kyeong , Yeom Seung Jin , Roh Jae-Sung , Sohn Hyun-chul , Kim Jin Woong
Published: February 2005

High-temperature Pb(Zr,Ti)O3 (PZT) metal-organic chemical vapor deposition (MOCVD) at 620°C was performed on two major bottom electrode candidates, namely, a hybrid Pt/IrO2/Ir stack electrode and a single-layer Ir electrode. The structural stabilities of both PZT/electrode stacks were investigated. Severe interaction between PZT and the underlayered Pt films was observed, and the interaction resulted in a pyrochlore phase in the PZT film and blister-type deformation in the Pt film. On the other hand, structural stability, which served as the basis for a well-crystallized perovskite PZT film, was preserved in the case of the Ir electrode. Therefore, it could be determined that the Ir electrode as a bottom electrode was better than the Pt electrode from the point of view of the structural stability of a capacitor stack, when high-temperature MOCVD is chosen as a preparation method.
Adsorption and Desorption of Dibutyl Phthalate on Si Surface Measured in Controlled Atmosphere using Quartz Crystal Microbalance Method
Authors: Okamura Shigeru , Shimada Manabu , Okuyama Kikuo
Published: February 2005

The adsorption of dibutyl phthalate (DBP) molecules on the surface of Si was studied using a highly sensitive quartz crystal microbalance (QCM) and new sliding chamber system, and using the accurate decomposition analysis of the decay curve method. It has been understood that the DBP molecules are adsorbed on the Si surface at three different kinds of adsorption sites that require different desorption energies; two of the three are in equilibrium with the DBP molecular density in the vapor phase, one being a site that has a 400 s desorption time constant at 23°C which seems to be the isolated admolecules, and the other site has a 1900 s desorption time constant which seems to be the cohesion of the admolecules. The third site is a site that has an 18000 s desorption time constant that seems to be restricted by something on the surface, such as an atomic terrace edge or crystal defect.
Etching Characteristics of Manganese-Doped Zinc Sulfide Film Using Cl2/CF4 Inductively Coupled Plasma
Authors: Yun Sun Jin , Kwon Kwang-Ho , Lee Yong-Eui , Kim Chang-Il
Published: February 2005

The etching characteristics of manganese-doped zinc sulfide (ZnS:Mn) films were investigated using the inductively coupled plasma (ICP) of Cl2/CF4 gas mixture. The chemical surface reaction of ZnS:Mn etching with Cl2/CF4 ICP plasma was studied by plasma analysis using the Langmuir probe (LP) method and optical emission spectroscopy (OES), and surface analysis using X-ray photoelectron spectroscopy (XPS). The maximum ion saturation current was obtained with a gas mixture of 30% CF4-70% Cl2 and the ion current of pure Cl2 plasma was higher than that of pure CF4-plasma. The etch rate of ZnS gradually decreased with increasing flow rate of CF4 gas at a fixed total flow rate. XPS indicated that Mn had accumulated on the surface after etching of the ZnS:Mn (0.39 wt.%) layer using Cl2 plasma. The OES analysis of Cl2/CF4 plasma revealed the presence of C–Cl and CF2 radicals as well as Cl and F atoms.
Possible Deviation from the well-known Threshold Behavior of Field-Effect Doping Phenomenon in Extremely Thin Organic Semiconductor Layer
Authors: Ikegami Keiichi
Published: February 2005

Field-effect doping in a metal/insulator/semiconductor/metal four-layer model indicates that the well-known threshold behavior Q∝(V
G-V
th), where Q is the induced charge and V
G and V
th are the bias voltage and its threshold value, respectively, should be realized even when the thickness of the semiconductor layer (d
s) is on the 10 nm scale. At the same time, however, this model suggests that the doping phenomenon deviates from this simple threshold behavior when the density of states is small and d
s is on the 1 nm scale.
Effects of Ultra Low Energy Nitrogen Ion Irradiation on Carbon Nanotube Channel Single-Electron Transistor
Authors: Kamimura Takafumi , Yamamoto Kazuhiro , Matsumoto Kazuhiko
Published: February 2005

The effects of ultra low nitrogen ion irradiation on room-temperature-operated carbon nanotube channel single-electron transistor have been investigated. The ion irradiation energy was 30 eV and the total number of ions was 2.5×1014 ions/cm2 and 3.7×1015 ions/cm2. After the irradiation, the Coulomb diamonds became larger with increasing in density of irradiated ions. Nitrogen ion irradiation was found to be effective in reducing the quantum dots size in the carbon nanotube channel single-electron transistor.
Photoelectric Properties Based on Electric Field Modulation of Photoinduced Electron Transfer Processes in Flavin-Porphyrin Hetero-type Langmuir–Blodgett Films
Authors: Isoda Satoru , Hanazato Yoshio , Ueyama Satoshi , Nishikawa Satoshi , Akiyama Kouich
Published: February 2005

Metal–insulator–meal devices composed of flavin-porphyrin hetero-type Langmuir–Blodgett films showed highly efficient photoelectric properties mainly attributable to the fast charge separation process at a molecular heterojunction (MHJ) between flavin and porphyrin. The photoelectric properties of the MHJ devices showed different characteristics depending on the redox state of the central metal of porphyrin, i.e., Ru(III) or Ru(II). The rectifying behavior of the photocurrent was observed for the Ru(III)-MHJ device, whereas the Ru(II)-MHJ device did not show the rectifying behavior. We concluded that the rectifying behavior was mainly controlled by the electric field dependence of the charge recombination process. Furthermore, a bell-shaped photocurrent-voltage curve was observed for the Ru(II)-MHJ device. The mechanism underlying the negative resistance might be based on the electric field dependence of the charge shift process in flavin monolayers controlled by the inverted region mechanism of the Marcus electron transfer theory.
Measurement of Temperature in Sonoplasma
Authors: Mukasa Shinobu , Nomura Shinfuku , Toyota Hiromichi
Published: February 2005

Stable plasma can be generated in a liquid hydrocarbon such as n-dodecane or benzene by simultaneous microwave and ultrasonic irradiation. The authors refer to this plasma as “sonoplasma” and distinguish it from “sonoluminescence” on the basis of the continuity of emission. The temperature in the plasma was obtained by measuring two specified emission intensities from the plasma which reached approximately 5000 K. To analytically estimate the temperature, numerical simulations of the behavior of a single bubble in sound field, taking into account the absorption of microwave energy, were carried out. The temperature inside the bubble in n-dodecane reached approximately 8000 K. In benzene, the temperature inside the bubble, which continued expanding through absorption of microwave energy, exceeded 2000 K.
Analysis of Sound Field of Aerial Ultrasonic Sensor by Three-Dimensional Finite-Difference Time-Domain Method Using Parallel Computing
Authors: Yamada Yasuhiro , Maeda Satoshi , Tsuchiya Takenobu , Endoh Nobuyuki
Published: February 2005

The three-dimensional (3D) finite-difference time-domain (FDTD) method is applied to acoustics analysis in this paper. The disadvantages of its method are large memory requirement and long calculation time. We developed the 3D-FDTD method using parallel computing with the Message-Passing Interface (MPI) in the personal computer (PC) cluster because it could shorten the calculation time and could treat larger memory. In this paper, basic algorithm of the proposed method is described. The acoustic fields of point sources and the real aerial sensor are calculated for verifying the validity of the method.
Rectangular-Plate-Type Piezoelectric Ceramics Ultrasonic Motor Using Double 1st Resonance Modes of Longitudinal and Width-Bending Vibrations
Authors: Suetomo Atsutoshi , Tomikawa Yoshiro
Published: February 2005

This paper deals with a piezoelectric ceramics ultrasonic motor of rectangular plate type using double resonance modes of longitudinal (L
1) and width-bending (B
1) vibrations. First, the motor construction and its operating principle are described, and second, the measured characteristics of this prototype motor are presented.
Composite Materials and Measurement of Their Acoustic Properties
Authors: Kondo Toshio , Kitatuji Mituyoshi
Published: February 2005

A composite material consists of two or more materials and its optimum acoustic properties can be designed by selecting its constituents. Unidirectional composite materials have a very low transverse Poisson's ratio of less than 0.1. By considering such composite material features, the applications of carbon fiber-epoxy and highly crystalline polyethylene fiber-polyurethane composite materials to a medical transducer array are proposed. The sound velocities and densities of the composite materials are measured and their transverse Poisson's ratios are calculated from experimental data.
Investigation of the Electron Nonradiative Transition in Extremely Thin GaInNAs/GaAs Single Quantum Well by Using a Piezoelectric Photothermal Spectroscopy
Authors: Imai Kenji , Fukushima Shin-ichi , Ikari Tetsuo , Kondow Masahiko
Published: February 2005

Room-temperature piezoelectric photothermal spectroscopy (PPTS) measurements were carried out for the single-quantum-well (SQW) structures of GaInNAs. Four as-grown samples with thicknesses of 10, 7, 5 and 3 nm were used to investigate the quantum confinement effect in the SQW. The exciton contribution was clearly distinguished from the two-dimensional step like band-to-band transition. The thickness dependence of PPT signal peak energy were well understood by quantum mechanics. The decrease in well thickness results in increases in quantized energy level and exciton binding energy. The present results showed that the newly developed PPT methodology is a unique and powerful tool for investigating the optical absorption spectra of extremely thin quantum well structures.
Characterization of Nanostructured TiO2 Electrodes Sensitized with CdSe Quantum Dots Using Photoacoustic and Photoelectrochemical Current Methods
Authors: Shen Qing , Toyoda Taro
Published: February 2005

Two types of nanostructured titanium dioxide (TiO2) electrodes were prepared with anatase TiO2 nanoparticles of different sizes (average diameters of 15 and 27 nm). CdSe quantum dots were adsorbed onto each of the two types of TiO2 electrodes, by a chemical deposition (CD) technique, the average sizes of which increased to 7 nm on increasing the deposition time. Optical absorption and photoelectrochemical properties were characterized by using photoacoustic (PA) and photoelectrochemical (PEC) current methods. Redshift of the PA and PEC current spectra with increasing CdSe sizes was clearly observed, which indicates quantum confinement effects and photosensitization by the CdSe quantum dots. It was found that the PEC current spectra in the visible region were quite different for the two types of TiO2 electrodes for the same deposition time, although the PA spectra were very similar to each other. The correlation of the PEC current spectra with the microstructures of the two types of TiO2 electrodes was discussed, which provided information that could lead to the optimization of dye-sensitized solar cells (DSSC).
Investigation of Wavefront Fidelity of Phase Conjugate Waves by the Schlieren Method
Authors: Ohno Masahiro
Published: February 2005

The fidelity of ultrasonic phase conjugate waves has been experimentally investigated at the wavefront level. Phase conjugate waves at 3.7 MHz were generated via nonlinear piezoelectricity of PZT (PbZr
x
Ti1-x
O3) ceramics, and wavefronts of the incident wave and the phase conjugate wave were visualized by the schlieren method. Wavefronts of an incident wave and those of the phase conjugate wave agreed with the errors of 1/6 the wavelength. A possible cause of the error is the diffraction effect due to the finite aperture of the phase conjugator. Some additional, noise-like ultrasonic fields were detected in schlieren images.
Development of Novel Atomization System Based on SAW Streaming
Authors: Chono Katsumi , Shimizu Norifumi , Matsui Yoshikazu , Kondoh Jun , Shiokawa Showko
Published: February 2005

In this paper, we describe a novel atomization system using surface acoustic wave (SAW) devices. The SAW radiates its energy into a liquid, if the liquid is loaded on the SAW propagating surface. The various liquid motions, such as vibration, flow and droplet formation, due to interaction between SAW and liquid are called SAW streaming. The liquid dynamics depends on the SAW input power. First, the relationships between input voltage to the SAW device and water dynamics are observed. For atomization, an input voltage larger than 30 VP-P is required. Second, a stable method of generating a mist is discussed. The thin liquid layer plays an important role in continuous mist generation. The fundamental properties, such as the angle and height of mist, are measured using a filter paper to keep a thin liquid layer on the surface. We also demonstrate the control of mist direction with an electrostatic field. Based on these fundamental experiments, a practical atomization system is designed and performed.
Experimental Study of Gyro Sensor Using Double-Ended Tuning Fork Quartz Resonator
Authors: Sato Kenji , Ono Atsushi , Tomikawa Yoshiro
Published: February 2005

In this study, we focus on a flatly supported gyro sensor using a double-ended tuning fork quartz resonator set in parallel with the rotating plane. The resonator has the advantages of flat form, high precision and strong shock resistance; moreover, fundamentally, the resonator is able to detect two-axial angular velocities. We clarified the features of the resonator by discussing the advantages and disadvantages of the resonator as a gyro sensor. The resonator was designed to have high detection efficiency, applying the vibration theory and using the finite element method. The resonator was finely fabricated by photolithography and wet etching. As a result, the resonators, without any problem as a gyro sensor, have been fabricated; we also confirmed experimentally that the practical angular velocity could be detected by the prototype gyro sensor. Consequently, we can conclude that the double-ended tuning fork quartz resonator could be used as the flatly supported gyro sensor.
Multilayer Ceramic Resonators Using a Flexural Vibration Mode and their Application to Filters
Authors: Unami Toshihiko , Inoue Jiro
Published: February 2005

Multilayer ceramic resonators using a piezoelectric longitudinal-effect flexural vibration mode have been developed. The resonators are able to be designed in a much smaller format while maintaining high performance than the multilayer longitudinal resonators which we previously presented. Utilizing internal divided electrodes and floating electrodes makes it possible to generate a flexural vibration mode without complicating the process of connecting electrodes or polarizing. The relationship between the ratio of piezoelectric area in the length direction and the bandwidth, and the effects of the gap and distance from the internal electrodes on the resonator characteristics, are analyzed by the finite element method. Resonators and ladder filters are investigated and their superior characteristics and small size have been demonstrated.
Characteristics of Reflection of Resonators Using Lamb Wave on AT-Cut Quartz
Authors: Nakagawa Yasuhiko , Momose Masayuki , Kakio Shoji
Published: February 2005

Lamb waves propagating on an AT-cut quartz substrate were studied. In this study, we propose a high-frequency resonator using a Lamb wave. A Lamb wave is excited on an extremely thin AT-cut quartz substrate which thickness is comparable to the wavelength of an elastic wave propagating on a substrate. This Lamb wave propagates at a higher phase velocity mode than surface acoustic waves. This realizes an RF resonator operable in a high frequency range in which a conventional quartz resonator hardly operates. A theoretical analysis of the reflection coefficient of a Lamb wave with a grating reflector was conducted. The analysis results and experimental results are compared and discussed in this study. A reflection coefficient which is 10 to 20 times higher than that for a Rayleigh-type surface acoustic wave is obtained.
Energy Trap for Axial-Shear-Wave Resonance in a Stepped Cylindrical Rod: Theory and Measurement
Authors: Ogi Hirotsugu , Wada Kayo , Hirao Masahiko
Published: February 2005

The methodology to trap the vibrational energy of an axially polarized surface-shear wave (axial-shear wave) in a stepped cylindrical rod is presented. The central part of the rod where the resonance vibration was trapped had a slightly larger diameter. The magnetostriction effect of steel enabled us to generate and detect the resonance with noncontacting. An approximated analysis was used to derived a resonance equation and displacement distribution of trapped axial-shear-wave modes. The displacement was measured along the axial direction and it exponentially decreased with the distance from the center. This trend agreed with the theoretical calculation.
Acoustic Waveguides for Actuators
Authors: Friend James , Nakamura Kentaro , Ueha Sadayuki
Published: February 2005

Using a 3×4×5 mm torsional microtransducer attached to a 30-cm long, 0.3-mm diameter flexible stainless steel wire, torsional vibration and coupled torsional-flexural vibration is transmitted to a remotely-placed rotor. The torsional microtransducer uses flat, thickness-poled lead zirconate titanate (PZT) elements attached to the surface of a square-sided prism with a tapered horn and tip; the elements twist the structure and generate torsional vibration amplified by the horn and tip at 150–260 kHz. Swaged to the wire–the `acoustic waveguide'–torsional vibration is transmitted into the wire, and flexural vibration is developed in the wire due to strong torsional-flexural coupling, demonstrated by measurement of the vibration velocity. Standing wave vibration was generated (standing wave ratio, SWR≈7.5) in the waveguide with nothing on the waveguide tip, but upon using a rotor, traveling wave vibration transmitted energy to the rotor (SWR≈4), which acted essentially as a loss; by placing a damping material on the tip instead of a rotor, very similar traveling wave motion was obtained (SWR≈1.5). The few torsional resonances of the transducer were found to be greatly increased in number by the waveguide, and rotors, with a contact radius of 300 µm, were found to rotate for most of these resonances in either direction at up to 11,500 rpm and 3.5 µN-m.
Basic Consideration of Slope Sensor Using Piezoelectric Thin Plate Bending Vibrator Loaded with Moment Impedance
Authors: Sato Taeko , Tomikawa Yoshiro
Published: February 2005

This paper deals with a new type of slope sensor using a thin plate piezoelectric bending vibrator loaded with moment impedance. This sensor is fabricated on the basis of the gyro-moment motor already reported by one of the authors. In the first part of this paper, the construction of this sensor and its operation principle are described. In the second part, basic experimental results proving the principle are presented. Moreover, we show the results of finite element method simulations of some constructions of the slope sensor.
Vibration-Type Viscometer Using a Triangular Bimorph Transducer –Measurement of High Viscosity by Low-Frequency Operation–
Authors: Tai Hidekazu , Seki Jyouji , Kida Takuro , Kobayashi Tsutomu
Published: February 2005

For the measurement of very high viscosity, we attempted to use a cantilever-type viscosity sensor using a triangular bimorph with a needle. Thus, the frequency-phase characteristics of the sensor in each viscosity were investigated at a low frequency range by changing the length of the triangular bimorph. As a result, it was clarified that we could develop a viscosity sensor with high sensitivity for very high viscosities up to 100,000 mm2/s(=cSt), using frequencies below 100 Hz.
Estimation of Local Displacement Vector in Random Medium Utilizing Synthetic Aperture Array Signal Processing
Authors: Minochi Yusuke , Yagi Shin-ichi , Nishiyama Tomohide
Published: February 2005

Real-time imaging of dynamical movement or stress distribution across living tissues by physiological internal or clinical external stress forces could be a promising tool for clinical diagnosis as visualized palpation. However, the transversal components of tissue local motion across an ultrasonic beam cannot be obtained utilizing conventional beam scanning. We proposed the combined algorithm of phase sensitive spatial cross-correlation between two sequential speckle echo frames and signal processing for a synthetic aperture of an array transducer which realizes a uniform spatial resolution through these echo frames. The two-dimensional local motion vector can be directly calculated from the sequentially estimated local phase changes by successive irradiation of different point sources. The accuracy and the statistical variance of the estimated two-dimensional displacement were investigated for the simulated random tissue and the received speckle echo frames from it. The obtained results showed the excellent performance of the proposed algorithm, both for local values and for the entire distribution of estimated displacement vectors throughout the measured medium.
Measurements of Elastic Properties of Plasma-Sprayed Coatings Using Bulk Ultrasonic Pulses
Authors: Sugasawa Shinobu
Published: February 2005

A new theory is proposed to extend the limit of the application of bulk ultrasonic pulses, which have been thought to be unsuitable for the evaluation of sound velocity in thin coating layers because of interference with echoes. This extension is accomplished by introducing the new concept of the group delay spectrum. We first made a model representing waves reflected from a coating layer and found that many acoustic properties, for example, sound velocity, acoustic impedance, and coating density, can be derived easily by a group delay analysis. Next, the theory was applied to the analysis of a layer plasma-sprayed coated with alumina particles on a stainless steel substrate. To confirm the validity of the theory, we prepared coated specimens of varying thicknesses which covered from 0.16 mm to 0.48 mm, and we succeeded in evaluating sound velocity and coating density.
Resonance Ultrasound Spectroscopy for Measuring Elastic Constants of Thin Films
Authors: Nakamura Nobutomo , Ogi Hirotsugu , Hirao Masahiko
Published: February 2005

We show an advanced technique for measuring elastic constants C

i
j
of thin films deposited on substrates. Thin films often show anisotropy between the in-plane and out-of-plane directions because of their columnar structure, residual stress, texture, and incohesive bond. Then, thin films show macroscopically transverse isotropy and have five independent C

i
j
. All the film C

i
j
affect free-vibration resonance frequencies of the film/substrate layered specimen. Therefore, measuring the resonance frequencies permits us to determine the thin-film C

i
j
with the other known parameters. In order to yield reliable C

i
j
of thin films, we have to measure the resonance frequencies with sufficient accuracy and identify vibration modes of the measured resonance frequencies. We overcome these problems by developing a tripod and using a laser-Doppler interferometer, respectively. We applied the present technique to a copper thin film. Measured C

i
j
are smaller than those of bulk and show elastic anisotropy. We attribute these features to the incohesive bond regions.
Evaluation of Adhesive Strength of Chemical Vapor Deposition Diamond Films by Laser Spallation
Authors: Ikeda Ryuji , Tasaka Syun , Cho Hideo , Takemoto Mikio
Published: February 2005

The adhesive strength of polycrystalline chemical vapor deposition (CVD)-synthesized diamond films deposited on sintered SiC substrates was estimated using laser spallation. A strong pulse expansion wave was produced on the surface opposite the diamond film by the pulse laser breakdown of silicone grease confined by a silica plate and used to cause Mode-I fracture at the interface between the diamond and SiC. The amplitude of the expansion wave was monitored by a fast laser interferometer as a function of laser characteristics and the confining method. The critical laser energy for causing film spallation changed depending on the diameter of the laser beam and the thickness of the energy-absorbing layer (grease) confined by the silica plate. The driving force of the spallation was estimated to be the tensile stress of the expansion wave following the first compression wave, and it was changed significantly by the dynamics of dielectric breakdown. This was demonstrated by the waveform simulation of the out-of-plane displacement using a theoretical Green's function of the second kind for the dipole source. A pulse dipole source with short rise and decading times generates strong expansion waves.