bluuebunny/crossref_metadata_2025 huggingface dataset:
Nanoimprinted Focusing Grating Coupler for an Ultra Slim Optical Pickup Head
Authors: Paek Mun Cheol , Ryu Hojun , Suh Dongwoo , Park Yongwoo , Kang Kwang Yong
Published: July 2005

Nanoimprinted focusing grating couplers (FGCs) for ultra slim optical pickup head application have been investigated. Inorganic electron beam resist hydrogen silsesquinoxane (HSQ) was used as a master for FGC replication, and polymethylmethacrylate (PMMA) as a transparent stamper for ultra violet (UV) exposure embossing. UV embossing was employed to replicate the fine featured grating patterns in FGC. The focused spot size measured from the replicated coupler showed almost the same quality as theoretically predicted one.
Fabrication of Focusing Grating Coupler Using e-Beam Lithographed Hydrogen Silsesquioxane
Authors: Ryu Hojun , Suh Dongwoo , Park Yongwoo , Paek Mun Cheol , Kang Kwangyong
Published: July 2005

A focusing waveguide grating coupler made of hydrogen silsesquioxane is fabricated successfully. The size of the focusing grating coupler is 1 mm×1 mm and the total device size is 8 mm×2 mm. The numerical aperture and the minimum line width of the device are 0.85 and 85 nm, respectively. The spot size of this coupler is 335 nm for blue laser and the out-coupling efficiency is 25.7%.
Correlation between Residual Stress and Boron Concentration in Boron-Doped Silicon Films
Authors: Jeong Ok Chan , Yang Sang Sik
Published: July 2005

This paper represents the correlation between the residual stress and the boron concentration in boron-doped silicon films. Residual stress measurement structures of different thicknesses are simultaneously fabricated for the quantitative determination of residual stress profiles. All structures are diffused by various boron diffusion processes and consecutively etched by an improved etch process on the same silicon wafer. The obtained residual stress profiles illustrate that as the drive-in process temperature or the time increases, the average residual stress and the maximum residual stress decrease. For cases of several drive-in process conditions, correlation coefficients between the boron concentration and the residual stress are calculated and the lattice contraction of a boron-doped silicon wafer is measured by high-resolution X-ray diffractometry(HRXRD). The calculated correlation coefficients illustrate that the residual stress profile is closely correlated with the boron concentration after drive-in.
Integrated Simulation Technique for Volume Holographic Memory Using Finite-Difference Time-Domain Method
Authors: Kinoshita Nobuhiro , Shiino Hirotaka , Ishii Norihiko , Shimidzu Naoki , Kamijo Koji
Published: July 2005

We developed an integrated simulation technique for volume holographic memory. Volume holographic gratings were expressed as the permittivity distribution in the media. The distribution derived from the interference fringes of a reference beam and an object beam. These fringes were calculated using the angular spectrum of plane waves, instead of the diffraction integral formula. The finite-difference time-domain method was used to simulate the light wave propagation in the volume holographic gratings. The diffracted electromagnetic waves on the observation plane were obtained by the irradiation of the reference beam from the source plane. The simulation of an angularly multiplexed hologram was performed. The simulation results showed that two different data pages are reproduced separately at the same angle as those recorded in a numerical computation.
Signal Processing Method of Holographic Memory Using Image Distortion Correction and Soft Decision Viterbi Decoding Method
Authors: Sato Daisuke , Nishimoto Kazumasa , Katayanagi Yasutaka , Yamamoto Manabu
Published: July 2005

The signal quality of holographic memory is greatly lowered by the pixel mismatch between the charge-coupled device (CCD) and the reproduced image caused by image distortion. This paper discusses an approach to improve the signal quality by using two step decoding method. By this method, first, distortion correction is done to improve the degree of pixel mismatch to obtain better signal to noise ratio (SNR). Then, to eliminate errors such as noise that cannot be removed by distortion correction, soft decision Viterbi decoding using the newly defined reliability is used to correct errors. The effectiveness of this two step decoding method was tested by computer simulation, and its effect to improve SNR and reduce errors was confirmed.
Three-Dimensional Error Correction Schemes for Holographic Data Storage
Authors: Hwang Euiseok , Yoon Pilsang , Park Jooyoun , Park Jongyong , Nam Haeun
Published: July 2005

Three-dimensional (3D) error correction coding (ECC) provides volumetrically coupled ECC blocks, the possible errors of which can be controlled powerfully by correcting errors from three different directions, iteratively. However, increased parities cause a large overhead, which limits the application of strong ECC schemes. In this study, a new efficient 3D ECC scheme and its decoding algorithm for holographic data storage were developed and evaluated. The proposed scheme has 3D ECC capability with a relatively low coding overhead, similarly to that of conventional 2D error correcting schemes, such as RSPC. It gives favorable ECC performance with a high efficiency in a page-based recording and retrieving system, which enables the use of a 3D ECC scheme for various applications.
Two-Dimensional Optical Storage: High-Speed Read-Out of a 50 GByte Single-Layer Optical Disc with a 2D Format Using λ=405 nm and NA=0.85
Authors: Bruls Dominique M. , Immink Andre H. J. , Lee Alexander M. van der , Coene Wim M. J. , Riani Jamal , Beneden Steven J. L. van , Ciacci Massimo , Bergmans Jan W. M. , Furuki Motohiro
Published: July 2005

With ever increasing storage capacities, long read-out times of content are becoming a bottleneck for the convenient use of optical storage devices. Two-dimensional optical storage (TwoDOS) is a new concept that solves this data-rate problem through parallel read-out. Furthermore, an increase of at least a factor of 2 in storage capacity is achieved by exploiting a two-dimensional format. The advantages offered by TwoDOS are obtained without the need of changing the physics of the read-out system. Using Blu-ray Disc optics, single-layered 12 cm discs with capacities up to 50 GByte have been read out successfully. Signal level and error analysis show the feasibility of a further capacity increase. Also, bit-rates as high as 700 Mbit/s during read-out have been reached. All this is achieved by applying advanced signal processing and advanced disc mastering techniques and the proper design of the optical path.
Growth of Twinned Epitaxial Layers on Si(111)√3×√3-B Studied by Low-Energy Electron Microscopy
Authors: Hibino Hiroki , Watanabe Yoshio
Published: July 2005

Low-energy electron microscopy (LEEM) was used to investigate Si homoepitaxial growth on Si(111)√3×√3-B. Dark-field LEEM images using the (1,0) spot clearly indicate that two-dimensional islands twinned with respect to the substrate nucleate in the initial growth stage. Coalescence of the twinned islands forms twinned epitaxial layers at low growth temperatures. At high temperatures, however, twinned islands are transformed into untwinned islands even during growth, which suggests that small islands favor the twinned orientation, but that the energy difference between twinned and untwinned islands is reversed at a certain island size. After twinned epitaxial layer growth, we also observed transformation into untwinned layers by annealing. The transformation proceeds through the motion of the boundary between twinned and untwinned layers along the surface.
Optical Disc for Small Form Factor Optical Drive
Authors: Ro Myong-do , Lee Kyung-geun , Park Chang-min , Park Hee-sung , Park In-sik
Published: July 2005

We investigated the signal characteristics of a 46 mm small optical disk in a blue laser system [laser wavelength, 405 nm; numerical aperture (NA), 0.85]. To determine the physical dimensions of the rim area of the disk, we considered some factors affecting this rim area. We confirmed the transcription of the substrate, and the thickness of the cover layer of the disc. Also, by spin coating and selecting the optimum viscosity of the resin used for the 0.1-mm-thick cover layer, it was possible to reduce rim area from 1.5 mm to 1.0 mm. Also, we confirmed that the thickness of the substrate for sufficient mobility should be thicker than 0.5 mm.
Initialization-Free Blue-Laser Optical Disc
Authors: Miao X. S. , Shi L. P. , Tan P. K. , Xu W. , Li J. M. , Lim K. G. , Chong T. C.
Published: July 2005

An initialization-free method of producing blue-laser rewritable optical discs is proposed. After designing the disc, finding a suitable additional layer material and optimizing the film thickness of each layer, the initialization-free Blu-ray Disc was successfully fabricated. No obvious deterioration of writing/erasing properties was observed in the initialization-free Blu-ray Disc compared with a conventional Blu-ray Disc. Moreover, the initialization-free Blu-ray Disc is more suitable for high-speed recording.
Optical Property of PtOx at Elevated Temperatures Investigated by Ellipsometry
Authors: Li Xuezhe , Kim Chang Il , An Sung Hyuck , Oh Soo Ghee , Kim Sang Youl
Published: July 2005

The optical properties of PtO
x
thin films used for the optical recording layer of super resolution near-field structures (super-RENS) are studied at high temperatures. A series of PtO
x
thin films for various molar oxygen fraction x were prepared using the reactive magnetron sputtering technique. From the ellipsometric studies, it is found that the complex refractive index of PtO
x
changes monotonically from that of metallic Pt to that of dielectric PtO2 as the molar oxygen fraction increases. When temperature increases from 30 to 700°C, all PtO
x
is completely decomposed at 549°C and, for the samples with x larger than 1.3, the condensation of porous Pt films is completed at 700°C. The surface roughness of PtO
x
thin films with x larger than 1.3 increases markedly after temperature ramping and PtO
x
thin films evolve into Pt metal by passing through three steps of oxidization, decomposition and condensation.
Super-RENS Disk for Blue Laser System Retrieving Signals from Polycarbonate Substrate Side
Authors: Shima Takayuki , Nakano Takashi , Kim Jooho , Tominaga Junji
Published: July 2005

Super-resolution near-field structure (super-RENS) technology was applied to the high definition digital versatile disk (HD DVD) based system that retrieves signals from the polycarbonate substrate side using a blue laser. We used an optics with a laser wavelength (λ) of 405 nm and a numerical aperture (NA) of 0.65, and have obtained high carrier-to-noise ratios (CNRs) of 45 dB at a 100 nm mark length and 40 dB at 60 nm, which are smaller than the resolution limit (λ/4NA=156 nm). The results demonstrate that the technology can also be used in the HD DVD-based system. We discussed how well the CNR is obtained below the resolution limit when this technology is used in the DVD-, Blu-ray Disc- and HD DVD-based systems. Comparison of the best results to date strongly suggests that the difference between these systems simply comes from their λ and NA.
Organic Thin-Film Transistors with High Electron Mobility Based on Perfluoropentacene
Authors: Inoue Youji , Sakamoto Youichi , Suzuki Toshiyasu , Kobayashi Masafumi , Gao Yuan , Tokito Shizuo
Published: July 2005

We report on n-channel organic thin-film transistors (OTFTs) based on the novel n-type organic semiconductor, perfluoropentacene. The transistor exhibits excellent electrical characteristics, with a high electron mobility of 0.22 cm2/(V s) and a good current on/off ratio of 105. The electron mobility is comparable to the hole mobility of a pentacene OTFT. By combining the n-type perfluoropentacene and the p-type pentacene, we have fabricated ambipolar OTFTs and complementary inverter circuits. The OTFTs with heterostructures of the p- and n-type organic semiconductors can operate as an ambipolar device with high electron and hole mobilities of 0.042 and 0.041 cm2/(V s). The complementary inverter using an n-channel perfluoropentacene OTFT and a p-channel pentacene OTFT exhibits excellent transfer characteristics with a voltage gain of 45. A complementary inverter using the ambipolar OTFTs is also demonstrated.
Millimeter Wave Compact Branch Line Coupler Using Metal–Air–Metal Capacitors
Authors: Yun Tae-Soon , Kim Ki-Byoung , Lee Han-Shin , Shin Dong-Hoon , Lee Jong-Chul
Published: July 2005

In this paper, a compact branch line coupler fabricated on a GaAs substrate using surface micromachining. It is composed of a dielectric-supported air-gapped microstrip line (DAML) structure, which is a low-loss transmission line with an air-post and is useful for integration with other micro electro-mechanical system (MEMS) and/or MMIC components. The size reduction of the branch line coupler is accomplished by the insertion of metal–air–metal (MAM) capacitors within the structure. The coupler shows an isolation characteristic of approximately 21 dB and differences in magnitude and phase of less than 0.3 dB and 2°, respectively.
Improving the Performance of Organic Field Effect Transistor by Optimizing the Gate Insulator Surface
Authors: Zen Achmad , Neher Dieter , Silmy Kamel , Holländer Andreas , Asawapirom Udom , Scherf Ullrich
Published: July 2005

The effect of oxygen plasma treatment and/or silanization with hexamethyldisilazane (HMDS) on the surface chemistry and the morphology of the SiO2-gate insulator were studied with respect to the performance of organic field effect transistors. Using X-ray photoelectron spectroscopy (XPS), it is shown that silanization leads to the growth of a polysiloxane interfacial layer and that longer silanization times increase the thickness of this layer. Most important, silanization reduces the signal from surface contaminations such as oxidized hydrocarbon molecules. In fact, the lowest concentration of these contaminations was found after a combined oxygen plasma/silanization treatment. The results of these investigations were correlated with the characteristic device parameters of polymer field effect transistors with poly(3-hexylthiophene)s as the semiconducting layer. We found that the field effect mobility correlates with the concentration of contaminations as measured by XPS. We, finally, demonstrate that silanization significantly improves the operational stability of the device in air compared to the untreated devices.
Detection of Trace Amount of Impurity in Smectic Liquid Crystals
Authors: Ahn Hyonsoo , Ohno Akira , Hanna Jun-ichi
Published: July 2005

An effective method for detecting a trace amount of chemical impurity, e.g., a few ppm or less, that degrades the charge carrier transport properties in smectic liquid crystalline (LC) semiconductors was investigated using a model LC semiconductor and a chemical impurity system, i.e., a 2-phenylnaphthalene derivative of 2-(dodecyloxy)-6-(4-octylphenyl)naphthalene (8-PNP-O12) and a terthiophene derivative of 2,5-bis(5-hexylthiophene-2-yl)thiophene (6-TTP-6), respectively. A transient photocurrent measurement disclosed the contamination of chemical impurity of a few ppm or less that could not be detected by conventional analytical methods such as high-performance liquid chromatography (HPLC) and gas chromatography (GC): the slow transit induced by the ionic conduction of ionized impurity molecules allowed us to detect it, which was clearly distinguished from a fast transit induced by the electronic conduction of the host LC semiconductor. This systematic study provided a semiquantitative basis for evaluating the contamination of chemical impurity.
Interface-Trap-Assisted Emission in Si Complementary Metal–Oxide–Semiconductor Light-Emitting Devices
Authors: Lee Hsiu-Chih , Lee Shyh-Cheng , Lin Yi-Pen , Liu Cheng-Kuang
Published: July 2005

A metal–oxide–semiconductor (MOS) structure or a forward-biased p
n junction with an interdigitated structure has been investigated for light-emitting devices using the standard Si complementary metal-oxide-semiconductor (CMOS) process. Current hysteresis is observed to be associated with the reduction of light emission in the MOS structure. An oxide trap level of 1.1±0.1 eV is found and contributes to Frenkel–Poole conduction in the high-current region. Furthermore, traps at the interface between silicon and oxide are believed to be responsible for light emission in both MOS structure and p
n junction diodes.
Properties of High-Performance Porous SiOC Low-k Film Fabricated Using Electron-Beam Curing
Authors: Yoda Takashi , Fujita Keiji , Miyajima Hideshi , Nakata Rempei , Miyashita Naoto , Hayasaka Nobuo
Published: July 2005

In this paper, we describe the effect of electron-beam (EB) curing on ultra-low-k dielectric porous SiOC material (k=2.2) and the application of this technology to the 90-nm-node Cu/low-k multilevel damascene process. A significant improvement of dielectric porous SiOC films with EB curing has been demonstrated. The mechanical and adhesion strength of these films were increased by a factor of 1.5–1.6 without degrading the film's k. This result can be explained by the reconstruction of a Si–O random network structure from cage Si–O bonds and Si–CH3 bonds through EB curing. Additionally, the EB curing of spin-on dielectric (SOD) porous low-k films contributes to a decrease in their curing temperature and a decrease in their curing time. Under optimum EB curing conditions, no degradation of transistor performance was revealed. The excellent adhesion strength obtained by EB curing, has contributed to the success of multilevel damascene integration. On the basis of our findings, this EB curing technology can be applied in devices of 65-nm-node and higher.
Short-Channel Characteristics of Variable-Body-Factor Fully-Depleted Silicon-On-Insulator Metal–Oxide–Semiconductor-Field-Effect-Transistors
Authors: Ohtou Tetsu , Nagumo Toshiharu , Hiramoto Toshiro
Published: July 2005

The short-channel characteristics of variable-body-factor fully-depleted silicon-on-insulator (FD SOI) metal–oxide–semiconductor field-effect-transistors (MOSFETs), which we previously have proposed, are investigated by two-dimensional device simulation. It is found that, although the advantages of dc characteristics diminish in the short channel regime, improved ac characteristics can be obtained by the reduction in parasitic drain capacitance. The optimization of device parameters for variable-body-factor FD SOI MOSFETs is also discussed.
Impact of H2-Preannealing of the Sapphire Substrate on the Crystallinity of Low-Temperature-Deposited AlN Buffer Layer
Authors: Tsuda Michinobu , Balakrishnan Krishnan , Iwaya Motoaki , Kamiyama Satoshi , Amano Hiroshi , Akasaki Isamu
Published: July 2005

Effect of H2-preannealing of sapphire substrate on low-temperature-deposited (LT) AlN buffer layer deposited by metalorganic vapor epitaxy has been investigated. Crystallinity of LT-AlN buffer layer drastically changes with preannealing temperature variation. It is found that H2-preannealing of sapphire substrate is a requisite to get a better quality LT-AlN and as a consequence it leads to growth of better quality GaN epi-layer on it.
Silylethynylated Anthracene Derivatives for use in Organic Light-Emitting Diodes
Authors: Landis Chad A. , Parkin Sean R. , Anthony John E.
Published: July 2005

We have prepared a series of trialkylsilylethynylated anthracenes (a–d) to investigate the effects of solid-state interactions and acene substitution on the electroluminescence spectra of OLED devices. We designed these materials to have differing amounts of π-face interactions and various film morphologies. We were particularly interested in intermolecular interactions between aromatic faces, which would manifest in the electroluminescence spectrum as a bathochromic shift and broadening of the emission peak when compared to the solution photoluminescence spectrum. The anthracene derivatives with no electronic interactions, as determined by single-crystal X-ray crystallography, produced devices that showed no bathochromic shift and better efficiencies.
Growth and Characterization of Si-Based Light-Emitting Diode with β-FeSi2-Particles/Si Multilayered Active Region by Molecular Beam Epitaxy
Authors: Sunohara Tsuyoshi , Li Cheng , Ozawa Yoshinori , Suemasu Takashi , Hasegawa Fumio
Published: July 2005

We fabricated single-, double- and triple-layered β-FeSi2-particles structure on Si(001) substrates by reactive deposition epitaxy (RDE) for β-FeSi2 and by molecular beam epitaxy (MBE) for Si, and realized electroluminescence (EL) at 310 K. Photoluminescence (PL) measurements revealed that the 77 K PL intensity of β-FeSi2 increased almost proportionally with the number of β-FeSi2-particles/Si layers. It was also found that the multilayered structure enhanced the EL intensity of β-FeSi2 particularly at low temperatures.
Hydrogen Evolution by Plasma Electrolysis in Aqueous Solution
Authors: Mizuno Tadahiko , Akimoto Tadashi , Azumi Kazuhisa , Ohmori Tadayoshi , Aoki Yoshiaki , Takahashi Akito
Published: July 2005

Hydrogen has recently attracted attention as a possible solution to environmental and energy problems. If hydrogen should be considered an energy storage medium rather than a natural resource. However, free hydrogen does not exist on earth. Many techniques for obtaining hydrogen have been proposed. It can be reformulated from conventional hydrocarbon fuels, or obtained directly from water by electrolysis or high-temperature pyrolysis with a heat source such as a nuclear reactor. However, the efficiencies of these methods are low. The direct heating of water to sufficiently high temperatures for sustaining pyrolysis is very difficult. Pyrolysis occurs when the temperature exceeds 4000°C. Thus plasma electrolysis may be a better alternative, it is not only easier to achieve than direct heating, but also appears to produce more hydrogen than ordinary electrolysis, as predicted by Faraday's laws, which is indirect evidence that it produces very high temperatures. We also observed large amounts of free oxygen generated at the cathode, which is further evidence of direct decomposition, rather than electrolytic decomposition. To achieve the continuous generation of hydrogen with efficiencies exceeding Faraday efficiency, it is necessary to control the surface conditions of the electrode, plasma electrolysis temperature, current density and input voltage. The minimum input voltage required induce the plasma state depends on the density and temperature of the solution, it was estimated as 120 V in this study. The lowest electrolyte temperature at which plasma forms is ∼75°C. We have observed as much as 80 times more hydrogen generated by plasma electrolysis than by conventional electrolysis at 300 V.
Discrimination of Strain and Temperature Sensitivities Based on Temperature Dependence of Birefringence in Long-Period Fiber Gratings
Authors: Han Young-Geun , Lee Sang Bae
Published: July 2005

We experimentally demonstrate the simultaneous measurements of strain and temperature on the basis of the temperature dependence of birefringence in a long-period fiber grating (LPFG) fabricated with a birefringent fiber. Birefringence induces dual peak formation in LPFG corresponding to the grating's polarization state. Depending on the temperature sensitivity of birefringence in LPFG, the differences in the wavelength shift and wavelength spacing change of dual peaks with variations in strain and temperature allow accurate and simultaneous measurements of strain and temperature, respectively. The rms errors of the measured strain and temperature were 7.5 µstrain and 0.5°C, respectively.
Resonant Third-Order Optical Nonlinearities of Silicon 2,3-Naphthalocyanine Dioctyloxide Measured by Femtosecond Degenerate Four-Wave Mixing Technique
Authors: Fu Gang , Asada Osamu , Kasatani Kazuo , Okamoto Hiroaki , Takenaka Shunsuke
Published: July 2005

The third-order optical nonlinearities of silicon 2,3-naphthalocyanine dioctyloxide (SiNc) were measured by a femtosecond degenerate four-wave mixing technique under resonant conditions. The electronic second molecular hyperpolarizability γe of SiNc was determined to be as high as 9×10-29 esu. The electronic third-order susceptibility of polystyrene films doped with SiNc was measured to be on the order of 10-9 esu. The nonlinear response of the doped films was found to be very fast and almost instantaneous in the perpendicular configuration.
Spectroscopic Ellipsometry of 3C-SiC Thin Films Grown on Si Substrates Using Organosilane Sources
Authors: Kubo Naoki , Moritani Akihiro , Kitahara Kuninori , Asahina Shuichi , Kanayama Nobuyuki , Tsutsumi Koichi , Suzuki Michio , Nishino Shigehiro
Published: July 2005

Dielectric function spectra of 3C-SiC films on Si substrates in the energy region of 0.73–6.43 eV were measured by spectroscopic ellipsometry. Hexamethyldisilane (Si2(CH3)6) and tetraethylsilane (Si(C2H5)4) were used as safe organosilane sources for the growth of SiC films. The measured spectra were compared with those of 3C-SiC on a Si(001) substrate grown with disilane (Si2H6). First, the pseudodielectric function spectra gave a shoulder structure corresponding to the direct X
5–X
1 interband transition in the Brillouin zone. Secondly, the dielectric function of 3C-SiC was determined by applying a four-layer model in which we took into account the surface roughness and mixed crystals of a carbonized interface layer. Finally, the third-derivative lineshape of the imaginary part ε
2 of the complex-dielectric function provided the values of the interband transition energy E
g and the broadening parameter Γ for the X
5–X
1 interband transition. The measured values of Γ indicated that the crystalline quality of SiC films grown using organosilane sources is comparable to that of SiC films grown using Si2H6.
First Principles Interpretation of Cyclohexane Dehydrogenation Process Using Pt
Authors: Tsuda Muneyuki , Diño Wilson Agerico , Nakanishi Hiroshi , Watanabe Susumu , Kasai Hideaki
Published: July 2005

In this present study, we investigate cyclohexane (C6H12) dehydrogenation process using a Pt cluster by performing total energy calculations based on density functional theory (DFT). We consider the process where cyclohexane initially approaches a Pt3 cluster. After interacting with the Pt cluster, the Pt cluster draws an H atom from the cyclohexane, and an H–Pt bond is formed. With a C–H bond broken, the cyclohexyl intermediate (C6H11) desorbs from the Pt cluster. Since the most stable structures of C6H10 and C6H9 are obtained by removing H atoms from the adjacent C atoms of the cyclohexane, we suggest that cyclohexane dehydrogenation process involves the sequential cleavage of one H atom at a time from the cyclohexane.
In-Situ Observation of Fiber-Fuse Propagation
Authors: Todoroki Shin-ichi
Published: July 2005

Ultrahigh-speed photographs of fiber-fuse propagation in single-mode silica fibers revealed a new factor, other than pumping laser power that affects the morphology of damage sites: the length of the running optical discharge. Nine W pumping of 1480 nm light generated a discharge of ∼130 µm in half-width moving rapidly and leaving discrete voids along the fiber core, whereas 2-W-pumped discharge was ∼27 µm long, moved slowly and left nearly continuous thin voids. This is because 9-W-pumped discharge takes a longer time to travel its half-width, about 5/3 times longer than that of the 2-W-pumped discharge, which provides longer interaction time for modifying the fiber core.
Space-Charge-Limited Currents in La2O3 Thin Films Deposited by E-Beam Evaporation after Low Temperature Dry-Nitrogen Annealing
Authors: Kim Yongshik , Ohmi Shun-ichiro , Tsutsui Kazuo , Iwai Hiroshi
Published: July 2005

The electrical characteristics of metal–oxide–semiconductor capacitors with Lanthanum oxide (La2O3) gate dielectrics with 1.1 nm equivalent oxide thickness (EOT) are investigated. La2O3 was deposited by E-beam evaporation on n-Si(100), and annealed at 200°C in dry-nitrogen ex-situ for 5 min. From comparing the leakage currents of as-deposited and annealed oxides, it is shown that the leakage currents of annealed oxide were of two types: low and high leakage currents. The behavior of high leakage currents with applied voltage was similar to that of as-deposited oxide. For the explanation of these two kinds of leakage currents, it is shown that conduction mechanisms strongly related to oxide traps are not responsible for leakage currents, except space-charge-limited current (SCLC). From the applied voltage and temperature dependences of the current of the gate oxide, it is shown that the main conduction mechanisms for the two types of leakage current are SCLC and Schottky conductions at low and high applied voltages, respectively. The dielectric constant obtained from Schottky conduction was 27 and consistent with the C–V result. Based on SCLC theory, trap levels in the oxide band gap composed of both exponential and localized distributions were extracted using the differential method.
Generation of Bonding Structure Due to Organic Carbon and Organometallic Carbon as a Function of Gas Source
Authors: Oh Teresa
Published: July 2005

SiOC films with low dielectric properties were deposited by high density plasma chemical vapor deposition (CVD) using mixed source gases by considering of oxygen and bistrimethylsilylmethane. SiOC films can be divided into two bonding structures on the basis of the chemical shift according to the flow rate ratio: the cross-link and cross-link breakage structure. The chemical shift is determined as the result of the Diels–Alder reaction between a carbocation and a substituent group induced by both the resonance and inductive effects during the nucleophilic deposition reaction. The relative carbon content decreases as the oxygen flow rate increases, but the lowest dielectric constant of 2.1 was obtained for an annealed film with an organometallic carbon structure. The different bonding structures between organic carbon due to the dominant resonance and organometallic carbon due to the dominant inductive effect can be analyzed from FTIR and Raman spectra.
Photochemical Identification of a Possible Adsorbed Pentacene Molecule on the SrTiO3(001)
Authors: Ohsawa Takeo , Matsumoto Yuji , Koinuma Hideomi
Published: July 2005

Photocatalytic decomposition of the pentacene ultrathin film grown on the TiO2-terminated SrTiO3(001) single crystal substrate is studied. There are two kinds of pentacene on the SrTiO3: One is forming the crystal island as observed by atomic force microscope (AFM), the other is the precursor state adsorbed on the substrate. The latter is photochemically more reactive than the former. The pentacene molecule is released from the crystal island even at a low temperature such as 373 K due to its chemical nature of the van der Waals molecule.
Correlation Field Splitting of Intramolecular Vibrations of Crystalline Tetracene in Terahertz Region
Authors: Yago Tomoaki , Ishikawa Youichi , Ito Hiromasa , Tanaka Hiromasa , Kwon Eunsang , Sakamoto Kenkichi , Suto Ken , Watanabe Minro , Nishizawa Jun-ichi
Published: July 2005

The temperature dependence of terahertz (THz) absorption was observed for molecular crystals of tetracene using the Fourier transform infrared (FT-IR) spectroscopy. Over the frequency range of 1 to 6 THz (33 to 200 cm-1), THz absorptions corresponding to phonon and intramolecular vibrational modes were confirmed. Furthermore, the intramolecular vibrational modes exhibited correlation field splitting that originated from crystallization. A temperature-induced phase transition was successfully detected for the intramolecular vibrational modes of tetracene, even in powder form. Our results showed that these THz absorptions are highly sensitive to the molecular orientations within the crystal.
Fabrication of Liquid Crystal Polymer Films and Their Passivation Effect for Organic Devices
Authors: Arai Keiichiro , Yamaguchi Jun , Haemori Masamitsu , Itaka Kenji , Koinuma Hideomi
Published: July 2005

We have investigated the fabrication of liquid crystal polymer (LCP) thin films by thermal evaporation, and pulsed laser deposition (PLD). Due to the carbonization of LCP, no films were fabricated by thermal evaporation. The laser desorption time-of-flight mass spectra of a LCP target exhibited that the main ablation species were the fragments of the LCP in the case of low laser fluence, indicating the possibility of film fabrication by PLD. Thin films fabricated by PLD using a KrF excimer laser have a pale yellow color and a surface roughness of 1 nm, as measured by atomic force microscopy. The spectra obtained by Fourier transform infrared spectroscopy exhibit a peak corresponding to carbonyl bond at approximately 1730 cm-1, indicating a polyester structure similar to that of the original LCP. The breakdown field of the films was 1 MV/cm. We demonstrate that this film acts as a passivation films for organic field-effect transistors.
Production of Reflection Point Sources for Hard X-Ray Gabor Holography
Authors: Aoki Sadao , Watanabe Norio , Ohigashi Takuji , Yokosuka Hiroki , Suzuki Yoshio , Takeuchi Akihisa , Takano Hidekazu
Published: July 2005

The production of point X-ray sources for hard X-rays of approximately 8 keV is proposed and their application to Gabor holography is examined. Small X-ray sources less than 100 nm in diameter are obtained by total reflection from a limited surface area at grazing incidence. A microstrip plated with heavy metal on a glass plate is used for a one-dimensional small X-ray source and crossed glass rods for a two-dimensional X-ray source. A virtual source width smaller than approximately 80 nm is demonstrated. Young's X-ray interference fringes are obtained using beams reflected from two microstrips. Gabor X-ray holograms of a gold wire and a diatom are recorded with a virtual point source and their reconstructed images are numerically obtained.
Numerical Analysis of Discharge Characteristics in Lithium Ion Batteries Using Multiphase Fluids Model
Authors: Kawano Satoyuki , Nishimura Futoshi
Published: July 2005

A simple mathematical model for discharge characteristics in lithium ion batteries is developed based on a novel multiphase fluids model. The species of lithium, lithium ion, anion, and the electron are considered in the present model for transport phenomena. Maxwell's equations for an electric field and the Butler–Volmer equation for electrochemical reaction are also included. The numerical code based on the finite differential technique and the implicit successive overrelaxation (SOR) scheme is developed here and numerical solutions of discharge phenomena are obtained successfully for a wide range of operating conditions. Furthermore, comparisons of discharge characteristics between experimental and numerical results are performed in detail. They are in good agreement from the viewpoint of engineering applications. Consequently, it is concluded that numerical scheme proposed here is sufficiently practical for computer-aided design of lithium ion rechargeable batteries.
Diagnosis of Laser-Induced Shock Waves in Brass Foil Using a Fiber-Optic Interferometer
Authors: Zhang Ping , Bian Bao-Min , Li Zhen-Hua
Published: July 2005

A fiber-optic interferometer is developed to investigate shock waves in brass foil impacted by a Neodymium:Yttrium–Aluminium–Garnet (Nd:YAG) laser at a wavelength of 1064 nm and pulse width (FWHM) of 7 ns. Because of introduction of an optical transceiver module, the interferometer is compact and reliable. Appreciable signals due to shock waves have been detected using this interferometer. The shock-wave velocity is deduced from the measured arrival times of shock waves in brass foils with different thicknesses (0.200 and 0.300 mm), and is found to be 8.33 km/s.
Photoluminescence Degradation and Passivation Mechanisms of Si Nanoclusters in Silicon Oxide Matrix
Authors: Lee Ching-Ting , Lin Chun-Hung , Lee Tsung-Hsin , Tsai Tai-Cheng
Published: July 2005

The Si nanoclusters embedded in a silicon oxide matrix were prepared using a laser-assisted chemical vapor deposition (LACVD) system. A degradation of photoluminescence (PL) by irradiating the sample with helium–cadmium (He–Cd) laser was observed. The dependence of PL degradation on long-term irradiation of He–Cd laser was investigated. We found that the He–Cd laser-induced breakage of Si–H-related bonds resulted in the formation of Si dangling bonds such as D centers and Pb centers, which are known to decrease PL intensity. The PL intensity of He–Cd laser-irradiated samples can be increased to that of as-deposited samples after exposing the samples to a H2 ambient at 400°C for 5 min. Post annealing in H2 could also help increase PL intensity by passivating the defect centers in as-deposited samples.
Time-Dependent Ballistic Phenomena of Electron Injected into Half-Ellipse Confined Room
Authors: Koiso Takuji , Muraguchi Masakazu , Takeda Kyozaburo , Watanabe Naoki
Published: July 2005

We theoretically studied the time-developing ballistic phenomena of a single-electron confined in a half-ellipse infinite-potential wall by solving the time-dependent Schrödinger equation numerically. We also solved the corresponding Newton equation in order to compare the classical results with the quantum ones, and extracted the quantum features. The ellipse-shaped potential wall completely reflects an electron and causes the focusing ratio of unity in the classical limit. The dispersion of the wave packet of an electron, however, weakens this characteristic nature, and reduces the focusing ratio from unity. Because the dispersion also lets an electron arrive at the collector indistinctly, we define the effective arrival time by finding inflections in the time-dependent profile of the probability density at the collector. Based on the second-derivation technique, we further determine the quantum arrival time (QAT) at which the intrusion of the wave packet occurs dominantly. The comparison of this QAT with the classical arrival time (CAT) determines whether the corresponding ballistic propagation can be discussed on the basis of the quantum consideration or the classical prediction. We further studied how the change in the half-ellipse potential wall shape affects the ballistic phenomena through the change in the ellipticity γ, the system size L and the dispersion degree σ of the wave packet. Using the ellipse-shaped infinite-potential wall, the application of the magnetic field causes irrational cyclotron motion assisted by the ellipse potential, in addition to the rational cyclotron motions. The numerical solution of the time-dependent Schrödinger equation determines the unique cyclotron motion whose peculiarity is caused by the dispersion of the wave packet and is rarely predicted by the classical limit.
Real Time Imaging of Surface Acoustic Waves on Crystals and Microstructures
Authors: Wright Oliver B. , Matsuda Osamu , Sugawara Yoshihiro
Published: July 2005

The use of acoustic pulses to image materials is well-known in echography or sonar applications. We are extending this field by generating point-excited sound pulses on solid surfaces with ultrashort laser pulses and imaging the resulting surface wave propagation in real time. To see the tiny vibrations of the surface, smaller in amplitude than the dimensions of a single atom, we use another set of laser pulses for scanned probing. The typical surface phonon wavelength is of the order of a few microns, corresponding to frequencies up to 1 GHz. With such a system we can watch coherent acoustic wave packets in two dimensions rippling across crystal surfaces and microscopic landscapes.
Evaluation of Strength of Concrete by Linear Predictive Coefficient Method
Authors: Tao Liang , Mori Yahiro , Motooka Seiichi
Published: July 2005

In this paper, we describe a method of evaluating the strength of concrete by the quality factor of the resonant peak of multireflected elastic waves propagating inside the concrete. An electromagnetic-induction-type sound source and a piezoelectric transducer are employed as an elastic wave transmitter and a receiver, respectively. Linear predictive coefficient processing and resonant analysis methods are employed for spectrum derivation and quality factor calculation, respectively. Three types of concrete specimen with the same dimensions but different strengths are measured, with variations in the geometrical arrangement of the sound source and receiver. Although it is difficult to distinguish the differences in strength from the time domain signals, the quality factors of the resonant peaks of multireflected elastic waves corresponding to different types of concrete show stable results, and this tendency agrees well with that of the concrete strengths.
Sensitivity Enhancement by Sample Surface Coatings on Photothermal Metal Thin-Film Thickness Measurements
Authors: Okamoto Yoshitsugu , Yarai Atsushi , Nakanishi Takuji
Published: July 2005

An effective and stable method to enhance the sensitivity for photothermal measurements was proposed. The effectiveness of our method was proven by measuring the thickness of metal thin-film samples. It features sample surface coatings to improve the pumping beam's absorption of the sample as well as radiation efficiencies from the sample. Two solutions, graphite and dye, were used as coating materials. As metal thin-film samples, aluminum films formed by vacuum deposition on sapphire substrate were used. The inclination of the line showing the relationship between detection signals to the aluminum film thickness (i.e. measurement sensitivity) with coatings is more than three times larger than without coatings. Resolution on the order of a few nm film thickness measurement was achieved by using this coating method for metal films whose thickness ranged from 0 to several hundred nm. The effectiveness of our method functions for other photothermal measurements.
Elastic Constants and Magnetic Anisotropy of Co/Pt Superlattice: Resonance-Ultrasound-Spectroscopy Method
Authors: Nakamura Nobutomo , Ogi Hirotsugu , Ono Teruo , Hirao Masahiko , Nishiyama Masayoshi
Published: July 2005

The Co/Pt superlattice shows perpendicular magnetic anisotropy, which makes the magnetization direction of the Co layer perpendicular to the film surface when the Co layer is less than about 20 Å thick. One possible cause of perpendicular magnetic anisotropy is large elastic strain at the interfaces between the Co and Pt layers. The elastic strain also changes the macroscopic elastic constants of the Co/Pt superlattice through lattice anharmonicity. In this study, we determined the anisotropic elastic constants of Co/Pt superlattice thin films using resonance ultrasound spectroscopy coupled with the laser/Doppler-interferometry method and studied the relationship between elastic and magnetic properties. We clearly observe a correlation between them, which is interpreted in terms of lattice anharmonicity.
Photoacoustic and Photoelectrochemical Characterization of CdSe Quantum Dots Grafted onto Fluorine-Doped Tin Oxide (FTO) Substrate
Authors: Toyoda Taro , Arae Dai , Shen Qing
Published: July 2005

We report on the optical absorption properties, measured by the photoacoustic (PA) method, and photoelectrochemical current (PEC) characteristics (including transient measurements) of CdSe quantum dots (Q-dots) grafted onto a planar fluorine-doped SnO2 (FTO) substrate. CdSe Q-dots were fabricated by the chemical solution deposition (CD) technique. With increasing deposition time, the redshift of the PA spectra can be clearly observed and optical absorption in the visible region due to CdSe Q-dots can be demonstrated. The average diameters of the CdSe Q-dots for each deposition time can be estimated using an effective mass approximation producing diameters of 5.1 nm to 5.6 nm for deposition times of 5 h to 25 h, respectively. Thus, PA spectroscopy is useful in obtaining the Q-dots sizes even though there is no use of a high-resolution scanning electron microscope (SEM). An increase in PEC and the clear shift of the spectra to the lower energy region are observed with increasing deposition time, indicating the photosensitization of the FTO electrodes in the visible region resulting from CdSe Q-dots. It can be seen that the maximum value of incident photon to current conversion efficiency (IPCE) is ∼10%, which is higher than that previously reported (∼6%). Transient PEC measurements show that electron recombination in a smaller amount of CdSe Q-dots is lower than that in a higher amount of Q-dots.
Evaluation of Quality of Rice Grains by Photoacoustic Imaging
Authors: Suzuki Manabu , Miyamoto Katsuhiko , Hoshimiya Tsutomu
Published: July 2005

Recently, quality evaluation and control has become increasingly important in biology and agriculture. The evaluation of the quality of food plants has been performed by many inspection methods. To date, the evaluation of the grain of crops by photoacoustic spectroscopy in the infrared region has only been performed for corn. We have developed a method of applying a photoacoustic microscope (PAM) to pollen analysis. In this study, a PAM was used to evaluate the quality of crop grains, rice in this case, for the first time. Due to differences in the absorption of the laser beam, the homogeneity of rice grains was measured and shown as thermal images. The resolution was sufficiently good to evaluate a single grain of rice. This method has an advantage in that it can be used to measure the existence of both the surface and back surface colored regions. In addition to conventional video image evaluation or the macroscopic optical absorption method, PA imaging can enable the evaluation of the quality and condition of rice grains.
Triaxial Quartz Gyrosensor Using a Threefold Rotatory Symmetric Form Vibrator
Authors: Tamura Hideki , Takano Takehiro , Tomikawa Yoshiro
Published: July 2005

In this paper, we deal with the operation principle and structures for a monolithic quartz gyrosensor which can detect three-axis angular velocities. In order to detect three-dimensional angular velocities, the sensor device needs two or more directional vibrating components. However, a majority of tuning-fork-type resonators have vibrational velocities of only one direction. Here, we propose a new vibrator structure, which is formed with threefold rotational symmetry, the same as the crystal symmetry of a quartz crystal. This vibrator has three symmetrically placed driving beams. These driving beams can be vibrated symmetrically by a single driving mode, and the initial vibrational velocities are excited in three individual directions. We analyze this vibrator using the finite element method. The analysis results prove that the new proposed structure can be excited and detect the necessary vibration modes by the piezoelectric method, and show that the three-dimensional angular velocities are detected and separated. Finally, the operating simulation shows that the triaxial quartz gyrosensor can be realized.
Theoretical and Experimental Results of Ultrawide-Band Zero-TCF Ladder-Type SAW Filters and Arbitrary Bandwidth Filters Using High-Coupling SiO2/Y-X LiNbO3
Authors: Yamanouchi Kazuhiko , Satoh Yusuke , Isono Hiroyuki , Kawasaki Daisuke
Published: July 2005

We show ladder type SAW resonator filters using high-coupling SiO2/5°Y-X LiNbO3 with zero temperature coefficients of frequency (TCF). The experimental results showed lower than below 1.6 dB insertion loss with a wide band and zero TCF in the 2 GHz range. Also, we show the narrower band width of ladder-type filters using a new configuration of IDTs and reflectors on high-coupling substrates.