bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential of Thermo-Sensitive Hydrogel as an Actuator
Authors: Kim Jinseok , Kim Byungkyu , Ryu Jaewook , Jeong Yongwon , Park Jungyul , Kim Hyeon Cheol , Chun Kukjin
Published: September 2005

To use poly-N-Isopropylacrylamide (PNIPAAm) as an actuator, we investigated its general characteristics such as swelling/deswelling ratio, response time and swelling force. Through out the variation, a change in volume of over 600% of PNIPAAm and a force generation of gram force order was obtained. Furthermore, we measured the significant change of friction caused by phase transition phenomena that is hydrophobic and hydrophilic. Surface condition that influences friction force can be reversed from swelling phase to deswelling phase by controlling the temperature of PNIPAAm. To verify the potential application of PNIPAAm using this characteristic, we compared its friction force under glass and small-intestine tissue of a pig. It was found that the level of friction differs significantly depending on phase change of PNIPAAm. Based on this knowledge, we could conclude that PNIPAAm can be applied to the stopping mechanism of in-body locomotion in order to replace the clamping mechanism of in body robot for locomotion on the gastrointestinal tract.
Electrical Erasing of Holographic Grating in Amorphous Chalcogenide Thin Films
Authors: Yeo Choel-Ho , Lee Ki-Nam , Shin Kyung , Kim Jong-Bin , Chung Hong-Bay
Published: September 2005

We investigated the electrical erasing of information recorded by a holographic method in an amorphous As40Ge10Se15S35 chalcogenide thin film. Even though the amplitude of photoinduced birefringence (Δn) strongly depends on applied DC voltage (V
DC), the kinetics exhibits a tendency. For V
DC=0–3 V, Δn increases with increasing induction time and eventually saturates to its maximum (Δn
max) even though its saturation time and amplitude are not the same at different V
DC's. For V
DC>4, Δn increases rapidly at the start of the induction process (within several seconds), reaches Δn
max and then decreases very slowly. In addition, phase gratings in amorphous As40Ge10Se15S35 films were formed by the holographic method and diffraction efficiency (η) was monitored in real time. Immediately after reaches its maximum (ηmax), a short pulse was applied to the sample which cause a marked decrease in diffraction efficiency (η=0.25%→η≪10-3).
Electrostatic Droplet Ejection Using Planar Needle Inkjet Head
Authors: Hakiai Kazunori , Ishida Yuji , Baba Akiyoshi , Asano Tanemasa
Published: September 2005

For the purpose of investigating the electrostatic droplet ejection event, a planar needle inkjet head with a projected cone-shaped needle (3-D head) was prepared to observe the phenomenon of droplet ejection. As the initial approach to developing a liquid ejection monitoring method, electric current was also measured. The ejection was found to take place as a series of single events that are composed of fine droplet ejections forming the Taylor cone and the subsequent swing back of the liquid front owing to the relationship between surface tension and electrostatic force. The critical factors for ejecting fine droplets in the case of using the inkjet head having a protruding needle were back pressure from the reservoir and the wetting control of the structures. The fast Fourier transform of electric current revealed the appearance of periodic signals during ejection, which may be used in developing a technique of sensing droplet ejection.
Fabrication of Silicon and Germanium Nanostructures by Combination of Hydrogen Plasma Dry Etching and VLS Mechanism
Authors: Yang Ming-Che , Shieh Jiann , Ko Tsung-Shine , Chen Hsuen-Li , Chu Tieh-Chi
Published: September 2005

Silicon and germanium nanostructures were fabricated by the combination of dry etching and vapor-liquid-solid (VLS) mechanism. Gold nanoparticles, about 20 nm in diameter, captured by self-assemble monolayer were adopted as the hard mask for dry etching and catalyst of germanium growth. Reactive ion etching in an inductive coupled plasma chemical vapor deposition (ICPCVD) system was used to fabricate various silicon nanostructures. Instead of CF4, SF6, and SiCl4gases, hydrogen plasma was used alone as the etching species to construct high-aspect-ratio silicon nanowires. Germanium nanostructures were then fabricated on the surface of silicon nanowires by dry etching and VLS mechanism.
Impact of Tunnel Etching Process on Electrical Performances of SON Devices
Authors: Caubet V. , Borel S. , Arvet C. , Bilde J. , Chanemougame D. , Monfray S. , Ranica R. , Mazoyer P. , Skotnicki T.
Published: September 2005

The removal of a sacrificial SiGe layer by isotropic etching has been newly improved for silicon-on-nothing (SON) technology by increasing etching selectivity to the Si conduction channel. Still based on CF4 plasma chemistry, power and pressure are adapted in order to decrease etch rate and improve SiGe:Si selectivity. Both electrical characteristics and morphological observations are used to evaluate the characteristics of this technological step in terms of selectivity and uniformity. An original nonvolatile memory (NVM) concept based on this process will illustrate the interest in such etching development.
Formation of Nanowires Based on π-Conjugated Polymers by High-Energy Ion Beam Irradiation
Authors: Tsukuda Satoshi , Seki Shu , Sugimoto Masaki , Tagawa Seiichi
Published: September 2005

High-energy ion beam irradiation of cross-linking type polymers gives nanowires formed by cross-linking reactions along the ion track trajectories. A fairly simple technique has been developed to control the size and number density of nanowires based on polystyrene (PS) by selecting appropriate ion beam characteristics and molecular sizes of the target polymers. This technique has also been extended to the formation of nanowires based on polyaniline (PANi) and poly(3-hexylthiophene) (P3HT). Characteristic optical properties (absorption and photoluminescence) observed for the various sizes of nanowires based on P3HT on a quartz substrate are different than those from solid state P3HT, suggesting that the nanowires are not just the finely patterned analogs of the conjugated polymers.
Gold Seed Arrangement on Nanoporous Anodic Aluminum Oxide Membrane by Centrifugal Force
Authors: Chu Fengmin , Tanaka Miyoko , Shimojo Masayuki , Kajikawa Kotaro , Furuya Kazuo
Published: September 2005

Large-area gold seed arrays were patterned by filling closed-ended nanoholes on anodized aluminum oxide (AAO) templates with colloidal gold seeds using a centrifuge at various rotation speeds and times. The microstructures of gold seeds, AAO membranes, and AAO membranes with gold seeds were characterized by transmission electron microscopy. Annealing treatments were performed in a vacuum chamber and TEM observations confirmed that the gold seeds exist separately in the nanoholes in all samples annealed up to 900°C.
ArF Photoresist Deformation in Dual Frequency Superimposed Capacitively Coupled Plasma (DFS-CCP) with Different Frequency Combinations
Authors: Kim Duck Ho , Cho Su Hyun , Lee Nae-Eung , Kwon Ki Chung
Published: September 2005

In this study, we investigated deformation and etching characteristics of the ArF photoresists in a dual frequency superimposed capacitively coupled plasma (DFS-CCP) etcher by varying the process parameters such as low-frequency (LF)/high-frequency (HF) power ratio (P
LF/P
HF), CF4/CHF3 flow ratio, and O2 flow rate in the CF4/CHF3/O2/Ar capacitively coupled plasmas. In the DFS-CCP etcher, HF power (13.56, 27.12 and 60 MHz here) is used to enhance plasma density and LF power (2 MHz here) is used to control ion bombardment energy to the wafer. Morphological investigation of blanket ArF resist surfaces and patterned line and space patterns of the resists after etching by field-emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) generally shows an increased surface roughness and deformation with increasing the P
LF/P
HF, the HF source frequency ( f
HF), CF4/CHF3 flow ratio, and O2 flow rate. The increased surface roughening and deformation with the increasing the CF4/CHF3 flow ratio and O2 flow rate is presumably attributed to an increase in the density of reactive O and F radicals in the plasma. The etch rates of the ArF resists were also increased significantly with the P
LF/P
HF, f
HF, CHF3 flow rate increased due to the increased ion energy and increased ion/radical flux density, respectively. The etching of the ArF PR was found to proceed by an ion-assisted sputtering mechanism under the experimental conditions investigated.
Minimum Size of Oxygen Precipitates in Czochralski Silicon Wafers Detected by Improved Light Scattering Tomography
Authors: Nango Nobuhito , Ogawa Tomoya , Irisawa Toshiharu
Published: September 2005

The minimum size of oxygen precipitates within Czochralski-grown (CZ) Si wafers detectable by light scattering tomography (LST) is completely dependent upon the correctness of the intensity measurement of scattered light, because the intensity is exactly proportional to the size of the precipitates. To assure precise intensity measurement, an adequately adjusted intensity and a well-shaped focusing of the laser beam were realized by instrument enhancement for illumination, and analytical software for brightness correction of and noise elimination from the light scattering tomograms were installed in a computer. With this well-developed system, the minimum diameters of oxygen precipitates in CZ Si wafers detected by improved LST was quantitatively determined using 1.06 µm radiation from a Nd:YAG laser to be 10 nm, compared with oxygen precipitates which were directly measured by transmission electron microscopy (TEM).
Improved In0.45Al0.55As/In0.45Ga0.55As/In0.65Ga0.35As Inverse Composite Channel Metamorphic High Electron Mobility Transistor
Authors: Chen Yeong-Jia , Lee Ching-Sung , Wang Tzong-Bin , Hsu Wei-Chou , Chen Yen-Wei , Su Ke-Hua , Wu Chang-Luen
Published: September 2005

A δ-doped In0.45Al0.55As/InGaAs metamorphic high-electron-mobility transistor (MHEMT) using an In0.45Ga0.55As/In0.65Ga0.35As inverse composite channel has been fabricated successfully and demonstrated. The inverse composite channel significantly reduces Coulomb scattering and consequently improves electron mobility as well as carrier confinement. Experimentally, a high extrinsic transconductance of 321 mS/mm and a drain–source saturation current density of 342 mA/mm are obtained for a 0.65 ×200 µm2 gate at 300 K. Meanwhile, degradation of the studied device, in terms of parameters such as G
m,max, I
DSS, and V
th, with increasing temperature is not evident. A positive temperature coefficient of V
th is observed. The measured f
T and f
max for a 0.65-µm-gate device are 41.6 and 53 GHz, respectively. In addition, the studied device also shows good microwave performances in a flat and wide operation region. From V
GS = -2.5 to 0.5 V, the values of f
T and f
max are still over 33 GHz.
Photoluminescence, Reflectance and Photoreflectance Spectra in CdS Epilayers on Si(111) Substrates
Authors: Seto Satoru
Published: September 2005

Photoluminescence (PL), reflectance and photoreflectance (PR) spectra were measured on hexagonal CdS films grown directly on hydrogen-terminated Si(111) substrates with 3° off-orientation by hot-wall epitaxy technique. By comparing the PL spectrum to the reflectance and PR spectra in the excitonic energy range, we have unambiguously identified free A- and B-exciton transitions in the CdS films on Si(111) substrates. The peak energies of the A- and B-exciton transitions slightly shift to lower energy by about 3 meV than that of bulk crystal. This peak shifts were caused by a tensile strain parallel to the epilayer surface due to a difference of the thermal expansion coefficients between the grown CdS film and Si substrate. Donor–acceptor pair emission and defect-related “Y” bands as well as free and bound exciton peaks in PL spectra were also studied by means of their temperature (10–250 K) and excitation intensity dependences.
Design and Preparation of AlN/GaN Quantum Wells for Quantum Cascade Laser Applications
Authors: Ishida Akihiro , Matsue Kazuma , Inoue Yoku , Fujiyasu Hiroshi , Ko Hang-Ju , Setiawan Agus , Kim Jung-Jin , Makino Hisao , Yao Takafumi
Published: September 2005

An envelope function framework was used to calculate the conduction band structure of AlN/GaN quantum wells for application to quantum cascade lasers. We took into account the piezo- and spontaneous polarization fields in the nitride quantum wells. The design of the quantum cascade structures in the AlN/GaN system becomes much simpler if we utilize the effect of polarization fields. [(AlN)1/(GaN)
n1]
m
/(AlN)
n2 quantum wells were prepared using hot-wall epitaxy for mid-infrared quantum cascade laser applications, and X-ray diffraction and transmission electron microscopy (TEM) measurements were performed on them. The X-ray diffraction measurements of the quantum wells were in good agreement with the theoretical pattern, and the coherent growth of quantum wells on the GaN buffer layers was ascertained by X-ray reciprocal mapping. The existence of a single atomic layer of AlN was observed by TEM measurements.
Comparison of Pt-Based Ohmic Contacts with Ti–Al Ohmic Contacts for p-Type SiC
Authors: Mohammad F. A. , Cao Y. , Chang K.-C. , Porter L. M.
Published: September 2005

In this study, two Pt-based ohmic contacts were systematically compared with a conventional Ti–Al ohmic contact on p-type 4H– and 6H–SiC substrates in terms of specific contact resistance, contact morphology, and phase chemistry. The average specific contact resistance (SCR) values measured for the Ti/Al, Pt and Pt/Si ohmic contacts on 4H–SiC were 7.0 ×10-5 Ω cm2, 1.5 ×10-4 Ω cm2 and 4.4 ×10-5 Ω cm2, respectively. The corresponding standard deviations of the SCR values are 3.4 ×10-5 Ω cm2, 3.8 ×10-5 Ω cm2 and 1.3 ×10-5 Ω cm2. Microstructural analysis showed that both Ti/Al and Pt ohmic contacts reacted with the SiC substrate during annealing to form several phases and a rough interface. In contrast, single-phase PtSi contacts, formed using the required thickness ratio of 1:1.32 Pt/Si, yield a smooth interface. A correlation between the electrical properties and the morphology is discussed.
Emission Statistics for HfC Emitter Arrays after Residual Gas Exposure
Authors: Nicolaescu Dan , Nagao Masayoshi , Sato Takanobu , Filip Valeriu , Kanemaru Seigo , Itoh Junji
Published: September 2005

Field emission arrays (FEAs) consisting of hafnium carbide (HfC)-coated silicon (Si) emitters (HfC emitters) have been fabricated. The FEA emission properties were measured in ultrahigh-vacuum conditions and after being subjected to Ar and O2 residual gases with partial pressures in the range of 10-6 to 10-4 Pa. The influence of residual gases on the FEA field emission properties has been assessed using the model parameter extraction method. The array field emission model considers emitters with different radii and work functions. Fast and accurate results are obtained using a nonlinear parameter extraction procedure. HfC emitters achieve high emission currents, low noise levels and long-term emission stability.
Alignment Focus Optimization and Image Contrast
Authors: Sugaya Ayako
Published: September 2005

In LSI mass production, an alignment sensor must be installed in an exposure system to detect the pattern position accurately even if the pattern condition is changed. To satisfy such a requirement, the defocus effect of improving the image contrast is studied. Particularly under optical conditions with large illumination σ, the theory of image profile change induced by defocus is clarified in this paper. For a field image alignment sensor (FIA) with large illumination σ, FIA focus optimization (FFO) is developed as a technique that realizes alignment with both high accuracy and better image contrast by optimized defocus. FFO makes this possible regardless of the pattern phase and/or pattern duty ratio. The effects are confirmed by simulations and experiments. The versatile advantages of FFO for LSI production are confirmed.
Effects of Base Oxide Thickness and Silicon Composition on Charge Trapping in HfSiO/SiO2 High-k Gate Stacks
Authors: Wu Wei-Hao , Chen Mao-Chieh , Tsui Bing-Yue , Hou Yong-Tian , Yao Liang-Gi , Jin Yin , Tao Hun-Jan , Chen Shih-Chang , Liang Mong-Song
Published: September 2005

This work investigates the fundamentals of charge trapping and the effects of base oxide thickness and Si composition on charge trapping in HfSiO/SiO2 high-k gate stacks using positive-bias temperature (PBT) stressing scheme. During the PBT stress, threshold voltage shift and saturation drain current degradation induced by charge trapping continue to grow and eventually become saturated, whereas the subthreshold swing and maximum transconductance remain unchanged. The extent of charge trapping increases with the decrease of base oxide thickness and Si composition in the HfSiO film, which can be explained by considering the channel-to-bulk tunneling time constant and the amount of neutral Hf–OH trapping centers in the HfSiO bulk layer. The power law dependence of saturation drain current degradation on the gate bias voltage indicates that charge trapping would become more significant if thin base oxide and low Si composition were employed in the further scaled HfSiO/SiO2 high-k gate stacks.
Heat Treatment Effect on Superconductivity and Specific Heat of Pr1.85Ce0.15CuO4+δ
Authors: Meen Teen-Hang , Chen Wen-Ray , Huang Chien-Jung
Published: September 2005

Polycrystalline samples of electron-doped Pr1.85Ce0.15CuO4+δ have been prepared under different annealing conditions and investigated by X-ray diffraction analysis, oxygen content analysis, electrical resistivity, magnetic susceptibility and low-temperature specific heat measurements. X-ray-diffraction patterns show that the samples contain a single T' phase. The superconducting transition temperatures T
cm taken with the onset of diamagnetism in magnetic-susceptibility measurements are 20 and 19.5 K for the samples annealed in flowing Ar gas and in vacuum (∼10-3 Torr), respectively. The data of the samples annealed in flowing Ar gas show clear evidence of αT
2 term at zero magnetic field in superconducting electronic specific heat, and are consistent with d-wave superconductivity. However, this behavior is not observed in the other sample, which is annealed in vacuum. These results indicate that different heat treatments affect the oxygen content, homogeneity, superconducting transition temperature T
c, superconducting volume fraction, and the superconducting pairing symmetry of Pr1.85Ce0.15CuO4+δ. We also discuss the results of specific heat in La2-x
Sr
x
CuO4 (x=0.1, 0.16 and 0.22) to explain these behaviors observed in the specific heat of Pr1.85Ce0.15CuO4+δ.
Growth and Properties of c-Axis Epitaxial Thin Films for La2-2xSr1+2xMn2O7 Bilayer Manganates by Sputtering
Authors: Lmouchter Mohamed , Iwayama Masayoshi , Tanaka Yosuke , Suzuki Minoru
Published: September 2005

c-Axis epitaxial thin films of a layered manganate La2-2x
Sr1+2x
Mn2O7 have been grown on SrTiO3(100) substrates by on-axis rf-magnetron sputtering. The films have been characterized using energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), high resolution scanning electron microscopy (HRSEM), magnetoresistivity, and magnetization measurements. It is shown that the film chemical composition is sensitive to the deposition parameters, and that a small deviation of composition or deposition condition causes nucleation of the (La,Sr)MnO3 structure. It is found that the deposition rate is crucial for the c-axis film growth; stoichiometric c-axis La2-2x
Sr1+2x
Mn2O7 films have been grown under limited conditions of a low rate of 0.8 nm/min, an (Ar, O2 50%) atmospheric pressure of 120 mTorr, and a substrate temperature of 760°C. From X-ray diffraction simulation, it is inferred that the c-axis La2-2x
Sr1+2x
Mn2O7 films thus grown contain intergrowths comprised of (La,Sr)MnO3 and presumably (La,Sr)2MnO4 structures, and the total intergrowth fraction amounts to about 40%.
Measurement of Hyperfine Structure and Isotope Shift of Transitions in Gadolinium Using Blue Diode Laser
Authors: Niki Hideaki , Tanikawa Tomoya , Tokita Shigeki , Izawa Yasukazu
Published: September 2005

Laser-induced fluorescence spectroscopy using a single-longitudinal-mode diode laser has been applied to investigating isotope shifts and the hyperfine structures of gadolinium in the wavelength region of 400 nm. Six absorption spectra of transitions from the ground and low-lying metastable levels were measured. The isotope shift per unit mass change varied from 0.6 to 1.0 GHz depending on the transition. The hyperfine splitting constants of 157Gd and 155Gd isotopes were determined for the six upper levels of the transitions. The absorption spectrum of the 999–25661 cm-1 transition showed the narrowest spectral width for odd isotopes.
Line Segment Hologram Writer Using Single-Mode Blue Laser and One-Dimensional Spatial Light Modulator
Authors: Takasaki Koji , Kobayashi Shigeo , Sugiki Mikio , Watanabe Kenjiro
Published: September 2005

We have developed a holographic writer using a one-dimensional spatial light modulator and a single-mode blue laser. This writer has the potential of achieving a 5 µm pitch phase correlation multiplexing.
Numerical Investigation of Optical Chaotic Multiplexing Communications
Authors: Sano Eiichi
Published: September 2005

A novel chaotic multiplexing communication system based on a one-way coupled map lattice configuration is proposed and numerically investigated with semiconductor laser rate equations that include the Langevin noise source. Calculations show that dual synchronization and duplex communication can be achieved under an ideal condition in which no wavelength and phase differences between lasers exist. The impact of the wavelength and phase differences between lasers on synchronization is discussed briefly.
Micro Photo Detector Fabricated of Ferroelectric–Metal Heterostructure
Authors: Zomorrodian A. , Wu N. J. , Song Y. , Stahl S. , Ignatiev A. , Trexler E. Brady , Garcia C. A.
Published: September 2005

The anomalous photovoltaic effect (APE) in ferroelectric thin films has been utilized for the development of an optical micro-detector active in the visible range (from 350 to 800 nm). La-doped Pb(Zr,Ti)O3 (PLZT) ferroelectric films epitaxially grown on Pt(001)/Mg(001) substrate were fabricated into micro-detector arrays and characterized as to their optical response. The Au/PLZT/Pt/MgO device was self-polarized in the as-deposited form with the polarization vector perpendicular to film surface. The heterostructure photovoltage response ranged from 100 to 200 mV, and the photocurrent was ∼ 30 nA/cm2 for devices of ∼ 250 µm diameter under illumination of 100 mW/cm2 at wavelengths from 400 to 580 nm. Such micro-detectors can be used for optical sensors in MEMS devices as well as for electrical stimulators of biological cells.
New Write-Once Medium with NiOx Film Using Blue Laser
Authors: Chang Hung-Lu , Jeng Tzuzn-Ren , Chen Jung-Po , Yen Wen-Hsin , Yen Pofu , Huang Derray , Ju Jau-Jiu
Published: September 2005

Both a new write-once medium with a sputtered NiO
x
film and a write-once optical disk using a blue laser has been fabricated. The optical constant of sputtered NiO
x
films for different ratios of O2/Ar was determined, and showed little dependence on sputtering ratios of O2/Ar and wavelength. The X-ray photoelectron spectra (XPS) data indicated those films have two major components, NiO and Ni2O3. Most NiO
x
films released oxygen gradually below 300°C. Over 300°C, there was an apparent transition due to the decomposition of the Ni2O3. At a writing power of 12 mW and a reading power of 0.5 mW under conditions of a numerical aperature (NA) of 0.65 and a wavelength of 405 nm, the carrier to noise ratio (CNR) was more than 47 dB and jitter was less than 13%. The recording principle depends primarily on the explosive pressure of the O2 released due to laser heating of the NiO
x
film.
Structures and Electronic States of Gadolinium Oxide Clusters
Authors: Doi Kentaro , Fujitani Kiwamu , Kadowaki Naoki , Nakamura Koichi , Tachibana Akitomo , Hattori Takeo
Published: September 2005

We have carried out ab initio quantum chemical calculations for gadolinium oxide clusters and clarified the most suitable combination of a theoretical method, basis sets, and effective core potentials for large systems of gadolinium oxides. We confirmed the reliability of our calculation by computing the electronic state of GdO molecule whose bond length and binding energy are well known. In order to examine how the electronic states depend on the size of clusters, we calculated several cluster series: GdO
n
clusters (n=2–4) with negative net charge, (GdO)
n
colinear and zigzag chain clusters (n=1–4), (GdO)
n
square pillar clusters (n=4,6,8), and large clusters based on the Gd2O3 cubic crystal (Gd4O18
24-·8Q
3+ and Gd4O19
26-·8Q
3+), where Q denotes the point charge. New images of electronic stresses in the clusters can be visualized in terms of the electronic stress tensor density based on the regional density functional theory.
Physical and Microstructural Properties of Radio-Frequency Plasma-Enhanced Chemical Vapor Deposition Grown n-Type Phosphorus Doped Amorphous Carbon Films on the Contribution to Carbon-Based Solar Cells
Authors: Rusop Mohamad , Ebisu Hiroshi , Adachi Mitsuhiro , Soga Tetsuo , Jimbo Takashi
Published: September 2005

The physical and microstructural properties of phosphorus doped n-type amorphous carbon (n-C:P) films grown from a radio-frequency (rf) discharge in methane gas as a function of rf power (P
rf) was previously determined, and their influence on the electronic properties is now analyzed. It is shown that P
rf plays a major role in the deposition of n-C:P films. The Raman scattering, Fourier transform infrared spectroscopy (FTIR), optical spectroscopy, Electron spin resonance (ESR) analyses and electrical resistivity measurement have confirmed successfull phosphorus doping. Moreover, the fabricated n-C:P on p-type silicon substrates (n-C:P/p-Si) heterojunction solar cells, when exposed to AM 1.5 illumination (100 mW/cm2, 25°C) is also studied. The maximum open-circuit voltage (V
oc) and short-circuit current density (J
sc) for the cells are observed to be approximately 236 V and 7.34 mA/cm2, respectively for the n-C:P/p-Si cell grown at low P
rf of 100 W. The highest energy-conversion efficiency (η) and fill factor (FF) were found to be approximately 0.84 and 49%, respectively. We have observed that the rectifying nature of the heterojunction structures is due to the nature of n-C:P films.
Nano powder and Microwave Dielectric Properties of Sol–Gel-Derived Zr0.8Sn0.2TiO4 Ceramics
Authors: Ho Yung-Shou , Weng Min-Hung , Dai Bun-Ton , Wang Shuen-Shian
Published: September 2005

The Nano powder and microwave dielectric properties of zirconium tin titanate (Zr0.8Sn0.2TiO4, ZST) ceramics prepared by sol–gel process were investigated. Pure and fine ZST powders with particle sizes of 10–20 nm were derived by thermal decomposition of an amorphous gel precursor at about 700°C. They formed a single orthorhombic ZST phase and appeared fine and well-dispersed in both scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM). The high sintering ability of the prepared powders enabled the fabrication of dielectric ceramics at low sintering temperatures (1250–1300°C). The well-sintered ZST ceramics with high relative densities (96%) showed excellent microwave dielectric properties compared with those prepared by a conventional method at the same sintering temperature.
Combinatorial Fabrication and Characterization of Ternary La2O3–Mn2O3–Co3O4 Composition Spreads
Authors: Kukuruznyak Dmitry Anatolyevich , Ahmet Parhat , Yamamoto Atsushi , Ohuchi Fumio , Chikyow Toyohiro
Published: September 2005

We describe the screening of large combinatorial oxide libraries for determining their electric transport characteristics. Complete full ternary composition spreads of La2O3–Mn2O3–Co3O4 oxide alloys were deposited onto single conducting Nb-doped SrTiO3 substrates by the pulsed laser deposition technique incorporating a moving shutter and a rotating substrate holder. The electrical resistance of the spreads was determined using a custom-designed scanning conducting probe. We found that a single electrically conducting area in the ternary spread develops into two branches to LaMnO3 perovskites close to the ideal LaMnO3 stoichiometry and to a wide La0.65Co0.35O
X
–La0.20Co0.80O
X
system with perovskite-related structures. We also discovered that compositions along the tie line [La0.20Co0.65Mn0.15O
X
–La0.57Co0.20Mn0.23O
X
] exhibit the weakest temperature dependence and therefore could be used in fabricating of stable thin film resistors and gas sensors.
Study of the Hysteretic Behavior in Polymer-Stabilized Ferroelectric Liquid Crystal System
Authors: Lee Ji-Hoon , Lim Tong-Kun
Published: September 2005

We have studied the hysteresis-free switching behaviors of a polymer-stabilized ferroelectric liquid crystal (PSFLC) as well as a pure ferroelectric liquid crystal (FLC) system and found that they coincided with the model suggested by Blinov et al. [Phys. Rev. E 66 (2002) 021701] The hysteresis inversion frequency was promoted to up to 7000 Hz by connecting an external capacitor and resistor in series. In addition, the influence of temperature on the hysteresis-free switching of the cell could be optimized.
Dose Dependence of Recrystallization Processes in Amorphous SiC
Authors: Bae In-Tae , Ishimaru Manabu , Hirotsu Yoshihiko
Published: September 2005

Ion-beam-induced amorphous layers of silicon carbide (SiC) as well as their recrystallized layers have been characterized by transmission electron microscopy (TEM). Single crystals of 6H–SiC with the (0001) orientation were irradiated with 150 keV Xe ions to fluences of 1015 and 1016/cm2, followed by thermal annealing at 940°C. Full recrystallizations took place in both specimens. Electron diffraction patterns and bright-field TEM images revealed that full epitaxial recrystallization occurred in the specimen implanted with 1015 Xe ions, while both epitaxial recrystallization and the occurrence of the cubic phase of SiC (3C–SiC) were observed in the specimen implanted with 1016/cm2 Xe ions. This is attributed to the difference in amorphous structures between the 1015 and 1016 Xe/cm2 implanted samples: the former shows a greater chemical short-range order in the amorphous state than the latter, and the chemical short-range order deteriorates with increasing ion dose. In addition, a higher Xe impurity concentration is also considered to be associated with the occurrence of 3C–SiC in a high-dose sample.
Sample-and-Hold Operation in Kelvin Probe Force Microscopy
Authors: Ono Shiano , Takahashi Takuji
Published: September 2005

To achieve a more accurate determination of surface potential in Kelvin probe force microscopy (KFM), we have proposed and demonstrated a sample-and-hold operation of KFM (SH-KFM), in which a sample-and-hold (S/H) circuit is inserted between an optical deflection sensor and a lock-in amplifier, to sample the deflection signal at a tapping frequency. Owing to the sampling operation, the cantilever bending due to the electrostatic force can be extracted at a desired phase in the tapping oscillation by intentional tuning of a time delay for sampling. We performed SH-KFM measurements on InAs quantum dots, and successfully observed a very clear site dependence of the potential with a large contrast. The results also indicated that the spatial resolution in the potential images was estimated to be better than 10 nm, and that the amplitude of an ac modulation bias in KFM could be reduced to 10 mVp–p without any remarkable degradation of the potential images.
Reduction of Pyrochlore Phase and Pronounced Improvement of Ferroelectric Properties in Ultrathin SrBi2Ta2O9 Films Derived from Bi-Rich Sol–Gel Solution
Authors: Aizawa Koji , Ishiwara Hiroshi
Published: September 2005

The crystallinity and ferroelectric properties of sol–gel-derived sub-100-nm-thick SrBi2Ta2O9 (SBT) films with different Bi contents were investigated. The remanent polarization value of a 35-nm-thick SBT film formed using a Sr0.8Bi2.5Ta2O9 precursor solution was 5.2 µC/cm2 at an applied voltage of 1.4 V, which was much larger than that (1.2 µC/cm2) of a 33-nm-thick SBT film formed using a Sr0.8Bi2.2Ta2O9 precursor solution. It was found by X-ray diffraction analysis that this pronounced improvement was caused by the reduction of the pyrochlore phase. It is concluded from these results that a Bi content of around 2.5 is effective in preventing the growth of the pyrochlore phase and improving the ferroelectric properties of sub-50-nm-thick SBT films.
Calculation of Ion Mobilities and their Effects on Gas Discharge of AC Plasma Display Cells
Authors: Lee Insook , Choi Kwang-Yeol
Published: September 2005

We have found that ion mobilities in a gas mixture greatly affect discharge characteristics of a plasma display cell. Therefore, correct ion mobilities are required to obtain meaningful simulation results on plasma display cells. Since plasma display panels use microdischarges in the Xe mixed gas to generate vacuum ultraviolet light to excite phosphor for visible light emission, the condition of the discharge gas mixtures is one of the main factors that determine luminous efficacy. Thus, intensive studies on the discharge gas mixture are essential to optimize it and the accurate determination of ion mobilities in it is necessary. We have discussed how to determine necessary values of ion mobilities in various discharge gas mixtures including the three-species He–Ne–Xe mixture. Calculated ion mobilities and their effect on the discharge of an AC plasma display cell have also been presented and discussed. We have revealed that the enhanced ion mobilities in the gas mixture resulting from adding He gas to the conventional Ne–Xe mixture play an important role in increasing the luminous efficacy of a plasma display cell sustained in the He–Ne–Xe mixture by decreasing the cathode fall potential.
Dual-Frequency Superimposed RF Capacitive-Coupled Plasma Etch Process
Authors: Kojima Akihiro , Hayashi Hisataka , Sakai Itsuko , Nishiwaki Junya , Takase Akihiro , Ohmura Mitsuhiro , Matsushita Takaya , Shinomiya Eiichiro , Ohiwa Tokuhisa , Yashiro Jun , Himori Shinji , Nagaseki Kazuya
Published: September 2005

A dual-frequency superimposed (DFS) 100 MHz and 3.2 MHz rf capacitive-coupled plasma etch process for sub-90 nm devices has been developed. The electron density of DFS reactive ion etching (RIE) plasma at 40 mTorr was controlled from 4.0×1010 to 3.6×1011 cm-3 by adjusting the 100 MHz rf power, and the self-bias voltage (-V
dc) was controlled from 20 to 760 V by adjusting the superimposed 3.2 MHz rf power. DFS RIE demonstrated independent control of electron density and self-bias voltage in a wide range. In the damascene etch process of SiOC film using Si3N4 as an etch mask, it was found that mask edge erosion is dependent on ion energy regardless of the selectivity of SiOC to Si3N4. DFS RIE offers the most suitable process for damascene etching of SiOC, which requires precise ion energy control.
Organic Electroluminescence Devices Based on Mixture of Aluminum–Hydroxyquinoline Complex and Compound with Low Dielectric Constant
Authors: Fukuno Katsuhisa , Osasa Takahiro , Iwasaki Yohei , Kimura Akira , Matsumura Michio
Published: September 2005

The quantum efficiency and lifetime of fluorescence of an aluminum–hydroxyquinoline (Alq3) complex in solution increased with decreasing polarity of the solvent. Similarly, the fluorescence quantum efficiency and lifetime of Alq3 films were increased by mixing the complex with a compound with a low dielectric constant. These results suggested that the nonradiative decay process of Alq3 is retarded in less polar media. The quantum efficiency and lifetime of fluorescence of Alq3 films were 20±2% and 17 ns, respectively. When Alq3 was mixed with a less polar substance in the film state, the quantum efficiency and lifetime were increased to 25±2% and 20 ns, respectively. These results indicate that the nonradiative decay process in the film state is also retarded as the polarity decreases. Using a film consisting of Alq3 and a compound with a low dielectric constant as the light emitting layer of organic electroluminescence devices, the luminance efficiency was increased by about 20%.
Stress Gradient Weighted by Surface Acoustic Wave Displacement: A Tool for Understanding Break-In Procedure in Friction Wear Test
Authors: Kwon Sung D. , Song Sung-Jin , Kim Young H. , Lee Young Z.
Published: September 2005

The characteristics of the Rayleigh surface wave are investigated indirectly using the backward radiation of the incident ultrasonic wave in the scuffing specimens of AISI 1045 steel with various lubricated sliding surface conditions, and are then compared to the residual stress distribution measured by X-ray diffraction. Quantitative model analysis showed that the peak frequency of the spectrum of the backward radiated ultrasound mainly varies with the gradient of residual stress, which is sensitively related to the microfatigue density, and that the break-in procedure suppresses the variation of the gradient. The result in this study demonstrates the high potential of backward radiated ultrasound as a tool for nondestructive evaluation of subsurface gradients.
Hydrodynamic Radius Sizing of Nanoparticles in Dense Polydisperse Media by Low-Coherence Dynamic Light Scattering
Authors: Xia Hui , Ishii Katsuhiro , Iwai Toshiaki
Published: September 2005

The hydrodynamic radius sizing of nanoparticles in dense polydisperse media is investigated by low-coherence dynamic light scattering (low-coherence DLS). A conventional CONTIN algorithm is used to analyze the amplitude autocorrelation function of single scattered light detected preferentially from multiply scattered light. The great potential of the low-coherence DLS is confirmed experimentally for the noninvasive characterization of the hydrodynamic and structural properties of dense polydisperse media. As a result, the new particle-sizing technique for dense polydisperse media based on the low-coherence DLS is established in this study.
Theory of Pulsed Photothermal Radiometry for Transmission and Lateral Geometries
Authors: Webb Jeffrey F.
Published: September 2005

Pulsed photothermal radiometry (PPTR) employs a pulsed laser excitation to heat a sample and the resulting change in emitted IR radiation is detected remotely, which gives rise to the PPTR signal. A theory for analysing experimental data is considered for transmission geometry where excitation and detection are on opposite sides of the sample, and lateral geometry where excitation and detection are on the same side, but laterally displaced. For transmission geometry it is shown in detail how absorption coefficients at the excitation and detection wavelengths, α and β respectively, appear in a symmetrical way in this theory. In doing this an alternative way of calculating PPTR signals is introduced using a Laplace transform technique. For lateral geometry a similar symmetry for disc excitation and detection areas, with radii r
1 and r
0, is also demonstrated. The Laplace transform technique is also used to give signal expressions for transmission geometry which converge quickly for small values of time. Furthermore, ways of applying the theory to experimental data in order to extract material properties α, β and thermal diffusivity D are developed.
Observations of Lattice Distortions near Silicon Surfaces Implanted with Low-Energy Nitrogen Ions by Reflection X-ray Topography
Authors: Futagami Koji , Fukumori Taichiro , Tsukuda Noboru , Kuroki Kiyohiro
Published: September 2005

Mirror-polished Czochralski-grown wafers with near-(100)-oriented surfaces were implanted with N+ at 8 keV energy at a dose of 1 ×1015 cm-2. Lattice distortions produced by the implantation process were observed by X-ray double-crystal topography using extremely asymmetric reflection. The intensity contrast caused by the lattice extensions in thin layers was clearly visualized. By annealing at 700°C for more than 90 min, the imperfect crystal in the ion-implanted region evidently recovers to a more perfect one, except for the boundary of the implanted region. The lattice distortions at the boundary, consisting of a narrow striated region, are thought to be due primarily to variations in the lattice spacing that has been deformed nonelastically. From a series of topographs taken by changing the glancing angle from the low-angle to the high-angle side of the Bragg peak, the differences in lattice spacing between the striated portions and the unimplanted regions were estimated.
103-km-Long Remote Measurements of End Standards Using Low-Coherence Optical-Fiber Tandem Interferometer in Experimental Room
Authors: Matsumoto Hirokazu , Sasaki Kaoru , Hirai Akiko
Published: September 2005

The length information of end standards is transmitted through a 103-km-long optical fiber in the experimental room. The system uses a low-coherence tandem interferometer and a single-mode optical fiber in the wavelength range of 1500 nm. Interference fringes are generated when the optical path difference of the first interferometer compensates that of the second interferometer. The end standards of up to 50 mm in length have been calibrated remotely with a standard deviation of about 34 nm.
Change in Elasticity Caused by Flow-Mediated Dilation Measured Only for Intima–Media Region of Brachial Artery
Authors: Sugimoto Masataka , Hasegawa Hideyuki , Kanai Hiroshi
Published: September 2005

Endothelial dysfunction is considered to be an initial step of arteriosclerosis [R. Ross: N. Engl. J. Med. 340 (2004) 115]. For the assessment of the endothelium function, brachial artery flow-mediated dilation (FMD) caused by increased blood flow has been evaluated with ultrasonic diagnostic equipment. In the case of conventional methods, the change in artery diameter caused by FMD is measured [M. Hashimoto et al.: Circulation 92 (1995) 3431]. Although the arterial wall has a layered structure (intima, media, and adventitia), such a structure is not taken into account in conventional methods because the change in diameter depends on the characteristic of the entire wall. However, smooth muscle present only in the media contributes to FMD, whereas the collagen-rich hard adventitia does not contribute. In this study, we measure the change in elasticity of only the intima–media region including smooth muscle using the phased tracking method [H. Kanai et al.: IEEE Trans. Ultrason. Ferroelectr. Freq. Control 43 (1996) 791]. From the change in elasticity, FMD measured only for the intima–media region by our proposed method was found to be more sensitive than that measured for the entire wall by the conventional method.
Observation on Effect of Optical Stimulation to Human Using Optical Topography
Authors: Yanai Hiro-Fumi , Yorimoto Akiyoshi , Kubota Toshio , Fujii Kan-ichi , Kawaguchi Fumio , Yamamoto Etsuji , Ichikawa Noriyoshi , Koshino Yoshihumi
Published: September 2005

We have observed the time course features of cerebral response while a subject is performing the visual tracking task or visual tracking plus finger tapping task using Optiocal Topography (OT). The distribution maps of both oxygenated and deoxygenated hemoglobins are demonstrated in contrast with the time course diagram. The response of the cerebrum differs, depending on whether the optical stimulation is static or dynamic, even when the overall nature of the pattern and intensity of the stimulation is the same. The cerebral response to a dynamic optical stimulation is very rapid and clear, and greater in magnitude than that to static optical stimulation, but it is suppressed when an auxiliary finger tapping task is also performed. From these results, it was confirmed that OT is sensitive to both static and dynamic optical stimulations.
Break Conductance of Pt Nanocontacts
Authors: Minowa Takeshi , Tsutsui Makusu , Kurokawa Shu , Sakai Akira
Published: September 2005

We have studied the high-bias/current break of Pt nanocontacts at room temperature by measuring the conductance (“break conductance”) at the contact break. The distribution of the break conductance exhibits a broad single peak, the position of which shifts linearly with the contact current. From the observed peak shift, we showed that the contact break most likely takes place when the contact current density reaches a critical valuejc∼5 ×1010A/cm2. Thisjcof Pt nanocontacts is lower than that of noble metals and disproves the speculated positive correlation betweenjcand the melting point of metals. Possible mechanisms responsible for the observed lowjcof Pt are discussed.
Temporal Saturation Effects of Nanoscale Contact Holes Fabricated by Chemical Shrink Techniques
Authors: Li Tsung-Lung , Ting Jyh-Hua
Published: September 2005

The temporal saturation effects of the critical dimensions of nanoscale contact holes are investigated by a two-dimensional reaction–diffusion simulator for the chemical shrink techniques of nanolithography. Models included with the simulator are the crosslinking reaction of water-soluble polymers and crosslinkers, the diffusion of photoacids, and the inactivation of photoacids. Within the the statistical errors of the experimental data, the simulation critical dimensions agree with the experiment for baking temperatures over 105°C and for all baking times. It is found that the temporal saturation of the contact holes' critical dimensions can be explained by the photoacid inactivating reaction included in the simulator.
AlGaN/GaN High-Electron-Mobility Transistor Employing an Additional Gate for High-Voltage Switching Applications
Authors: Ha Min-Woo , Lee Seung-Chul , Her Jin-Cherl , Seo Kwang-Seok , Han Min-Koo
Published: September 2005

We have proposed and fabricated an AlGaN/GaN high-electron-mobility transistor (HEMT) with an additional gate, which exhibits a low leakage current and a high breakdown voltage for high-voltage switching applications. The additional gate between the main gate and the drain is specially designed to decrease the electric field concentration at the drain side of the main gate. The leakage current of the proposed HEMT is decreased considerably and the breakdown voltage increases without sacrificing the transconductance and the drain current. The experimental results show that the off-state breakdown voltage and the leakage current of the proposed HEMT are 362 V and 75 nA while those of the conventional HEMT are 196 V and 428 nA, respectively.
Analysis of DC Characteristics and Small Signal Equivalent Circuit Parameters of GaAs Metal–Semiconductor Field Effect Transistors with Different Gate Lengths and Different Gate Contours by Two-Dimensional Device Simulations
Authors: Meng C. C. , Su J. Y. , Yang S. M.
Published: September 2005

The gate length and gate contour of a GaAs metal–semiconductor field effect transistor (MESFET) device play important roles in determining the small signal circuit parameters and large signal breakdown voltage behavior. GaAs MESFETs with different gate lengths and gate contours were studied by the two-dimensional (2-D) semiconductor device simulations to investigate the dependence of small signal circuit parameters and breakdown voltage on gate length and gate contour. The results show that gate length affects small-signal circuit parameter C
gs while gate contour affects C
gd. The breakdown voltage has strong dependence on gate contour and little dependence on gate length.