bluuebunny/crossref_metadata_2025 huggingface dataset:
A Coupled Model for Active Vibration Control of Beam System with Piezoelectric Actuators
Authors: Zhai Baonian , Lim Siak-Piang , Lu Pin
Published: October 2002

This study deals with the dynamics of a flexible beam with piezoelectric actuators for active vibration control. A mathematical model, comprising two mathematical formulae of generalized forces for bending modes and longitudinal modes, is established. Instead of treating actuators as an external excitation source for the structure in previous studies, in this study, the mechanical dynamics of the actuators is incorporated into the model. Therefore, the model is more accurate and offers a better theoretical basis for the implementation of active vibration control.
Nanofabrication Using Atomic Force Microscopy Lithography Combined with Optical Lithography
Authors: Kato Midori , Ishibashi Masayoshi , Heike Seiji , Hashizume Tomihiro
Published: October 2002

A scanning probe lithography (SPL) system based on atomic force microscopy (AFM) enables the drawing of patters having high resolution. We fabricated fine electrodes on a carbon nanotube (CNT) having large contact pads by using a hybrid process of AFM lithography and optical lithography. This hybrid process is well-suited for simultaneously drawing patterns consisting of structures several tens of nanometers and millimeters in scale.
Room Temperature Sub-Micron Magnetic Imaging by Scanning Hall Probe Microscopy
Authors: Sandhu Adarsh , Masuda Hiroshi , Oral Ahmet , Bending Simon J.
Published: October 2002

An ultra-high sensitive room temperature scanning Hall probe microscope (RT-SHPM) system incorporating a GaAs/AlGaAs micro-Hall probe was used for the direct magnetic imaging of localized magnetic field fluctuations in very close proximity to the surface of ferromagnetic materials. The active area, Hall coefficient and field sensitivity of the Hall probe were 0.8 µm×0.8 µm, 0.3 Ω/G and 0.04 G/√Hz, respectively. The use of a semiconducting Hall probe sensor enabled measurements in the presence of externally applied magnetic fields. Samples studied included magnetic recording media, demagnetized strontium ferrite permanent magnets, and low coercivity perpendicular garnet thin films. The RT-SHPM offers a simple means for quantitatively monitoring sub-micron magnetic domain structures at room temperature.
Scanning Tunneling Spectroscopy of c(2×2) Reconstructed Fe Thin-Film Surfaces
Authors: Hirofumi Oka Hirofumi Oka , Agus Subagyo Agus Subagyo , Makoto Sawamura Makoto Sawamura , Kazuhisa Sueoka Kazuhisa Sueoka , Kōichi Mukasa Kōichi Mukasa
Published: October 2002

Fe thin films with flat surfaces are obtained on a MgO(001) substrate at a growth temperature of 550 K. The surfaces with atomically flat and wide terraces exhibit a c(2×2) reconstructed structure. To evaluate the effect of impurity atoms at the surface on the surface structures, scanning tunneling spectroscopy (STS), reflection high energy electron diffraction (RHEED) and X-ray photoelectron spectroscopy (XPS) studies were performed. The differential conductivity (d
I/d
V) spectrum of the c(2×2) Fe(001) thin-film surfaces indicates an intense peak at the sample bias voltage of 0.4 V. Since there is no clear evidence of impurity adatoms forming such a surface structure, we expect that the topmost atoms are Fe, and that the observed peak originates from surface states.
Determination of Aerosol Extinction-to-Backscattering Ratio from Multiwavelength Lidar Observation
Authors: Hideki Kinjo Hideki Kinjo , Hiroaki Kuze Hiroaki Kuze , Tamio Takamura Tamio Takamura , Masanori Yabuki Masanori Yabuki , Nobuo Takeuchi Nobuo Takeuchi
Published: October 2002

We propose a method to determine the extinction-to-backscattering ratio (S
1 parameter) in the troposphere from multiwavelength (355, 532, 756, and 1064 nm) lidar data. In our approach, reference profiles are prepared by using the wavelength dependence of the extinction coefficient as derived either from the sun photometer data or from the Mie calculation. By comparing these reference profiles with the profiles calculated using the conventional Fernald inversion method, the S
1 parameter is determined for each wavelength. When a reasonable range is covered at 532 nm, this method makes it possible to determine the S
1 parameters for shorter or longer wavelengths for which full range observation cannot be attained, due presumably to small laser power or limited detector efficiency. In addition, information about the vertical uniformity of aerosol properties can be derived from the S
1 dependence of the difference between the reference and retrieved profiles.
Frictional Properties of Organosilane Self-Assembled Monolayer in Vacuum
Authors: Hayashi Kazuyuki , Sugimura Hiroyuki , Takai Osamu
Published: October 2002

Frictional properties of methyl (CH3)- and fluoromethyl (CF3)-terminated organosilane self-assembled monolayers (SAMs) have been studied by lateral force microscopy (LFM). The SAMs were prepared on Si substrates by means of chemical vapor deposition using n-octadecyltrimethoxysilane or heptadecafluoro-1,1,2,2-tetrahydro-1-trimethoxysilane as a precursor. In spite of the fact that the CF3-terminated SAM was more hydrophobic than the CH3-terminated SAM, the CF3-terminated SAM was adsorbed a larger amount of water than the CH3-terminated SAM because of the strong electron negativity of F atoms. Consequently, the capillary force effect in LFM appeared more distinctly on the CF3-terminated SAM. The difference in capillary force between the CH3- and CF3-terminated SAMs was responsible for greater friction forces in air on the CF3-terminated SAM, in addition to the intrinsic difference in frictional properties between the CH3 and CF3 groups. With increasing temperature, CH3- and CF3-terminated SAMs became more lubricant due to more increasing molecular vibration. Furthermore, both SAMs were so robust that no damage was induced by probe scanning in vacuum even at a temperature of 300°C and an applied load force of 600 nN.
Fundamental Study on Nano Domain Engineering Using Scanning Nonlinear Dielectric Microscopy
Authors: Kaori Matsuura Kaori Matsuura , Yasuo Cho Yasuo Cho , Hiroyuki Odagawa Hiroyuki Odagawa
Published: October 2002

Scanning nonlinear dielectric microscopy (SNDM) is the first successful purely electrical method for observing the ferroelectric domain on the sub-nanometer order. As another high-resolution method for measuring ferroelectric domains, the piezoelectric response imaging method is often reported. In this study, it is confirmed that SNDM has a much higher resolution than piezoelectric imaging under the same experimental condition using the same system. First, the resolution of SNDM is described, and then, the resolution of SNDM is compared with that of piezoelectric imaging. Finally, a fundamental study for applying the SNDM system to a ferroelectric reading-recording system is performed, and it is concluded that SNDM has sufficient performance for application to the ferroelectric memory system.
Scanning Probe Microscopy and Lithography of Ultrathin Si3N4 Films Grown on Si(111) and Si(001)
Authors: Gwo Shangjr , Wu Chung-Lin , Chien Forest Shih-Sen , Yasuda Tetsuji , Yamasaki Satoshi
Published: October 2002

Scanning tunneling microscopy (STM) was used to study the surface structure of ultrathin single-crystal Si3N4 film prepared by thermal nitridation on an [111]-oriented Si substrate. High-resolution STM images indicate that both 8×8 and 8/3×8/3 orderings exist on the surface of the single-crystal Si3N4 film. We also found that ultrathin Si3N4 films (< 5 nm) formed by thermal nitridation or low-pressure chemical vapor deposition on doped Si(111) and Si(001) substrates are excellent mask materials for nanolithography. Local oxidation of crystalline or amorphous silicon nitride films can be reliably performed with a conductive-probe atomic force microscope (AFM) with an extremely fast initial oxidation rate (five to six orders of magnitude higher than the thermal oxidation rate at 1000°C) at a sample bias of +10 V. The nanopatterned silicon nitride masks can be used for selective-area high-aspect-ratio etching and epitaxial growth with large selectivities. Using an AFM-patterned SiO2/Si3N4 bilayer mask, selectively grown Si dots and lines of high crystalline perfection were successfully obtained.
Kelvin Probe Force Microscopy Images of Microstructured Organosilane Self-Assembled Monolayers
Authors: Hiroyuki Sugimura Hiroyuki Sugimura , Kazuyuki Hayashi Kazuyuki Hayashi , Nagahiro Saito Nagahiro Saito , Osamu Takai Osamu Takai , Nobuyuki Nakagiri Nobuyuki Nakagiri
Published: October 2002

A difference in surface potentials between organosilane self-assembled monolayers (SAMs) was measured by means of Kelvin probe force microscopy (KFM). The SAMs were deposited on a single Si substrate from alkylsilane, that is, octadecyltrimethoxysilane (ODS) [H3C(CH2)17Si(OCH3)3], and fluoroalkylsilane (FAS), that is, heptadecafluoro-1,1,2,2-tetrahydro-decyl-1-trimethoxysilane [F3C(CF2)7(CH2)2Si(OCH3)3]. The locations of these SAMs on the substrate were defined by means of a photolithographic technique. The regions terminated with ODS and FAS were clearly distinguished by KFM with the surface potential difference between the ODS- and FAS-terminated surfaces under optimized imaging conditions. The surface potential of the FAS-terminated region was 170∼180 mV lower than the potential of the ODS-terminated surface. The origin of such a low surface potential of FAS-SAM was ascribed to the larger dipole moment of the FAS molecule induced by the electron negativity of F atoms as estimated from a molecular orbital calculation.
Low-Temperature Plasma-Enahanced Chemical Vapor Deposition of Crystal Silicon Film from Dichlorosilane
Authors: Liu Haiping , Jung Sughoan , Fujimura Yukihiro , Fukai Chisato , Shirai Hajime , Toyoshima Yasutake
Published: October 2002

Low temperature growth of hydrogenated chlorinated crystal silicon [µc-Si:H(Cl)] films from dichlorosilane (SiH2Cl2) by conventional rf glow discharge (13.56 MHz) is investigated. The role of chlorine and hydrogen in crystal formation is discussed in terms of studies on gas phase and surface chemistry through film deposition, plasma diagnostics and in situ monitoring of the surface reaction. The electron temperature in the SiH2Cl2/H2 plasma significantly depends on not only pressure but also substrate temperature. The surface termination species depend on substrate temperature and hydrogen flow rate. The growing top surface is mainly terminated by chlorine as SiCl
n
(n=1, 2). Specific features of crystal formation at low temperatures from SiH2Cl2/H2 plasma are demonstrated and compared with those from SiH4/H2.
Scanning Tunneling Microscopy Observation of CO on Pd(110) at Cryogenic Temperature; Imaging Mechanism and Novel One-Dimensional Array Formation
Authors: Komeda Tadahiro , Kim Yousoo , Kawai Maki
Published: October 2002

Scanning tunneling microscopy (STM) is used to observe carbon monoxide (CO) on Pd(110) surface at cryogenic temperature. We observe the change of appearance of CO in the STM images with the variation of bias voltage and also the existence of CO on the tip apex. This is well explained by assuming a V-shaped density of states at O atom which is formed by the mixing of CO 2π* and Pd 4d. An intriguing one-dimensional ordering is observed along the [110] direction, when CO is dosed at RT and observed at 4.8 K even at coverages less than 0.1 ML. The CO spacing is twice the Pd lattice spacing. The diffusion in such arrays is observed above 110 K. It is found that the diffusion of CO molecules is anisotropic and practically restricted along a single Pd row; inter-row hopping is hardly observed. It is observed that CO molecules in longer chains are more stable than isolated CO molecules.
Scanning Tunneling Microscopy Study on c(6×2) Structure of Ag/Si(001)
Authors: Osamu Takeuchi Osamu Takeuchi , Masami Kageshima Masami Kageshima , Hiroshi Sakama Hiroshi Sakama , Akira Kawazu Akira Kawazu
Published: October 2002

The c(6×2) phase of a silver monolayer on Si(001) substrate was investigated by scanning tunneling microscopy (STM). The c(6×2) structure appeared when silver was deposited at room temperature and then annealed at temperatures between 100°C and 250°C, and always coexisted with a 2×3 structure. In contrast, when silver was deposited onto a substrate at a temperature in this range, only the 2×3 structure grew. In the STM images with negative and positive sample bias voltages, one and two maxima were observed, respectively, in a c(6×2) unit cell. The finding of a lack of mirror symmetry in the unit cell reveals that the previously reported “single-domain” c(6×2) surface actually consists of two crystalographically equivalent domains on a single-domain substrate.
Attenuated Total Reflection-Scanning Near-Field Raman Spectroscopy
Authors: Futamata Masayuki , Bruckbauer Andreas
Published: October 2002

A facility for scanning near-field Raman spectroscopy (SNRS) using the attenuated total reflection (ATR) method was built to obtain topographic and Raman images with a spatial resolution higher than the diffraction limit. A Raman spectrum of copper phthalocyanine (CuPc) was obtained with an accumulation time of 1000 s without using surface plasmon excitation or the electronic resonance effect of the molecules. The optimum conditions for enhancing the Raman signal using localized surface plasmon (LSP) on Ag island films were found to be 5 nm in thickness and an incident angle of 50°. Under these conditions, the Raman signal from CuPc (1.5 nm) was enhanced by a factor of ca. 300, which gives 36 counts/s for ca. 30,000 molecules, and enables us to obtain the Raman spectra in 2 s. Interestingly, the scanning near-field optical microscopy (SNOM)-Raman intensity increases with decreasing thickness of CuPc samples below 3 nm due to the near-field effect between the fiber probe and Ag films, while it remains constant for 5–30 nm in CuPc thickness. The polarization dependence of the signal intensity supports this interpretation. In contrast, without the Ag underlayer, the SNOM-Raman scattering intensity is not prominently enhanced due to the weaker interaction between the dielectric sample and the probe. In both cases, the SNOM-Raman scattering signal arises within ca. 5 nm from the sample surface.
Review of Layer Transfer Processes for Crystalline Thin-Film Silicon Solar Cells
Authors: Brendel Rolf
Published: October 2002

Layer transfer processes provide a new and largely unexplored route for the fabrication of highly efficient monocrystalline thin-film Si solar cells. Monocrystalline Si wafers serve as a substrate for epitaxial growth. A special surface conditioning of the substrate permits the transfer of a thin epitaxial film to an arbitrary carrier substrate. The growth substrate is then re-used to fabricate further cells. The possibility to use different materials for growing the thin film and for carrying the devices broadens the design flexibility and opens a new path for cost reduction. We describe and discuss the various layer transfer processes that are currently being developed for Si. A particular important point to work on in the future is the demonstration of a frequent re-use of the substrate and the development of a large-area and low-cost epitaxy technique.
Characterization of Tensile Strained Si1-yCy Alloy Grown by Photo- and Plasma Chemical Vapor Deposition at Very Low Temperature
Authors: Abe Katsuya , Yagi Shuhei , Okabayashi Takashi , Yamada Akira , Konagai Makoto
Published: October 2002

Epitaxial growth of Si1-y
C
y
films on Si(001) by photochemical vapor deposition (photo-CVD) and plasma-enhanced chemical vapor deposition (plasma-CVD) is reported. We obtained the epitaxial Si films by the addition of C2H2 or CH4 to SiH4 and H2 gases using both methods at a very low substrate temperature of 200°C. Hydrogen incorporation in the epitaxial films and lattice expansion by H atoms were observed. The H atoms in the film desorbed by thermal annealing in N2 atmosphere. The C local vibration mode in the Si network (607 cm-1) was detected in the films annealed at temperatures higher than 600°C. X-ray diffraction peak of the Si1-y
C
y
layer shifted to a higher angle by the annealing. The X-ray reciprocal lattice space mapping indicated pseudomorphic growth of Si1-y
C
y
alloys. Thus, the tensile strained Si1-y
C
y
alloy with a high substitutional C content of 2.7% was successfully obtained.
The Effective Control of Pd/GaAs Interface by Sulfidation and Thermal Hydrogenation
Authors: Kang Min-Gu , Park Hyung-Ho
Published: October 2002

A new technique using sulfidation and subsequent thermal hydrogenation is reported to minimize defective interfacial bonds of Pd/GaAs Schottky contact, ultimately improving the electrical properties. Sulfur-passivation of GaAs surface prior to Pd metallization was very effective to exclude interfacial compounds such as Ga oxides and As oxides, and resulted in both the reduction of reverse leakage current and the enhancement of barrier height. However, a defective interfacial bond of excess As inevitably appeared during Schottky metallization. The interface was annealed under vacuum and H2 ambient at various temperatures from 100°C to 500°C, respectively. Pd/HCl-cleaned GaAs degraded its Schottky contact property after anneal at 400°C, while Pd/S-passivated GaAs maintained its property after anneal up to 400°C. Unlike to the vacuum annealed contact system, thermally-hydrogenated one showed a further improvement of electrical property. With nondestructive interface analysis using X-ray photoelectron spectroscopy, the hydrogenated Pd/GaAs interface turned to be free of defective bond, metallization-induced excess As. During the thermal hydrogenation of Pd/GaAs Schottky contact, the interfacial excess As effectively sublimated by forming volatile As-hydrides through the reaction with hydrogen, and the interfacial hydrogenation at relatively low temperature could be expounded with a catalytic role of Pd metal.
Photoluminescent Properties of Se-doped GaN
Authors: Yi Gyu-Chul , Park Won Il
Published: October 2002

The nature of Se donors in GaN was investigated using temperature dependent photoluminescence spectroscopy. Near-bandedge emission of the doped films was investigated at temperatures between 15–300 K. Based on the temperature dependence of the near-bandedge emission, the Se donor level in GaN was estimated to be 38±4 meV below the conduction band minimum.
Electromodulated Photoluminescence Study of CdS/CdTe Thin-Film Solar Cell
Authors: Nakamura Kyotaro , Gotoh Masahiro , Fujihara Toshihiko , Toyama Toshihiko , Okamoto Hiroaki
Published: October 2002

The n
+-CdTe1-x
S
x
layer, in which the most of the photocarriers are generated in the CdS/CdTe thin-film solar cell, has been characterized using a novel spectroscopic technique called electromodulated photoluminescence (EMPL), which is the first derivative spectroscopy monitoring electric-field-induced changes in the PL signal. In conjunction with the results of PL measurements, the ultraviolet-light-excited (UVE-) EMPL measurements reveal that the depletion layer is extended to a quite shallow region in the n
+-CdTe1-x
S
x
layer from the CdS/CdTe(S) metallurgical interface by <15 nm and not extended into the n-CdS layer. Also demonstrated here is that the strong UVE-EMPL signal is closely connected with the high photovoltaic (PV) performances because it is obtained from the shallow depleted n
+ -CdTe1-x
S
x
region with low density of nonradiative recombination centers.
Galvanomagnetic Effect and Magnetization Process in CoO/Co/NiFe Film with Antidot Array
Authors: Kimura Takashi , Wakaya Fujio , Gamo Kenji
Published: October 2002

The effects of antidot structures of the CoO layer in the CoO/Co/NiFe film were studied by measuring the magnetoresistance (MR) and Hall resistance (HR) of the films. In the MR and the HR, the resistance changes corresponding to the magnetization reversals of the antidot regions were observed, in addition to the main resistance changes caused by the magnetization reversals of the regions coupling with the CoO. This suggests that the domain structure in the Co/NiFe layer can be controlled by the patterned CoO. The magnetization of the covered region showed broad switching compared with that in the uniformly-coupled film because of the magnetostatic interaction caused by the magnetic charges at the boundary between the covered and uncovered regions.
Electronic and Magnetic Structures in Slab Models Including Al/Co and O/Co Interfaces
Authors: Masahiko Ichimura Masahiko Ichimura , Toshiyuki Onogi Toshiyuki Onogi , Jun Hayakawa Jun Hayakawa , Kenchi Itoh Kenchi Itoh
Published: October 2002

On the basis of the density-functional theory, we numerically calculated the interfacial magnetism of slab models including Al/Co and O/Co interfaces. We obtained the local magnetic moments and spin polarizations for various types of models. We found that the interfacial Al layers exhibit positive spin polarizaition in specific atomic arrangements, such as O/Al/Co. The sign is consistent with the experimental result of the ferromagnet/insulator/superconductor junction. This result suggests that in the junction Co/Al2O3/Co, the tunneling of s-character electrons in Al is favored to that of d-character electrons in Co.
Mössbauer Effect of Fe Particles in Metal Audio Tape
Authors: Kohmoto Osamu , Hanafusa Toshiki , Yokoyama Masaru , Haneda Koichi
Published: October 2002

The composition of the core of the magnetic pigment of an audio tape has been determined to be 2 at.% Co–1.8 at.% Ni–Fe by the Mössbauer technique and X-ray fluorescence analysis. The hyperfine field H
hf is 336±2 kOe, which is slightly stronger than that of pure Fe.
Estimation of Extreme Ultraviolet Power and Throughput for Extreme Ultraviolet Lithography
Authors: Chiba Akira , Ota Kazuya , Ogawa Taro , Okazaki Shinji
Published: October 2002

Extreme ultraviolet (EUV) power and wafer throughput were estimated based on a scanning imaging system. The EUV power on a mask was estimated from the number of reflective mirrors, their reflectivity, resist sensitivity, scanning speed and exposure time. Wafer throughput was estimated for one-way scanning exposure. The EUV power required for a given wafer throughput was determined. For a given acceleration of the mask stage and scanning length, there is an optimal scanning speed that yields the maximum throughput. Assuming an exposure time of 0.1 s and a resist sensitivity of 5 mJ/cm2, the estimated EUV power on a mask is about 10 W. For a scanning speed of 100 cm/s and a stage acceleration of 3×g, the resultant throughput should be 80 or more. The present analysis has shown that a high EUV power is required to obtain the same throughput as that of optical lithography.
Use of Bessel J1 Laser Beam to Focus an Atomic Beam into a Nano-scale Dot
Authors: Kenji Okamoto Kenji Okamoto , Yasushi Inouye Yasushi Inouye , Satoshi Kawata Satoshi Kawata
Published: October 2002

We propose a novel scheme to guide atomic beams with submicrometer spot sizes and beam propagation lengths of more than 1 centimeter. By using a Bessel J
1 beam for guiding atoms, the atoms are confined to the center dark region of the doughnut mode of J
1 beam. Our numerical analysis results show that a guided atomic beam maintains its width which is less than 100 nm. We also propose a scheme which combines the Bessel J
1 beam with a magneto-optical trap and a Bessel J
0 beam, where the unfocused part of an atomic flux, i.e., the background component, is suppressed.
Compact High-Efficiency CO2 Slab Waveguide Lasers with Segmented RF Excitation
Authors: Chang Ruey-Shyan , Shaw Sen-Yen
Published: October 2002

RF-excited slab waveguide CO2 lasers based on either internal or external electrodes were studied. A compact multisegment RF excitation configuration was used for pumping the gain medium. The use of a separate driving circuit to excite each discharge segment led to a very uniform discharge along the slab waveguide. A resultant maximum output power of 82 W with efficiency up to 20.5% was recorded from a 3 mm×10 mm×450 mm slab waveguide. The gain coefficient, saturation power and the effect of Xe in the gas mixture were also studied. These lasers can be easily scaled to obtain low-cost high-power operation.
Defect Printability for 100 nm Patterns in X-Ray Lithography
Authors: Watanabe Hiroshi , Marumoto Kenji , Matsui Yasuji
Published: October 2002

In order to estimate the sensitivity required for the next-generation inspection system for X-ray masks, we studied defect printability using the lithographic simulator, Toolset. In a previous work, based on 10nm critical dimension (CD) error, we reported the sensitivity of defect inspection for 100 nm line-and-space (L&S) patterns. In this study, we focused on have investigated the CD errors due to various defects such as adhesion of organic materials, and clear and opaque defects at the edge or the center of the space in 100 nm L&S, isolated space, and hole patterns, particularly for a low-contrast mask. From the present study, it has been confirmed that organic defects are rarely printed in X-ray lithography. Moreover, the maximum critical defect size resulting in 10 nm CD errors is estimated to be 30 nm for clear defects and 24 nm for opaque defects in 100 nm patterns. Therefore, the required detection sensitivity is somewhat more relaxed than the critical defect size (20 nm) required by the International Technology Roadmap for Semiconductors (ITRS).
Dielectric, Piezoelectric and Structural Studies on the Intermediate Composition Region of Pb(Zn1/3Nb2/3)O3–PbZrO3 Ceramics
Authors: Yokosuka Masaru
Published: October 2002

Binary solid solutions of the xPb(Zn1/3Nb2/3)O3–(1-x)PbZrO3 system were synthesized by the conventional ceramic process, where both constituents are not ferroelectric in their ceramic forms. Various physical properties of highly dense ceramic specimens with various compositions were investigated. As a result, structural conversion between the perovskite and the pyrochlore phase was found to occur in the range of x=0.4 to 0.7. In this region, the ratio of the perovskite to the pyrochlore phase increased with the increase in sintering temperature, and relaxor-type ferroelectricity was observed. Dielectric constants were also found to be very sensitive to the variation in the ratio of these two phases. A ferroelectric perovskite single phase was shown to exist in the range of x of approximately 0.1 to 0.4. Maximum values obtained are as follows: remanent polarization P
r=28.8 µC/cm2, electromechanical coupling factors k
31=11.0%, k
P=18.8% and k
33=37.2%, and piezoelectric constants d
31=20.9×10-12 C/N and d
33=74.1×10-12 C/N.
Characterization of Tantalum Pentoxide Dielectric Films Grown by Low-Pressure and Plasma-Enhanced Chemical Vapor Deposition
Authors: Sue Chen Yi-Sheng Lai
Published: October 2002

The material properties as well as the electrical behavior of tantalum pentoxide (Ta2O5) thin films prepared by low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD), in the same reactor, were studied. Ta2O5 films were grown on Si and Pt substrates by reacting pentaethoxy tantalum [Ta(OC2H5)5] with oxygen and were annealed in an oxygen furnace at 700°C or oxygen plasma at 350°C. Scanning electron microscopy (SEM), secondary ion mass spectroscopy (SIMS), Auger electron spectroscopy (AES), capacitance–voltage (C–V) and current–voltage (I–V) measurements were employed to characterize the Ta2O5 films before and after annealing. Compared to the LPCVD Ta2O5 film, the PECVD Ta2O5 film deposited at an rf power of 80 W exhibited a denser structure and better dielectric characteristics. Oxygen plasma annealing further densified the Ta2O5 films and improved their electrical performance on either Si or Pt substrate, without deteriorating the substrate materials.
High Temperature Thermodynamic Properties and Pseudo-Binary Phase Diagram of the Pb(Zn1/3Nb2/3)0.91Ti0.09O3–PbO System
Authors: Dong Ming , Ye Zuo-Guang
Published: October 2002

The high temperature thermodynamic properties of the relaxor-based ferroelectric Pb(Zn1/3Nb2/3)0.91Ti0.09O3(PZNT91/9) and the related PZNT91/9–PbO system have been studied by means of micro-thermogravimetry and differential thermal analysis (TG/DTA), combined with optical microscopic examination. A pseudo-binary phase diagram for the system has been established, which exhibits a typical eutectic behavior. The eutectic temperature of the pseudo-binary system is determined to be 828±2°C with a eutectic composition of 25 wt%PZNT91/9–75 wt%PbO. PZNT91/9 crystals partially decompose into a pyrochlore phase above 1140°C. Upon further heating, they incongruently melt at 1225±2°C. The liquidus melting behavior of Pb(Zn1/3Nb2/3)0.91Ti0.09O3in the PbO flux for less than 75 wt% PbO (xPbO<0.75) follows a liquidus curve that is represented by the equation:TL(°C)=-435.34xPbO2-214.34xPbO+1227.6. The established phase diagram and the thermodynamic data provide a valuable guidance for the growth of large and high quality PZNT piezocrystals.
Remarkable Effects of Introduction of SiON Materials into Shallow Trench Isolation Fabrication Process on Metal-Oxide-Semiconductor Field-Effect Transistors
Authors: Shiozawa Katsuomi , Oishi Toshiyuki , Abe Yuji , Tokuda Yasunori
Published: October 2002

As an advanced fabrication process of fine shallow trench isolation (STI) to preserve sufficient active regions, we investigated the introduction of SiON materials, which are compatible with a well-developed metal-oxide-semiconductor (MOS) process. The use of an SiON sidewall spacer attached to a trench etching hard mask, which makes it possible to form a desirable T-shaped STI configuration, was very effective to remarkably expand the effective channel widths of metal-oxide-semiconductor field-effect transistors (MOSFETs) and to completely suppress field oxide thinning at the trench edges. On the other hand, it was revealed that an SiON liner enveloped at the trench inside suppressed reduction of the effective channel width as well as the concentration of the electric field at the channel edges. These favorable effects, which are brought about by the etching characteristics of the SiON materials, were directly reflected on enhancement of the drivability of the MOSFETs together with improvement of the subthreshold characteristics.
Phenomenological Analysis in Fabricating Defect-Free Ferroelectric Liquid Crystal Displays with C-1 or C-2 Uniform States
Authors: Xu Jun , Kurihara Ryuji , Kobayashi Shunsuke
Published: October 2002

The most important issue in developing liquid crystal displays (LCDs) utilizing ferroelectric liquid crystals (FLCs) is how to obtain defect-free FLCDs. In this report, a phenomenological theory of transition between C-1 and C-2 states in FLC cells is suggested. Free energy that includes bulk elastic and surface parts has been theoretically simulated depending on parameters such as surface topography, anchoring energies, thickness of the LC medium and so forth. The critical conditions of the state transition from C-1 to C-2 have been determined. Based on this theory, we succeeded in fabricating defect-free FLCDs with uniform C-2 states by rubbing and that with uniform C-1 states by the photoalignment technique.
1H–13C Nuclear Cross-Relaxation and Molecular Motion in Single Crystalline Film of Vinylidene Fluoride and Trifluoroethylene Copolymer with 75 mol% Vinylidene Fluoride
Authors: Ishii Fumiaki , Tsutsumi Akihiro , Ohigashi Hiroji
Published: October 2002

1H–13C nuclear cross relaxation and molecular motion in a highly double-oriented film of vinylidene fluoride (VDF) and trifluoroethylene (TrFE ) copolymer with 75 mol% VDF were studied using the cross-polarization/magic angle spinning nuclear magnetic resonance technique. A transient oscillation was observed in the 13C peak intensity vs. contact time plots for the CH2, CHF and CF2 groups. Based on the cross relaxation theory of the spin diffusion process, it was clarified that the oscillation behavior was caused by the TrFE-rich domain and that the crystal consisted of VDF-rich and TrFE-rich domains. The spin-lattice relaxation time T
1ρH in the rotating frame in both domains showed the two T
1ρH minimum processes of β and αb in the ferroelectric phase, which are respectively due to the flip-flop motion of the TrFE segment and the oscillational motion of the VDF segment, and the T
1ρH minimum process of α1D is due to the one-dimensional diffusion motion of the conformational defects along the chain, accompanied by the trans and gauche transformations of the VDF conformers in the paraelectric phase on cooling. The anomaly of the T
1ρH minimum at the Curie temperature depended on the conformational stability of both segments. The deflected trans TrFE segment did not experience any conformational change in the transition region, in contrast to the trans-gauche conformational change in the VDF segment.
AlSb Compositional Nonuniformity Induced by Different Ga–Al Exchange Modes in the Melt Growth of AlxGa1-xSb
Authors: Huang Weidong , Nishinaga Tatau , Naritsuka Shigeya
Published: October 2002

The AlSb compositional nonuniformity in a melt grown Al
x
Ga1-x
Sb crystal around the macrostep and the boundary between the facet and off-facet was measured using a spatially resolved photoluminescence (SRPL) technique. It was found that the AlSb composition is higher in the riser part of a macrostep than in the terrace part. It was also found that in the riser part the AlSb composition increases continuously as the step density increases. In the facet/off-facet transition region, it is shown that the AlSb composition in the off-facet area is 13% higher than in the facet area. The experimental result is explained qualitatively by assuming that the AlSb compositional nonuniformity is induced by different degrees of Ga–Al exchange, which depends on the step velocity. It is concluded that even at temperatures as high as the melting point, the Ga–Al exchange cannot reach an equilibrium and the incorporation of Al depends on the degree of misorientation.
Minimum Coating Thickness in Pore Size Reduction of Inorganic Substrates through Particle Deposition
Authors: Lu Shih-Yuan , Yen Yi-Ming
Published: October 2002

The determination of minimum coating thickness for covering substrate holes through particle deposition is achieved with a combined, three-dimensional, on-lattice model, in which both deterministic and non-deterministic driving forces are taken into account. The relative importance of deterministic forces to non-deterministic forces is quantified by a dimensionless parameter, Peclet number. The minimum covering thickness normalized with the characteristic hole size (h
c/H
w) is investigated subject to variation in Peclet number (Pe) and normalized size (D
p/L) of the depositing particle, normalized hole size (H
w/L), and degree of post-contact restructuring allowed (N
r). It is found that there exists a scaling relationship between the normalized minimum covering thickness and the normalized hole size as h
c/H
w∼(H
w/L)
E
with E=0.53, 0.54, 0.96, and 1.42 for Pe of 1000, 10, 0.5, and 0.1, respectively. The magnitude of the scaling exponent implies that the hole covering ability of diffusive particle movement varies more than that of ballistic particle movement over variation in hole size. It is also found that h
c/H
w increases with increasing H
w/L and D
p/L. At low Pe (<1), h
c/H
w increases with increasing Pe for smaller holes, but decreases with increasing Pe for larger holes. For larger Pe, h
c/H
w decreases with increasing Pe, implying that ballistic particle movement is more efficient in covering holes. Post-contact surface restructuring deteriorates the hole covering efficiency of particle deposition for ballistic movement dominated situations (large Pe). But for low Pe situations, there exists an optimal surface restructuring extent, at which h
c/H
w is a minimum.
TiN Diffusion Barrier Grown by Atomic Layer Deposition Method for Cu Metallization
Authors: Uhm Jangwoong , Jeon Hyeongtag
Published: October 2002

The effects on the impurity content, microstructure, resistivity and barrier characteristics of TiN film deposited by an atomic layer deposition (ALD) method have been evaluated. The TiN films were deposited on Si(100) substrates at 450°C using the reactant gases TiCl4 and NH3. The chemical and physical properties of ALD TiN thin films were measured. The TiN films had a randomly-oriented columnar grain microstructure. The chlorine content in the films was below the detection limit of Auger electron spectroscopy (<0.5 at.%) due to the complete surface reaction by self-limiting reaction in ALD method. This low Cl content in film induced a low film resistivity of 120 µΩcm. The barrier properties of this ALD films were tested by the etch-pit method. The result showed a retardation of the interdiffusion between Cu and Si in samples annealed for one hour at temperatures up to 450°C.
Studies of Self-Organized Steps and Terraces in inclined SrTiO3 (001) Substrate by Atomic Force Microscopy
Authors: Bong Cho Gyu , Yasuhiro Kamada Yasuhiro Kamada , Masahiko Yamamoto Masahiko Yamamoto
Published: October 2002

Features of self-organized steps and terraces present in SrTiO3 (001) substrates with various inclined angles (α) have been investigated by atomic force microscopy (AFM). The details of the shape of step edges, the direction of the straight step edges, the distribution of step heights and terrace widths are described. The existence of various step heights such as single, double and triple heights are observed in the self-organized substrates. The surface after the self-organization conserves the same ratio of the step height and terrace width as that before the self-organization. The features of the self-organized steps and terraces, as well as the relative amount of step interaction energy required to influence the formation of the self-organized surface structure are discussed theoretically.
Critical Thickness of AlN Thin Film Grown on Al2O3(0001)
Authors: Kim Jin Woo , Hwang Yoon-Hwae , Cho Jin Hyung , Kim Hyung Kook
Published: October 2002

High-quality thin aluminum nitride films of different thicknesses between 17 Å and 1000 Å, were grown on sapphire (0001) by DC-faced target sputtering at 500°C. A change in lattice constants of films due to a lattice mismatch between films and substrates was observed. The growth mechanism of epitaxial AlN film in the early stage was found to be consistent with the extended atomic distance mismatch (EADM) model. From the fitting result of the lattice constant as a function of thickness based on the equilibrium theory, the critical thickness at which dislocations are introduced into AlN films grown on Al2O3(0001) was estimated as ∼ 4.5 Å.
Characterization of MoO3-x Thin Films
Authors: Ohtsuka Hideaki , Sakurai Yoji
Published: October 2002

Solid state thin film batteries with MoO3-x
films as their cathode active material exhibit good battery performance. The chemical composition of the MoO3-x
thin film has been difficult to determine by chemical analysis, because of the difficulty in weighing ultra light samples located on massive substrates. To surmount this problem, we fabricated fairly thick MoO3-x
films and used thermal analysis to examine the MoO3-x
samples peeled from substrates. The weight change observed after complete oxidation suggested that the chemical composition of MoO3-x
is MoO2.69. The thermal analysis and X-ray diffraction results showed that the MoO3-x
film did not have a single phase but had mixed phases and we believe that the main and second phases are Mo9O26 and MoO2, respectively. The presence of MoO2 provides the film with high electrical conductivity and good cathode performance. Scanning electron microscope (SEM) observation of the film surface showed that the grain size was 20–100 nm and that the film had high density.
Development of Plasma Based Ion Implantation System using an Electron Cyclotron Resonance Plasma Source with a Mirror Field and Synthesis of Carbon Thin Films
Authors: Watanabe Toshiya , Yamamoto Kazuhiro , Koga Yoshinori , Tanaka Akihiro
Published: October 2002

A new type of plasma based ion implantation system was developed. An electron cyclotron resonance (ECR) plasma with a mirror field was used to generate a high density plasma with an electron density of 2×1011 cm-3. It was possible to apply negative high voltage pulses to the substrate up to -10 kV/20 A using a tube switch. Carbon films were prepared on Si wafer substrates with or without applying negative high voltage pulses. Diamond-like carbon (DLC) films were formed on each substrate placed on the hexagonal prism holder by the application of negative high voltage pulses to the substrate, though the polymer-like carbon films were formed without applying the pulse bias to the substrate. The mean surface roughness and the hydrogen content in the DLC films were decreased with decreasing the applied voltage. It is considered that the remaining hydrogen atoms were not bonded to the carbon atoms and that existed in the interstitial sites in the film from the results of the IR spectra which showed that the C–H bonds in the film had been terminated by applying the pulse bias. The DLC film prepared by the application of the pulse bias of low voltages such as -2 kV showed excellent tribological property.
The Formation of Nitridation Damage during the Growth of GaN on GaAs(001)
Authors: Zsebök Otto , Thordson Jan V. , Andersson Thorvald G.
Published: October 2002

We report a correlation between the surface reconstruction transition during the initial phase of the molecular beam epitaxy growth of GaN on GaAs(001) and the nitridation damage determined final layer morphology. In order to study the formation of the nitrogen damage under a wide range of growth conditions, a series of layers were grown by changing the V/III-ratio through the Ga-flux, while keeping all other growth parameters constant. The results, describing the strong effect of the first N-terminated GaN (3×3) monolayer, were summarised in defect formation models for N-rich and Ga-rich conditions, defining the means of near-stoichiometric growth.
Specific Impedance of Liquids during Ultrasonic Cavitation
Authors: Hashiba Kunio , Kawabata Ken-ichi , Umemura Shin-ichiro
Published: October 2002

The macroscopic change in the specific impedance of a liquid was analyzed from a microscopic viewpoint on the basis of bubble dynamics. A shift of the electrical characteristics of an ultrasonic vibration system, whose acoustical load includes a contribution from cavitating bubbles, was clarified analytically. Namely, when the bubbles begin to collapse, the real part of the specific impedance decreases gradually. On the other hand, the imaginary part rapidly becomes significant compared to the real part. Therefore, the liquid becomes a light acoustical load, and the amplitude of the electric admittance at the resonant increases rapidly. Moreover, the resonant frequency approaches that in a system without an acoustical load.
Measurement of Spatial Distribution of SiF4 and SiF2 Densities in High Density SiF4 Plasma Using Single-Path Infrared Diode Laser Absorption Spectroscopy and Laser-Induced Fluorescence Technique
Authors: Nakamura Masayuki , Hori Masaru , Goto Toshio , Ito Masafumi , Ishii Nobuo
Published: October 2002

The measurement method for determining absolute densities of SiF4 molecules in a reactive plasma has been established using infrared diode laser absorption spectroscopy (IRLAS). The spatial distribution of line averaged absolute densities of SiF4 molecules has been investigated in the electron cyclotron resonance (ECR) plasma reactor employing SiF4 gas using infrared diode laser absorption spectroscopy without a multiple reflection cell, namely, single-path IRLAS. Furthermore, the spatial distributions of SiF2 radical densities are measured using laser-induced fluorescence (LIF) technique. It was found that the line averaged absolute density of SiF4 molecules indicated the hollow-type distribution in the reactor, while SiF2 radical densities had the maximum value near the plasma boundary. On the basis of these measured results, the formation mechanism of spatial distribution of SiF4 and SiF2 densities in the plasma reactor are clarified.
Data Averaging Effect on Roughness Measurement using Phase-Shifting Interferometry for a Few-Ten-Angstrom and Sub-Angstrom Rough Surfaces
Authors: Jo Min-Sik , Oh Moon-Su
Published: October 2002

The phase and intensity data averaging effect on roughness measurement using phase-shifting interferometry was investigated for a few-ten-Å and sub-Å rough surfaces. For a few-ten-Å rough surface, the roughness value did not depend on the data average. In contrast, the sub-Å rough surface determination was strongly influenced by the data average so that measurement error was significantly improved as the number of data averages increased. As an optimal data average condition that the measurement noise was minimized, 30 phase data and 20 intensity data averages were experimentally determined. Sub-Å roughness measurement under the optimal data average condition had high measurement accuracy of the absolute roughness and small measurement reproducibility error.
Cross-Sectional Elastic Imaging of Arterial Wall Using Intravascular Ultrasonography
Authors: Hitoshi Mita Hitoshi Mita , Hiroshi Kanai Hiroshi Kanai , Yoshiro Koiwa Yoshiro Koiwa , Masataka Ichiki Masataka Ichiki , Fumiaki Tezuka Fumiaki Tezuka
Published: October 2002

There have been several studies on the imaging of the distribution of the elasticity of the arterial wall using intravascular ultrasonography (IVUS). In those studies, the elasticity is estimated only during ventricular diastole. However, the viscous characteristics of the smooth muscle in the media of the arterial wall are also included in the strain measured during diastole. Alternatively, during systole, the smooth muscle has an almost purely elastic characteristic. However, the IVUS probe moves greatly due to the arrival of the pulsatile wave at the beginning of the ejection period. Therefore, in this paper, we propose a method to compensate for the movement of the IVUS probe in order to precisely measure the regional change in thickness of the arterial wall during one cardiac cycle. Basic experiments using a silicone rubber tube, in which pulsatile flow is generated by an artificial heart, determined the two-dimensional (2-D) distribution of the regional change in thickness and the elasticity. The obtained incremental elastic modulus coincides with that determined by the static pressure-strain test. Furthermore, in an in vitro experiment performed on an extracted human iliac artery, the 2-D distribution of elasticity is obtained and compared with pathological results.
Advantages of AlN/GaN Metal Insulator Semiconductor Field Effect Transistor using Wet Chemical Etching with Hot Phosphoric Acid
Authors: Ide Toshihide , Shimizu Mitsuaki , Suzuki Akira , Shen Xu-Qiang , Okumura Hajime , Nemoto Toshio
Published: October 2002

An AlN/GaN metal insulator semiconductor field effect transistor (MISFET) was fabricated using a technique of wet chemical etching with hot phosphoric acid. This technique improved ohmic contact resistances for the source and drain, and provided a new and simple fabrication process for the MISFET. In our MISFET with a 3 µm gate length, a maximum transconductance (g
m max) of 130 mS/mm and a maximum drain current (I
D max) of over 600 mA/mm were obtained. We also fabricated the AlGaN/GaN heterostructure field effect transistor (HFET) with the conventional fabrication process and compared the operating characteristics.