bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of RcsF in Signaling to the Rcs Phosphorelay Pathway inEscherichia coli
Authors: Majdalani Nadim , Heck Michael , Stout Valerie , Gottesman Susan
Published: September 2005

Thercsphosphorelay pathway components were originally identified as regulators of capsule synthesis. In addition to the transmembrane sensor kinase RcsC, the RcsA coregulator, and the response regulator RcsB, two new components have been characterized, RcsD and RcsF. RcsD, the product of theyojNgene, now renamedrcsD, acts as a phosphorelay between RcsC and RcsB. Transcription of genes for capsule synthesis (cps) requires both RcsA and RcsB; transcription of other promoters, including that for the small RNA RprA, requires only RcsB. RcsF was described as an alternative sensor kinase for RcsB. We have examined the role of RcsF in the activation of both therprAandcpspromoters. We find that a number of signals that lead to activation of the phosphorelay require both RcsF and RcsC; epistasis experiments place RcsF upstream of RcsC. The RcsF sequence is characteristic of lipoproteins, consistent with a role in sensing cell surface perturbation and transmitting this signal to RcsC. Activation of RcsF does not require increased transcription of the gene, suggesting that modification of the RcsF protein may act as an activating signal. Signals from RcsC require RcsD to activate RcsB. Sequencing of anrcsCallele,rcsC137, that leads to high-level constitutive expression of bothcpsandrprAsuggests that the response regulator domain of RcsC plays a role in negatively regulating the kinase activity of RcsC. The phosphorelay and the variation in the activation mechanism (dependent upon or independent of RcsA) provide multiple steps for modulating the output from this system.
Crystal Structure of Tetrameric Homoisocitrate Dehydrogenase from an Extreme Thermophile,
Thermus thermophilus
: Involvement of Hydrophobic Dimer-Dimer Interaction in Extremely High Thermotolerance
Authors: Miyazaki Junichi , Asada Kuniko , Fushinobu Shinya , Kuzuyama Tomohisa , Nishiyama Makoto
Published: September 2005

The crystal structure of homoisocitrate dehydrogenase involved in lysine biosynthesis from
Thermus thermophilus
(TtHICDH) was determined at 1.85-Å resolution. Arg85, which was shown to be a determinant for substrate specificity in our previous study, is positioned close to the putative substrate binding site and interacts with Glu122. Glu122 is highly conserved in the equivalent position in the primary sequence of ICDH and archaeal 3-isopropylmalate dehydrogenase (IPMDH) but interacts with main- and side-chain atoms in the same domain in those paralogs. In addition, a conserved Tyr residue (Tyr125 in TtHICDH) which extends its side chain toward a substrate and thus has a catalytic function in the related β-decarboxylating dehydrogenases, is flipped out of the substrate-binding site. These results suggest the possibility that the conformation of the region containing Glu122-Tyr125 is changed upon substrate binding in TtHICDH. The crystal structure of TtHICDH also reveals that the arm region is involved in tetramer formation via hydrophobic interactions and might be responsible for the high thermotolerance. Mutation of Val135, located in the dimer-dimer interface and involved in the hydrophobic interaction, to Met alters the enzyme to a dimer (probably due to steric perturbation) and markedly decreases the thermal inactivation temperature. Both the crystal structure and the mutation analysis indicate that tetramer formation is involved in the extremely high thermotolerance of TtHICDH.
A Metabolic Enzyme as a Primary Virulence Factor ofMycoplasma mycoidessubsp.mycoidesSmall Colony
Authors: Pilo Paola , Vilei Edy M. , Peterhans Ernst , Bonvin-Klotz Laetitia , Stoffel Michael H. , Dobbelaere Dirk , Frey Joachim
Published: September 2005

During evolution, pathogenic bacteria have developed complex interactions with their hosts. This has frequently involved the acquisition of virulence factors on pathogenicity islands, plasmids, transposons, or prophages, allowing them to colonize, survive, and replicate within the host. In contrast,Mycoplasmaspecies, the smallest self-replicating organisms, have regressively evolved from gram-positive bacteria by reduction of the genome to a minimal size, with the consequence that they have economized their genetic resources. Hence, pathogenicMycoplasmaspecies lack typical primary virulence factors such as toxins, cytolysins, and invasins. Consequently, little is known how pathogenicMycoplasmaspecies cause host cell damage, inflammation, and disease. Here we identify a novel primary virulence determinant inMycoplasma mycoidessubsp.mycoidesSmall Colony (SC), which causes host cell injury. This virulence factor, released in significant amounts in the presence of glycerol in the growth medium, consists of toxic by-products such as H2O2formed byl-α-glycerophosphate oxidase (GlpO), a membrane-located enzyme that is involved in the metabolism of glycerol. When embryonic calf nasal epithelial cells are infected withM. mycoidessubsp.mycoidesSC in the presence of physiological amounts of glycerol, H2O2is released inside the cells prior to cell death. This process can be inhibited with monospecific anti-GlpO antibodies.
Novel
nirK
Cluster Genes in
Nitrosomonas europaea
Are Required for NirK-Dependent Tolerance to Nitrite
Authors: Beaumont Hubertus J. E. , Lens Sylvia I. , Westerhoff Hans V. , van Spanning Rob J. M.
Published: September 2005

Nitrite reductase (NirK) of
Nitrosomonas europaea
confers tolerance to nitrite (NO
2
−
). The
nirK
gene is clustered with three genes of unknown physiological function:
ncgABC
. At present, this organization is unique to nitrifying bacteria. Here we report that the
ncgABC
gene products facilitate NirK-dependent NO
2
−
tolerance by reversing the negative physiological effect that is associated with the activity of NirK in their absence. We hypothesize that the
ncg
gene products are involved in the detoxification of nitric oxide that is produced by NirK.
Regulation of
sigL
Expression by the Catabolite Control Protein CcpA Involves a Roadblock Mechanism in
Bacillus subtilis
: Potential Connection between Carbon and Nitrogen Metabolism
Authors: Choi Soo-Keun , Saier Milton H.
Published: September 2005

A catabolite-responsive element (CRE), a binding site for the CcpA transcription factor, was identified within the
sigL
structural gene encoding σ
L
in
Bacillus subtilis
. We show that CcpA binds to this CRE to regulate
sigL
expression by a “roadblock” mechanism and that this mechanism in part accounts for catabolite repression of σ
L
-directed
levD
operon expression.
ASSOCIATIVE CONVOLUTIONS ARISING FROM CONDITIONALLY FREE CONVOLUTION
Authors: KRYSTEK ANNA DOROTA , WOJAKOWSKI ŁUKASZ JAN
Published: September 2005

We define two families of deformations of probability measures depending on the second free cumulants and the corresponding new associative convolutions arising from the conditionally free convolution. These deformations do not commute with dilation of measures, which means that the limit theorems cannot be obtained as a direct application of the theorems for the conditionally free case. We calculate the general form of the central and Poisson limit theorems. We also find the explicit form for three important examples.
Three-Dimensional Micro- and Nano-Fabrication in Transparent Materials by Femtosecond Laser
Authors: Shimotsuma Yasuhiko , Hirao Kazuyuki , Kazansky Peter G. , Qiu Jiarong
Published: September 2005

Femtosecond pulsed lasers have been widely used for materials microprocessing. Due to their ultrashort pulse width and ultrahigh light intensity, the process is generally characterized by the nonthermal diffusion process. We observed various induced microstructures such as refractive-index-changed structures, color center defects, microvoids and microcracks in transparent materials (e.g., glasses after the femtosecond laser irradiation), and discussed the possible applications of the microstructures in the fabrication of various micro optical devices [e.g., optical waveguides, microgratings, microlenses, fiber attenuators, and three-dimensional (3D) optical memory]. In this paper, we review our recent research developments on single femtosecond-laser-induced nanostructures. We introduce the space-selective valence state manipulation of active ions, precipitation and control of metal nanoparticles and light polarization-dependent permanent nanostructures, and discuss the mechanisms and possible applications of the observed phenomena.
Foundry Metal–Oxide–Semiconductor Field-Effect-Transistor Electrometer for Single-Electron Detection
Authors: Clement Nicolas , Inokawa Hiroshi
Published: September 2005

A conventional metal–oxide–semiconductor field-effect-transistor (MOSFET) fabricated by a foundry complementary metal–oxide–semiconductor (CMOS) process has been investigated for use as an electrometer. The estimation of sensitivity in the linear and subthreshold regimes shows that the sensitivity of MOSFETs is comparable to that of single-electron transistors (SETs). In the experiments, charges in an island, which is electrically isolated by two MOSFETs in the “off” state and efficiently coupled to the electrometer via a floating gate, are detected sensitively. The results show clear steps in the drain current corresponding to electrons entering the island one by one, which demonstrates that conventional foundry MOSFETs have the ability to detect single electrons.
High-Power Operation of 1 cm Laser Diode Bars on Funryu Heat Sink Cooled by Fluorocarbons
Authors: Miyajima Hirofumi , Suzuki Noriyasu , Oh-ishi Satoru , Itoh Hiroaki , Kan Hirofumi , Yamanaka Masanobu , Izawa Yasukazu
Published: September 2005

We have investigated the properties of fluorocarbons as coolants for a high-power laser diode bar mounted on a funryu-jet heat sink. The thermal conductivities of fluorocarbons are about ten times lower than that of water, but they are less corrosive to the funryu copper heat sink and their boiling points may be higher than that of water. Since the cooling efficiency of such a high power laser diode (LD) bar may be a result of the dynamic viscosity, the heat capacity, the thermal resistance, and the boiling temperature of the coolant, we have compared two types of “Fluorinert”, 3M's FC77 and FC43, and water as coolants. Wavelength distributions along a 1 cm bar, operated under a 52 A driving current, are measured to be ±1.1 nm for FC77, ±2.1 nm for FC43 and ±0.6 nm for water. From their thermal and material characteristics given by 3M, the lower viscosity of FC77 is important for our funryu heat sink, which has a high flow resistance. A thermal resistance of 0.7°C/W is achieved at a flow rate of 1.0 L/min for FC77. FC77 is adopted as the coolant for CW 30 W operation and has operated continuously for over 800 h.
Ladder-Type Tunable Filter Connected by High-Diffraction-Order Ladder Interferometer for Use in Widely Tunable Laser Diodes
Authors: Jeong Seok-Hwan , Matsuo Shinji , Yoshikuni Yuzo , Segawa Toru , Ohiso Yoshitaka , Suzuki Hiroyuki
Published: September 2005

We propose and demonstrate a novel ladder-type tunable filter cascade-connected by a high-diffraction-order ladder interferometer, and discuss its potential application to a high-performance laser source having high output power and a wide tuning range. We design a novel ladder interferometric tunable filter that satisfies such essential requirements as having a narrow bandwidth for stable single longitudinal oscillation mode control together with a low insertion loss, a low wavelength-sensitive filter spectrum, a wide free-spectral range and a wide tuning range. We successfully demonstrate all of these characteristics in the fabricated device.
Low-Temperature Sintering of Microwave Dielectrics (Zn,Mg)TiO3
Authors: Hsieh Ming-Liang , Chen Lih-Shan , Wang Shu-Ming , Sun Chian-Hao , Weng Min-Hung , Houng Mau-Phon , Fu Shen-Li
Published: September 2005

Dielectrics (Zn,Mg)TiO3, having a high dielectric constant and a near zero temperature coefficient of resonant frequency are promising materials for microwave applications. In this work, Bi2O3 was added to (Zn,Mg)TiO3 as a low-temperature-sintering dopant. The addition of Bi2O3 significantly improved the densification of (Zn,Mg)TiO3, which were densified below 1000°C. In addition, the decomposition temperature of (Zn,Mg)TiO3 increased as the magnesium substitution increased. Microwave dielectric properties of (Zn,Mg)TiO3 ceramics depend on crystalline structure. By properly adjusting the amount of magnesium, a small temperature coefficient of resonant frequency was obtained for (Zn,Mg)TiO3 dielectrics.
Role of Dielectrics in Discharge Voltage Decrease
Authors: El-Koramy Reda A.
Published: September 2005

A brief review is given on the role of dielectrics in gas discharge processes. Attention is focused on the key features of the charging mechanism of dielectric films on electrode surfaces and the subsequent breakdown of the discharge. It is experimentally shown that the explosion of surface dielectric films plays a decisive role in discharge voltage decrease. This is a direct result of the electric field distortion between the electrodes due to the accumulation of volume charge.
Epitaxial Pt Films with Different Orientations Grown on (100)Si Substrates by RF Magnetron Sputtering
Authors: Okamoto Shoji , Watanabe Takayuki , Akiyama Kensuke , Kaneko Satoru , Funakubo Hiroshi , Horita Susumu
Published: September 2005

Epitaxial Pt films with (111) and (100) orientations were grown on Y2O3-stabilized ZrO2 (YSZ)-covered (100)Si substrates by RF sputtering. (111)Pt films were epitaxially grown on (100)YSZ∥(100)Si substrates at 580 and 680°C, but competitive crystal orientations of (111) and (100) at 780°C. In contrast, a (100)-oriented epitaxial Pt film was grown at 550°C on a (100)YSZ∥(100)Si substrate with a (100)-oriented epitaxial (100)Ir buffer layer. This orientational control of epitaxial Pt films enables the epitaxial growth of perovskite layers with different orientations on thermally and chemically stable Pt bottom electrodes grown on (100)Si substrates.
High Quality Microwave Zr0.8Sn0.2TiO4 Dielectric Thin Film Prepared by Sol–Gel Method
Authors: Ho Yung-Shou , Weng Min-Hang , Wang Shuen-Shian
Published: September 2005

High-quality zirconium tin titanate (Zr0.8Sn0.2TiO4, ZST) thin films are deposited along the (100) plane on a p-type Si substrate by the sol–gel method. The effects of two different heat treatment temperatures, 250 and 450°C, for organic burn-out between each spin coating on the crystal structure, morphology, roughness and thickness of the films are investigated. X-ray diffraction confirms a pronounced preferred orientation in thinner films and a polycrystalline structure in thicker films. Microstructure analyses by scanning electronic microscopy (SEM) and atomic force microscopy (AFM) prove that a high-quality ZST film approximately 75 nm thick with a smooth surface (surface roughness of 4 nm) is obtained under suitable processing conditions.
Performance of Prototype Liquid Xenon Scintillation Detector System for Time-of-Flight Type Positron Emission Tomography with Improved Photomultipliers
Authors: Nishikido Fumihiko , Doke Tadayoshi , Kikuchi Jun , Mori Toshinori , Murayama Hideo , Ooshita Tatsuro , Takahashi Hidehiro
Published: September 2005

The properties of liquid Xe are considered to be advantageous for application to time-of-flight positron emission tomography (TOF-PET). Previously, we constructed a prototype liquid Xe TOF-PET detector using photomultiplier tubes (PMTs), which can operate at liquid xenon temperature, and investigated their performance. Their poor quantum efficiency and low gain, however, were not sufficient for use in TOF-PET. Recently, new PMTs with five times higher quantum efficiency in liquid Xe and ten times higher gain than the previous PMTs have been developed by Hamamatsu Photonics Co. The prototype PET detectors, presented here, were constructed using these new PMTs and tested. An energy resolution of 15.9% (FWHM), a position resolution of 2.1–3.5 mm (FWHM), and a timing resolution of 260 ps (FWHM) were achieved.
Aluminum Implantation in Kapton® for Space Applications: Magnetic Field Effects on Implantation in Vacuum Arcs
Authors: Tan Ing Hwie , Ueda Mario , Dallaqua Renato , Rossi José Osvaldo , Beloto Antonio Fernando , Demarquette Nicole Raymonde , Gengembre Leon
Published: September 2005

Aluminum was implanted in samples of Kapton®, a polyimide commonly used in spacecrafts, in order to form a protective layer against degradation by atomic oxygen, abundant in space. Implantation was carried out in a vacuum-arc-generated aluminum plasma, with and without the presence of a confining magnetic field. The main effect of the magnetic field is to increase plasma density by two orders of magnitude and, as a result, the dielectric Kapton® sample should charge much faster than in the unmagnetized case. Implantation depths should therefore be larger in the unmagnetized case. Results of X-ray Photoelectron Spectroscopy depth profile analysis, however, showed similiar implantation depths in both cases, with magnetized samples having a slightly deeper and larger mixing layer. Possible mechanisms to explain this result are discussed. Both treatments resulted in an excellent protective layer as demonstrated by samples exposed to oxygen plasmas, adhesion, thermal cycling, transmission and reflectance tests.
Photoexcited-Charge Transfer and Energy–Storage Reaction of Photorechargeable TiO2/Carbon Fibers Composite Electrodes
Authors: Nomiyama Teruaki , Takeuchi Hideki , Kawazoe Kouji , Horie Yuji , Miyazaki Tomoyuki
Published: September 2005

A TiO2/carbon fibers (CFs) composite electrode is a solar device that converts photon energy to electrochemical energy and stores it in situ. The photoexcited-charge transfer and energy–storage reaction were studied. The results of photoelectrochemical measurements showed that the photoexcited electrons generated in TiO2 moved to CFs via ohmic contact. From a frequency response analysis of the electrochemical impedance, it was found that the electrical energy storage was realized by the formation of lithiated carbons at the CFs side. Since a large time constant was observed in the time variation of photo-emf, it was concluded that the low formation rate of lithiated carbons was one of the causes of small photocharged quantities.
Correlation of Mutual Viscosity and NMR Spin–Lattice Relaxation Time with Dielectric Relaxation Time in some Benzaldehydes
Authors: Singh Ajay Kumar , Mehrotra Nand K.
Published: September 2005

Present communication reports on the experimental values of NMR spin–lattice relaxation time (T1) of 3-hydroxy, 4-methoxy benzaldehyde, 4-hydroxy, 3-methoxy benzaldehyde,o-nitrobenzaldehyde,o-hydroxy benzaldehyde andp-chlorobenzaldehyde and Mutual viscosity (η12) ofo-chlorobenzaldehyde,m-chlorobenzaldehyde andp-chlorobenzaldehyde. The experimental values ofT1have been correlated with the calculated values ofT1obtained using various equations of the dielectric relaxation time (τ). It has been concluded that the equations of Writz and Murty are better representations of the dielectric relaxation phenomenon. From the correlation of τ and η1it has been found that the coefficient of mutual viscosity (η12) is a better representation of the hindrance to the rotation of the individual solute molecules.
Technique for Measurements of Elastic Wave Velocities and Thickness of Solid Plate from Access on Only One Side
Authors: Kim Young H. , Song Sung-Jin , Lee Jeong-Ki
Published: September 2005

A novel method is proposed for the simultaneous measurement of longitudinal and transverse wave velocities and the thickness of isotropic solid plates from access on only one side. Line contact transducers were placed on the same side of the specimen, and waveforms were acquired at various distances between the transducers. Longitudinal wave velocity and the thickness of the specimen can be simultaneously determined from the relationship between the transit time of the longitudinal wave mode and the ultrasonic beam path. A least-squares fitting method was employed to increase the accuracy of measurements. Transverse wave velocity also can be determined from the transit time of the mode-converted transverse wave and the corresponding beam path determined by Snell's law. Experimental results for several specimens of different materials as well as different thicknesses show good agreement with those measured by conventional methods.
Experimental Verification of Velocity Bunching via Shot-by-Shot Measurement at S-Band Photoinjector and Linac
Authors: Iijima Hokuto , Uesaka Mitsuru , Sakamoto Fumito , Ueda Toru , Kumagai Noritaka , Serafini Luca
Published: September 2005

We present an experimental verification of a bunch compression method named “velocity bunching”. Velocity bunching based on the rectilinear compression uses a traveling wave accelerating tube as a compressor. The experiment was performed using an S-band photoinjector and a linac at the Nuclear Engineering Research Laboratory, University of Tokyo. The shot-by-shot bunch length was measured to be 0.5±0.1 ps (rms) on average using a femtosecond streak camera at a bunch charge of 1 nC. The experimental result is in good agreement with the PARMELA simulation result.
Selective Epitaxial Growth for Buried Microchannels in Monocrystalline Silicon
Authors: Denoual Matthieu , Sagazan Olivier De , Guilloux-Viry Martine , Gaudin Denis
Published: September 2005

A simple and single-step technique is presented for the formation of buried channels in monocrystalline silicon wafers. The channels are formed by surface migration of silicon during the selective epitaxial growth of monocrystalline silicon. Various buried-channel shapes and sizes from 1 to 30 µm were formed. This technique is compatible with semiconductor industry processes and allows postprocessing for the integration of microelectronics circuits. The applications targeting heat pipes for integrated circuits or microfluidic channels for microsystems are numerous and promising.
Preparation of Room-Temperature Photoluminescent Nanoparticles by Ultrafast Laser Processing of Single-Crystalline Ge
Authors: Jeoung Sae Chae , Kim Hyun Sun , Park Myung-Il , Lee Jonggoo , Kim Chang Soo , Park Chong-Ook
Published: September 2005

A nanostructured germanium surface was prepared by irradiating single-crystalline Ge with femtosecond laser pulses under an ambient condition. The processed samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction, and Raman spectroscopy. The results have demonstrated that the processed area contains small, nanosized particles attached to microstructures. Photoluminescence in the visible region as well as asymmetric broadening of the Raman spectral feature and its downward peak shift were observed from the processed Ge surface. Our approach can be applied to pattern photoluminescent Ge nanostructures with a spatial resolution of what?
Scanning Near-Field Optical Microscopic Observation of Surface-Enhanced Raman Scattering Mediated by Metallic Particle-Surface Gap Modes
Authors: Hayashi Shinji , Konishi Toshitaka
Published: September 2005

Samples consisting of a copper phthalocyanine (CuPc) thin film sandwiched between Au particles and a Ag film were prepared and their Raman scattering was investigated with a scanning near-field optical microscope (SNOM). The Raman intensity of CuPc was found to be greatly enhanced by the presence of the Au particles and takes a maximum on top of the particles. It was also found that the enhancement factor depends strongly on the diameter of Au particles and the excitation wavelength. With the aid of reflection-absorption spectra, which exhibited an absorption peak attributable to the gap mode of the particle–surface system, the observed behavior of the enhancement factor could be explained by the resonance of incident and scattered light to the gap mode. The present results clearly demonstrate that the gap between the metallic particle and surface is a hot site of Raman scattering.
Mach–Zehnder Interferometers Composed of µ-Bends and µ-Branches in a Si Photonic Wire Waveguide
Authors: Ohno Fumiaki , Fukazawa Tatsuhiko , Baba Toshihiko
Published: September 2005

We fabricated compact Mach–Zehnder interferometers consisting of µ-branches and/or µ-couplers in a Si photonic wire waveguide. Clear interference spectra with a maximum extinction ratio of more than 20 dB and an alternating light output between two output ports were observed. A high diffraction order of 300 was also demonstrated within a small foot space of 30×20 µm2.
Dissipation Imaging with Low Amplitude off-Resonance Atomic Force Microscopy
Authors: Özer H. Özgür , O'Brien Simon J. , Norris Andrew , Sader John E. , Pethica John B.
Published: September 2005

A small amplitude non-contact atomic force microscope/scanning tunnelling microscope (nc-AFM/STM) is used to study dissipative interactions at atomic resolution on Cu(100) and Si(111) surfaces. For Cu(100) atomic resolution images of phase contrast are obtained, showing energy dissipation as high as 100 meV/cycle at each atomic site during constant tunnel current scans. In contrast, the Si(111) 7×7 surface usually did not exhibit significant phase contrast during normal STM operating conditions. However, when the driving oscillation frequency was set to a sub-harmonic of the lever resonant frequency, atomic contrast in phase could be readily observed. We believe this harmonic coupling is due to the nonlinearity of the tip-sample interaction, and at these frequencies part of the energy is dissipated via the lever Q.
Exploiting Metal Coating of Carbon Nanotubes for Scanning Tunneling Microscopy Probes
Authors: Murata Yuya , Yoshimoto Shinya , Kishida Masaru , Maeda Daisuke , Yasuda Tatsuro , Ikuno Takashi , Honda Shin-ichi , Okado Hideaki , Hobara Rei , Matsuda Iwao , Hasegawa Shuji , Oura Kenjiro , Katayama Mitsuhiro
Published: September 2005

By exploiting the metal coating of carbon nanotube (CNT) tips for a scanning tunneling microscope (STM), we demonstrated atomic imaging/spectroscopy and showed their potential for electrical nanoprobes. A CNT glued to a W tip was uniformly coated with a thin W layer 3–6 nm thick. Using this tip, stable atomic imaging and spectroscopy were carried out on clean Si(111)-7×7 and Si(100)-2×1 surfaces. The mechanical flexibility of the coated CNT was maintained by virtue of the thin-layer coating, enabling repeated direct contact to the sample surface. Two W-coated CNT tips were brought together within a distance of approximately 50 nm. These results indicate that the tips are useful for electronic transport measurements on a nanometer scale after installation into a multiprobe STM.
Alkyl-Chain-Length Dependence of Frictional Properties of Alkyl-Substituted Phthalocyanines Physisorbed on Graphite Surfaces
Authors: Miyake Koji , Hori Yukari , Ikeda Taichi , Asakawa Masumi , Shimizu Toshimi , Ishida Takao , Sasaki Shinya
Published: September 2005

The frictional properties of alkyl-substituted phthalocyanines physisorbed on a graphite substrate are investigated by atomic force microscopy. Normal load dependence of the friction force of phthalocyanine derivatives consists of two parts. One is that friction force varies approximately as a power law with an exponent of 0.6–0.7, and the other is that friction force is substantially constant. From simultaneous observation of topography and friction force, we find that a monolayer of phthalocyanine derivatives exists at the normal load below the transition point. They are completely desorbed from the surface at a load beyond the transition point. The experimental data are qualitatively explained by a simplified model, which assumes that the alkyl-substrate and alkyl-alkyl interactions are approximated by Lennard-Jones interactions.
Formation of Molecular Wires by Nanospace Polymerization of a Diacetylene Derivative Induced with a Scanning Tunneling Microscope at a Solid-Liquid Interface
Authors: Nishio Satoru , I-i Daizo , Matsuda Hiroshi , Yoshidome Masahito , Uji-i Hiroshi , Fukumura Hiroshi
Published: September 2005

A nanospace polymerization reaction was initiated using a scanning tunneling microscope in a monolayer of a diacetylene derivative, 10, 12-nonacosadiynoic acid (NCDA), at a solid-liquid interface to obtain molecular wires. The polymerization threshold with respect to the applied voltage was 2 V, which was 1 V lower than that observed at a solid-air interface. The presence of ionic species considerably enhanced the reaction probability. At more than ±2 V, the addition of N(CH3)4ClO4 resulted in the expansion of the reaction region and the increase in reaction probability regardless of the sign of the bias voltage applied. Different from the case at the solid-air interface, polymerization at the solid-liquid interface was probably induced through the multiple vibrational excitation of NCDA by repetitive collisions with charged carriers activated by the strong electric field involved in electron avalanche.
Visualization of Elasticity Distribution of Single Human Chromosomes by Scanning Probe Microscopy
Authors: Nomura Keisuke , Hoshi Osamu , Fukushi Daisuke , Ushiki Tatsuo , Haga Hisashi , Kawabata Kazushige
Published: September 2005

We succeeded in visualizing the spatial distribution of the local elasticity of mitotic human chromosomes in a liquid environment using scanning probe microscopy (SPM). Force-versus-indentation curves (force curves) were collected over an entire single chromosome. To estimate the local elasticity of thin chromosomes from the force curves, we examined the validity of a previously proposed model that takes into account the effect of the finite thickness of samples on the estimation of the local elasticity. The force curves obtained are well represented by the model within a small indentation range. The elasticity obtained is independent of the indentation within an indentation range of 100 nm. Such fitting procedures for the force curves collected are carried out over the entire chromosome, and the elasticity distribution of a single chromosome is visualized.
Prototype of Atomic Force Cantilevered SNOM Based on Through-The-Lens-Type Optical Lever and Polarized Illumination and Detection System
Authors: Ono Masayuki , Sone Hayato , Hosaka Sumio
Published: September 2005

Atomic force cantilevered scanning near-field optical microscopy (ANOM) has been proposed for observing a micromagnetic structure of a recorded magneto-optical (MO) disc. The prototype system has an ability to obtain both atomic force microscopy (AFM) and scanning near-field microscopy (SNOM) images simultaneously. This system has some special functions: (1) it keeps the sample-probe gap constant with atomic force and an AFM cantilever, (2) it generates near-field light from the small aperture formed on the tip of the cantilever, (3) it uses a polarized light in the laser beam illumination and detection systems, and (4) it adjusts laser beams incident on fixed positions of the cantilever in ANOM optics. As an experimental result, we obtained SNOM and contact mode AFM images of a commercial MO disc. We can detect a polarized plane at a minimum angle of less than 0.2 deg. and observe submicron recorded magnetic domains on a 640 MB MO disc.
Defect-Induced Charge Freezing on Epitaxial Fe3O4(001) Film Surfaces Studied by Spin-Polarized Scanning Tunneling Microscopy
Authors: Subagyo Agus , Sueoka Kazuhisa
Published: September 2005

We report the role of atom defects on the charge freezing of Fe3O4(001) surfaces studied by spin-polarized scanning tunneling microscopy (SP-STM) using a Ni tip. Epitaxially grown Fe3O4(001) films on a MgO(001) substrate were used as samples. Atomically flat surfaces are obtained by annealing in an ultrahigh vacuum and in oxygen. The surfaces exhibit a (√2×√2)R45° reconstruction as revealed by STM with a W tip. STM images indicate surface termination at B-sites. An atomic structure with a 0.3 nm periodicity is observed within the cation rows that are aligned along the [110] direction. SP-STM images show a pronouncedly different periodicity of 1.2 nm on areas having surface defects such as cation vacancies. This corrugation with a 1.2 nm periodicity can be attributed to a charge localization of Fe3+ and Fe2+ ions that are trapped by cation vacancies and then isolated from the electron hopping process. The results also indicate the important role of oxygen vacancies in modifying the 1.2 nm periodicity.
Investigation of Interaction of Hydrogen with Oxygen-Induced Nb(100) Surfaces by Scanning Tunneling Microscopy
Authors: An Bai , Zhang Lin , Wen Mao , Fukuyama Seiji , Yokogawa Kiyoshi , Yoshimura Masamichi
Published: September 2005

The structural conversions of oxygen-induced surfaces of Nb(100) are investigated during exposure to hydrogen at room temperature and subsequent heating at 640 K in ultrahigh vacuum (UHV) by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). The oxygen-adsorbed c(2×2)-O structure is gradually converted into a (1×1)-H structure with dark spots and bright clusters upon exposure to 15 L of hydrogen at room temperature, and then into a disordered structure by further exposure to 50 L of hydrogen. Such a disordered structure is changed into a (1×1) structure with line defects after continuous heating at 640 K in UHV. The oxide-covered (3×1)-O structure is not significantly altered upon exposure to 300 L of hydrogen at room temperature. The interaction of hydrogen with the oxygen-induced Nb(100) surfaces is discussed.
Intrinsic Problem Affecting Contact Hole Resolution in Hyper NA Era
Authors: Matsuura Seiji , Kurose Eiji , Fujii Kiyoshi
Published: September 2005

We studied the effects of polarization control that is expected to minimize image degradation caused by the polarization effect for various patterns. The resolution of line-and-space (L&S) patterns was most enhanced by dipole illumination under polarization control. However, the polarization control did not improve resolution in dense contacts, although this was improved by normal quadrupole illumination. Consequently, it will be difficult to achieve the same resolution in dense contacts as in L&S patterns, even when advanced illumination and polarization control are applied. The resolution gap between L&S and dense contacts may reach up to a 40 nm pitch in the 45 nm node, particularly for immersion lithography using a hyper numerical aperture. We also found that 157 nm dry/immersion lithography has an advantage over 193 nm immersion lithography from the viewpoint of resolution gaps, on the basis of the assumption that both technologies would achieve the same resolution in L&S patterns.
Full-Chip Implementation of IDEALSmile on 90-nm-Node Devices by ArF Lithography
Authors: Yamazoe Kenji , Cantú Pietro , Capetti Gianfranco , Evangelista Elena , Hasegawa Yasuo , Iwasa Junji , Toublan Olivier , Loi Sara , Lupo Marco , Pepe Annalisa , Kuno Toshihisa , Suzuki Akiyoshi , Saitoh Kenji
Published: September 2005

Contact holes are one of the most challenging features to be printed in the semiconductor manufacturing process. In 2002, Canon introduced a new technology, entitled innovative double effective-source aided lithography with single mask implemented lithographic enhancement (IDEALSmile), that was proven to be able to define contacts with high resolution and a sufficiently large through-pitch process window using a binary mask, modified illumination and single exposure, without any negative impact on throughput or any increase of cost of ownership. The technology was further improved in 2003 with the introduction of Enhanced IDEALSmile. STMicroelectronics, Mentor Graphics and Canon joined their competences to implement this technology to the production of devices. In this paper, we analyze the issues encountered and solutions developed to overcome problems raised in different areas. Experimental results are shown and compared with both expectations based on results of simulation and what is obtained by conventional approaches. Directions for future developments have been identified and are illustrated in their guidelines.
Reducing off Hydrocarbon Contaminants for EUVL
Authors: Tanaka Yuzuru , Hamamoto Kazuhiro , Tsubakino Harushige , Watanabe Takeo , Kinoshita Hiroo
Published: September 2005

An extreme ultraviolet (EUV) lithography exposure system is operated in vacuum. During irradiation by EUV light, hydrocarbons were decomposed in vacuum and the surfaces of the imaging optics and mask, which were coated with a Mo/Si multilayer, became contaminated with organic compounds. Thus, the reflectivity and resolution of athe imaging optics and the mask were reduced. In this study, we examined the rate of outgassing and the species that desorb from the structural material, such as those of the wires, the driving motor and the detector in vasuum in vacuum. The rate of outgassing for metals was found to depend on surface roughness. Because the coatings of the wires are made from organic materials, they show the largest figure outgassing rate compared with the structural metal. Furthermore, most of the desorbed hydrocarbons, which are primary contaminants, come from the wires and other components rather than from the metals used for the stages, even though the metals have a large surface area.
Deposited Energy Dependence of Surface Roughness of Polymethylmethacrylate Irradiated by Electron Beam
Authors: Kotera Masatoshi , Niu Hirohisa , Hosokawa Taro , Yagura Kei
Published: September 2005

A polymethylmethacrylate board is irradiated by an electron beam, and a spatial variation of the roughness in the cleaved cross-sectional surface below the irradiated point is observed. The equi-roughness contour of the surface almost agrees with the equi-energy-deposited contour obtained by a Monte Carlo simulation of electron trajectories. The relationship between the energy deposited and the granule size is obtained on the basis of the g-value in radiation chemistry; we find that the more the energy deposited, the smaller the granule size obtained, neglecting the roughness found around the maximum electron range. Upon changing the dose, the roughness also varies, and a variation of characteristic features is observed. The granule size expected from the energy deposited, however, gives less than 1/9 of the granule size obtained in the experiment. Although it is expected that there is a close correlation among the granule size observed by scanning electron microscope, the size of the molecule, and the local molecular weight, the quantitative correspondence is not well known. There might be some other mechanisms to explain the difference.
Resolution in New Nanofabrication Technique Combining Electron-Beam-Induced Deposition and Low-Energy Ion Milling
Authors: Mitsuishi Kazutaka , Shimojo Masayuki , Tanaka Miyoko , Takeguchi Masaki , Furuya Kazuo
Published: September 2005

A new nanofabrication technique in which the deposits fabricated by electron-beam-induced deposition (EBID) are used as masks for low-energy ion milling was performed with various masks deposited at different deposition times, and the shape changes of the W mask and GaAs substrates caused by ion milling were observed. From these results, the time evolution of the shape change of the fabricated structures was studied, and the resolution dependence of the structure to the mask size was determined. The W mask showed a lower etch rate, proving its effectiveness as a mask for ion milling. Nanostructures less than 10 nm in diameter can be fabricated by this method.
Fabrication of Alpha-Iron and Iron Carbide Nanostructures by Electron-Beam Induced Chemical Vapor Deposition and Postdeposition Heat Treatment
Authors: Takeguchi Masaki , Shimojo Masayuki , Furuya Kazuo
Published: September 2005

We succeeded in fabricating crystalline alpha-iron nanostructures with desired shapes. Electron-beam-induced chemical vapor deposition with iron carbonyl gas, Fe(CO)5, was carried out at room temperature in a field-emission-gun scanning electron microscope to fabricate nanodots, nanorods and square frames. The as-deposited structures exhibited an amorphous phase containing iron, carbon and oxygen in their entire volumes and iron oxide nanocrystals existed near their surfaces. Postdeposition heat treatment at about 600°C resulted in the formation of crystalline alpha-iron and iron carbide phases in their structures, while maintaining their shapes. Quantitative elemental analyses using electron energy loss spectroscopy suggested that the original as-deposited iron-to-carbon compositional ratio is crucial in determining the stoichiometry of the produced structures after the heat treatment.
Fabrication and Characterization of Self-Standing W-Nanodendrites on Insulator SiO2 Substrate by Electron-Beam-Induced Deposition under HVTEM
Authors: Xie Guoqiang , Song Minghui , Mitsuishi Kazutaka , Furuya Kazuo
Published: September 2005

Self-standing W-nanodendrite structures were fabricated on an insulator SiO2 substrate by electron-beam-induced deposition under a 1000 kV high-voltage transmission electron microscope (HVTEM). The growth process and as-fabricated structures were characterized by conventional and high-resolution transmission electron microscopies (CTEM and HRTEM) and X-ray energy dispersive spectroscopy (EDS). The nucleation and growth of nanodendrite structures are attributed to a mechanism involving charge-up produced on the substrate surface, and the movement of charges to and charge accumulation at the convex surface of the substrate as well as the tips of the deposits. The as-fabricated nanodendrite structures possess a high crystallinity and a high content of tungsten. The structures consist of many nanometer-scale body-centered cubic (bcc) W crystals.
Transport Properties of Pt Nanowires Fabricated by Beam-Induced Deposition
Authors: Tsukatani Yosuke , Yamasaki Naoki , Murakami Katsuhisa , Wakaya Fujio , Takai Mikio
Published: September 2005

Pt nanowires were fabricated using electron-beam (EB)- and focused-ion-beam (FIB)-induced deposition. The resistance of the EB-deposited nanowires was high (≈107Ω) as deposited and increased markedly when cooled down. The observed temperature dependence of the resistance of the EB-deposited wires indicates that the electron transport in the wires is dominated by variable range hopping (VRH). Coulomb oscillations were observed at temperatures up to ≈200 K for EB-deposited wires simultaneously with VRH. Postannealing was effective to reduce the resistance. The resistance of the FIB-deposited nanowires, in contrast, hardly depended on temperature. Positive magnetoresistance due to weak antilocalization was observed in the case of the FIB-deposited wires.
Fabrication and Evaluation of Floating Gate Memories with Surface-Nitrided Si Nanocrystals
Authors: Naito Shinya , Ueyama Tomonori , Kondo Hiroki , Sakashita Mitsuo , Sakai Akira , Ogawa Masaki , Zaima Shigeaki
Published: September 2005

A floating-gate memory with surface-nitrided Si nanocrystals buried in a SiO2 matrix has been fabricated employing radical nitridation. Si nanocrystals with a number density higher than 1×1012 cm-2 and an average grain size smaller than 6 nm have been grown using an ultrathin amorphous Si layer predeposited on the SiO2 surface. Since the radical nitridation of the formed Si nanocrystals effectively suppresses excess oxidation of nanocrystals during the control oxide formation, the Si nanocrystals have been successfully buried in the SiO2 matrix without losing their number density, grain size and fine spherical shape. Electrical properties of the floating-gate memory were also examined. A flat band voltage shift larger than 1 V, which is consistent with the number density of Si nanocrystals, was observed in capacitance–voltage measurements.
Study of Chirped Quantum Dot Superluminescent Diodes
Authors: Han Il Ki , Bae Hyung Cheol , Cho Woon Jo , Lee Jung Il , Park Hong Lee , Kim Tae Geun , Lee Joo In
Published: September 2005

Superluminescent diodes (SLDs) utilizing an InAs chirped quantum dot (QD) active layer were fabricated. The chirped QD active layer was designed as a three-stack InAs QD part with a band-gap energy of 0.95 eV and another three-stack InAs QD part with a band-gap energy of 1.03 eV. From the electroluminescence (EL) measurement of SLDs, it was observed that there were two peaks separated by 80 nm. Such separation of the two peaks was consistent with that shown in the photoluminescence curve obtained at room temperature, indicating that the chirped QD characteristics of the active layer are directly reflected on the EL spectra of SLDs. The 3 dB bandwidths of both peaks were measured a 30 nm and 37 nm.
Characteristics of Thermally Treated Quantum-Dot Infrared Photodetector
Authors: Hwang Sung Ho , Shin Jae Cheol , Song Jin Dong , Choi Won Jun , Lee Jung Il , Han Haewook , Lee Seung-Woong
Published: September 2005

We investigated the device performances for a post-growth thermally treated In0.5Ga0.5As/GaAs quantum-dot infrared detector (QDIP). Device characteristics, such as dark current, photoluminescence (PL), and photocurrent spectra, have been studied and compared for the as-grown and thermally treated QDIPs. After the thermal treatment with a SiO2 capping layer, the dark current was increased, the PL peak position was blue-shifted, and the detection wavelength was redshifted due to In/Ga interdiffusion in the quantum dot (QD) structure. Furthermore, the activation energies estimated from the integrated PL intensities agreed well with the peak positions of the photocurrent spectra.
A New Micro-Chemical Reactor Using Fluid Filters for Vertical Fluid Flow Operation
Authors: Utsumi Yuichi , Asano Toshifumi , Ukita Yoshiaki , Matsui Katsuhiro , Takeo Masahiro , Negoro Seiji
Published: September 2005

We proposed and fabricated a new chemical reactor with a vertical fluid flow operation for the environment analysis, post-genome analysis, gene diagnosis, and screening of useful materials for medicine manufacture. This reactor is characterized as a simple structure with new aspects of the vertical fluid transportation induced using a fluid filter with micro-through bores. The deep X-ray lithography process using synchrotron radiation was used for the fabrication of such a fluid filter. Computational fluid dynamics (CFD) simulation results revealed that fluid can be sustained on the surface of the fluid filter and easily transported by pneumatic operation. It was confirmed that the fluid flow velocity through the filter can be controlled by varying the loaded pressure around several kPa. It was demonstrated that the proposed chemical reactor has a good vertical fluid flow operation performance.
Biochip: Cellular Analysis by Atomic Force Microscopy Using Dielectrophoretic Manipulation
Authors: Muys James , Alkaisi M. M. , Evans J. J. , Nagase J.
Published: September 2005

Non-uniform AC electric fields generated by interdigitated microelectrode arrays have been used to manipulate and control biological cells by dielectrophoresis. This technique is incorporated on an integrated Biochip platform designed as a non-destructive system for trapping and immobilising living cells into cavities. Using dielectrophoresis-based single particle traps, cells have been directed into cavities aligned between the interdigitated electrodes by both positive and negative dielectrophoresis. The motivation for development of the Biochip is to analyse the cell structure in response to various stimuli by atomic force microscopy.