Table of contents

This paper reports selected recent topics in high-T_c superconductive electronics. Improved process technology for high-T_c digital electronics, the development of a sampling oscilloscope, magnetic immunoassay using a high-T_c superconducting quantum interference device (SQUID), scanning laser-SQUID for integrated circuits testing, terahertz radiation from high-T_c superconductors, and optical control of vortices are reviewed.

We propose a new extraction method for mobility limited by high-k dielectrics, and discuss the scattering mechanism for halfnium aluminate (HfAlO_x) in the strong inversion region. In our method, mobility degradation properties are evaluated as a function of interfacial SiO₂ thickness. The temperature dependence of the mobility in the strong inversion region is analyzed with the expression 1/µ=1/µ_Rexp (-2k_FT_int)+1/µ_SiO2/Si, where µ is the measured mobility, µ_R is the prefactor mobility limited by a high-k dielectric, k_F is the Fermi wavenumber of the channel carriers, T_int is the thickness of the interfacial SiO₂ layer, and µ_SiO2/Si is the mobility for n⁺poly-Si/SiO₂ n-channel metal–oxide–semiconductor field-effect transistors (MOSFETs). This analysis method is applied to n⁺poly-Si/HfAlO_x [Hf/(Hf+Al)=60 at. %]/SiO₂/p-Si n-channel MOSFETs. It is found that the mobility limited by the HfAlO_x film, µ_R, decreases with a temperature increase in the range of 77–297 K. This temperature dependence indicates the predominance of non-Coulomb scattering for the mobility limited by HfAlO_x in the strong inversion region. The mobility due to the non-Coulomb scattering shows a weak temperature dependence that is explainable by surface optical phonons (i.e., those appearing at the Si-surface channel region due to the longitudinal-optical (LO) modes of HfAlO_x) with the corresponding transverse-optical (TO) phonon energy in the range of 10–20 meV.

The effect of nitrogen (N) on diffusion in silicon oxynitride was investigated through the simulation of silicon oxynitridation. We assumed that the incorporation of N reduces the SiO diffusivity in SiO₂ because oxynitride layers retard B penetration, or B diffusion, which is enhanced by SiO. In order to validate this assumption, we simulated the thickness of thermally grown oxynitride. The simulation was based on our oxidation model in which SiO molecules emitted to the oxide during oxidation modulate the oxidation rate. The assumption that the SiO diffusivity exponentially decreases with increasing N concentration was introduced to our oxidation model. The simulation results fit the experimental oxynitride thickness, and this indicates the validity of our assumption of the N effect on diffusion. During oxynitridation, the diffusion of SiO molecules generated at the interface is strongly retarded by the N atoms, which are incorporated and piled up at the interface. This retardation increases the SiO concentration in SiO₂ near the interface as oxynitridation proceeds, which decreases the oxynitridation rate with time. The formation of Si₃≡N bonds, which should block the reconstruction of Si–O bonds, is most likely the cause of the retardation of SiO diffusion in SiO₂.

A distinguishing property of copper impurities in silicon is their very fast diffusivity, which is undesirable in silicon device processes. This paper is the first attempt to simulate the fast diffusion of Cu by first-principles calculations. It is shown that, even near room temperature, the amplitude of Cu vibrations is very large; this is a consequence of the fact that the local mode of Cu has very low frequencies. At T>1000 K, the simulations demonstrate clear migration between adjacent cells. The diffusion path is from an interstitial T site to the next T site through an H site. The Arrhenius plot of the calculated diffusion constants agrees with the experimental data on the intrinsic diffusion of Cu, which are currently most reliable data available.

TiCl₄-based chemical vapor deposition (CVD) of TiN films was studied for the application of the top electrode of TiN/Ta₂O₅/TiN metal–insulator–metal (MIM) capacitors in embedded dynamic random-access memories (eDRAMs). In order to achieve a low level of capacitor leakage current, TiN-CVD at low deposition temperatures of 450°C or less was effective. At such low deposition temperatures, the resistivity of the TiN films increased rapidly as the film thickness decreased. On the other hand, the density of the anomalous growth substances on the TiN film surfaces was higher for the thicker TiN films. We clarified that these two problems were simultaneously unsolvable by means of the usual TiCl₄-based TiN-CVD method. In order to avoid the appearance of these phenomena, we applied the divided TiN deposition method to the top electrode formation of the MIM capacitors. This method consists of several repetitions of the deposition step and a subsequent NH₃ annealing step. The low film resistivity (∼1800 µΩ cm) and the low capacitor leakage current were achieved without the anomalous growth by using the divided deposition method at 350°C. It is expected to be a promising method for the top electrode formation of MIM capacitor structures of the eDRAMs.

The effects of various slurry manufacturing conditions, such as suspension pH, abrasive contents, and the calcination temperature of abrasive ceramic particles on the formation of agglomerated large particles of ceria slurry were investigated. The agglomerated large particles in slurry have much influence on the micro-scratches on the wafer surface in shallow trench isolation chemical mechanical polishing (STI CMP). The formation of large agglomerated particles is affected by the conformation of the organic additives in the slurry as a function of the suspension pH and the specific surface area of the abrasive particle. Regarding the solid content, abrasive particles are more easily dispersed at lower solid loading, which prevents additional agglomeration even under acidic conditions. The influence of agglomerated large particles on STI CMP was investigated through a polishing experiment with plasma-enhanced tetra-ethyl-ortho-silicate (PETEOS) and a low-pressure chemical vapor deposition (LPCVD) nitride layer.

In this work, low temperature growth of GaAs epitaxial layers on Ge substrates by metalorganic vapor phase epitaxy has been studied. The experiments show that a growth temperature of 530°C and a V/III ratio of 3.5 result in smooth GaAs surfaces. Atomic force micrographs do not show any anti-phase boundaries on the surface of GaAs grown on a misoriented substrate. X-ray diffraction curves show that the layer tilt is reduced as the growth temperature is lowered. Synchrotron X-ray topography reveals very low threading dislocation densities of 300 cm^-2 for the GaAs epitaxial layers. Additionally, no misfit dislocations are observed. If a single layer is deposited at low temperature, secondary ion mass spectrometry shows a considerably reduced arsenic diffusion into Ge. When an additional layer is deposited at higher temperature on top of the initial low temperature layer, a substantial increase for the deep concentration-dependent arsenic diffusion is found.

We have deposited amorphous silicon thin films from monosilane (SiH₄) gas by photochemical vapor deposition using a vacuum ultraviolet excimer lamp (VUV-CVD). We used an argon excimer lamp (λ=126 nm, hν=9.8 eV) whose photons are strongly absorbed by SiH₄ gas. The substrate temperatures were changed from 25 to 300°C. When the temperature was lower than 150°C, the films included H–Si–H units and H₂ molecules in its structure. When it was higher than 150°C, the main structural unit was Si–H.

RF diamond transistors have been developed on a hydrogen-terminated surface conductive layer. f_T and f_max of 23 and 25 GHz, respectively, have been achieved in a diamond MISFET with a 0.2 µm gate length. Utilizing de-embedding and small-signal equivalent circuit analysis, parasitic components are extracted. The intrinsic f_T and f_max of the 0.2-µm-gate diamond MISFET are estimated to be 26 and 36 GHz, respectively. In this report, some of the challenging steps in device fabrication processes such as the development of a low-resistivity ohmic layer, a high-quality gate insulator and acceptor density control technology, toward high-power and high-frequency diamond transistors with high reliability, are introduced.

A CuInSe₂ (CIS) thin film was electrodeposited (ED) on a Au-coated plastic substrate using an aqueous acidic solution containing 1 mM CuCl₂, 5 mM InCl₃, 1 mM SeO₂ and 1 M triethanolamine (TEA) adjusted to pH 1.65. With this new technology, the quality of ED-CIS thin film can be suitably improved with 0.1 M Na citrate to control the growth solution. The composition of the CIS thin film was "Cu:In:Se=25.6%:25.0%:49.4%" prepared at -1.5 V (SCE) after annealing at 150°C for 1 h in a N₂ atmosphere. Neither the CIS thin film nor the plastic substrate was found to have cracked after the heat treatment. The ED-CIS thin-film quality demonstrates its potential in the fabrication of a flexible CIS-based solar cell.

Hydrogen-terminated (111)Si was treated by Zn-contained hydrogen plasma at low temperatures ranging from 200–500°C prior to ZnO growth at 400°C by plasma-assisted epitaxy using oxygen gas plasma excited by rf-power at 13.56 MHz. Spot pattern corresponding to c-ZnO surface was observed by reflection high-energy electron diffraction from the layer grown on the Si treated by Zn-contained hydrogen gas plasma at 500°C, in contrast to the ring-pattern from the layers on the Si non-treated or treated at lower temperatures. Optoelectronic property was significantly improved by the surface treatment at 500°C, because the photoluminescence spectra of the ZnO layers grown on the Si treated at 500°C showed strong and sharp bandedge emissions due to bound exciton accompanied with free-exciton emission without significant deep-level emissions at 10 K, while the weak bandedge emissions and green emission due to deep level can be observed from the layers on the substrates non-treated or treated below 400°C in the plasma.

Spherical Si solar cells are fabricated using polycrystalline Si spheres with a diameter of 1 mm produced by a high-speed dropping method. The distribution and types of electrically active defects in spherical Si solar cells have been directly characterized using electron-beam-induced current (EBIC) and transmission electron microscopy (TEM). Many recombination sink areas in grains and grain boundaries can be directly observed with EBIC in low-efficiency cells. The electrically active defects in grains are stronger recombination sinks than grain boundaries. The electrically active defect areas confirmed using EBIC were selectively etched with a Dash etching solution. TEM images revealed that the area showed a high dislocation density. These results suggest that the dislocations in grains deteriorate the performance of spherical Si solar cells.

Experimental and theoretical characteristics of sub-terahertz and terahertz oscillations in resonant tunneling diodes (RTDs) integrated with slot antennas are reported. In the experiments, oscillations up to 0.6 THz were obtained in GaInAs/AlAs double-barrier RTDs. The oscillation characteristics were theoretically analyzed for the total device structure including RTD and slot antenna. The equivalent circuit with all parasitic elements was taken into account for the RTD, and the actual structure of the antenna was analyzed using a three-dimensional electromagnetic simulator. The theoretical analysis was in good agreement with the measurements of oscillation frequency and output power. It was shown from the theoretical results that the RTD itself has the potential to oscillate up to 3.0 THz, and that the RTD oscillator with slot antenna is able to oscillate up to 2.8 THz if the device structure is optimized. The output power analysis showed that 90 µW at 1 THz is possible by optimizing the device structure.

The electrical properties of a split-gate-type flash cell are investigated and optimized by junction engineering to obtain a high reliability. Phosphorus implantation is conducted to form a cell source junction, and the following three different anneal conditions change voltage coupling ratio between the source and the floating gate. As the ratio increases, it is observed that program characteristic is improved and endurance property is degraded, which matches well with simulation result. Therefore, cells in the pure N₂ group are considered to be optimized cells. Optimized cells guarantee 10⁵ cycle endurance, and show excellent program disturbance and bake retention properties.

The effects of electron–electron Coulomb scattering on electron quantum transport under high electric fields in silicon metal–oxide–semiconductor field-effect transistors (MOSFETs) has been studied based on a quantum-corrected Monte Carlo and molecular dynamics simulation, where the electron–electron Coulomb interaction is split into short-range and long-range interactions. The short-range interaction is included using a molecular dynamics approach, while the long-range electron–plasmon interaction is treated in two different ways: an analytical model based on quantum mechanics, and a numerical model within semiclassical treatment. The electron velocity in the inversion layer was calculated as a function of tangential electric field using a high-resistive gate MOSFET and compared with the experimental results reported by Takagi et al., which indicated that the saturation velocity depends on surface electron concentration. The analytical model for describing the long-range interaction qualitatively agrees with the experimental results in the high electric field regime. We also evaluated the role of the plasmon scattering and short-range Coulomb scattering.

Electronic-controlled routes to chaos in a quantum-well laser diode are produced using a delayed-feedback technique. By introducing an extra delayed-feedback control term cS_n(t-τ), chaotic light output can be achieved at a relatively low bias and a small modulation depth. The interaction between external modulation and delay forms quasi-two-period routes to chaos by varying modulation amplitude b and intermittency routes to chaos by varying modulation frequency f₀. Numerical analysis and experimental results agree qualitatively.

Deep-ultraviolet (DUV) photodiodes are fabricated using tungsten carbide (WC) Schottky and Ti/WC ohmic contacts on lightly boron-doped homoepitaxial diamond thin films. The thermal stability of the electrical and optical properties of the photodiodes upon isothermal annealing at 500°C for 5 h in argon/air ambient is demonstrated. The ideality factor is improved to unity after annealing for 1 h and increases to around 1.5 after subsequent annealing for longer time periods. The leakage current for at least 30 V reverse bias is lower than 10^-14 A before and after annealing for 4 h. The photoresponsivity at 220 nm is enhanced markedly by a factor of 10³ after annealing, resulting in a DUV/visible blind ratio as large as 10⁶ at 2 V reverse bias. In addition, the effects of annealing and applied bias on decay times and photoresponse spectra are examined, respectively. These results are discussed in terms of surface modification of the initially oxidized diamond epilayer.

The surface texturing method for crystalline Si using hydrogen radicals generated by a tungsten hot filament was developed. We found that tungsten particles supplied from a tungsten filament work as an etching mask against hydrogen radicals. The surface morphology and feature size of the texture structure could be controlled by the particle deposition condition on the Si(100) surface. An inverted pyramid structure was obtained when the particle density was high, suggesting that the etching reaction induced by hydrogen radicals is anisotropic. The reflectance spectra of hydrogen-treated Si surface using this method showed a very low surface reflectance of less than 1% in the range from 200 to 900 nm without any antireflection coatings. The particles on the silicon surface can easily be removed using HF+HNO₃ solution. This method is also effective for the texturing of Si(111) wafer, having a potential for the texturing of multicrystalline silicon.

An optical technique for flow diagnostics is developed to study the slurry transport on the surface of a pad and in an inter-pad-wafer region during chemical mechanical polishing. In this paper, we show that the variations in mean gray scale and nonuniformity with the wafer and pad rotation speeds agree in trend with the existing data of removal rate and nonuniformity for a 150 mm wafer. The simulation results of wafer-scale-averaged slurry shearing stress and nonuniformity also agree in trend with the data of mean gray scale and nonuniformity for a 200 mm wafer. The present flow diagnostics technique can be further used for the optimization of slurry injection rate and injection position to simultaneously obtain a high removal rate as well as a low nonuniformity. In this paper, we also show the optimum slurry injection rate.

In this paper we report source–drain engineering for the realization of low contact resistance between CoSi₂ and p⁺ Si with low junction leakage current and low junction capacitance using laser thermal processing (LTP) and the optimization of ion implantation conditions. We first demonstrate the impact of pre-amorphization on the reduction of the contact resistivity of a CoSi₂/p⁺ deep source–drain (deep-SD) interface using laser thermal processing (LTP). A highly activated dopant profile at the CoSi₂/deep-SD interface is required to reduce the contact resistivity there. Dopant profile can be finely controlled by implanting heavy ions to preamorphize a region to the desired depth and then using an appropriate laser power to selectively melt the amorphous Si, which has a melting temperature lower than that of single-crystal Si. We can thus form a highly activated boxlike dopant profile suitable for a deep-SD by using LTP and relatively deep preamorphization. Then, we discuss how to suppress the leakage current and the capacitance of the junctions. The larger junction capacitance and junction leakage current due to the abrupt deep-SD profile can be greatly reduced by combining LTP with lower-dose, higher-energy implantation and RTA prior to preamorphization (predoping and pre-RTA) to form a graded deep-SD profile beyond the abrupt deep-SD profile and overwhelm the channel doping profile, resulting in a wide depletion layer.

We consistently performed computer fluid dynamics (CFD) analysis in a reactor (macroscale analysis) and deposition profile analysis on a submicron hole (microscale analysis) for Si low-pressure chemical vapor deposition (LPCVD). For the gaseous phase and the surface reaction of the SiH₄ source gas, we adopted the dominant reaction model, which involved two intermediates, SiH₂ and Si₂H₆, and was based on the Kleijn Model. We analyzed the fluid flow, heat transfer and chemical reactions throughout the entire batch-type reactor, and estimated the Si growth rate, gaseous species concentration, and relative contributions of SiH₄, SiH₂ and Si₂H₆ to Si growth. Moreover, the Si-filling profile on a submicron hole was predicted by topography simulation in which the parameters were the growth rate, the relative contribution and the sticking coefficient of each species. The relationship between the relative contribution of SiH₂, which has a high sticking coefficient, to Si growth and the hole-filling capability was quantitatively clarified from the results of a combination of the two analyses. The hole-filling capability at the wafer edge was deteriorated by the influence of SiH₂ gas produced in the decomposition of Si₂H₆ gas, which was diffused from outside the wafer. This effect became considerable with increasing temperature. Reducing the wafer pitch will be effective in improving the hole-filling capability because both the SiH₂ generation reaction in the region between wafers and SiH₂ gas diffusion from outside the wafer will be inhibited.

High-density plasma chemical vapor deposition (HDP-CVD) is a deposition method of current interest for the gap-filling process of the intermetal dielectric (IMD) in semiconductor circuits. We first demonstrated that hydrogen ions drift into underlying thermal oxides during HDP-CVD with a SiH₄–O₂–Ar system, and that they degrade the reliability of gate oxides. The characteristics of the oxides were investigated using secondary ion mass spectroscopy (SIMS), thermal desorption spectroscopy (TDS), and capacitance–voltage (C–V) measurements of metal–oxide–semiconductor (MOS) capacitors. The hydrogen ions that are dissociated from SiH₄ in plasma penetrate into the HDP-CVD oxides, and some of the hydrogen ions in the HDP-CVD oxides drift into the underlying thermal oxides by rf bias. The drifting hydrogen creates two chemical bonding states and generates hole trap sites in the underlying thermal oxides.

In this work, we found that employing a post deposition N₂O plasma treatment following the deposition of HfO₂ film can effectively improve the electrical characteristics of p-type channel metal–oxide–semiconductor field-effect transistors (pMOSFETs) with a HfO₂ gate stack in terms of lower gate leakage current, lower interface state density, superior subthreshold swing, higher normalized transconductance and enhanced driving current even though it had led to a slightly higher equivalent oxide thickness (EOT) value of the HfO₂ gate stack by around 0.3 nm. In order to clarify the attributes of the improvements, we used charge pumping (CP) measurement to analyze the densities of interface states and bulk traps in the HfO₂ gate stacks. The improvements are then ascribed to the higher interface quality offered by the post deposition N₂O plasma treatment. Moreover, we found that to more accurately estimate the bulk traps from the CP measurement, the leakage should be taken into account especially at low frequencies. Finally, it was found that the levels of the bulk traps and interface states can be reduced by the N₂O plasma treatment, which also helps significantly eliminate the degradation of the gate stack during the subsequent voltage stress.

The material parameters for organic low-k dielectrics usable in the damascene process were studied using two different types of polymers with similar low dielectric constants, namely, the PQ-600 thermoplastic polymer and the SiLK thermosetting polymer. The resistibility of these polymers in the damascene process was investigated through hard-mask (SiO₂) deposition, etching and chemical mechanical polishing (CMP) processes using scanning probe microscopy (SPM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and a modified edge liftoff test (m-ELT). For the PQ-600 film, damage was observed in the deposition process and dissolution of the film occurred during chemical cleaning in the etching process. On the other hand, the SiLK film was combinable with the Cu damascene process and usable as an interlayer dielectric (ILD) in one-level Cu wiring. A high glass transition temperature (T_g) and chemical resistance resulting from the thermosetting structure are considered to be the essential properties required for the desired organic low-k dielectrics. In eddition, the electrical properies of the SiLK film were investigated using a one-level test element group (TEG) formed through a single Cu damascene process. The dielectric constant of the SiLK film extracted from the Cu damascene TEG compared with that of bulk SiO₂ was reduced by 24%. The leakage current measured at 1 MV/cm between the adjoining Cu lines at the TEG pattern with a hard mask was 9.7×10^-10 A/cm², and dielectric breakdown occurred at 5.5 MV/cm.

We have developed high-speed rotating-disk chemical vapor deposition (CVD) equipment for polycrystalline silicon (poly-Si) films. This CVD equipment has an enhanced ability to reduce the boundary layer thickness at a given temperature above a wafer surface, and to suppress vapor-phase reactions. We investigated in-situ arsenic-doped poly-Si film deposition using silane (SiH₄), arsine (AsH₃) and nitrogen (N₂) in a high-speed rotating-disk CVD as functions of AsH₃ flow rate and deposition temperature. Both the deposition rate and resistivity decreased with increasing AsH₃ flow rate. A deposition rate of 120 nm/min, a resistivity of 16 mΩ·cm, a film thickness nonuniformity of ±5%, and a number of particles of less than 20 (over 200 nm in diameter) were achieved at a deposition temperature of 680°C for in-situ arsenic-doped poly-Si deposition on a 200-mm-diameter silicon (Si) wafer. Moreover, it was confirmed that the concentration of As in the poly-Si film was low at the initial stage of deposition, and that this process has a high gap filling capability in a hole of 0.18 µm width and 7 µm depth. It was also confirmed that there were conditions for a high step coverage of more than 1. These properties are inferred to be due to the adsorbed AsH₃ preventing the adsorption of SiH₄.

The device performance of AlGaN/GaN-based metal–insulator–semiconductor heterostructure field-effect transistors (MIS-HFETs) with an ultrathin (1 nm/0.5 nm) Al₂O₃/Si₃N₄ bilayer has been investigated at elevated temperatures up to 200°C. The devices exhibited excellent transconductance characteristics with high maximum transconductances and ultralow gate current leakages under reverse gate bias conduction at both room and high temperatures due to the employment of an ultrathin bilayer with large dielectric constants and the large conduction band offset between Al₂O₃ and nitrides. The excellent characteristics observed at high temperatures might indicate the very high interfacial quality between nitrides and bilayer insulator. The results in this report demonstrate that Al₂O₃/Si₃N₄ bilayer insulator is a superior candidate for nitride-based MIS-HFET devices operating at high temperatures.

In this paper, we report on the band discontinuities of the wurtzite-InN/GaN interface. X-ray photoemission spectroscopy studies reveal that the offset ratios of conduction bands and valence bands are approximately 80 and 20%, respectively. The valence band offset (0.5 eV) is close to the theoretical value determined on the basis of the density functional theory from first principle that was reported by Wei and Zunger [Appl. Phys. Lett. 69 (1996) 2719]. The photoluminescence signals of InN/GaN quantum wells were also studied. The luminescence of the wells showed a 60 meV quantum confinement shift from the bulk InN signal. The finite potential well model of quantum mechanics is used to show that this shift supports the above results.

The effects of a GaN single-crystal target (SC-GaN) of laser-ablated GaN thin films on sapphire were investigated. GaN thin films were grown on a single-crystalline c-plane sapphire substrate using the SC-GaN. Unlike the usual growth behavior in laser ablation of a sintered ceramics GaN target (CR-GaN), the rocking curves of the obtained GaN films were superimposed patterns composed of sharp and broad components. The interface between the GaN film and sapphire substrate was atomically flat and sharp. To investigate the effects of the target on the plume of a pulsed laser deposition process in detail, the plume was analyzed by Langmuir probe methods and optical emission spectroscopy (OES). The Langmuir probe results showed that the electron temperature for the plume of an SC-GaN was nearly one third of that of a CR-GaN, although the ion density in the plume of the SC-GaN was found to be greater than the ion density in that of the CR-GaN. OES data showed a significant fraction of the oxygen species in the plume of the CR-GaN. These are thought to be the primary cause of damage and/or impurity to growing films in the plume of the CR-GaN.

Nanocrystalline dilute magnetic semiconductor, Mn-doped ZnO, has been prepared by chemical route. The amorphous nature of the as-prepared sample was confirmed by X-ray diffraction analysis. Reitveld analysis of the annealed sample heated at 500°C for 30 min shows it is an anisotropic nanocrystalline phase. Transmission electron microscopy also confirms the anisotropic growth of Mn-doped ZnO. Saturation magnetization around 0.2 emu/gm has been achieved for the same sample, which is substantially higher than previously reported value. A decrease in magnetization with increasing annealing temperature is observed, which might be related to the effect of particle size.

In the silicon device process, there is a strong demand for eliminating copper contamination. Gettering of Cu by dopant atoms is a useful method for this purpose. In this paper, the gettering of Cu is theoretically studied. We have assessed the efficiency of gettering through the evaluation of the binding energies between Cu and electronic dopants and the dissociation energies. The calculated dissociation energies well describe the efficiency of various dopants, which have been found experimentally. It is shown that B and Al are the most efficient gettering centers among single dopants. The present study provides the basis for further study of the gettering mechanism and for the design of efficient gettering centers.

We have developed a novel antistatic technique for suppressing focused ion beam (FIB)-induced charging in a combined system of an FIB and a scanning electron microscope. Microprobing and FIB-assisted carbon deposition are utilized to make a current path through which FIB-induced positive charges flow to ground. The effects of our method on charge neutralization capability were investigated by measuring parameter shifts of n-channel metal–oxide–semiconductor transistors. The results showed that our method prevents parameter shifts of transistors even for high-current (nanoampere-order) FIB irradiation. We also evaluated the upper-limit resistance of the current path formed by FIB-assisted carbon deposition to prevent charging induced by a given FIB current.

Large-area p-side-down InGaN light-emitting diodes (LEDs) 1000×1000 µm² in size have been fabricated by laser lift-off (LLO). The p-side-down LEDs with different geometric patterns of n-electrodes were fabricated to investigate electrode pattern-dependent optical characteristics. The current crowding effect was observed in the large-area p-side-down InGaN LLO-LEDs. A LED with a well-designed n-electrode pattern shows a uniform distribution of light emission and a higher output power due to uniform current spreading. The output power saturation induced by the current crowding effect was investigated. In the absence of a transparent contact layer for current spreading, the n-electrode pattern has a marked influence on the current distribution and the consequent light output power of the large-area p-side-down LEDs.

A low-temperature (30–40°C), low-cost and reliable method of liquid phase deposition (LPD) has been employed to grow SiO₂ layers on GaN. The LPD process uses a supersaturated acid aqueous solution of hydrofluosilicic (H₂SiF₆) as a source liquid and an aqueous solution of boric acid (H₃BO₃) as a deposition rate controller. In this study, the LPD SiO₂ was prepared at 40°C with concentrations of H₂SiF₆ and H₃BO₃ at 0.2 and 0.01 M, respectively. The minimum interface-trap density, Dit, of a metal–insulator–semiconductor (MIS) capacitor with a structure of Al/20 nm LPD-SiO₂/n-GaN was estimated to be 8.4×10¹¹ cm^-2 V^-1. Furthermore, a MIS photodetector with a 10-nm-thick LPD-SiO₂ layer has been fabricated successfully. The dark current density was as low as 4.41×10^-6 A/cm² for an applied field of 4 MV/cm. A maximum responsivity of 0.112 A/W was observed for incident ultraviolet light of 366 nm with an intensity of 4.15 mW/cm². Defect-assisted tunneling was invoked to explain these results.

Laser performance of an InGaN edge-emitting laser using a quaternary InAlGaN electronic blocking layer is investigated. Varying the aluminum (Al) composition in InAlGaN with a fixed indium (In) value (Al:In=5:1) indicates that a lower threshold current and higher characteristic temperature (T₀) value can be obtained when the Al composition is higher than 20%. When Al=25%, the threshold current is reduced at the expense of a decreased T₀ value from 149 to 130 K when the In composition increases from 1 to 7% in a temperature range of 300–370 K. The decreased T₀ value is mainly attributed to the increase in electronic leakage current.

M-plane and A-plane ZnO films were grown on M-plane and R-plane sapphire substrates respectively. At high growth temperatures and/or VI/II ratios, ZnO grew along the direction perpendicular to the c-axis. On the other hand, at low growth temperatures and/or VI/II ratios, ZnO grew along the c-axis direction. A very smooth ZnO film was achieved on R-plane sapphire under a very low VI/II ratio condition. This was because the lateral growth was accelerated by a very strong tendency of growing along the c-axis. In contrast, on M-plane sapphire, C-plane ZnO nanorods tilted by 30° from the normal of the surface were formed under this growth condition.

The use of Raman spectroscopy to characterize strain in strained Si and strained SiGe has been widely accepted. To use Raman spectroscopy for quantitative biaxial strain measurements, the strain shift coefficient for Si–Si vibration from strained Si (b_Si–Si^StSi) and strained SiGe (b_Si–Si^StSiGe) must be known. So far, b_Si–Si^StSiGe is commonly used to calculate strain in strained Si, which may result in inaccurate strain values. In this work, we report the first direct measurement of b_Si–Si^StSi by correlating high-resolution X-ray diffraction and Raman spectroscopy, which yields a measured value of -784±4 cm^-1. We also show that the strain shift coefficient of SiGe, b_Si–Si^StSiGe, is a strong function of Ge concentration (x), and follows the empirical relation: b=-773.9-897.7x for x<0.35.

In this study, Teflon was employed as the anode buffer layer of red doped organic light-emitting diodes (OLEDs) with a 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) dopant dye and a bis(salicylidene-o-aminophenolato)-bis(8-quinolinoato)-bisgallium(III) [Ga₂(Saph)₂q₂] host. The OLEDs with the Teflon buffer layer achieved a higher efficiency than OLEDs with a copper phthalocyanine (CuPc) buffer layer. It was also found that the color purity of devices was improved due to the introduction of the Teflon buffer layer.

In this letter, we describe the electrical behavior of the GeO_x and p-type Ge interface on the basis of capacitance and conductance measurements. The primary conclusion of this work is that when the Ge surface is biased in the depletion region, the frequency response of interface traps in the lower half of the Ge band-gap is so fast that there is no significant frequency dispersion observed in the capacitance measurements over a typical frequency range of ≤ 1 MHz. As a result, the density and energy distributions of the interface traps cannot be determined by a conventional method of combined high-frequency and low-frequency capacitance measurements. Instead, a comparison of the measured capacitance with a theoretical capacitance calculated for a system with no interface traps must be conducted to obtain information on the interface traps. Furthermore, the conductance method provides information on the interface traps in the upper half of the p-type Ge band-gap.

We report the morphological evolution of a-plane GaN thin films grown on r-plane sapphire substrates by atmospheric metalorganic vapor-phase epitaxy. The surface flatness is improved under optimized growth conditions which are different from those of c-plane epitaxy. The peak-to-valley height of surface roughness is reduced from 4 to 0.8 µm when GaN is grown at 1120°C on a 40-nm-thick low-temperature GaN (LT-GaN) buffer layer, as well as at 1150°C on a 20-nm-thick LT-GaN. These samples show their highest electron mobility of 220 cm²/(V s) at an electron concentration of 1.1×10¹⁸ cm^-3 at room temperature.

Solid-state-reacted polycrystalline Nd(Ba_2-xPr_x)Cu₃O_7+δ materials have been prepared and investigated using X-ray diffraction and resistivity measurements. Our results show that Nd(Ba_2-xPr_x)Cu₃O_7+δ is a superconductor when x<0.3. The T_c depression in superconductivity of Pr at Ba sites is due to both hole filling/localization and depairing effects. The normal state conductivity undergoes a dimensional crossover from two-dimensional to three-dimensional in the frame of the variable range hopping regime. The localization length of carriers shows that Pr doping localizes carriers in the normal state and causes the T_c depression. The magnetoresistance of the samples has been investigated within the thermally activated flux creep (TAFC) and Ambegaokar and Halperin (AH) phase slip models. The pinning energy and critical current density decrease with the applied magnetic field and Pr doping. A scaling relation as a power-law dependence of pinning energy on the magnetic field has been obtained. The derived pinning energy shows that Pr doping plays the role of a weak link.

The effect of two different initial sintering routes, (1) initial sintering in the rod shape (RS) and (2) initial sintering in the tube shape (TS), has been studied especially on the critical current density (J_c) and diametric fracture strength (σ) of Bi-2223 as 10 wt % Ag bulk rod conductors from a cold isostatic pressing (CIP) process. Apart from studying J_c and σ, these rods have been characterized by X-ray diffraction (XRD), energy dispersive analysis for X-rays (EDAX) and scanning electron microscopy (SEM). These studies showed that the final Bi-2223 rods achieved using the tube shape initial sintering route (TSR) in a for shorter duration exhibit higher J_c and σ values compared with final rods prepared from the rod shape using the initial sintering route (RSR).

It is widely assumed that heat-assisted magnetic recording (HAMR) technology can further push magnetic recording technology to and beyond 1 Tb/in² in area density. However, one of the major concerns of HAMR technology is the robustness and long-term stability of its head-disk interface. In this paper, we report our efforts in answering the uncertainties of head-disk interface design and stability of HAMR systems. The investigations focuses on (a) heating-induced pressure change by air and evaporation and its possible effects to a slider's flying stability (b) a laser-induced slider's thermal protrusion and its effects to the slider's flying stability. Results suggest that, among the factors under consideration, the thermal protrusion effects are much more severe. Possible solutions on how to reduce such effects are also discussed.

We investigate the electric and magnetic properties of a benzene–vanadium complex chain [V(C₆H₆)]_∞. By performing first principles calculation based on the spin-polarized density functional theory, we find that this system shows a half metallic ferromagnetic behavior, i.e., majority-spin (spin-up) electrons have a semiconducting band gap, while minority-spin (spin-down) electrons are metallic. We suggest that this ferromagnetic order is due to a double-exchange mechanism.

c-Axis oriented face-centered-tetragonal (fct)-FePt magnetic nanoparticles are a promising candidate for high density perpendicular magnetic recording media. In this study, TiN was investigated as a seed layer to achieve c-axis orientation of fct-FePt nanoparticles. First, a (200)-oriented, polycrystalline TiN layer with grain size around 10 nm was prepared by reactive sputter-deposition at 873 K on SiO₂, and then FePt was sputter-deposited at 973 K on it. Both in-plane and out-of-plane X-ray diffraction revealed that FePt had fct structure with c-axis orientation. Plan-view field emission scanning electron microscopy showed that FePt formed well-isolated nanoparticles. The particle diameter increased with increasing nominal thickness of FePt, and it was similar to the size of the TiN grains when nominal thickness was 1.4 nm. Cross-sectional transmission electron microscope images indicated that single FePt nanoparticles grew on single TiN grains, namely, one nanoparticle per grain, with an epitaxial relationship. Superconducting quantum inference device measurement at 300 K revealed that the FePt nanoparticles had coercivity of 6.2 and 0.8 kOe for the out-of-plane and in-plane directions, respectively. The FePt nanoparticle monolayer sputter-deposited on polycrystalline TiN seed layer is a promising candidate for perpendicular magnetic recording media.

The slow group-velocity femtosecond autosolitons in a dispersion flattened fiber are investigated, in which there is no third-order dispersion and there is no fourth-order dispersion. When the femtosecond pulse velocity is reduced to 50% of the normal group velocity, the analytical solutions of the bright and dark solitons are found. The magnitude of the fourth-order dispersion parameter is related to the high-order nonlinearity coefficient. The peak power and period of the solitons are determined by the magnitude of the fourth-order dispersion parameter and high-order nonlinearity coefficient.

The effect of the introduction of polymer cholesteric liquid crystal (PCLC) films on the threshold of dye-doped cholesteric liquid crystal (CLC) distributed feedback (DFB) cavity lasing has been investigated. A PCLC film used to reflect a pump beam brings about the efficient use of incident energy, whereas a PCLC film used to reflect the emission contributes to amplifying the stimulated emission. As a result, the cell, in which both PCLC films are introduced, gains about a 60% reduction in the lasing threshold. It is also found that a lasing threshold exists not only for the excitation energy but also for the emission intensity. Namely, the lasing starts to occur at a certain emission level irrespective of the cell structures.

In this paper, the effects of an axial longitudinal movable external magnetic field (EMF) on a CuBr laser tube have been explored. Results show that applying a DC EMF on the cathode area of the laser induces a significant effect on its performance. With the application of the EMF to the cathode area, the laser output power increases, the power decreases when the EMF is placed on the anode region. Application of the EMF between the anode and cathode does not have a significant effect on the laser output power.

Coherent radiation in the millimeter and sub millimeter wavelength regions can be generated using short electron beam bunches and laser-sliced beam bunches in a storage ring. Longitudinal dipped profiles produced by the laser slicing are rapidly smeared by the synchrotron motion and by the electron diffusion due to a random photon emission. In the present work, the characteristics of the diffusion are studied in detail but simply for practical applications. Diffusion effects are expressed as a point transfer probability function, with which the smearing of dipped profiles can be calculated straightforwardly. The emittance of diffusion gradually increases and finally reaches the natural emittance of the beam. Smeared profiles by the diffusion can be observed as a pulsed coherent radiation at the time of half multiples of synchrotron oscillation period, when there is almost no smearing by the synchrotron motion. Expected coherent radiation spectra due to the dipped profiles are given for the New SUBARU storage ring.

Nonlinear absorption properties of Ce³⁺-doped LiCaAlF₆ (Ce:LiCAF) crystals at wavelength of 266 nm are studied using open-aperture Z-scan method and a Q-switch Nd:YAG laser. Saturable absorption of solid-state materials in ultraviolet region is demonstrated for the first time.

In order to construct future optical interconnecting board providing ultra-broadband chip-to-chip signal transmission, integrated-optic configuration from two-dimensional array of surface emitting lasers to two-dimensional array of photodiodes was discussed with wavelength-division-multiplexing technique. TE₀ guided mode was used for signal transmission while TE₁ mode was used for input/output coupling of free-space waves to/from waveguide. Guided-mode-selective focusing grating coupler and different-guided-mode-coupling distributed Bragg reflector were integrated in thin-film waveguide to form free-space-wave add/drop multiplexer. Two-channel multi-/demultiplexing function was experimentally demonstrated for the first time with 5 nm wavelength spacing around 850 nm wavelength, although insertion loss and crosstalk noise were estimated to be not sufficient but -30 and -5 dB, respectively.

We present nanohole array fabrication on a silicon substrate using a femtosecond laser pulse at 820 nm and 100 fs, and a subwavelength polystyrene (PS) particle array as a template. Nanohole array fabrication uses a particle field enhancement effect and two-dimensional (2-D) arrayed PS nanoparticles deposited on a (100) silicon (Si) substrate. PS spheres 200, 450, and 820 nm in diameter are used. The fabricated nanohole profiles in terms of the particle diameter and irradiated laser fluence are investigated. The nanohole diameter and depth become larger and deeper, respectively, as the diameter of the particles used or the irradiated laser fluence is increased. Light intensity enhancement by the particles is obtained experimentally by comparing ablation rates of the Si substrate with and without particles. The enhanced light intensity between a PS particle and a Si substrate is also calculated by the finite difference time domain (FDTD) method. The calculated optical enhancement factor is consistent with the experimental value.

We have analyzed a drilling process with a femtosecond laser on a silicon surface in order to investigate the degree of the thermal effect during the dicing of a very thin silicon substrate (thickness: 50 µm). A femtosecond laser pulse (E=30–500 µJ/pulse, τ=200 fs, λ=780 nm, f=10 Hz) was focused on a thin silicon substrate using a lens with a focal length of 100 mm. An image-intensified charge-coupled device (CCD) camera with a high-speed gate of 200 ps was utilized to take images of a drilled hole during the drilling process. As a result, it was found that the smaller the pulse energy, the faster the formation of the hole. Therefore, we tried to estimate the degree of the thermal effect semi quantitatively by analyzing the rise time of the formation of the hole. By measuring the rise time in 8 kinds of metallic material, it was found that the rise time strongly correlates with the thermal conductivity in these materials. This knowledge is thought to be very important and useful for developing a dicing technique for thin silicon wafers using a femtosecond laser.

The photon number distribution is reconstructed from the measured statistics of vacuum states in single-photon detection. Numerical results are presented for the coherent, thermal, number and squeezed-vacuum states. The quantum efficiency of single-photon detection should be high for the successful evaluation of the number state. The quantum efficiency provides the marginal influence for the evaluation of the coherent, thermal and squeezed-vacuum states. However, the accuracy of the reconstructed photon number distribution of the squeezed-vacuum state is low even though the quantum efficiency is unity. For a more accurate reconstruction, we must obtain a priori information on the photon number distribution of the squeezed-vacuum state.

Maps of the room temperature photoluminescence (PL) yield from SiO_x/Si/SiO_x coated semiconductor laser facets were made during the course of accelerated lifetesting. A localized degradation of the PL yield was detected under the active region after aging, which signifies a localized decrease of the radiative recombination efficiency. The surface reflectance was also investigated and was found to be uncorrelated with the localized degradation of the PL yield.

We have fabricated a semiconductor optical amplifier-based Mach–Zehnder interferometric wavelength converter with preamplifiers. For 2R regeneration, we have measured the extinction ratio (ER) and the bit-error-rate (BER) penalty of the wavelength-converted signal by optimizing the applied currents to the preamplifiers in varying the ER of a non-return-to-zero input signal at 10 Gbit/s. The ER was more improved and the BER showed a larger negative power penalty for an input with a smaller ER. For a typical input signal with a 5 dB ER, the ER improvement was 5.5 dB and the power penalty was -2.6 dB.

We report on the generation of debris in the femtosecond laser drilling of silica glass in water. The morphology of the debris ejected from the amorphous synthesized silica is examined by scanning electron microscopy and the chemical structures are investigated by X-ray diffraction analysis and Fourier transform infrared spectroscopy.

In this paper, a new computational reconstruction technique for three-dimensional (3-D) objects in integral imaging using a lenslet array is proposed and its usefulness is discussed. Experimental results show that this technique improves the visual quality of a 3-D reconstructed image when compared with that of the conventional technique.

We analyzed the dark-current density obtained from solar cells based on multicrystalline SiGe (mc-SiGe) using a modified two-diode model that includes two diodes with diode ideality factors of 1 and 2, shunt resistance, and several series resistances. The ratio of recombination area r, which corresponds to the domination of recombination current, is almost independent of the average Ge composition, while the shunt resistance R_sh shows little change up to 5% and a drastic reduction at an average Ge composition of 10%. These results indicate that the deterioration of solar cell properties with an average Ge composition of 10% is mainly due to its lower shunt resistance, which is caused by the generation of defects. It can also be said that the quality of mc-SiGe is preserved at an average Ge composition of up to 5%. This strongly supports the suitability to high-efficient solar cells of mc-SiGe that has the proper average Ge composition due to its enhanced absorption coefficient and the resultant increase in short-circuit current density.

The high-temperature characteristics of donor-doped SrTiO₃/indium tin oxide (ITO) Schottky solar cells were investigated by current–voltage and impedance analyses at various oxygen partial pressures (P_O2) (1–10^-4 bar) at 873 K. Both current–voltage and impedance characteristics showed a reversible oxygen partial pressure dependence. The junctions demonstrated the photovoltaic effect even at high temperatures, which means the nonohmic behavior of the heterojunction remains even at high temperatures. The highest open circuit voltage and short circuit current density were 123 mV and 1.37 mA cm^-2, respectively, at 1 bar O₂ under 261 mW cm^-2 UV irradiation. Incident photon-to-current conversion efficiency and energy conversion efficiency improved as P_O2 increased. The influence of oxygen partial pressure on the solar cell characteristics is discussed.

High-quality transparent conductive aluminum-doped ZnO (AZO) thin films were deposited on quartz glass substrates using pulsed laser deposition (PLD). We varied the growth conditions in terms of substrate temperature and oxygen pressure. The crystallographic structure and electrical and optical properties of the as-grown AZO films were mainly investigated. In X-ray diffraction (XRD), (002) and (004) peaks were detected, indicating that Al doping did not cause structural degradation of wurtzite ZnO. The AZO films formed at a substrate temperature of 300°C showed a low electrical resistivity of 1.33×10^-4 Ω cm, a carrier concentration of 1.25×10²¹ cm^-3 and a carrier mobility of 37.6 cm²/(V s) at an oxygen pressure of 5 mTorr. A visible transmittance of above 88% was obtained. The AZO films show comparable electrical and optical properties to those of indium tin oxide (ITO) films and are emerging as a potential good challenger to ITO films.

The ZnS:Mn²⁺ nanocrystal colloidal solution is prepared by the in situ surface modification co-precipitation method in the presence of 3-mercaptopropyl trimethoxysilane (MPS). The increase in the fractional photoluminescence (PL) intensity by the aging of this solution is represented as a first-order reaction. Judging from the small activation energy, we conclude that Mn²⁺ ions are exchanged with Zn²⁺ ions at the surface of ZnS nanocrystals during aging to increase the PL intensity.

Effects of a DC-biasing field on the real part of the relative dielectric constant of barium strontium titanate powder prepared by the sol–gel process for application in phased array antennas have been studied. The real part of the relative dielectric constant of specimens decreases with increasing applied DC biasing field. An overall tunability of 15.7% at 1.5 kV/cm is achieved. The real part of the relative dielectric constant of specimens decreases rapidly before 1.0 kV/cm and slowly after 1.0 kV/cm when compared with the fitting data obtained by curve fitting with Johnson's bias equation. With the introduction of a bias exponent coefficient in the denominator of Johnson's bias equation, a modified bias equation is proposed. The data obtained by fitting with this proposed modified bias equation provide a more accurate description of the DC biasing field dependence behavior than those obtained by fitting with Johnson's bias equation.

Microwave dielectric properties of the complex perovskite compound CuO-doped 0.95Ba(Zn_1/3Nb_2/3)O₃–0.05BaZrO₃ ceramics have been investigated using the conventional solid state method. Copper oxide effectively lowers the sintering temperature of 0.95Ba(Zn_1/3Nb_2/3)O₃–0.05BaZrO₃ ceramics as a sintering aid. Ordering of structures was not observed at sintering temperatures from 1240 to 1360°C. The dielectric constant (ε_r) saturated at a value of 38–40 from 1270 to 1360°C. The Q×f values of 15000–70000 (at 7 GHz) can be obtained in all cases when the sintering temperatures are in the range of 1240–1360°C. The temperature coefficient of the resonant frequency τ_f was independent of the sintering temperature. An ε_r value of 39.7, a Q×f value of 70000 (at 7 GHz), and a τ_f value of 17 ppm/°C were obtained for 1 wt % CuO-doped 0.95Ba(Zn_1/3Nb_2/3)O₃–0.05BaZrO₃ ceramics sintered at 1360°C for 2 h.

The dielectric properties and microstructures of MgNb₂O₆ ceramics with Fe₂O₃ additions (0.5–2 wt %) prepared with a conventional solid-state route have been investigated. It is found that MgNb₂O₆ ceramics can be sintered at 1140°C due to the liquid phase effect of Fe₂O₃ additions. At 1140°C, MgNb₂O₆ ceramics with 0.5 wt % Fe₂O₃ addition possess a dielectric constant (ε_r) of 20.5, a Q×f value of 70000 (9 GHz) and a temperature coefficient of resonant frequency (τ_f) of -49 ppm/°C. The Fe₂O₃-doped MgNb₂O₆ ceramics can find applications in microwave devices requiring low sintering temperatures.

In order to clarify thermodynamic relationships of the various phases of KNbO₃, enthalpies of formation for cubic (Pm3m), tetragonal (P4mm), orthorhombic (Bmm2) and rhombohedral (R3m) phases of KNbO₃ were calculated using a plane-wave pseudopotential method within a density functional formalism. The KNbO₃ phase with the lowest symmetry was found to have the lowest enthalpy of formation. Moreover, we quantitatively evaluated the formation energies of neutral vacancies in KNbO₃ as functions of the atomic chemical potentials of the constituent elements by the use of the same procedure. Relaxation of the first- and the second-neighbor atoms around the vacancy was considered in a 40-atom supercell. The formation energy of a K vacancy was found to be the lowest under an oxidizing atmosphere and that of an O vacancy was found to be the lowest under a reducing atmosphere. The formation energy of a Nb vacancy was the highest under both oxygen-rich and -poor conditions. These results are in agreement with the empirical rule that B site defects in perovskite-type oxide do not exist. These results are discussed on the basis of the band structure of KNbO₃.

Bi_0.5Na_0.5TiO₃ (BNT) bulk ceramics with a preferred <100> orientation (texture) were prepared by the reactive-templated grain growth method using platelike Bi₄Ti₃O₁₂ (BiT) particles as templates for BNT. The texture did not develop extensively in stoichiometric BNT, but the addition of excess Bi₂O₃ to BNT enhanced the texture development. The role of excess Bi₂O₃ was examined. The calcined compacts were composed of matrix grains with random orientation and <100>-oriented grains transformed from aligned BiT particles, and texture developed by the preferential growth of oriented grains at the expense of matrix grains. In stoichiometric BNT, the growth rate of matrix grains was high and the conditions for the preferential growth of the oriented grains were disrupted. Excess Bi₂O₃ reduced grain growth rate, and the conditions for preferential growth were maintained, resulting in the development of highly textured BNT. The resultant textured BNT ceramic exhibited 70% higher piezoelectric d₃₁ and electromechanical k_p coefficients than nontextured BNT.

Parasitic capacitances in the measurement of the hysteresis properties of ferroelectric microcapacitors are estimated. A scanning probe microscope with a conductive cantilever was used for contacting various-sized Pb(Zr,Ti)O₃ (PZT) microcapacitors fabricated by electron-beam-induced patterning. A parasitic capacitance under the condition in which the cantilever was lifted up by 40 µm from the contact point was estimated to be 0.88 pF. Although all the PZT microcapacitors showed well-saturated hysteresis curves with compensation for the parasitic capacitance of 0.88 pF, the slopes of the compensated hysteresis curves around the maximum field increased with decreasing capacitor area. From the capacitor area dependence of the slopes, the increase in parasitic capacitance caused by bringing the cantilever near substrates for contact was estimated to be 0.049 pF. This increased parasitic capacitance evidently decreased the apparent coercive fields of the PZT microcapacitors with areas lower than 10 µm² while it had no influence on remanent polarization.

The A₂BWO₆ (A=Sr, Ba; B=Co, Ni, Zn) microwave dielectric ceramics were prepared by conventional solid-state ceramic route. According to the X-ray diffraction (XRD) results, the ceramics have cubic perovskite structure for all compounds. In addition, the Ni-containing compounds showed apparent supperlattice reflections at low angles, whereas the others didn't. The results of Raman spectroscopy show that the degree of B-site ordering is different with different B²⁺ ions. The dielectric properties of the ceramics were measured in the frequency range 6.5 to 8.5 GHz using resonance methods. The ceramics have dielectric constant in the range 18 to 30, high quality factor (Q×f value up to 56000 GHz) and negative temperature coefficient of resonant frequencies in the range -72.9 to -31.1 ppm/°C. The dielectric constant increased with increasing B²⁺ ionic polarizability, and the quality factor was enhanced due to the increase in B-site ordering. The relationship between temperature coefficient of dielectric constant and tolerance factor was accordant in comparison with the other perovskites.

Inorganic alignment materials were deposited on indium–tin-oxide (ITO) glass by reactive sputtering deposition. After deposition, inorganic alignment materials such as a-SiO_x and a-SiO_x:H were irradiated using an Ar⁺ ion beam (IB) for liquid crystal (LC) alignment. On the basis of the experimental results, an a-SiO_x film deposited by sputtering does not align LCs regardless of IB treatment, but an a-SiO_x:H film treated with varying IB energies, IB incident angles, IB doses, and IB irradiation times has excellent alignment properties and electro optical properties, the same as polyimide (PI). We investigated period of the stability of an inorganic alignment layer treated with IB after a long time. From the experimental results, the inorganic alignment layer irradiated with an IB does not experience degradation of its electro optical properties. These results imply that an inorganic alignment layer irradiated with IB can be adopted as an LC alignment layer instead of rubbed PI and that hydrogen plays an important role in LC alignment due to the difference in alignment properties between a-SiO_x films and a-SiO_x:H films.

The electrooptical characteristics of carbon nanotube-doped liquid crystal (LC) devices were investigated. Two complementary operation modes of the liquid crystal cells were fabricated. The measured results reveal that anisotropic carbon nanosolids modify the dielectric anisotropy and the viscosity of the liquid crystal carbon nanotube mixture, hence significantly modifying the threshold voltage and the switching behavior of a liquid crystal device. Doping a small amount of carbon nanotubes into the liquid crystal mixture is effective in improving the electrooptical characteristics of an LC device when the employed LC mixture is viscous.

We studied the voltage–dependent liquid crystal (LC) dynamic stability corresponding to the pixel edge shape in the fringe field switching (FFS) mode. LC dynamics is very unstable near the edge of the pixel slit, where there is a horizontally different field direction compared with the active region, particularly when the slit angle decreases to 3°. Actually, there are strong field competitions near the edge of the pixel slit due to the patterned pixel shape. Also, a dark disclination line (D/L) at the domain boundary is generated with increasing operation voltage and the D/L extends into the active area at a high applied voltage. It is possible to control LC dynamics near the pixel edge by using different pixel edge shapes. In this paper, we propose an advanced edge shape. This shape has no reverse twist region, unlike the conventional structure, and therefore, LC dynamics is very stable near the edge of the pixel slit. This result indicates that a pixel edge shape with no reverse twist is very important in the design of a high-image-quality FFS mode.

The temperature dependence of the isothermal compressibility of vitreous silica has been studied by molecular dynamics simulation. The compressibility discontinuously jumps from ≈2×10^-11 to ≈6×10^-11 Pa^-1 with a change in temperature up to ≈3200 K at which the thermal expansivity changes from positive to negative. The compressibility values were on the same order as that obtained by the light scattering experiment in the literature reported previously.

An internal friction peak due to hydrogen in Fe₅₅Cr_45-xNi_x (x=20–45) and Fe_100-xNi_x (x=35–100) alloys was observed. A gas-equilibration method was employed in order to charge specimens homogeneously with hydrogen. In Fe₅₅Cr_45-xNi_x alloys, the peak height significantly increased as the nickel content increased, whereas in Fe_100-xNi_x alloys the peak height did not show a monotonic change versus the increasing nickel content. In both alloys the peak height depended strongly on the alloy composition.

Reactions of hydrogen-terminated Si(100) surfaces with oxygen at very low pressures during heating are characterized by a method that combines heating and cooling in thermal desorption spectroscopy. Surface hydrogen coverage as a function of temperature is estimated from the hydrogen desorption spectrum obtained by the combination measurement. The surface coverage under the condition with or without introducing oxygen gas indicates that the hydrogen of silicon monohydride begins to desorb after almost half the hydrogen of silicon dihydride desorbs. The hydrogen desorption behavior under the introduction of oxygen gas suggests that bonding between Si and hydrogen atoms for silicon monohydride at the Si(100) surface is stabilized by adsorption of oxygen atoms on surface Si back bond sites during heating.

The variation in 111 d-space of Pt thin-film electrodes during heat treatment was precisely measured by an X-ray diffraction system with a heating stage. The 111 d-space of Pt films deposited at 200°C linearly increased as the temperature was increased to 450°C and was almost constant over the temperatures range from 450 to 600°C due to stress relaxation. The generation of hillocks was observed in the Pt films which were relaxed in this way. On the other hand, in the case of Pt films deposited at temperatures higher than 500°C, the d-space linearly increased and then linearly decreased to almost the same value in the heat treatment at a maximum temperature of 600°C, and no hillocks were observed on the surface after the heat treatment. Furthermore, Pt films prepared at room temperature (RT) at different deposition rates showed different variations in d-space and different sizes of hillocks. These results suggest that knowing the variation in 111 d-space during heat treatment is beneficial for predicting the generation of hillocks in 111-oriented Pt thin films.

The chemical shift of organic materials is one of the important factors in view of the bonding structure, and an amorphous bonding structure in low-dielectric-constant materials is a basic requirement for decreasing the dielectric constant. The chemical shift originates from the conjugated C=C bond and the peculiar phenomenon of the appearance of the terminal C–H bond due to neighboring highly electronegative atoms during the deposition of fluorinated amorphous carbon films. The blueshift due to the condensation of the C–H bond was researched in fluorinated amorphous carbon films, but the redshift due to the elongation of the C–H bond was not observed because the broken C–H bond by fluorine attack becomes an HF bond and evaporates. The breaking of the cross-link structure can be accelerated by annealing and the lowest dielectric constant of the films is 1.98 at the as-deposited film with the cross-link amorphous structure.

Thiourea is a well-known additive in the electroplating industry due to its excellent ability to reduce surface roughness. However, sulfur dissociated from the thiourea is often incorporated into the plated Cu film as the byproduct CuS, which then increases the film's resistivity. The two-step Cu electroplating method proposed here deposited a smoother Cu surface film and matched the resistivity (after annealing) attained using methods that employ a thiourea-free electroplating of the Cu film. The Cu film obtained through two-step plating contained a sulfur concentration that was below the detection limit of Auger electron spectroscopy (AES).

The effect of heat treatment at 60–70°C has been studied for merocyanine (MS)–Cd arachidate mixed Langmuir–Blodgett (LB) films. MS chromophores are found to be reorganized by the heat treatments to form a novel phase of a redshifted band with spectra sharper than those of the J-band in the as-deposited films. The reorganization of MS seems to be closely related with the mobility of alkyl chains in the LB system, suggesting that the mild heat treatments will introduce another possible method of modifying the properties of films.

We have measured cantilever resonance frequency versus sample bias voltage and generated frequency vs bias ( f–V) curves using an ultrahigh-vacuum noncontact atomic force microscope (UHV NC-AFM). Using the f–V data, we calculated the contact potential difference (CPD) between the tip and the sample. These CPD measurements were compared with those that were directly observed with a scanning Kelvin probe force microscope (SKPM) on the same atomically resolved area of the sample using a UHV-AFM. The CPD values obtained by both methods were similar, however, it was difficult to obtain CPD values that agreed precisely on the atomic scale.

Nanometer-sized particles of MoS₂ were synthesized on mica and MoS₂ surfaces and observed using an atomic force microscope. Molybdenum oxide was deposited on each substrate and sulfided with H₂S gas to simulate catalysts used in petroleum refining. The height of the sulfided particles was regulated to be single or double layers of S–Mo–S suggesting basal-bonded, flat-lying MoS₂. When Ni metal was simultaneously deposited with molybdenum oxide, the sulfided particles remained basal-bonded and the number of stacked layers increased by one or two.

To make a useful contribution to the development of the compact X-ray laser, a modified quasi-steady-state approximation is applied to the fast numerical calculation of rate equations for the rapid ionization phase of a laser-produced plasma, to which the usual quasi-steady-state model by Bates et al. is not applicable. The set of nonlinear rate equations for the excited level populations coupled with the electron density and temperature for the plasma are numerically calculated with sufficient accuracy for their temporal evolution. The calculation also shows that a suitable combination is possible between the power and pulse width of a heating laser so that a high-density plasma can be obtained as the X-ray laser medium. The mathematical meaning of our approximation is briefly mentioned and its applicability is discussed.

Neutron emissions in a low energy 3.3 kJ (15 kV) plasma focus are studied. The system is operated in deuterium and deuterium-argon admixtures. Enhancement of the neutron yield is obtained with a suitable amount of high Z admixture. Time resolved neutron measurements are made by using four detectors positioned at two different distances at both the end-on and side-on direction. Maxwellian pulse fitting techniques are employed to resolve a two phase neutron emission history. The neutron energy and anisotropy for the two phases are determined. The energy and anisotropy of the two phases are found to be different and that the second phase is of high anisotropy. These results confirm the presence of two phases of neutron emission that are possibly due to at least two different kinds of neutron production mechanisms in the low energy plasma focus.

In this study, using two different types of linear internal type inductively coupled plasma sources with a serpentine-type antenna and a novel double-comb type antenna having the size of 1020×830 mm², the characteristics of their plasmas were compared as the application to the flat panel display manufacturing. The use of the double-comb type antenna instead of the serpentine-type antenna showed two times higher plasma and radical densities, and more stable plasma when rf power higher than 2000 W was applied. By the application of 5000 W of rf power with 15 mTorr Ar, a high plasma density of 2.2×10¹¹/cm³ with the plasma uniformity of 8% could be obtained for the double-comb type antenna. The increase of plasma density, radical density, and plasma stability for the double-comb type antenna compared to the serpentine-type antenna appears from the higher inductive coupling and less standing wave effect compared to the serpentine-type antenna.

We produced an intense beam of Zn^14+–16+ ions from the RIKEN 18 GHz electron cyclotron resonance ion source by inserting a ZnO rod into the plasma directly. This method was successfully applied to produce the intense beam of ⁷⁰Zn¹⁶⁺ for searching for a superheavy element (atomic number of 113).

A narrow-gap silent discharge has been successfully applied to the resolution of halide compounds (CCl₂F₂ and CF₄) diluted in mixed gases of H₂O, O₂, N₂ and Ar with a varied composition at an atmospheric pressure. The optimum composition of the discharge gas is discussed in terms of an effective decomposition energy E_d defined as the energy necessary for e^-1-fold reduction of the halide concentration. Efficient decomposition of CF₄ gas is realized with the use of Ar gas as the dilution gas; the minimum value of E_d approaches 760 eV/CF₄-molecule, which must be compared with the value of 18 keV/CF₄ obtained when N₂ is used as the dilution gas.

We present a numerical model for the quantitative simulation of electrical characteristics for organic light-emitting devices (OLEDs) with fluorescent dopants in the host. We use drift-diffusion equations in terms of the electron and hole current densities coupled with the Poisson's equation. Compared with other models proposed in previous literature, we include charge carrier trapping and direct carrier recombination phenomena on the fluorescent dopants in the simulation. Furthermore, current density, charge distribution, and recombination data in the device are obtained from this numerical study. Results for several multilayer devices with different fluorescent dopant concentrations are presented in this article. On the basis of the experimental data of a typical doped device, we have found good agreement between the simulation results and the experimental results.

Electrochemical polypyrrole (PPy) actuators, prepared electrochemically from a methyl benzoate solution of tetra-n-butylammonium trifluoromethanesulfonate (TBACF₃SO₃), have been studied to improve the response rate by two methods; 1) a PPy film attached with plural auxiliary electrodes of thin Au coils, 2) a PPy film equipped with a compliant Au electrode on one side of the film. With increasing the number of auxiliary electrodes for the first method, the film responded faster as if it were a shorter film. These results are due to the decrease in the IR voltage drop along the film from the electrodes and also due to the increased current to the whole film via plural electrodes. The PPy film with the Au thin layer (the second method) exhibited up to 8.8%/s strain rate, which was much faster than that (0.5%/s) without the auxiliary electrodes, keeping the maximum strain of 12–13%. The auxiliary electrodes improved not only the response speed of the PPy actuators but also the durability upon cycling electrochemically.

It was found that electrochemiluminescence is enhanced by the use of nanoporous TiO₂ electrodes. The nanoporous TiO₂ electrodes were fabricated by cumulating nano-TiO₂ crystals on the transparent conductive layers (SnO₂/F). The device was composed of the porous TiO₂ electrodes (10 µm) and SnO₂/F electrodes as counterelectrodes. The gap was filled with electrolytes containing Ru(bpy)₃(PF₆)₂ (bpy: bi-pyridyl) in various solvents. The electrochemiluminescence was much larger than that from the cell composed of two flat SnO₂/F electrodes. It is likely that the increase in elecrochemiluminescence is associated with the nanopores as well as with the large surfaces of porous semiconductive oxide electrodes.

We have demonstrated a new type of lasing mode in a dye-doped 100-µm-thick nematic liquid crystal layer sandwiched between two polymeric cholesteric liquid crystal films functioning as a photonic crystal. The fabricated cell exhibits several characteristic dips in the transmittance spectrum in addition to fine fringes originating from a Fabry–Perot cavity mode. These dips are due to the phase retardation between optical eigenmodes in the birefringent medium, which is not realized in an isotropic layer. The cell shows multimode lasing at wavelengths corresponding to transmittance maxima within the stopband region when the nematic layer is doped with dyes.

A new, simple apparatus for measuring the surface adhesion properties of soft materials was designed, where the adhesion force of a point contact between soft materials and the total energy required to separate the contact can be measured using the springs of phosphor–bronze thin plates with strain gauges. The adhesion between swollen hydrogels was studied here by this simple technique in air at room temperature. The gels used in the present preliminary experiments were poly(sodium acrylate) hydrogels physically cross-linked by aluminum ions. The adhesion force and the separation energy showed a power-law increase with separation velocity. The apparatus was applied to evaluate the adhesion properties of seven anti-inflammatory analgesic cataplasms on the market. It was found that the easiness to separate (rank of adhesion force and the separation energy) was consistent with the results of those obtained by organoleptic evaluations.

Previous studies on liquid gallium ion sources used an electrochemically etched tungsten wire with a coil-type heater. Such a structure requires excessive power consumption in the course of heating the liquid metal. In this study, a new structure is proposed that replaces the coil-type heater. It uses a gallium reservoir made of six pre-etched 250 µm tungsten wires that surround the needle electrode. Gallium loading at the reservoir is observed to be much more stable, resulting in an improved beam stability.

In this paper, we describe a novel packaging technology for use in microelectromechanical-system (MEMS) device fabrication and its application to an optical MEMS micromirror array that consists of a mirror chip and an electrode chip that controls the micromirrors. Chip-on-chip technology, which involves the selective deposition of silver paste by screen printing, is used to join the two chips. The experimental results ensure a high production yield and heat cycle test results indicate good reliability.

Computational fluid dynamics is used in order to clarify the air flow in a spin cleaner for a square quartz plate (150×150×10 mm³), which is used as a mask substrate. The influences of the rotation rate and the distance between the square quartz plate and its support plate on the air flow are studied. When the distance between the two rotating plates is small, 15 mm, air simply flows downward around the square quartz plate; only a small amount of air enters the region below the rotating square quartz plate. However, by increasing the distance between the plates, air tends to enter the region below the rotating square quartz plate. Such a complicated air flow easily transports very small water droplets or mist existing in the air to the region below the square quartz plate; thus water marks are formed at the surface. Therefore, water mark formation can be reduced by optimizing the air flow in the spin cleaner.

We developed a lift-off process for a nanoimprint lithography (NIL) using poly(vinyl alcohol) (PVA) as the replicated material. PVA could easily be dissolved in water. A conventional lift-off process using poly(metyl methacrylate) (PMMA) uses acetone as a solvent, while the lift-off process using PVA uses water as a solvent, which is an ecologically friendly process. We demonstrated Au patterns with sub-µm dimensions using a lift-off process with a PVA single layer. In addition, an Hydrogen silsesquioxane (HSQ)/PVA bilayer structure was used for the lift-off process. This bilayer structure could be fabricated by room-temperature NIL and dry etching. Au patterns were easily obtained using the bilayer structure having an inverse tapered shape. In the lift-off process without using HSQ/PVA bilayer, Au wiring with sub-µm linewidth could be obtained, however, 100-nm-linewidth patterns did not remained. Line-and-spacing gratings of 100 nm in the Au patterns were demonstrated using the water lift-off process with the HSQ/PVA bilayer structure.

The effect of a magnetic field on water mist (diamagnetic) is studied both experimentally and numerically. The water mist is produced by ultrasonic atomizers and is fed to a Plexiglas pipe (90 mm inner diameter and 1 m long) which is horizontally placed in a horizontal bore (d=100 mm) of a superconducting magnet (10 T at the magnet center). The water mist is found to flow out of the other end of the pipe opening when there is no magnetic field (b=0 T). At b=8 and 10 T, the mist is stopped at an intermediate location in the pipe and flows out from the inlet opening. In the computation, the water mist is simulated with 1000 particles of 0.01–5 µm in diameter. Brownian motion is considered and the Langevin equation is solved. Various magnitudes of magnetic strength, particle diameters and pressure gradients for air flow are numerically tested. The magnetic effect is obvious for particles with diameters larger than 1 µm. For example, for 3 µm particles, only a small amount of particles are able to pass through the weak magnetic field near the cylinder axis to the downstream and sediment over the downward pipe wall.

A simple apparatus to control water flow through a hydrogel at a fixed temperature was designed, in which the hydrogel was mechanically constrained in a glass microcapillary at gelation. An evaluation of the friction between the polymer network of polyacrylamide gels and the solvent water measured by this simple technique is presented here. The effects of the experimental conditions, the pressure applied to the solvent, the temperature and the gel size (the length and the cross-sectional area), on the friction coefficients were examined. The results agreed well with the model of the flux of water flow in a capillary based on the Hagen–Poiseuille equation.

A new pump and probe experimental system was developed, the pump pulse duration of which is stretched and is much longer than that of the probe pulse. Using this system, time-resolved electronic excitation processes and damage mechanisms in CaF₂ crystals were studied. The measured reflectivity of the probe pulse begins to increase at the peak of the pump pulse and increases rapidly in the latter half of the pump pulse, when the pump pulse duration is stretched to 580 fs. Our experimental results indicate that both multiphoton ionization and impact ionization play important roles in the generation of conduction band electrons, at least they do so when the pump pulse durations are equal to or longer than 580 fs.

A cerium-target X-ray tube is useful in performing cone-beam K-edge angiography because K-series characteristic X-rays from the cerium target are absorbed effectively by iodine-based contrast media. The X-ray generator consists of a main controller and a unit with a high-voltage circuit and a fixed anode X-ray tube. The tube is a 1.0-mm-focus diode with a cerium target and a 0.5-mm-thick beryllium window. The maximum tube voltage and current were 65 kV and 0.4 mA, respectively. Cerium Kα rays were selected out using a barium sulfate filter, and the X-ray intensities without filtering and with a barium sulfate filter were 209 and 16.8 µGy/s, respectively, at 1.0 m from the source with a tube voltage of 60 kV and a current of 0.40 mA. Angiography was performed with an X-ray film using the filter and iodine-based microspheres 15 µm in diameter. In the angiography of nonliving animals, we observed fine blood vessels approximately 100 µm in diameter with high contrasts.

We have performed a series of molecular dynamics (MD) simulations on interactions between green fluorescent protein (GFP) and Si substrates. The results show that GFP adsorbs directly on the hydrophobic substrate, and via water molecules on the hydrophilic substrate. The adsorption-induced changes in the conformation of GFP are smaller on the hydrophilic substrate than on the hydrophobic substrate. On the other hand, the dynamic atom motions in GFP are larger on the hydrophobic substrate than on the hydrophilic substrate. In order to prevent the denaturation of proteins caused by immobilization on a substrate, the Si surface should be prepared from the viewpoints of both conformation and dynamic atom motions.

We previously developed a protein crystallization technique using a femtosecond laser and protein crystal processing and detaching techniques using a pulsed UV laser. In this study, we examine the effect of laser irradiation on protein integrity. After several kinds of laser were irradiated on part of a solution of glycerol-6-phosphate dehydrogenase from Leuconostoc mesenteroides, we measured the enzyme activity. Femtosecond and deep-UV laser irradiations have little influence on the whole enzyme activity, whereas the enzyme lost its activity upon high-power near-infrared laser irradiation at a wavelength of 1547 nm. These results suggest that suitable laser irradiation has no remarkable destructive influence on protein crystallization or crystal processing.

A feasibility test of phase tomography using diffraction-enhanced imaging (DEI) was performed with biological tissues consisting of not only soft tissues but also cartilages and bones. Reconstructed three-dimensional images indicated that phase tomography using DEI has an advantage from a biological viewpoint over phase tomography using a crystal X-ray interferometer, which cannot be applied to samples involving marked refractive index changes at boundaries between soft tissues and bones or cartilages.

Cadmium telluride nanoparticles dispersed in SiO₂ films have been grown by the co-sputtering of elemental Cd, Te and SiO₂ targets in argon atmosphere. The role of oxygen during annealing on the structural and optical properties of CdTe nanoparticles dispersed in SiO₂ films has been studied. Formation of a CdTeO₃ layer around the CdTe nanoparticle core due to ambient oxygen present in air results in structural defects and thus the formation of hexagonal CdTe nanoparticles in air-annealed samples. In vacuum-annealed samples, defect free and well-crystallized cubic CdTe nanoparticles are formed which show excitonic features in the absorption spectra. These results have been confirmed by carrying out i) annealing in vacuum and air ambiences in a sequence on the same sample and ii) by depositing an additional layer of SiO₂ on the CdTe:SiO₂ samples to prevent the diffusion of ambient oxygen.

We explored structural and electrical properties of single-walled carbon nanotube (SWNT) networks directly grown on alumina substrates. The netlike SWNTs were uniformly grown on the substrate at a high quality. From the Raman spectroscopy analysis it was found that the as-grown SWNT networks were a mixture of metallic and semiconducting SWNTs, while the SWNT networks after their electrical breakdown exhibited a predominance of the semiconducting property. The direct growth method and subsequent electrical breakdown facilitated high-throughput production of practical ultrasensitive sensors for pollutant gases with a high sensitivity, which was demonstrated by NO₂ detection.

The effects of oxygen plasma posttreatment (PPT) on the morphology and field emission properties of carbon nanotube (CNT) arrays grown on silicon substrates are proposed and experimental results are reported. Oxygen PPT led to an enhancement in the emission properties of CNTs, which showed an increase in total emission current density and a decrease in turn-on field after plasma treatment. Scanning electron microscopy (SEM) images showed reduced densities of the CNTs, which resulted in a decrease of the screening effect in the electric field. Raman spectra showed an increase in the number of defects which served as field-emission sites when the plasma power or treatment time with the plasma increased. Transmission electron microscopy (TEM) images were used to identify the quality of the nanotubes, so that we could clearly find evidences of improvement in the field emission properties after plasma treatment. The measurement of electrical characteristics revealed improved field emission properties under proper plasma conditions. The turn-on field decreased from 4.8 to 2.5 V/µm, and the emission current density increased from 78.7 µA/cm² to 18 mA/cm² at an applied field of 5.5 V/µm.

Oxygen ions with the ultralow-energy of 25 eV are implanted in single walled carbon nanotube (SWNT) field-effect transistors (FETs), which convert the SWNT from p-type to n-type. The dose amount ranged from 1.8×10¹¹ to 8.2×10¹² ions/cm². In the drain current–gate voltage characteristic, the hole current begins to decrease while the electron current begins to increase as the dose of the oxygen ions implanted in SWNT-FETs increases. Moreover, the threshold voltage of the hole transport shifted to the negative direction of the gate voltage. These changes in the electrical properties of SWNT-FET after the oxygen-ion implantation correspond to the n-type conversion and to the shift in Fermi level from the valence band edge to the conduction band edge. The implanted oxygen ions may substitute the carbon atoms in the SWNT and act as donor impurities.

We synthesized the peptide nanorings of cyclo[-(D-Ala-L-Gln)₃], cyclo[-(D-Cys-L-Gln)₃], cyclo[-D-Cys-L-His-D-Ala-L-Asn-Gly-L-Gln-] and cyclo[-(L-Gln)₅], and studied the way in which the difference in the type and/or number of component amino acid residues changes the self-assembling morphology of the nanorings on gold substrates by atomic force microscopy. The study revealed that cyclo[-(D-Ala-L-Gln)₃] formed nanotube bundles through inter-ring hydrogen bonds, while the nanorings of cyclo[-(D-Cys-L-Gln)₃] adhered to the gold surface directly due to the high affinity of thiol to gold. In contrast, a random amino acid sequence of cyclo[-D-Cys-L-His-D-Ala-L-Asn-Gly-L-Gln-] resulted in many isolated nanotubes, which were first observed in the present study. While the D,L-peptide nanotubes have very straight forms, the homo-L-peptide of cyclo[-(L-Gln)₅] formed interesting randomly branching nanotubes that were entwined and grew on the substrate. Scanning tunneling microscopy was also performed and high-resolution images of both the peptide nanotubes and the nanotube bundles were obtained.

We present the elastic and plastic parameters and the deformation patterns of a copper phthalocyanine (CuPc) thin film as compared with those of a polyester (PE) film and a metal copper (Cu) bulk. The yield stress of the CuPc film, σ_Y=51.9 MPa, was comparable to that of the PE film and was lower by a factor of 10 than that of the Cu bulk. In contrast, Young's modulus, E_S=9.29 GPa, of the CuPc film was intermediate between those of the PE film and Cu bulk, and the shearing strain energy per unit volume, U_S=8.74×10²³ eV/m³, was lower by a factor of 10 than those of these two materials. The load–displacement (P–h) curves of the CuPc film were similar to those of the Cu bulk, in contrast to those of the vsicoelastic PE film, indicating that these deformation patterns showed an elastoplastic behavior and could be expressed by the Maxwell model.

In order to evaluate accurately the thickness of SiO₂ films on Si substrates, we applied a heat cleaning method in the atmosphere to remove adsorbates on the SiO₂ surface using a hot plate. A high reproduciblity was obtained for the thicknesses of the sample just after heating. In addition, carbon-derived contaminants on the surface were markedly decreased by the heating. Since this method is extremely simple and requires no special equipment and chemicals, it has a potential to become an effective cleaning method for accurate thickness evaluation of SiO₂ thin films on Si substrates.

For the first time, ultrasound was applied to enhance the activity of anaerobic granules. Specific methanogenic activity (SMA), carbohydrate and acetic acid analyses were performed to investigate how the limited intensity of ultrasound improves anaerobic digestion and activates methanogenic bacteria. The results of our study showed increases in SMA by 26 to 84% (St. Louis plant) and 163 to 220% (Newark plant) under the conditions of 50, 100, and 150 W for 5 min at a frequency of 40 kHz. The concentrations of soluble carbohydrates also increased 1.9 to 6.1 times as a result of ultrasound treatment.