Table of contents

We studied the effect of electron irradiation on silicon by measuring X-ray diffraction, solar cell open circuit voltages, and optical transmission. The X-ray diffraction data shows an emerging feature indicating a 0.13% lattice expansion after 250 keV electron irradiation and H₂ annealing. Solar cell voltages could be predictably modified through different irradiation and annealing conditions. The optical transmission measured in 1500-Å-thick polycrystalline silicon indicated a 40 meV band-gap widening after 100 keV electron irradiation. We explain the results as being due to the damage and relaxation of the silicon lattice, as induced by electron irradiation and subsequent annealing.

We have investigated crystal defects in the epitaxial layer on nitrogen-doped Czochralski-grown silicon (CZ-Si) substrate. It was found that two types of crystal defects are generated in the epitaxial layer on the nitrogen-doped CZ-Si substrate. One is revealed to be a stacking fault and the other is a perfect dislocation pair. The origin of these defects is a rod like void and a dislocation loop in the nitrogen-doped CZ-Si substrate. We discuss the formation mechanism of the crystal defect in the epitaxial layer caused by the grown-in defect.

Two types of crystal defects, stacking fault induced by a nitrogen-doped substrate (N-SF) and elliptical pit (E-pit), are generated in the epitaxial layer due to grown-in defects in a nitrogen-doped Czochralski-grown silicon (CZ-Si) substrate. We investigate the dependence of N-SF and E-pit formation on the quality of nitrogen-doped substrates. It was revealed that the control of both nitrogen concentration and crystal growth parameter of the CZ-Si ingot is effective for suppressing N-SF and E-pit formation. We also examined crystal defect in the epitaxial layer on a nitrogen and carbon co-doped substrate, which is the other candidate for realizing the epitaxial wafer having a high intrinsic gettering ability. It was clarified that carbon co-doping in addition to nitrogen doping suppresses N-SF and E-pit generation.

Metal–oxide–semiconductor structures consisting of HfSiO_x as the gate dielectric were characterized by using monoenergetic positron beams. 200-nm-thick polycrystalline-Si (poly-Si) and 5-nm HfSiO_x films were grown on Si substrates by chemical vapor deposition. Doppler broadening spectra of the annihilation radiation and the lifetime spectra of positrons were measured as a function of incident positron energy for ion-implanted and unimplanted samples. For the unimplanted sample after rapid thermal annealing (RTA: 1030°C, 10 s), the lifetime of positrons in the HfSiO_x film was 448±2 ps. Since the obtained lifetime was longer than the lifetime of positrons trapped by point defects in metal oxides, the positrons in HfSiO_x films were considered to annihilate from the trapped state by open spaces which exist intrinsically in their amorphous structure. After P⁺, As⁺ and BF₂⁺-implantation into the poly-Si film and RTA, the lifetime of positrons was 420–430 ps. This decrease in the lifetime was attributed to the shrinkage of the open spaces in the HfSiO_x film due to the accumulation of implanted impurities in the film during RTA. The diffusion length of positrons in Si substrates was found to depend on the implanted species of ions. This fact was attributed to the electric field introduced by charged defects in the HfSiO_x films.

We obtained high-quality InGaAsN quantum wells (QWs) by metalorganic chemical vapor deposition (MOCVD). Our InGaAsN QWs showed low threshold current densities and high-temperature characteristics (550 A/cm², 150 K at 1275 nm for 3QWs) in broad-area lasers. High output power (2.8 mW at 1280 nm) was also obtained from the room-temperature continuous operation of InGaAsN 3QW vertical cavity surface emitting lasers. We revealed the first solid evidence that unexpected Al incorporation (Al contamination) occurred in InGaAsN QWs continuously grown on GaAs/AlGaAs structures by MOCVD. Our results suggest that Al contamination leads to a rough surface and low photoluminescence intensity of the InGaAsN QWs. By minimizing Al contamination, high-quality InGaAsN QWs were obtained. Al contamination in InGaAsN QWs should be carefully considered in the MOCVD growth of InGaAsN-based devices.

Bulk-like GaN with high structural and optical quality has been attained by hydride vapor-phase epitaxy (HVPE). The as-grown 330 µm-thick GaN layer was separated from the sapphire substrate by a laser-induced lift-off process. The full width at half maximum values of the X-ray diffraction (XRD) ω-scans of the free-standing material are 96 and 129 arcsec for the (1 0 -1 4) and (0 0 0 2) reflection, respectively, which rank among the smallest values published so far for free-standing HVPE-GaN. The dislocation density determined by plan-view TEM images is 1–2×10⁷ cm^-2. Positron annihilation spectroscopy studies show that the concentration of Ga vacancy related defects is about 1.5×10¹⁶ cm^-3. The high-resolution XRD, photoluminescence, µ-Raman, and infrared spectroscopic ellipsometry measurements consistently prove that the free-standing material is of high crystalline quality and virtually strain-free. Therefore it is suitable to serve as a substrate for stress-free growth of high-quality III–nitrides based device heterostructures.

High performance low temperature polycrystalline silicon (poly-Si) thin film transistors (TFTs) with large grains were created using diode pumped solid state (DPSS) continuous wave (CW) laser lateral crystallization (CLC), employing fabrication processes at 450°C. Field-effect mobilities of 566 cm²/Vs for the n-channel and 200 cm²/Vs for the p-channel were obtained for a thick Si film (100–150 nm) on a 300×300 mm non-alkaline glass substrate. The high performance of the TFTs is attributed to the predominantly (100)-oriented very large grains. With a decreasing Si-film thickness, the grain size decreases, and the surface orientation of the grain changes from (100) to other orientations. These effects lead to reduced field-effect mobility with decreasing Si-film thickness, but it is easy to obtain a high field-effect mobility of over 300 cm²/Vs, even with a 50 nm thick Si film, without special processing techniques. A complementary metal oxide semiconductor (CMOS) ring oscillator was fabricated using a thin Si film 65 nm thick to demonstrate the high circuit performance of CLC poly-Si TFTs by applying the simplest CMOS process technology. A delay of 400 ps/stage at a gate length of 1.5 µm and a supply voltage of V_dd=5.0 (V) was produced on a large non-alkaline glass substrate utilizing a fabrication temperature of 450°C. This crystallization method will lead to the fabrication of high-performance and cheap Si-LSI circuits on large non-alkaline glass substrates.

A new dual elementary-steps growth mechanism was observed during our research on the CdHg(SCN)₄(H₆C₂OS)₂ (CMTD) crystals. Namely two types of elementary-step sources with different step height can be produced on the same crystal surface during the growth of some crystals. Furthermore the sum of these elementary-step heights is equal to the corresponding interplanar distance d_hkl. The heights of these elementary steps were determined by crystal structure as well as growth motif and they have no relation to crystal defects. The elementary steps referred in this paper are completely different to sub-step mentioned by Min in 1988. Only one step height h was included in normal growth rate formulas for the dominant crystal growth theories at present such as BCF spiral growth mechanisms and the classic two-dimensional nuclear growth modes. Without considering the effects of the dual elementary-steps h₁ and h₂ to the growth procedure, the classic formulas containing the parameter h (step height) should be modified when they are applied to the research on crystals growing with dual elementary-steps growth mechanism.

Sequential lateral solidification (SLS) is known as a promising method for making low-temperature poly-Si thin film transistors (LTPS TFT) with superior performance for the fabrication of highly circuit-integrated flat panel displays such as TFT liquid crystal display (LCD) and TFT organic light Emitting diode (OLED). In this work we studied the dependence of TFT characteristics on SLS poly-Si grain width and suggested the methods of designing SLS mask pattern to achieve uniform TFT performance. We varied the width of the poly-Si grain by employing the 2-shot SLS mask pattern with different overlaps between the 1st and 2nd laser pulses. The width of the poly-Si grain decreased with decreasing the overlap. However, the measured TFT characteristics revealed that the width of the poly-Si grain negligibly influences the device properties. We could achieve the TFT mobility of approximately 350 cm²/V·s for the overlap of not less than 1 µm. We suggested that the SLS mask pattern (x, y) should be designed such that 2+y≤x<2 (C-SLG distance) and y > (optical resolution), where x is the spacing of the laser-absorbed region and y is the spacing of the laser-nonabsorbed region on the substrate.

We have demonstrated ZnSe-based white light emitting diodes (LEDs) with longer lifetimes of over 10,000 h at 14.5 A/cm² by introducing an i-ZnMgBeSe/p-ZnMgSe double cladding structure, which includes a very thin i-ZnMgBeSe layer for suppressing electron overflow and a p-ZnMgSSe layer for efficient p-type carrier concentration. By adopting the double cladding layer instead of only the conventional p-ZnMgSSe cladding layer, rapid degradation is suppressed and the lifetime tendency becomes similar to that of the LEDs consisting of a III–V semiconductor system. The device simulation and the temperature dependence of optical power showed that the i-ZnMgBeSe layer played the main role in increasing electron confinement. Our experimental data and reliability test results indicate that the suppression of the electron overflow is essential to achieve a long lifetime acceptable for practical use.

Sublimation boule growth of 6H-SiC on (1120) 6H-SiC substrates was investigated. Hollow defects were generated in the crystals grown on (1120) substrates, and they penetrated along the growth direction to the as-grown surface. A new growth model of SiC on (1120) SiC substrates that distinguishes between two-dimensional growth and three-dimensional growth is proposed. The generation of both the stacking faults and the hollow defects on (1120) substrates was attributable to the three-dimensional growth. The growth conditions were modified and applied to suppress the generation of hollow defects. These conditions included the reduction of the growth temperature in the initial stage of the growth, and the increase of the nitrogen concentration in the vapor phase. Due to the changes in the growth conditions, the density of the hollow defects on (1120) substrates was reduced by one order of magnitude to approximately 10³ cm^-2. An atomically flat as-grown surface was obtained by the sublimation boule growth technique in nitrogen ambient.

In this study, we compared the hot carrier effects of T-gate and H-gate Silicon on Insulator p-Type Metal–Oxide–Semiconductor Field Effect Transistors (SOI pMOSFETs) operating under dynamic threshold mode (DT-mode) and normal mode at various temperatures. By operating under DT-mode, the threshold voltage shift is reduced. However, enhanced degradations in maximum transconductance and drive current are observed when operating under DT-mode at room temperature, especially for the T-gate structure. The transconductance enlargement effect for devices operating under DT-mode, together with the non-uniform potential distribution in T-gate structure, are believed to be responsible for the observed enhanced degradations. At elevated temperatures, the hot-carrier-induced degradations are alleviated for devices operating under DT-mode, to levels close to those of the normal mode, due to reduced impact ionization at higher temperature.

We investigated the influence of different indium tin oxide (ITO) surface treatments on the performance of organic solar cells with different device architectures. Two types of devices (CuPc in contact with ITO treated with different treatments and C₆₀ in contact with ITO treated with different treatments) were fabricated. The surfaces of CuPc and C₆₀ layers deposited on ITO substrates treated with different surface treatments were examined using atomic force microscopy. The devices were characterized by measuring current-voltage characteristics in the dark and under AM1 illumination. We found that a one order of magnitude improvement in the AM1 power conversion efficiency for ITO/CuPc/C₆₀/Al cells can be achieved for optimal ITO surface treatment, while ITO/C₆₀/CuPc/Cu devices exhibit less sensitivity to surface treatments. Moreover, these devices exhibit better performance compared to ITO/CuPc/C₆₀/Al devices. The observed differences in sensitivity to surface treatments were attributed to difference in the dependence of the film surface on ITO surface morphology for CuPc and C₆₀.

We have investigated the Sb-induced phase transition of the reconstructed Si(112) surface by low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). A sharp sixfold hexagonal LEED pattern was observed when Sb was deposited on the clean Si(112) surface at 300°C, corresponding to the bulk-terminated 1×1 structure of the Si(111) surface. From the LEED pattern and the XPS results, we suggest a surface structure corresponding to the LEED pattern with (111) - 1×1 + weak 5×1 spots for the Sb/Si(112) surface.

An optical polishing technology utilizing a line shaped excimer laser beam was introduced to reduce the microroughness of the tungsten films deposited onto the Si wafer surface. The results of the microroughness reduction and the comparisons were made before and after the line beam irradiations for as-grown and post-chemical mechanical planarization (CMP) tungsten films as a function of irradiated laser wavelength, in 248 nm and 308 nm, laser fluence, and the irradiated number of pulses. Characterizations of the microroughness were performed by atomic forced microscopy. The root-mean-square (RMS) roughness and peak-to-valley, R_p-v, roughness of the as-grown tungsten films were decreased by about 30%–40% compared with the initial values. The RMS roughnesses of the post-CMP tungsten films were 25–30 Å for a 5 µm×5 µm measurement. Fluctuations of the reduced microroughness were mainly caused by the beam inhomogeneity and local distributions of the hot (peak energy) spots along or across the line beam. The lowest RMS roughness of 8.0–8.4 Å was obtained for the post-CMP tungsten films by the irradiation of 30 pulses of 308 nm with a fluence of 100 mJ/cm². Irradiation of the 248 nm and 308 nm homogenized flat-top line beam reduced the peak-to-valley roughness, R_p-v, of the post-CMP tungsten films down to 1/3 of its initial value. It was found that the optimum number of pulses for microroughness diminution of the post-CMP tungsten film is 50 pulses with a fluence of 150 mJ/cm². The wavelength dependency of the microroughness diminution was not surprising, but 308 nm irradiation showed a slightly better performance with consistent results than the 248 nm irradiation did.

The structure of nanometer-size pores in periodic porous silica low-dielectric-constant (low-k) films was investigated by in-plane and out-of-plane X-ray scattering and diffraction. The periodic porous silica films were prepared by spin coating of a tetraethoxysilane (TEOS)-based precursor solution mixed with self-organizing surfactant sacrificial template molecules. TEOS vapor treatment before the removal of the sacrificial templates was shown to help maintain the periodically ordered structure during the template removal process at 673 K. It was demonstrated that a successful control of pore structure is feasible by the selection of pore-generating surfactant template molecules. Namely, the pore diameter, porosity and dielectric constant were controlled successfully by varying the alkyl chain length in the surfactant template molecules.

Pore size distributions in a series of periodic porous silica low-dielectric-constant (low-k) films were determined by the analysis of adsorption/desorption isotherms of heptane. The isotherms were obtained from in situ spectroscopic ellipsometric measurements at room temperature in a vapor cell. The porous silica low-k films were prepared by the spin coating of a mixture of silica precursor and alkyltrimethylammoniumchloride surfactant template solutions. A systematic increase in pore diameter with an increase in the alkyl chain length of the template molecules was observed. It is concluded that the in situ spectroscopic ellipsometry in a vapor cell as a nondestructive technique of characterizing pore structures in porous low-k films has the potential to clearly distinguish such a slight difference in pore diameter as is caused by only –(CH₂)₂– in a template molecular structure.

A novel broadband superluminescent diode (SLD), which has a symmetric graded tensile-strained bulk InGaAs active region, is developed. The symmetric-graded tensile-strained bulk InGaAs is achieved by changing the group III TMGa source flow only during its growth process by low-pressure metalorganic vapor-phase epitaxy (LP-MOVPE), in which the much different tensile strain is introduced simultaneously. At 200 mA injection current, the full width at half maximum (FWHM) of the emission spectrum of the SLD can be up to 122 nm, covering the range of 1508–1630 nm, and the output power is 11.5 mW.

A traveling-wave amplifier in the terahertz range using two-dimensional electron gas is proposed and analyzed using quantum mechanics including electron scattering. It is shown theoretically that the terahertz amplification is possible with high net gain coefficient at the temperature of 100 K.

The effective demagnetizing factors (N_x^e and N_y^e) of the second-order magnetocrystalline anisotropies of cubic and hexagonal single crystals (K₂ and K_u2) for use in Kittel's ferromagnetic resonance formula are derived using previously proposed equations. The saturation magnetization is assumed to align with a static field. Six arrangements for films with the static field applied in the film plane are calculated: (1) perpendicular uniaxial anisotropy, (2) in-plane uniaxial anisotropy, (3) cubic-crystal (001) face, (4) cubic-crystal (011) face, (5) cubic-crystal (111) face, and (6) oblique anisotropy films.

A design procedure, based on the flip-flop tuning search algorithm, is applied to design universal visible antireflection coatings for various substrates with indices 1.45, 1.50, 1.55, 1.60, 1.65, 1.70, 1.75 and 1.784. The universal broadband antireflection coating designs obtained by the flip-flop tuning method for a two-material and a three-material system with 80 sublayers of 300 nm thickness starting at high index and middle index lead to 10-layer structures, and the average reflectivities of these designs for the eight different substrates over the entire visible spectral region (400–750 nm) decrease to lower than 0.199% and 0.201%, respectively. Although the antireflection performance for each substrate is somewhat less than the optimum, it is acceptable for most applications.

A design algorithm based on the minimizing search technique was proposed for designing the normal-incidence wideband visible or wideband infrared multilayer antireflection coating. The method utilized a tuning operation of the thickness of sublayers first, and then refined the antireflective performance and simplified the design by a layer minimizing operation. It was shown that the average visible spectral reflectivities of three-material thirty-layer and two-material thirty-layer minimizing search antireflection coating designs for glass substrates were reduced to less than 0.054% and 0.056% with a 12-layer structure, and the average infrared reflectivity of a two-material forty-layer minimizing search antireflection coating design for a germanium substrate over the broadband spectral region of 7.7–12.3 µm was reduced to less than 0.488% with a 22-layer structure.

Among potential inorganic thin films, perovskite-structured barium titanate (BaTiO₃) is particularly attractive due to its large ferroelectric response and large optical nonlinear coefficients. SiO₂ material is also important in semiconductor processing. Therefore, we study the nonlinear optical (NLO) thin film deposited on a SiO₂ substrate. We report our investigation of a BaTiO₃ thin film on a silica glass (SiO₂) substrate grown by rf magnetron sputtering. We measured the second-harmonic generation (SHG) and calculated the second-order nonlinear optical coefficients from the BaTiO₃/glass by using the Maker fringes technique. From our experimental results, we found that by applying corona poling, the nonlinear optical coefficients in BaTiO₃/glass can be increased. The SHG of the nonlinear thin film by poling is dependent on temperature.

The absorption spectra, single-photon induced fluorescence spectra, two-photon absorption (TPA) and optical limiting behaviors of organic dye trans-4-[p-(N-hydroxyethyl-N-methylamino)styryl]-N-methylpyridinium iodide (abbreviated as ASPI) have been studied in three solvents [chloroform, benzyl alcohol, dimethyl formamide (DMF)] with different polarities. The optical properties of ASPI were found to be strongly influenced by the solvents used. With increasing polarity of the solvents, the absorption and fluorescence peaks of ASPI solutions exhibit marked blue and red shifts, respectively, and the effective TPA cross sections and the optical limiting effects decrease. The TPA cross sections of ASPI measured in the three solvents are 3.41×10^-47 (chloroform), 1.86×10^-48 (benzyl alcohol) and 1.05×10^-48 (DMF) cm⁴·s·photon^-1.

A numerical analysis for far-field pattern distribution of an array grating compressor showed that alignment of segmental gratings can be achieved by adjusting only two tilted angles and the relative position distance of two segmental gratings. An alignment tolerance criterion was set up with a simple formula for an array grating with the size of meter order. For the example of an array grating with a size of 0.5 m, the angular and position tolerances are required to be 0.25 µrad and λ/13, respectively.

Through experiments, we demonstrate accurate pulse shaping of femtosecond optical pulses in both amplitude and phase, prior to chirped pulse amplification. The nonlinear transfer function of the amplifier was compensated with feedback control referring to the amplified pulse shape measured by frequency resolved optical gating (FROG) or temporal analysis, by dispersing a pair of light e fields (TADPOLE). In FROG-referring control, the pulse shaper is adaptively controlled using a control index calculated from the two-dimensional FROG trace image, while in TADPOLE-referring control, the shaping phase-mask is corrected only a few times using the reconstructed spectrum phase of the output pulse. The performance and limitations of pre-shaping systems are discussed by comparing two pulse shaper devices, namely a liquid-crystal spatial light modulator and an acoustic optical phase dispersion filter, two pulse measurement techniques, and two feedback control schemes.

We show that holographic retarders using form birefringence can be designed to allow accurate matching of the dispersion of a liquid crystal device. A twisted nematic (TN) liquid crystal display (LCD) is compensated using stacked, dispersion matched, holographic retarders and the results are compared with a TN-LCD compensated by a single, splayed optic axis retarder on both sides of the LC layer. The new compensator design is shown to have excellent qualities, and the potential to surpass previous designs.

We have fabricated air-bridge type two-dimensional photonic crystal waveguides (2D-PCWs) using two high-throughput processes only: holography and photolithography. Despite the existence of misalignments of a defect line with respect to the air-hole arrays, waveguiding in both straight and 90°-bent PCWs was clearly observed at the wavelength of 1.55 µm. We also estimated the upper bound in propagation loss of our straight PCWs, which was measured to be about 40 cm^-1.

As a preliminary experiment for achieving a monolithic integration of a semiconductor laser and an optical isolator, a Fabry–Perot laser integrated with an optical passive waveguide was fabricated using the wafer grown by a selective-area growth technique. We report the characteristics of the laser diode and the loss estimation in the fabricated device.

We propose a new structure for all-optical switch (AOS) and all-optical memory (AOM) devices that use the resonant photon tunneling effect in multi-layered GaAs/AlGaAs structures. Numerical calculations revealed a sharp peak in tunneling probability at a resonant incidence angle in double-barrier AOS structures. The resonance angle can be controlled by changing the refractive index of an active layer. During simulation, we demonstrated that the AOS with the new structure acts as an all-optical NOT gate. We also found that optical bi-stability occurs in the dependence of reflectivity on control light intensity. This bi-stability is caused by the penetration of intense input light to the active layer based on the resonant photon tunneling effect, and it is clear that an AOM can be achieved through this bi-stability effect. These results indicate that the resonant photon tunneling effect in multi-layered semiconductor structures can effectively be used to attain efficient all-optical devices.

The swing-arm-type voice coil motor (VCM) is widely used as an actuator in rotating data storage devices. Recently, it has been found that to achieve a faster data transfer rate and a higher data storage areal density, a high performance actuator is required. Moreover, a small form factor has become desirable for portable devices. In this paper, a novel magnetic circuit of VCM with multisegmented magnet array (MSMA) is proposed. Both the magnetic circuits of the conventional VCM and the MSMA VCM are optimized using the 3D finite element method. Sample magnetic circuits are fabricated with optimally designed parameters and a comparative analysis is carried out. The performances of magnetic circuits are evaluated and the experimental results prove the effectiveness of the proposed magnet array.

We report an optical configuration with a flying head for a near-field recording system. The configuration consists of a fixed optical unit and condensing optics based on the flying head structure. While the fixed optical unit includes a light source and a signal-detection unit, the condensing optics include a solid immersion lens (SIL) embedded in the flying slider and infinite objective lens arranged on the flying slider. Free-space propagation using a collimated beam is employed to optically connect these two units. After we investigated the head structure and its fabrication process, we evaluated the fabricated optical flying head, both as an optical head and a flying head. The jitter was 8.87% when the shortest mark length was 0.364 µm. The C/N ratio was 49.53 dB for 0.2 µm of the mark length. The tolerances of relative tilt and decenter between the two optical axes of the fixed optical unit and the condensing optics which were derived experimentally were ±0.3 deg and ±150 µm. These results suggest that the optical configuration is adequately practical even for use in mass production.

In the present paper, we propose a novel method which permits us to fabricate fluorine-doped silicon dioxide (F-doped SiO₂) films on various substrates at room temperature. The films were selectively grown on a substrate by simultaneous 157-nm F₂ laser illumination of a silicone rubber target, a polytetrafluoroethylene (PTFE) target, and the substrate. Fourier transform infrared spectroscopy (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) spectra showed that the films had a uniform fluorine concentration in the depth direction and no contaminants, such as carbon and hydrocarbon. The films were photochemically grown on the substrate in an atmosphere of gases evolved from silicone and PTFE by F₂ laser illumination. The relative dielectric constant of the films was lower than that of the SiO₂ films grown by F₂ laser illumination without a PTFE target, namely, 3.6 at a laser fluence of 22 mJ/cm². The F-doped SiO₂ film formed at a higher a laser fluence had a lower refractive index and lower relative dielectric constant.

We propose a novel driving method which is very efficient for the display of moving pictures on a π cell. In the proposed driving method, each scan pulse is divided into two parts for fast switching unlike the conventional active matrix driving method that uses one scan pulse for each frame. By overdriving or underdriving the π cell using an appropriate data voltage during the first scan time and applying a desired data voltage to the cell during the second scan time, we can achieve fast switching between all gray levels within the time between the first and second scan pulse.

For the improvement of the conversion efficiency of CdS/CdTe solar cells by applying the wavelength conversion properties, the spectroscopic studies of the fluorescent laser dye Rhodamine 6G (Rh6G)-doped into polyvinylbutyral (PVB) and polymethylmethacrylate (PMMA) were carried out. It was found that all the photoluminescence excitation (PLE) spectra below 540 nm were effectively converted to photoluminescence (PL) spectra in the wavelength region above 550 nm where the solar cell possessed a high spectral quantum efficiency. The external quantum efficiencies of PVB:Rh6G and PMMA:Rh6G films were estimated to be 0.9±0.05 and 0.4±0.1, respectively. When the PVB:Rh6G film was placed on the top of the CdS/CdTe solar cell, both short-circuit current and conversion efficiency increased by 11% compared with the cell with no film.

Thermoluminescence has been observed in X-ray-irradiated CdS-doped glass. The intensity of thermoluminescence is proportional to the X-ray dose up to 10 Gy. The intensity of thermoluminescence for Asahi Y-44 is approximately 0.5% of that of phosphor for a commercial radiation dosimeter: MSO-S (Mg₂SiO₄:Tb). Photofading of Y-44 is markedly lower than that for MSO-S.

The smallest discrete piezoelectric ultrasonic motor using bulk ceramics was developed. We are proposing basically a two-part motor: stator and rotor. The stator of the present motor consists of a hollow metal brass tube with outer diameter of 1.6 mm, inner diameter of 0.8 mm and length of only 4 mm with 2 PZT plates bonded onto it. Owing to the asymmetrical stator surface, two degenerated orthogonal bending modes were slightly split, resulting in a wobbling motion. Thus, the motor can be driven by a single driving source. The rotor is a spring, which is basically different from previous designs, pressed at both ends to the stator by a pair of ferrules. Consequently, the length of the whole motor assembly was reduced significantly; a final motor length of only 5 mm was obtained. The working frequency under zero load was approximately 227–233 kHz. Although the size is small, relatively high power was obtained under an optimized load condition: torque of 0.06 mNm, maximum power of 3.2 mW with a speed of 118 rad/s, and maximum efficiency of 11% under 48 Vrms at 221 kHz.

The time-dependent dielectric relaxation behavior of Ag(Ta,Nb)O₃ interdigital capacitors was investigated for tunable device applications. Ag(Ta,Nb)O₃ thin films, which have high k-factor (tunability/loss tangent), were deposited on the oxide substrates by pulsed laser deposition technique. Ag(Ta,Nb)O₃ thin film on the LaAlO₃ substrate has an epitaxial relationship with the substrate. The observed tunabilities and K-factors of Ag(Ta,Nb)O₃/LaAlO₃ and Ag(Ta,Nb)O₃/Al₂O₃ interdigital capacitors were 5.9% and 17.8 and 3.8% and 9.9, respectively, at ±40 V (maximum electric field of 100 kV/cm), 300 K, and 1 MHz. Capacitance relaxation follows the power law C(t)=C_∞+C₀(t/1s)^-β with a very small exponent negligibly fitted in the time domain. Due to this small exponent, the capacitance was changed by less than 0.05% in 2 V in 71 s. Time-dependent leakage current was measured by employing the Ag(Ta,Nb)O₃(0.4 µm)/Al₂O₃ interdigital capacitor. The time-dependent relaxation current follows the power law j(t)=j_leak+j₀(t/1s)^-α with an exponent α=0.98, j_leak=1.14×10^-14, and j₀=11.42 s.

The effects of Al₂O₃ additive on the microstructure and microwave dielectric properties of Ba(Zn_1/3Ta_2/3)O₃ (BZT) ceramics were investigated. The BZT ceramics has a 1:2 ordered hexagonal structure. The degree of the 1:2 ordering did not decrease with the addition of Al₂O₃. Grain growth occurred and the liquid phase formed for the Al₂O₃-added BZT ceramics sintered above 1580°C. The liquid phase contains high concentrations of Ba and Al ions, which could be responsible for the grain growth. When a small amount of Al₂O₃ was added, the relative density slightly decreased but the Q value was markedly enhanced. The increase in the Q value was not related to the relative density or the 1:2 ordering. In contrast, the improvement in the Q value occurred in specimens in which grain growth occurred. Therefore, the increase in the grain size is considered to be responsible for the improvement in the Q value of Al₂O₃-added BZT.

BST thin films and BSR interlayers were deposited by pulsed laser deposition (PLD) and liquid-delivery metalorganic chemical vapor deposition (LDMOCVD) onto Pt/TiO₂/Si substrates, respectively. Ultrathin BSR conductive layers were inserted at the BST/Pt interface to improve the dielectric properties of BST thin films. BST films deposited on ultrathin BSR interlayers showed an improvement in roughness and microstructure compared with those without BSR layers in an overall range of BST film thickness. The temperature-independent interface capacities in BST/Pt and BST/BSR/Pt structures are approximately 8.9 and 20 µF/cm², respectively. The dielectric properties of BST films were improved by the increase in interface capacity as well as roughness and microstructure using the BSR conductive layer which is similar to BST in crystal structure and chemical composition.

The object of our study was to clarify the mechanism of the bending-electrostrictive response of a polyurethane film. We investigated the mechanism using the pulsed electroacoustic method for measuring the space charge distribution in the film. The measurements revealed a similarity between the time courses of the bending-electrostrictive response and the space charge accumulation. That is, the film gradually bent to the cathode side during the first electric-field application to a virgin sample. However, it quickly bent during the succeeding second application. On the other hand, the measurement of the space charge showed that a negative space charge gradually accumulated inside the anode during the first application. However, it quickly accumulated during the second application. Time plots of the bending deformation and the space charge density clearly showed the above similarity in the response profile. Such a similarity suggests that the space charge is closely related to the bending electrostriction mechanism.

Bi₄Ti₃O₁₂ (BIT) thin films with TiO₂ anataze buffer layer were deposited on the Pt/Ti/SiO₂/Si substrates by metalorganic chemical vapor deposition (MOCVD) using Bi(CH₃)₃ and Ti(i-OC₃H₇)₄ sources. When the substrate temperature was fixed at 500°C, the as-deposited BIT thin film exhibited highly a- and b-axes-oriented BIT single phase. The interface between the BIT thin film and the substrate was very smooth. The as-deposited BIT thin film consisted of small grain and exhibited a good P–E hysteresis loop. Subsequently, the remanent polarization (P_r) of the as-deposited BIT thin film with film thickness of 400 nm was 2P_r=44.4 µC/cm².

The transformation of high-frequency vibrations of piezoelectric elements into continuous linear motion of a slider is one of the main tasks of a linear piezoelectric motor. To produce a high thrust force in the piezoelectric linear actuator, we proposed the compound piezoelectric linear actuator based on a "shaking beam" excited by two sources of longitudinal mechanical vibrations shifted by π/2. The compound actuator consists of two shaking beams and is rigidly fastened. The finite element method (FEM) was used to define structural and electrical boundary conditions for the compound piezoelectric actuator. FEM analysis showed that the compound actuator's trajectory was elliptical. Experimental research has shown that the compound piezoelectric actuator has high thrust force.

The P–E curves of Pb[Zr_0.52Ti_0.48(Mn_1/3Nb_2/3)]O₃ ceramic with different sintering temperatures and variations of strontium (Sr) compositions have been investigated. It has been demonstrated that the polarization–field hysteresis curves show "pinched" shapes instead of the normal square-like P–E loops. In this paper we present the temperature dependence of the P–E curves for the ceramic with different firing temperatures and Sr dopants and show that the critical transitional temperature at which disappearance of the "pinched" shape occurs is highly dependent on the tetragonality (c/a ratio). In the meantime, the peculiar hysteresis loops are assumed to be the result of the pinning effect of the defect dipoles, which are slowly oriented antiparallel to the poling direction, and are finally broken down by the thermal activation.

Excellent electrooptical (EO) characteristics of an amorphous in-plane switching twisted nematic liquid crystal display, which is fabricated without the conventional rubbing treatment, are demonstrated. A wide and uniform viewing angle characteristic without showing gray scale inversion or color shift can be realized by the multidomain alignment, which is called `amorphous alignment'. The response time was much less than 17 ms and relaxation time was as fast as 10 ms. The device may contribute not only to the simplification of the production process but also to significant improvement of the response time, compared with the conventional rubbed liquid crystal display.

The transition process between bistable states in the bistable nematic (Bi-Nem) cell based on the anchoring breaking phenomenon has been strictly simulated by computer. In our simulation, the surface tilt angle dependence of the contribution of azimuthal anchoring to the surface free energy density has been taken into account. This leads to successful reproduction of the bistable operation of the Bi-Nem cells by the computer simulation. As a result, it has been clarified that in the transition process from the uniform state to the twisted state, the molecular orientation takes the 270 deg. twisted state at first and then changes toward to the 180 deg. twisted state. From our simulations, it is confirmed that the bistable transition occurs in limited regions of polar and azimuthal anchoring energy on the slave plate.

In thin-film-transistor liquid-crystal display (TFT-LCD), particularly pixel-electrode configuration of in-plane switching (IPS) mode, crosstalk caused by capacitive coupling between pixel electrodes and data lines could result in image degradation. We derived the capacitive coupling ratio (CCR) of the IPS cell and analyzed the CCR of three conventional TFT-IPS pixel- and common-electrode structures to quantify the crosstalk properties. The effect of coupling voltage on electro-optics characteristics has been investigated. Our results showed that a common electrode placed adjacent to the data line could shield capacitive coupling between the data line and the pixel electrodes, and reduce CCR from 13% to 2.4% and crosstalk intensity ratio (CIR) from 21.2% to 3.9%. We also report the common-overlapping-pixel structure that not only increases the aperture ratio by 1.28 times but also reduces CCR from 13% to 9.1%.

A mechanical model is established to explain phase behaviors and thermal properties of liquid crystals (LCs). We postulate that LC phases are micro-machine systems consisting of an ensemble of molecular rotors. The phenomena of the thermal stability of phase and polymorphism are interpreted in terms of mechanics that involve basic parameters such as center of gravity (G), moment of inertia (I_A), eccentricity (ε) and mass deviation along the molecular axis (δ). A novel concept of "slim isomer" and "fat isomer" for the fluorinated LC system is proposed. Furthermore, the parameter ω_c, critical rotational velocity around the long molecular axis is adopted to analyze the thermal stability at the critical point. It is determined that the value of ω_c is a key parameter for the characterization of each homologous series.

The transient behavior of homeotropic-planar relaxation in surface stabilized cholesteric liquid crystals bounded by parallel substrates has been investigated both experimentally and numerically. By monitoring the evolution of transient transmittance, we observe that the homeotropic-planar relaxation after the electric field is switched off occurs via a transient planar state. The effect of bias waveform on the relaxation process is also studied. On the basis of this knowledge, we design a driving waveform to reduce the relaxation time.

Refractive index gratings into an azo-polymer waveguide were fabricated by irreversible photo-induced bleaching (photodecomposition) of the polymer. The waveguide grating was formed by exposure of an interference pattern from two laser beams. Coupling characteristics of the waveguide grating were investigated around the infrared wavelength region. The coupling efficiency of the grating was dependent on the polarization direction of the guiding beam. This phenomenon seems to result from the anisotropic refractive index change due to the photobleaching at the vertical plane of the film. Furthermore, we demonstrated a tunable wavelength filter with the refractive index gratings into the azo-polymer waveguide. This filter has a spatial tunability, i.e., wavelength tuning can be attained due to thermooptic refractive index change of the polymer. In the fabricated wavelength filter, the diffraction pass wavelength is tuned over 19 nm at around the 1.3 µm from 5°C to 65°C.

The density and the isobaric heat capacity of alumina in its liquid and undercooled states were measured using an electrostatic levitation furnace. Over the 2175 to 2435 K temperature interval, the density can be expressed as ρ(T)=2.93×10³-0.12(T-T_m) (kg·m^-3) with T_m=2327 K, yielding a volume expansion coefficient α(T)=4.1×10^-5 (K^-1). In addition, the isobaric heat capacity can be estimated as C_P(T)=153.5+3.1×10^-3(T-T_m) (J·mol^-1·K^-1) if the hemispherical total emissivity of the liquid remains constant at 0.8 over the 2120 K to 2450 K interval. The enthalpy and entropy of fusion have also been calculated respectively as 109.0 kJ·mol^-1 and 46.8 J·mol^-1·K^-1.

Structural, dielectric, ferroelectric and piezoelectric properties of lead magnesium niobate–lead titanate, PMN–PT (66:34), prepared at different sintering temperatures (1150–1250°C) are discussed for actuator applications. System sintered at 1200 and 1250°C showed better perovskite phase stabilization and higher values of dielectric constant (ε_r). Remnant polarization (P_r) was found to be higher (45 µC/cm²) for the system sintered at 1250°C. The piezoelectric coefficients, d₃₃, d₃₁, d_h and strain induced in the system by a large electric field were found to be sintering temperature dependent. Hysteresis free strain behavior of the system sintered at 1200°C showed the suitability of this material for actuator applications.

Nucleation experiments (metastable zone width) were carried out for 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) solutions at different saturation temperatures with and without the addition of a chelating agent. Using the results obtained from metastable zone width experiments, the slope nucleation method growth of DAST was performed. It was revealed that the addition of the chelating agent EDTA significantly suppresses spurious nucleation and cluster formation in the DAST solution, so that fewer, but larger, crystals can be easily obtained. With EDTA, the crystals grown also showed better crystallinity, hardness, and transparency in the visible/near-infrared region.

This research is focused on exploring the fluid loading effects on the dispersion spectra of Lamb modes propagating in a piezoelectric (X-LiNbO₃) plate. Theoretical calculations based on a partial wave analysis are used to characterize the shifting behaviors of dispersion spectra caused by the loading fluid with mechanical/dielectric properties. On the other hand, the fluid loading effects are experimentally investigated by measuring the dispersion spectra of an X-LiNbO₃ plate with free and immersed boundary conditions. Results of the theoretical calculations are supported by the measurement. It is also found that, for the case of water as a common immersion fluid for an X-LiNbO₃ plate, the dielectric loading effect dominates the shifting of the dispersion spectra, while the mechanical density loading effect can be neglected.

A high-pressure phase of TiO₂ with a baddeleyite-type related structure has been synthesized via very rapid heating-cooling under energetic Nd-YAG laser pulse irradiation of the Ti target in oxygen ambient. Spherical nanoparticles transformed martensitically into baddeleyite-type and then α-PbO₂-type structures with accompanied transformation twinning, shearing and shape change into ellipsoid upon electron irradiation. The relatively large particles followed the same transformation path yet with alternative lattice correspondence and additional multiple deformation twinning of the baddeleyite type.

We demonstrate the use of confocal fluorescence microscopy in visualizing the exotic 3D topological structure of pillared-hollow spheres of mesoporous silicates. The mesoporous structures are labeled by rhodamine 6G dye to facilitate visualization. The optical sectioning capability and noninvasiveness of confocal microscopy not only further clarifies these hollow spheres' unique topological structure but also enables mapping of their genus distribution.

The bottom electrode crystallization (BEC) method was applied to the crystallization of lead zirconate titanate (PZT) thin films deposited by laser ablation over Si/SiO₂/Ti/Pt structures, with the platinum films being deposited at two different temperatures. The results were compared with those obtained by rapid annealing with halogen lamps and furnace annealing. PZT films crystallized over platinum deposited at lower temperature have larger grains and tend to have a (111) preferential orientation, while those crystallized on platinum deposited at higher temperature have smaller grain sizes and tend to have a (101) preferred orientation. The results are consistent with the increase of titanium diffusion as the temperature for platinum deposition increases, having as a consequence a greater number of nucleation centers on the platinum surface. The ferroelectric properties of the films crystallized with the BEC method are good, being similar to those obtained with the other crystallization methods using the same parameters.

Yttria-stabilized zirconia (YSZ) was grown on Si(100) substrate by pulsed laser deposition (PLD). The laser used in this study was a 266 nm YAG laser with a second function generator modulating only the Q-switch while the primary generator modulated the flash lamp (slower Q-switch). Epitaxial growth was verified on YSZ film deposited without oxygen gas followed by primary deposition in oxygen atmosphere on Si substrate with a ∼0.4-nm-thin oxide layer. The crystallinity was strongly dependent on the thickness of the buffer layer deposited prior to the primary deposition of YSZ. The epitaxial growth was confirmed by φ scan, and ω scan (rocking curve) showed the full width at half maximum (FWHM) of 1.1 deg. The required oxygen pressure for epitaxial growth was quite high compared to that of excimer deposition.

Transparent conducting indium tin oxide (ITO) films were prepared on a glass substrate by DC magnetron sputter type negative ion source from a target of a mixture of In₂O₃ (90%) and SnO₂ (10%). In order to investigate the influence of cesium (Cs) partial pressure (P_Cs) on the optoelectronic property of ITO films, the P_Cs was varied from 1×10^-3 to 2.2×10^-3 Pa. The O₂/Ar flow rate, working pressure, power density, and substrate temperature were kept constant at 3.6%, 9×10^-2 Pa, 2.5 Wcm^-2 and 70°C, respectively. By optimizing the P_Cs at 1.7×10^-3 Pa, transparent (transmission ∼81% at 550 nm) and conducting (resistivity ∼4.3×10^-4 Ωcm) ITO films were prepared. Atomic force microscopy (AFM) images showed that the surface morphology also varied significantly with P_Cs and that the lowest surface rms roughness was 0.6 nm measured at P_Cs=1.7×10^-3 Pa. XPS measurement showed that the Cs concentration in the ITO films was less than 0.2 at%.

We have developed a new pulsed laser deposition method for fabricating Er-doped silicon-rich silicon oxide (SRSO:Er) films. A target composed of a pure Si disk and an Er metal strip was ablated by a line-focused laser beam in oxygen atmosphere. The oxygen concentration that determines the relative concentrations of the three phases (Si–Si, SiO_x, and SiO₂) in the film was easily controlled by varying the ambient oxygen pressure. The photoluminescence intensity at 1.54 µm from Er³⁺ ions was strongly dependent on the amount of the Si–Si phase in the SRSO:Er films.

In this paper, we, for the first time, present the effects of the thermal annealing of the W/SiO₂ multi-layer Bragg reflectors on the resonance characteristics of the ZnO-based film bulk acoustic wave resonator (FBAR) devices. In order to improve the resonance characteristics of the FBAR devices, we employed a thermal annealing process after the Bragg reflectors were formed on a silicon substrate using a radio frequency (RF) magnetron sputtering technique. As a result, the resonance characteristics of the FBAR devices were observed to strongly depend on the annealing conditions applied to the Bragg reflectors. The FBAR devices with the Bragg reflectors annealed at 400°C/30 min showed excellent resonance characteristics as compared to those with the non-annealed (as-deposited) Bragg reflectors. The newly proposed simple thermal annealing process will be very useful to more effectively improve the resonance characteristics of the future FBAR devices with multi-layer Bragg reflectors.

The adsorption states of nitrogen on a W(001) surface, particularly the β₁ state appearing at high coverage, have been studied by two new approaches based on thermal desorption spectroscopy (TDS). First, the isotope ¹⁵N was used to discriminate the β₁ state from the β₂ state saturated with ¹⁴N at low coverage. It is proposed for the β₁ state formation that ¹⁵N exposed later stamps ¹⁴N into the octahedral site of the subsurface mainly through single steps around which the atomic distance is extended by nitrogen-induced contracted islands. Secondly, a vicinal surface was investigated to elucidate the role of the steps. Only a small β₁ peak was found, which is interpreted to be a result of suppressed formation of contracted islands due to a large number of surface defects. Other features observed on the vicinal surface are well explained with the proposed model.

The features of self-organized steps and terraces on SrTiO₃ (001) substrates inclined in a [110] direction with various inclined angles (α) have been investigated by scanning tunneling microscopy (STM). The well-defined triangular step edges forming nanodot structures are observed on the surface. The surface features of SrTiO₃ substrates inclined in the [110] direction consist of the combinational features of substrates in the [100] and [010] inclined directions. Details of the distributions of step heights, terrace widths and lengths of step edge dependent on inclined angles are described. The formation of double, triple and triple half steps is observed in self-organized substrates. The surface after self-organization maintains the same ratio of step height to terrace width. The terminations of TiO₂ and SrO planes on the surface are observed visually by an analysis of surface structures. The inclined angle of the substrate inclined in the [110] direction is expected to be an important factor for controlling the density of nanodot structures.

Buried metal/Si interfaces were studied by X-ray reflectivity (XR) for samples which have macroscopically thick metal overlayers with rough surfaces. XR under transmission geometry (transmitted X-ray reflectivity (TXR)) was conducted so as to avoid the troublesome effects caused by the thick and rough overlayers. A 40-µm-sized X-ray beam of short wavelength (λ=0.06 nm) emitted from an undulator in a synchrotron radiation facility was used effectively. TXR of a [Au layer consisting of Au fine particles]/Si interface indicates a sharp contrast to the conventional XR scattered from the Au layer surface: The former (TXR) shows a distinct specular reflectivity from the interface. However, the latter (XR) indicates very weak specular reflectivity above the critical angle due to the microscopic surface roughness of the overlayer. Quantitative analysis of diffuse scattering in TXR profiles yielded a precise electron density at the interface. Both the specular and diffuse TXR from a [liquid Ga]/Si interface support an intermediate layer of approximately 2 nm thick. By considering the average electron density, it is most likely that Ga is sorbed to a large extent in the native oxide at unexpectedly low temperatures (<400 K).

Ruthenium (Ru) thin films were fabricated on TiN, as well as on SiO₂, by metal-organic chemical vapor deposition using tris(2,4-octanedionato)ruthenium. We characterized the Ru films grown on TiN, and compared them with the films prepared on SiO₂. The Ru films deposited on TiN showed weak crystallinity and random grain orientation similar to the films on SiO₂, but revealed notably rougher surfaces than the films on SiO₂. Moreover, deposition rates on TiN were lower than those on SiO₂. These properties of the Ru films grown on TiN originated from the difficulties in nucleation and growth at the initial stage of the deposition. The inferior surface flatness and deposition rate could cause structural instability and poor coverage of the Ru electrode at the bottom of a deep concave hole for a three-dimensional capacitor where the Ru film was in contact with a diffusion barrier metal TiN plug.

We have developed growth processes for HfO₂–TiO₂ composite films using a pulsed-laser-deposition (PLD) method and investigated the film structure which is characteristic to the growth sequences. Structural and electrical properties of the films sensitively depend on the growth conditions. It is observed that crystallization of the film is suppressed by increasing the TiO₂ content. In the case that HfO₂/TiO₂ composition ratio is set to be 50/50, the film is completely in the amorphous phase and, after annealing, the film texture consisting of large HfTiO₄ crystalline grains is formed. The dielectric constant of HfO₂–TiO₂ composite films increases with the increase in the TiO₂ content in the film when the content is less than 50 at%. A marked change in the leakage property of the film is observed when comparing two films with 10 and 20 at% TiO₂. We examine an optimum condition for the growth of HfO₂–TiO₂ composite film with both high dielectric constant and low leakage current.

Liquid crystal (LC) alignment property was investigated on hydrogenated amorphous carbon (a-C:H) thin films. a-C:H thin films were deposited by a remote plasma-enhanced chemical vapor deposition (RPECVD) method with C₂H₂ and He gases. The surface property of a-C:H thin films was controlled by low-energy Ar ion beams. Ion beam irradiation results in the decrease in optical band gap and transmittance, and the increase in the I_D/I_G ratio of a-C:H thin films. LC alignment was generated by ion beam irradiation on the surface of a-C:H thin films. LC alignment property was affected by ion-beam-induced anisotropic sp² structures on the surface of a-C:H thin films.

It was confirmed that the oxygen partial pressure that is used during DC reactive sputtering can influence the generation of oxygen defects on TiO₂ thin films and/or the surface structure, which then affects the photocatalytic characteristics. TiO₂ films were deposited by DC reactive magnetron sputtering on a Si wafer at 250°C under oxygen partial pressures of 0.1 Pa, 0.5 Pa and 0.8 Pa. Structural analysis of the TiO₂ thin films was conducted using X-ray diffraction (XRD), field-effect scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), the photo luminescence method (PL). Characterization of the photocatalytic properties was performed by measuring the concentration change of methylene blue (wet methylene blue method) and the change of the contact angle with pure water. All films showed a polycrystalline anatase structure. TiO₂ thin films deposited under reducing conditions (an oxygen partial pressure of 0.1 Pa) exhibited peaks that are characteristic of Ti³⁺ and can also contain a number of oxygen defects. The domain size was about 150–300 nm, and the domain boundaries were unclear. On the other hand, for TiO₂ thin films deposited in oxidizing mode (oxygen partial pressures of 0.5 Pa and 0.8 Pa), the peak corresponding to Ti³⁺ was not observed. The domain size was between 300–1000 nm and the boundaries were clear. TiO₂ thin films exhibit better photocatalytic properties when the domain size is large and there are fewer oxygen defects in the film. It has been suggested that the decreasing proportion of domain boundaries, which act as trapping centers for electrons, and the lower concentration of oxygen defects, which act as recombination centers for electron-hole pairs, improved the photocatalytic characteristics.

A new tracking detector, scintillating track image camera (SCITIC) was used for hyperon-scattering experiments. Since the hyperon lifetimes are short, the low-energy hyperon-nucleon scattering can be studied only with a track detector used as an active target. The present experiment has shown that the SCITIC is a promising detector for the hyperon scattering experiments. Polarized hyperons Σ⁺ were produced through p(π⁺, K⁺)Σ⁺ reactions with a 1.6 GeV/c pion beam on a liquid scintillator of the active target. Three sets of SCITIC were used to record the pictures of Σ⁺ production and scattering. A kaon spectrometer was used to trigger the SCITIC with a signal of kaon from the reaction. Left/right asymmetries of the Σ⁺p scattering were determined through analyses of the pictorial data, and the results were in accordance with a quark-model prediction that the asymmetry was large in the Σ⁺p scattering while it was small in the ΛN case.

A new type of track detector, scintillating track image camera (SCITIC) has been developed. Scintillating track images of particles in a scintillator are focused by an optical lens system on a photocathode on image intesifier tube (IIT). The image signals are amplified by an IIT-cascade and stored by a CCD camera. The performance of the detector has been tested with cosmic-ray muons and with pion- and proton-beams from the KEK 12-GeV proton synchrotron. Data of the test experiments have shown promising features of SCITIC as a triggerable track detector with a variety of possibilities.

We have investigated the breakdown characteristics of porous metals as discharge electrodes, for applications to multichannel arc gaps. We examined a single-needle/plane gap as a nonuniform electric field gap and a sphere/plane gap as a uniform one using a mirror-finished brass plate and a porous metal as plane electrodes. First, we examined the breakdown characteristics of the single-needle/plane gap. The characteristics we investigated are the DC flashover voltage of the gap, and the formative and statistical time lags of flashover when a flat-top nanosecond pulse was applied to the gap. We predicted that the formative and statistical time lags decrease when porous metals are used as a discharge electrode instead of a mirror-finished electrode. However, contrary to our prediction, a significant difference was not observed in the needle/plane experiments. Then we examined a sphere/plane gap. In this case, a significant difference was observed. Therefore, we confirm that the porous metal is a suitable electrode material for the rail gap.

Laser Plasma X-rays (LPX) with a duration of 10 ps or less, emitted from a solid target irradiated by a femtosecond laser pulse, is useful for time-resolved measurements. The intensity of this radiation is 4×10⁹ photons/shot/4πsr at maximum, which corresponds to the conversion efficiency of laser energy into Kα X-rays of 3.4×10^-5. By simulations of the interaction of a laser pulse with a solid target, the efficiency is shown to increase more than ten times by suppressing the energy of a laser prepulse.

Photoionization cross sections for ionization to Be⁺(2s, 2p, 3s, 3p, and 3d) states from the excited 2s3s ^1,3S states of atomic beryllium, which contain several autoionizing Rydberg series of resonances converging to the Be⁺(2p, 3s, 3p, and 3d) states, have been calculated by an enhanced noniterative eigenchannel R-matrix method. Lower members of the Rydberg series of resonances with n≤10 are identified along with the calculated resonance positions E_r, effective quantum numbers n^*, and widths Γ. The present results are compared with those of previous calculation and very good agreement between them is noted. There is excellent agreement between length and velocity gauges in the present calculation.

TiN films were deposited by using TiCl₄/NH₃ flow modulation chemical vapor deposition (FMCVD). FMCVD consists of repetitive TiN deposition periods by TiCl₄/NH₃, each of which is followed by Cl reduction period. TiN deposition periods are typically 3 s and Cl reduction periods are 1 s. The effect of the number of deposition/reduction cycles and the effect of the partial pressure of TiCl₄ and NH₃ on film uniformity and resistivity were investigated. For a total reduction period of 100 s, increasing the number of reduction periods from 100×1-s periods to 300×0.33-s periods decreased the step coverage. This decrease in coverage was due to residual TiCl₄ during the Cl reduction period by NH₃ that cleared out TiCl₄ at a constant rate, independent of the length of the period of reduction cycle. An Ar purge cycle was used between the deposition and reduction cycles to allow the residual TiCl₄ to clear out before the NH₃ was used for the film reduction cycle. This significantly improved the film step coverage from 50% to over 90%. The minimum film resistivity occurred when the NH₃ partial pressure was 0.25 Torr. NH₃ partial pressure less than 0.25 Torr inhibited film reduction, and NH₃ partial pressure higher than 0.25 Torr enhanced the deposition rate, which also inhibited film reduction. By using the optimum conditions determined in this study, we could obtain TiN films that had film resistivity of about 240 µΩ·cm and step coverage of about 98% at 410°C.

Novel nondestructive readout methods for near-field optical recording has been demonstrated with an amorphous photochromic film. Large refractive index change of an amorphous photochromic layer of 1,2-bis(5-(2,4-diphenylphenyl)-2,4-dimethyl-3-thienyl) perfluorocyclopentene induced by the photochromic reactions is detected by the use of a guided-wave mode and a substrate radiation mode with near-IR laser light. The modulation amplitude in the reflected light intensity before and after the photo-bleaching reaction was as high as 20%.

In this study, various Alq₃ amorphous layers are prepared by vacuum deposition at different substrate temperatures T_sub. The surface morphology, structural information, and electrical and optical properties of these as-deposited layers are studied by atomic force microscopy, X-ray diffraction, J–E curves, and photoluminescence studies, respectively. The optimum deposition conditions for Alq₃ amorphous layers with respect to T_sub are also discussed.

A simple polarization-stepping technique in combination with a common-path homodyne interferometer is proposed in order to measure the phase retardation and the fast-axis angle, which are defined as the linear birefringence vector (LBV), of a wave plate (WP). At three different orientation angles of the linear polarization of incident laser beam, two-dimensional (2-D) interference patterns with respect to different orientation angle are recorded by using a CCD camera. Thus, 2-D phase retardation and fast-axis angle distributions of WP are determined simultaneously. In addition, the elliptical polarization and misalignment of the orientation angle of the incident laser beam induced errors on LBV measurement are discussed.

A new three-dimensional tactile sensor has been developed imitating the human finger based on multifunctional sensing technology. This sensor consists of three coils and two mediums. A step-by-step method is used to realize the multifunctional sensing and in each step, a different quantity is sensed. The processing method in spherical coordinates is introduced to resolve the force vector. On the basis of the unique structure of the sensor and ingenious measurement methods, the authors realized the aim of testing more than one quantity, that is, the magnitude and two direction angles of the force vector, with a single sensor. Here, we discuss the design guideline for and the structure of the sensor, with in-depth studies of the step-by-step measurement method and the experimental results.

The performance of wavelength dispersive (WD) total reflection X-ray fluorescence (TXRF) equipment in conjunction with the high flux quasi monochromatic X-ray of beamline 40XU at the synchrotron radiation (SR) facility SPring-8 has been explored. To obtain a good detection limit for the trace elements, the origin of background events has been studied and we found that the main part of the background is generated in the substrate, presumably by the photoelectron bremsstrahlung. The optimization of the grazing angle of the incident X-ray has been carried out to minimize the background signals in addition to maximizing the fluorescence signals to obtain a good lower limit of detectability (LLD). We evaluated the LLD for light through heavy elements. We obtained the LLD of 5.0×10⁸ atoms/cm² for Ni with the energy resolution of 50 eV. Furthermore, by applying the surface concentration technique for an 8 inch Si wafer, we achieved the Ni LLD of 3.7×10⁶ atoms/cm² for the first time, which is lower than the LLD obtained from chemical analysis such as inductively coupled plasma-mass spectrometry (ICP-MS).

We investigated the curvature effect on the dynamics of long DNA using microfluidic devices. Long DNA has larger configurational entropy in a curved channel than in a straight channel. Under weak hydrodynamic flows, long DNA exhibited a curvature entropy trapping effect. The effect disappeared as the hydrodynamic flow was increased.

The instability of the electron field emission from a standalone multiwalled carbon nanotube with and without an insulator barrier has been investigated. The insulator barrier is an amorphous carbon layer formed by electron beam induced deposition and removed by a heat treatment during the field emission in situ. It is found that the emission current is quite noisy when the tip is covered with the amorphous carbon layer but stable after removing it. The instability is discussed in term of the applied voltage dependence of the noise frequencies and the behavior of the bright spots in the field emission microscope images.

The generation of a carbon nanotube and the first stage of carbon nanotube or carbon fiber formation were investigated in arc electric discharge in a gas mixture of helium and atmosphere with a negative carbon electrode containing lithium or potassium. A carbon stick with lithium and a carbon stick with potassium appeared to accelerate the generation of the carbon nanotube. It was found that the generation of the carbon nanotube is restricted in the range of atmospheric partial pressure from 10 kPa to 20 kPa, and an ideal spherical substance with a size from one hundred nanometers to five micrometers was generated. If the atmospheric partial pressure is lower than that range, the spherical substance changes into a carbon nanotube or carbon fiber. The carbon mesocell, which includes various kinds of elements, can be produced by choosing a carbon stick with additional elements.

Nanometer trenches were successfully produced by NaOH etching of the Ti oxide lines produced by atomic force microscopy (AFM) anodization on Ti thin films of 6 nm thickness on Si thermal oxidation films. The full width at half maximum (FWHM) of a nanometer trench is estimated to be approximately 20 nm, which is comparable to the radius of curvature of the AFM cantilever. It is found that the etching rate of the Ti oxide lines produced by AFM anodization depends on oxide lines height. The selection ratio of etching rate of the Ti thin film and oxide lines is 10 for oxide lines of 2 nm height, the etching rates being approximately 0.08 and 0.87 nm/min, respectively. Ti nanometer wires having 20 nm FWHM could be formed from two nanometer trenches placed close together in parallel.

The defect modes and transmission property of a two-dimensional quasiperiodic photonic crystal (QPC) with defects are studied experimentally and theoretically. It is found that the defects, introduced by removing the dielectric cylinders in the central octagon, may result in various defect modes and resonant frequencies. If the defects possess the same rotational symmetry, the resonant frequencies of the defects are identical. However, the corresponding transmittances can be quite different. This is attributed to the different field distribution leading to various coupling strength between the incident and transmitted waves. When it is symmetrically distributed against the central line which is perpendicular to the incident direction, the transmittance enhances drastically. Based on the wave coupling theory, a simple model is given to explain this phenomenon.