Table of contents

In this review article, we deal with the structures and properties of novel hybrid nanocarbon materials, which are created by the incorporation of atoms and molecules in hollow spaces of fullerenes and carbon nanotubes (CNTs); these hybrid materials are called endohedral metallofullerenes (in the case of metal atom incorporated fullerenes) and nano-peapods, respectively. Synthesis procedures, structural characterizations by synchrotron powder x-ray diffraction, electronic structures, and magnetic properties of endohedral metallofullerenes are discussed. The structure and properties of nano-peapods by high-resolution transmission electron microscopy (HRTEM), electron energy loss spectroscopy (EELS), scanning tunneling microscopy (STM) and field effect transistor (FET) transport measurements together with their synthesis procedures are described. The utilization of the low-dimensional nanosized spaces of CNTs to produce novel low-dimensional nanocluster, nanowire and nano-tube materials is also discussed.

Since a double-sided silicon strip sensor provides two-dimensional position information with high resolution, it has been developed for various uses as a medical imaging sensor, radiation detector, sensing detector in space science, and a silicon vertexing/tracking detector in experimental particle physics. We designed and fabricated a double-sided silicon position sensor in a 5 in. fabrication line. Silicon nitride with a silicon oxide layer was used to prevent damage during sensor fabrication. Since the temperature dependences of the silicon nitride and the silicon oxide are different, the thicknesses of the Si₃N₄ and SiO₂ layers were optimized using the ATHENA process simulation to avoid cracks. We present the measurement results of the electrical characteristics of the sensor such as leakage current and capacitance as a function of reverse bias voltage. We performed tests on the sensor using a ⁹⁰Sr radioactive source and measured the signal-to-noise ratio of the prototype sensor.

In this paper we report the results of our recent study on the semiconductor opening switch. Physical processes, which underlie the operating principle of high-power opening switches based on the nanosecond interruption of super-dense reverse currents in semiconductor diodes (semiconductor opening switch effect), are simulated. The physical processes that occur in the semiconductor structure during the pumping and interruption of the currents are analyzed. The measurement results for the semiconductor opening switch are given and compared with the theoretical calculation results. These calculation results agree well with the measurement results.

A novel low dielectric constant (low-k) film containing no oxygen was evaluated for barrier-free Cu interconnects. The film shows a time dependence dielectric breakdown (TDDB) lifetime which is more than 10 years under operating conditions in 65-nm-technology node. The film has a k of 2.9, a hardness greater than 0.87 GPa, and a modulus greater than 11.7 GPa. The strength of adhesion of the low-k film to Cu is equivalent to that of a conventional organic film to Ta.

We have studied the local motion of hydrogen around a platinum impurity in Si, which was directly probed by measuring the recovery process of stress-induced reorientation of the Pt–H₂ complex by isothermal deep-level transient spectroscopy (IT-DLTS). We found that hydrogen more easily moved in the singly negative charge state of the Pt–H₂ complex than in the doubly negative charge state, and determined the activation energies for the recovery process to be 0.28 and 0.4 eV in the singly and doubly negative charge states, respectively, from a series of isothermal annealing experiments. We also found that the recovery rate of the Pt–D₂ complex in the singly negative charge state is 80% that of the Pt–H₂ complex with the same activation energy of 0.28 eV. This isotope effect clearly proves that both complexes have the same atomic configuration and that their recovery process is governed by the atomic jump of hydrogen (deuterium).

Poly(3-hexylthiophene) thin-film transistors with anodized high-dielectric constant (κ) tantalum pentoxide (Ta₂O₅) and spin-coated poly(4-vinylphenol) (PVP) film dual insulator layers were demonstrated. The polymeric PVP layer covering the Ta₂O₅ can considerably improve the transistor performance. The mobility was increased up to 3.07×10^-2 cm²/(V·s), which is much higher than that obtained by only using a PVP or Ta₂O₅ single dielectric layer. The threshold voltage of the dual-insulator device was as low as 1.7 V, because the Ta₂O₅ insulator possesses a high-dielectric constant.

The effect of geometry on the RF power performance of silicon–germanium heterojunction bipolar transistor (SiGe HBT) unit cells is investigated using various emitter finger spacing (S). Two unit cells, namely, HBT-1 and HBT-2 with the same emitter area of 8×0.6×10 µm³ but with different S values are thoroughly discussed. The S values of HBT-1 and an HBT-2 are 2 and 5 µm, respectively. The obtained measurements, including DC characteristics and small- and large-signal performance characteristics of high-breakdown SiGe HBT unit cells, are presented. The HBT-1 in class-AB operations at 2.4 GHz achieves an output 1 dB compression point (OP_1dB) of 16.0 dBm, a maximum output power of 17.4 dBm, and a peak-power added efficiency (PAE) of 59.1%. Under the same testing conditions, HBT-2 achieves an OP_1dB of 19.6 dBm, a maximum output power of 20.6 dBm, and a PAE of 64.5%. HBT-2 yields significant improvements in all power performance parameters compared with HBT-1, such as 3.6 dB in an OP_1dB, a maximum output power of 3.2 dB, a PAE of 5.4%, and an improvement in the power performance figure of merit (FOM) of approximately 50%, which is attributed to the fact that HBT-2 has a lower thermal effect than HBT-1. The thermal effect affects both DC and output power characteristics. A 1 W power device fabricated by combining eight HBT-2 unit cells achieves a power gain of 14.5 dB and a maximum PAE (PAE_max) of 75% in a class-AB operation at 2.4 GHz. The power density is calculated to be up to 2.6 mW/µm². These results demonstrate that SiGe HBT technology has great potential for high-power amplifier applications.

We evaluated the dependence of ion-implanted B concentration profiles on dose in crystalline Ge substrates (c-Ge) and evaluated B concentration profiles in amorphous Ge (a-Ge) by a Monte Carlo simulation. We showed that channeling is as significant in c-Ge as it is in crystalline Si (c-Si). We found that the concentration profiles in a-Ge and c-Ge can be fitted using a Pearson IV function and a tail function that has additional parameters for expressing the channeling tail, and we established a corresponding database, which enables us to generate ion-implanted profiles at any dose and energy up to the maximum evaluated energy of 80 keV.

An efficient top-emissive polymer light-emitting diode (T-PLED) employing Ag as a semitransparent cathode is achieved by adding Au nanoparticles to a phenyl-substituted poly(para-phenylene vinylene) copolymer (HY-PPV). The efficiency of the T-PLED with Au nanoparticles is 3.4 cd/A, which is much higher than that of the T-PLED without such particles (0.15 cd/A). The superior performance of the device is attributed to the balance between the electron and hole currents induced by the Au nanoparticles, which increases the probability of hole–electron recombination. Furthermore, the device's stability in air can be significantly improved because of the use of stable electrodes.

The silicon wafer temperature change during flash lamp annealing is theoretically evaluated. A calculation model is developed on the basis of a finite difference method taking into account various heat transport phenomena, such as heat radiation from a lamp to a silicon surface, reflection at the silicon surface, heat radiation from a hot silicon surface, light absorption in silicon, and thermal conduction. The effect of the light absorption in a silicon wafer on the temperature profile is negligible at the position of ultrashallow junction formation. The largest temperature slope is shown to be formed by flash lamp annealing because of the agreement of the temperature slope obtained by taking into account heat absorption in silicon with that obtained by assuming heat absorption only at the surface, without accounting for the light absorption in silicon. This study further concludes that the surface reflectivity strongly affects the silicon temperature.

We investigated the influence on hole and electron mobilities of metal–oxide–semiconductors field-effect transistors with a multi-wall channel structure. Though electron mobilities are decreased, using a multi-wall channel structure enhances hole mobilities. We prepared samples with various wall-heights, widths and wall-pitches. The multi-wall channel structure produces a (110) surface channel and a strain produced by polycrystalline silicon gates. These enhance the hole mobility. The degree of hole mobility enhancement depends on the wall-height and wall-pitches. We also investigated the influence of bi-axial strain in the substrate on the multi-wall structure by using strained-Si substrate.

Sublimate reduction from the new bottom antireflective coating (BARC) and gap fill materials in bake process was investigated by means of absorption spectroscopy and the quantitative analysis of sublimation using the quartz crystal microbalance (QCM) sensing element. The small molecular components in BARC and gap fill materials were found to be related to a decrease in the number of sublimate defect. The application of the newly developed BARC and gap fill materials of the polymers with a self cross-link reaction system showed lower sublimate amount. In addition, good resist profiles and 130 nm via fill performance in the via-first dual damascene process were achieved using this self cross-link polymer system. This new system is one of the most promising systems ready to be tested for the mass production of 32–45 nm node IC devices and beyond.

A robust embedded ladder-oxide (k=2.9)/copper (Cu) multilevel interconnect is demonstrated for 0.13 µm complementary metal oxide semiconductor (CMOS) generation. A stable ladder-oxide intermetal dielectric (IMD) is integrated by the Cu metallization with a minimum wiring pitch of 0.34 µm, and a single damascene (S/D) Cu-plug structure is applied. An 18% reduction in wiring capacitance is obtained compared with that in SiO₂ IMDs. The superior controllability of metal thickness by the S/D process enables us to enhance the MPU maximum frequency easily. The stress-migration lifetime of vias on wide metals for the S/D Cu-plug structure is longer than that for a dual damascene (D/D) structure. Reliability test results such as electromigration (EM), the temperature dependant dielectric breakdown (TDDB) of Cu interconnects, and pressure cooker test (PCT) results are acceptable. Moreover, a high flexibility in a thermal design is obtained.

The hydrogen diffusion coefficient in silicon (Si) in an intermediate temperature region (429–800 °C) is obtained using an enhanced formation of thermal double donors (TDDs), which is a phenomenon caused by in-grown hydrogen. An as-grown Czochralski (CZ) Si ingot contains hydrogen as a low-concentration impurity. Although present in a very low quantity, it is possible to observe an enhanced TDD formation due to in-grown hydrogen as a variation of the resistance of the specimen using a high-resistance ingot (>500 Ω cm). The hydrogen diffusion coefficient obtained using the depth profile of TDDs, which are generated under the influence of the depth profile of the in-grown hydrogen, shows a value close to that given by Van Wieringen and Warmoltz (VWW) [Physica 22 (1956) 849]. Furthermore, it is found that the activation energy of hydrogen diffusion in the intermediate temperature region is almost the same as that obtained by VWW. This result indicates that the hydrogen diffusion coefficient can be expressed by an equation given by VWW at an intermediate temperature region.

The Cr/Pt/Au ohmic contact resistance on n-type gallium nitrogen (GaN) is reduced by the Cl₂ inductively coupled plasma (ICP) surface treatment of n-type GaN films following laser lift-off (LLO). X-ray photoelectron spectroscopy (XPS) shows the modified atomic ratio of the n-type GaN surface following the Cl₂ ICP treatment. The Cl₂ ICP treatment increases the atomic ratio of gallium to nitrogen. GaCl_x and NCl_x are suggested to be generated and then removed using a boiling HCl solution. Nitrogen vacancies at the n-type GaN surface are therefore produced and act as donors for electrons, reducing ohmic contact resistance induced by reducing the resistivity of electrons to conduction.

The aim of this study is to determine the diffusion coefficient of palladium (Pd) in gallium arsenide under different annealing conditions. The extent of diffusion was characterized using the secondary ion mass spectrometry (SIMS) technique. The temperature-dependent diffusion coefficients of Pd are 8.4×10^-13, 2.25×10^-12, and 9.51×10^-12 cm²/s, respectively, at temperatures of 400, 550, and 850 °C. The Pd diffusion constant and activation energy in GaAs are calculated as 3.54×10^-10 cm²/s and 0.35 eV, respectively. This indicates that the major diffusion mechanism of Pd in GaAs is interstitial diffusion.

Lasing actions are obtained from well-fabricated octagonal quasi-periodic photonic crystal (OQPC) microcavities. The defect modes in OQPC microcavities are investigated and compared with the calculation results obtained using the finite-difference time-domain (FDTD) method. A large single-mode lasing wavelength range over 200 nm without mode hopping and a high side-mode suppression ratio (SMSR) of over 30 dB are observed, which result from the mode dependence suppression mechanism on the cavity geometry.

Rapid thermal annealing (RTA) is proved to be more efficient in dissociating hydrogen complexes than using a constant period of voltage stress (CPVS). Without waiting for the bond breaking of complexes by minority carrier injection, RTA favors the critical base–emitter voltage (V_BE) responsible for the occurrence of burn-in (BI) from 1.75 to 1.4 V and thus assists CPVS in reducing V_BE by about 25% used in BI suppression. Besides eliminating the BI, the sample first prepared by RTA and followed by CPVS has larger base and collector current densities at V_BE>1.1 V and reaches 6 times those at V_BE>1.3 V compared with the sample only using by CPVS.

A new ternary oxide slurry, CeTi₂O₆ containing Ce⁴⁺ ions, was found to be effective as an abrasive in chemical-mechanical polishing (CMP). The ternary oxide was synthesized by the Pechini polymerizable complex (PC) method. X-ray diffraction (XRD) Rietveld analysis indicated that the oxide possesses a single CeTi₂O₆ phase of a brannerite structure (C2/m, No. 12). When CeTi₂O₆ was used as an abrasive slurry for polishing thin oxide film, the removal rate was as high as that of ceria (CeO₂) slurry.

ε-Fe₃N–CrN nanocomposite system is synthesized by wet chemical technique. Exchange bias coupling exists at the interface of the ferromagnetic (FM) ε-Fe₃N and antiferromagnetic (AF) CrN phases and the FM ε-Fe₃N and AF Fe–O–N/Cr–O–N surface layers. However, the exchange bias is not found to be dependent on the CrN concentration and the coupling of the spins at the surface Fe–O–N/Cr–O–N–ε-Fe₃N has a dominating influence. The maximum shift in hysteresis loop is observed to be 78 Oe and the low magnitude of exchange bias is attributed to the roughness of AF–FM interface that induces spin-disorder and random exchange anisotropy. The relaxation dynamics study indicates the presence of antiferromagnetic ordering in this system. Below 65 K, the broad peak in zero-field cooled (ZFC) magnetization curves (T_E\congT_f) indicates the presence of unidirectional anisotropy and spin-glass-like ordering. The spin-glass-like ordering, which arises from the freezing of the clustered randomly oriented spins, is confirmed from the frequency dependence in AC susceptibility measurements and dynamic scaling analysis.

The ground and 1s core-hole states have been calculated by a DV-Xα discrete-variational Hartree–Fock–Slater method for a 51-atom model of LaCoO₃ with Sr substitution within the fifth neighbor shell. First-principles calculations reproduced the experimental spectra of X-ray magnetic circular dichroism (XMCD) at the Co K-absorption edge, where a hybridization of Co 3d,4 p and O 2 p stabilizes a magnetic state of La_1-xSr_xCoO₃. It was found that the π bonding and σ^* antibonding orbitals exist near the Fermi level, which is consistent with the interpretation based on the ligand field theory. The XMCD calculation shows a change of Co 3d electrons between the low-spin and high-spin states within a narrow energy range of ±0.3 eV from the Fermi level, where the Co–O molecular orbital may contribute to produce an intermediate state.

The experimental investigations of a magnetic field-induced strain has been carried out in the Heusler alloy Ni₄₅Co₅Mn_36.7In_13.3 by a capacitance method in a single-shot pulse magnetic field with a frequency of 200 Hz. A 3% deformation has been observed on the application of a maximum pulse field of 70 kOe at 300 K. This indicates an almost complete recovery of the original shape of the alloy. Magnetization shows a clear metamagnetic transition and a large hysteresis at around 300 K, indicating a magnetic field-induced transition from an antiferromagnetic or paramagnetic martensitic state to a ferromagnetic parent phase.

The microscopic magnetic characteristics of CoCrPt-patterned media after magnetic recording by a ring head were investigated. The media consists of two rows of aligned CoCrPt dots with a diameter of 40 nm. The magnetization reversal of each dot is clearly observed by magnetic force microscopy (MFM). A few misreversed dots were observed in the written "bit" patterns. The distribution of coercivity H_c was investigated by MFM using dot-by-dot analysis. It was found that H_c is about 4 kOe on the average with a wide distribution ranging from 0.5 to 7.5 kOe. This large distribution of H_c causes these magnetization reversal defects. One possible origin of the large H_c distribution is the grain boundary observed in each grain of the CoCrPt layer.

Thermomagnetic writing was successfully performed on microfabricated TbFe films with a perpendicular anisotropy by applying current pulses. The magnetic domain was imaged after every pulse by magnetic force microscopy (MFM) to determine the minimum current required for writing on patterned films of different sizes. For a constant pulse width, the dependence of the required minimum current on the surface area (A) of square-patterned films was measured and showed an A^1/2 phenomenological variation. While it was also found that the current density and power density necessary for writing are invariable with the surface area of the patterned films for a given pulse width, and are about 5×10⁶ A/cm² and 0.3 mW/µm², respectively, using a pulse width of 100 ns in the presence of a "writing" field of 100 Oe.

In this study, we propose a new method of synthesizing Ni–Cu–Zn ferrite powder using steel pickled liquor and electroplating waste solutions as starting materials. It was found that the Ni–Cu–Zn ferrite powder prepared by a hydrothermal process from the waste solutions shows the formation of cubic ferrite with a saturation magnetization (M_s) of 31.5 emu/g and an intrinsic coercive force (H_ci) of 19.3 Oe. Upon annealing at 750 °C for 2 h, the saturation magnetization increases to 52.6 emu/g and the intrinsic coercive force reaches 42.8 Oe. This useful method can promote the recycling of industrial waste solution and contribute to the preservation of the earth. Moreover, this method decreases the manufacturing cost in the treatment of the industrial waste solution for electroplating and steel industries.

The magnetic susceptibility of A-type bead like zeolite is measured as a function of temperature between liquid helium and room temperatures under low pressure of oxygen gas. The zeolite specimen employed in the present work has micropores, the diameter of which is 5 Å. The magnetic susceptibility of oxygen molecules adsorbed by zeolite is evaluated from the results obtained before and after oxygen adsorption. The temperature dependence of the susceptibility of oxygen exhibits a sharp peak at about 50 K, suggesting that oxygen molecules incorporated into zeolite induce the formation of an antiferromagnetic state. The present results are compared with the magnetism of oxygen adsorbed on the surface of graphite and physisorbed into slit-shaped micropores in activated carbon fibers.

Experimental results are reported on the compensation of thermal lensing caused by the radial thermal gradient in an optically pumped Nd:YAG laser. Poly(methyl methacrylate) (PMMA) with a higher negative dn/dT, a high damage threshold and low absorbance is very useful for compensating thermal effects in the amplifier. The results revealed that the use of PMMA resulted in the complete reduction of the thermal lens effect by an order of magnitude.

In this study, we demonstrate that it is possible to fabricate a fiber grating external cavity laser (FGECL) module with a low cost while still maintaining a good performance using a low-cost antireflection (AR)-coated (5×10^-3) laser and a tapered hyperbolic-end fiber (THEF) microlens. Previously, high-performance FGECL modules have only been available by using a complicated AR-coated (1×10^-5) laser process that leads to a high packaging cost. Our FGECL consisted of a HR/AR-coated diode laser, a THEF microlens, and a fiber grating. The results showed that the FGECL module exhibits a side-mode suppression ratio (SMSR) higher than 44 dB, a higher output power of more than 2 mW, and a larger operation current range of over 50 mA. In addition, excellent wavelength stability and a low-penalty directly modulated 2.488 Gbit/s were also obtained for FGECL modules. The THEF microlens demonstrated up to 86% coupling efficiency for a laser with an aspect ratio of 1:1.5. Low-cost FGECL modules with good performance were achieved primarily owing to the THEF microlens having a high coupling efficiency (typically 75%) which enhanced the feedback power from the fiber grating external cavity to the HR/AR-coated laser compared with the currently available hemispherical microlens which has low coupling efficiency (typically 50%). Therefore, the packaged FGECL module is suitable for use in low cost 2.5 Gbit/s lightwave transmission systems.

In this paper, we describe the development of a high-average-power solid-state laser system and the derivation of equations for the amplification of a laser beam. This laser system is capable of generating an output energy of 10 J per pulse at a wavelength of 1,053 nm in a 10 Hz operation for scientific and industrial applications. The main amplifier of our system is a laser-diode-pumped solid-state amplifier. A water-cooled Nd:glass slab is pumped with two 803 nm AlGaAs laser-diode modules. The laser beam propagates through zig-zag optical paths four times and is amplified. To estimate laser output energy, we have derived and evaluated equations for the amplification of the laser beam, and designed and constructed a laser system based on the calculated results. Experimental results reveal an output energy of 10.6 J at 1 Hz, which closely fits the results calculated using the derived equations.

We present the dynamic all-optical flip-flop (AOFF) operation of a multimode interference (MMI) bistable laser diode (BLD) with distributed Bragg reflector (DBR) mirrors, which allow single-mode lasing and on-chip integration with other waveguide devices. The DBR-MMI-BLD has been operated by 10-ns-wide optical set/reset pulse, resulting in 320 ps rising time and 470 ps falling time. Self-routing of 10 Gbit/s optical packets has also been demonstrated using the Mach–Zehnder interferometer (MZI) semiconductor optical amplifier (SOA) all-optical switch driven by the DBR-MMI-BLD AOFF. The 10 Gbit/s optical packets were switched in the optical domain by cross-phase modulation of the SOA. The extinction ratio of the all-optical switch was 8 dB, and an error-free operation was obtained with 1.8 dB power penalty.

Al- and Ag-based top-emitting organic light-emitting diodes (TOLED) are investigated. Both MoO₃ and V₂O₅ have been used as hole-injection layer (HIL). The performance of the devices is significantly improved using the metal oxides as HIL. A C545T-doped Alq₃ TOLED with Al and MoO₃ can achieve a maximum current efficiency of 22 cd/A at 20 mA/cm². The power efficiency is 20 lm/W at a low brightness and about 8.9 lm/W at 1000 cd/m². For the Ag-based TOLED using V₂O₅ as HIL, very low operating voltages are obtained. For instance, 1000 cd/m² can be obtained at a voltage of 4.7 V with a power efficiency of about 10 lm/W. From the analysis of the current–voltage characteristics of the single hole transport layer devices, it is believed that the hole injection from the metal anodes was greatly enhanced because of the lowering of the injection barrier induced by the metal oxides. The interface dipole theory was applied to the metal-metal oxide interface to explain the experimental observations.

Rewritable optical digital versatile discs (DVDs) were analyzed to identify alterations in layer composition after repeated overwrite cycles. Elemental depth profiling revealed the presence of S in the phase-change layer in areas with high jitter values. This we relate to a decomposition of the ZnS:SiO₂ dielectric layer during repeated overwrite. The S concentration in the phase-change layer at the location of the repeatedly overwritten tracks is estimated to range between 0.1 and 1 at. %, depending on whether or not a caplayer is present between the ZnS:SiO₂ layer and the phase-change layer. From electron microscope images we established that repeated overwrite cycles induce voids in the phase-change layer. By analyzing the repeatedly overwritten areas of various recording stacks we collected evidence that a caplayer may suppress void formation. Both S diffusion and void formation will limit the overwrite cyclability of optical discs, which explains the frequently reported beneficial effect of a caplayer on overwrite performance.

An organic light-emitting diode (OLED) display panel using a charge-pump (CP) pixel addressing scheme was implemented and shown to be effective for information display applications. The panel luminance was 681 cd/m² when driven by control signals with an amplitude of 8 V and a common-cathode voltage of 6 V. It was found that the parasitic overlap capacitance between a common electrode and a column bus plays a crucial role in the operation of the CP-OLED display panel. The losses of panel luminance and contrast ratio due to the capacitance could be minimized by optimizing the pixel layout design and fabrication processes.

The light leakage caused by color filters between crossed polarizers was analyzed in terms of light scattering due to pigments inside color filter layers. Localized pigment particles in the color filter layers used in devices were observed with a scanning transmission electron microscope. The direct observation of the scattering light revealed that the pigment particles cause Rayleigh scattering. We found that the depolarized light leakage by color filters between crossed polarizers is governed by light scattering.

Efficient compensation of thermally induced birefringence with thermal lensing in a rod geometry Nd:YAG laser amplifier was achieved by an in-cavity 90° polarization rotator with three sets of image relaying optics between the laser rods. The measured birefringence loss per transit was 2.8% for pumping power of 580 W per rod. A nearly diffraction limited output beam of 38 W was observed.

We found that 325 nm He–Cd laser light irradiation reduces the resistivity of LiNbO₃ crystals by approximately 3 orders of magnitude. Moreover, under this UV light irradiation, it was proved that the threshold voltage for domain inversion can be reduced to 30% as compared with the case of non-UV light irradiation. Using this technique, we successfully formed a minute domain inversion of less than 1 µm at a low voltage, for the first time.

The imaging properties of multiview and integral photography based three-dimensional imaging systems are compared on the basis of their viewing-zone-forming principles. It is confirmed that 1) the images projected to the viewers' eyes in IP and the multiview have a conjugate relationship between them and 2) the quality of the image projected to viewers' eyes in integral photography will be increased if the image resolution of each lenslet in the microlens plate is minimized by reducing the field of the view angle of the microlens plate and the number of lenslets in the plate is increased.

For a full high definition plasma display panel, the method of high speed addressing is necessary. In order to decrease the addressing time and its jitter, separated dual electrodes are applied to the address electrode. The experimental results show the addressing time and jitter are reduced by about 20% compared with those of a conventional electrode. Additionally, the change in discharge characteristics is analyzed by using two-dimensional fluid simulation. The key feature of the suggested structure is that the distribution of wall charges and particles is controllable during address periods without a significant increase in capacitive load of the address electrodes.

Epitaxial (KNa)_0.1Sr_0.61Ba_0.39)_0.9Nb₂O₆ (KNSBN:61) thin films deposited on MgO(100) substrates have been prepared by pulsed laser deposition (PLD). The structural properties of the thin films have been examined by X-ray diffraction analysis. An X-ray diffraction 2θ scan indicates single crystalline layers with the (001) orientation perpendicular to the substrate plane. The optical transmission spectra of the thin films have been obtained in the spectral range of 200–900 nm, and their optical constants (refractive index n and extinction coefficient k) have been determined. It has been found that the refractive index of the thin films is similar to that of a KNSBN:61 single bulk crystal. The birefringent shift as a function of the applied voltage of the thin films on fused silica has been measured, and the quadratic electro optic coefficient R has been derived to be 0.4×10^-16(m/V)² at 6328 Å.

A comparative study of the electronic structures of BaTiO₃, SrTiO₃, and PbTiO₃ perovskite oxides is performed in order to identify the atomistic factors governing the occurrence of a ferroelectric or antiferrodistortive (rotating-type) phase transition in ATiO₃ perovskite oxides. The discrete variational-Xα molecular orbital method is employed to calculate the electronic structures of BaTiO₃, SrTiO₃, and PbTiO₃ in a cubic lattice. The changes in the strength of the A–O (A=Ba, Sr, and Pb) and Ti–O covalent interactions are determined as a function of the rotation angle of TiO₆ octahedron and the ferroelectric displacement of Ti and O. A comparison of the calculated results indicates that the rotation of TiO₆ octahedron and the ferroelectric displacement are dominated by the A–O and Ti–O covalent interactions, and that the type of phase transition that occurs (ferroelectric or antiferrodistortive) in these perovskite oxides is governed by the delicate balance between the strength of the A–O and Ti–O covalent interactions.

We report the crystal structures, magnetic susceptibilities and thermoelectric properties of a delafossite-type oxide, CuCr_1-xMg_xO₂ (0 ≤x ≤0.05) at temperatures in the range from 4 to 1100 K. The lattice parameter, c, linearly decreases with increasing Mg concentration in the range 0 ≤x ≤0.03. This decrease is mainly caused by the shrinking of O–Cu–O dumbbells which connect the CdI₂-type (Cr/Mg)O₂ slabs. Magnetic susceptibility measurements indicate that Cr³⁺ is in the high spin state in the paramagnetic phase above 25 K. The electrical resistivity, ρ, of CuCr_1-xMg_xO₂ exhibits semiconducting behavior (dρ/dT < 0) in the range from 350 to 1100 K, which decreases through the partial substitution of Mg²⁺ for Cr³⁺ with 0 ≤x ≤0.03. Positive and high Seebeck coefficients of CuCr_1-xMg_xO₂ at high temperatures are consistant with the theoretical values predicted by Koshibae, who considered the spin entropy flux for the high-temperature Seebeck coefficent. From the linear S vs ln σ plot, considerable contribution from the band structure and carrier concentraton to the Seebeck coefficient is indicated. The power factor, S²σ, reaches its maximum value at around x = 0.03 in this system. The thermal conductivity, κ, for CuCr_1-xMg_xO₂ ranges from 6 to 10 W·m^-1·K^-1 at 300 K, slowly decreasing with increasing temperature up to 1000 K. In the present system, the maximum dimensionless figure of merit, ZT=S²T/ρκ= 0.04, is realized for the case of x = 0.03 at 950 K.

The positive temperature coefficient resistance (PTCR) effects of Sm-doped BaTiO₃ have been studied in terms of annealing temperature, annealing time, and additive content. (Ba_0.85-xCa_0.15Sm_x)_0.997TiO₃ samples were prepared by a liquid mix method developed by Pechini. The specimen was sintered in a reducing atmosphere (P_O2<10^-9 atm) at 1350 °C, followed by annealing processes at 900–1200 °C and P_O2=1 atm. Room-temperature resistances were dependent on the donor concentration. At 0.5 mol % Sm, the electrical compensation mode of the donor impurity switched from electrons to cation vacancies. The specimens doped with Sm≤0.5 mol % showed low resistivities and large grains, whereas high resistivities and small grains were observed with Sm>0.5 mol %. The oxidation degree of grain boundaries increased with annealing temperature and time, leading to increased room-temperature resistances. This implies that the acceptor-state density at grain boundaries increases the potential barrier height.

In this study, Bi₂O₃-doped bismuth potassium titanate, (Bi_1/2K_1/2)TiO₃, (abbreviated to BKT-Bix; x=0, 0.1, 0.2, 0.4, and 0.6 wt %) ceramics were fabricated by hot-pressing method, and its electrical properties were investigated in detail. Moreover, BKT-Bi0.6 was annealed at 1040 °C for 4–20 h to develop grains [abbreviated to BKT-Bi0.6(y h); y=4, 10, and 20]. The ferroelectric properties were improved by grain growth, and the remanent polarization, P_r, of BKT-Bi0.6(10 h) was 27.6 µC/cm². The piezoelectric properties were improved by field cooling method, and the electromechanical coupling factor, k₃₃, and piezoelectric constant, d₃₃, of BKT-Bi0.6(10 h) improved up to 0.40 and 101 pC/N, respectively. Moreover, the temperature dependences of piezoelectric properties were measured, and piezoelectricity disappeared at 280 °C for BKT-Bi0.6(10 h).

We synthesized a series of (Ca,Ba)-layered compounds (Ba_xSr_1-x)Bi₂Ta₂O₉ (x=0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) by a solid-state reaction, and examined the structures, and the dielectric and ferroelectric properties. Structural analysis by X-ray diffraction (XRD) revealed that the structures of (Ba_xSr_1-x)Bi₂Ta₂O₉ for 0.0≤x≤0.4 are orthorhombic with A2₁am symmetry, whereas those of (Ba_xSr_1-x)Bi₂Ta₂O₉ for 0.6≤x≤1.0 are tetragonal (I4/mmm). The temperature dependence of ε_r' and tan δ were investigated in detail for various frequencies and compositions. We observed that the dielectric constant ε_r', tan δ, T_c, and hysteresis loop were strongly influenced by from Sr²⁺ to Ba²⁺.

Through analysis of low-field AC susceptibility data in relaxor ferroelectric and magnetic spin glass solids, the key parameters of activation energy, E_A, and freezing temperature, T_f, were extracted from the Vögel–Fulcher dependence of the maxima. At higher temperatures the deviation temperature, T_D, was obtained from departure of the high temperature Curie–Weiss behavior. Collectively, these parameters were found to scale across different compounds and solid solutions for both the magnetic spin glasses and relaxor ferroelectrics.

Lead-free ferroelectric (Na_0.5K_0.5)NbO₃ (NKN) thin films were fabricated by a sol–gel process on two types of Pt/Ti/SiO₂/Si substrate at different deposition temperatures, that is, a room temperature and 300 °C, for Pt/Ti layers. The Pt layer deposited at room temperature had a large variation in 111 d-space, and many hillocks were formed on the surface of the Pt layer owing to the relaxation of compressive stress with the elevation of annealing temperature. On the other hand, the variation in 111 d-space and the generation of hillocks in the Pt layer deposited at 300 °C were improved. By using the Pt layer deposited at 300 °C and a low heating rate (10 °C/min) during sintering, highly oriented NKN thin films were obtained at 500 °C. The P–E hysteresis loop of the NKN thin films showed a relatively good shape, and the remanent polarization P_r was estimated to be about 0.98 µC/cm² at 120 kV/cm. The leakage current density of the NKN thin films on the Pt layers deposited at 300 °C was 4.0×10^-6 A/cm² at 60 kV/cm.

Present investigation reports dielectric relaxation behaviour of a ferroelectric liquid crystal mixture with and without doping of Anthraquinone dye. Dielectric properties of dye doped and pure ferroelectric liquid crystal mixture has been investigated as a function of temperature and frequency. In the present investigation Goldstone mode has been observed in smectic C^* (SmC^*) phase, while soft mode is observed in smectic A (SmA) phase and they have been explained with the help of Cole–Cole function. It has also been observed that the addition of dye strengthens the helix in SmC^* phase, which is indicated by higher relaxation frequency and dielectric strength of the dye doped ferroelectric liquid crystal mixture. The SmC^*–SmA phase transition point become sharper with the addition of dye in ferroelectric liquid crystal material and also shifted towards lower temperature side.

Here, we study the influence of cross-linking density, X, on the swelling, thermal and electric field response of trifunctionally cross-linked liquid single crystal elastomers (V3 LSCEs) swollen with low molecular weight liquid crystals, 4-n-pentyl-4-cyanobiphenyl (5CB). The cross-linker concentrations are X_3V3=3.3 mol %, X_5V3=5 mol %, and X_7V3=7 mol %. LSCE networks are characterized by frozen-in orientation order, P. X_c is a constitutional critical point for LSCE networks. When X<X_c (P=0), there are no shape changes and a nematic-isotropic transition takes place at T_NI. When X>X_c (P>0), supercritical behavior prevails over a range of temperatures, ΔT_s. Taking ΔT_s∝(X-X_c)^1/2, we find a critical cross-linking density, X_c≈3%, for V3 LSCEs. 5CB diffuses ⊥n into V3 similar to isotropic gels with typical times, τ_⊥n in minutes, that decreases with increasing (X-X_c). Swelling with reorientation effects is initiated by 5CB propagating into V3 followed by relaxation of the front profile with τ_⊥⁽²⁾ (twist), and τ_|| ⁽¹³⁾ (splay-bend) that both increase nearly parabolically with increasing (X-X_c). Front speeds are 50% faster in 5V3 than in 7V3 but no fronts were observed in 3V3. Compared to dry V3 LSCE volumes, V_d, the swollen volumes, V_s, increased as X→X_c: V_s/V_d∼(X-X_c)^-0.27 reducing the frozen-in orientational order at X to \tildeX=X(V_d/V_s). The maximum electromechanical effect found in swollen V3 was δ_MAX∼(\tildeX-\tildeX_c) with \tildeX_c∼0.25%. The size of the effect is much smaller than observed in 8A2 which has a larger P. For 7V3 the effect is about 4 times smaller and for 5V3, it is an order of magnitude smaller.

A planar circuit type of a liquid crystal (LC) phase shifter is prepared using a coplanar waveguide (CPW) and an indium–tin-oxide (ITO) glass substrate. Since the upper ITO layer is set with a floating structure, the LC molecular orientation can be modulated by driving only the lower CPW electrodes. The upper floating electrode contributes extremely well to reducing the driving voltage of the device compared with the case without the electrode. However, the extra electrode increases the loss of the millimeter-wave (MMW) propagation and principle of the device operation has not been made clear yet. We investigate here the electric filed distribution phenomena of the propagating MMW inside the LC cell by finite difference time domain method (FDTD) calculation. Relationship between the LC molecular orientation and the MMW phase shifting properties are discussed in terms of the MMW propagation mode in the CPW device.

We investigated the role of precursors molecular symmetry in the self-assembled formation of organosilane monolayer by applying atomic force microscopy (AFM), grazing incidence X-ray diffraction (GIXD), Fourier transform infrared spectroscopy (FT-IR) and contact angle measurement. Octadencyltrichlorosilane (OTS), octadecylmethydichlorosilane (ODCS), and octadecyldimethylchlorosilane (ODMS) were used as raw materials to form organosilane monolayers. The organosilane monolayers were prepared by a liquid phase method at a reaction temperature of 5 °C and an humidity in reactor of 50%. AFM observations suggested that only OTS molecules grew two-dimensionally on the Si substrate surface. In GIXD results showed these OTS molecules to be arranged in a crystalline state on the Si surface. Thus "self-organization" occurred during OTS monolayer formation process. However, in the case of ODCS and ODMS, the monolayers formed were in an amorphous state. In addition, FT-IR and water contact angle measurement indicated that the packing density of the OTS monolayer was higher than that of the ODCS and ODMS monolayers. Only when the precursor molecules had an axis where the silanol groups were in three-fold did "self-organization" occurs in the formation of the organosiloxane monolayer.

In this study, we compared the effects of negative-bias temperature instability (NBTI) and hot-carrier injection (HCI) on the core and input/output (I/O) p-channel metal–oxide–semiconductor field-effect transistor (PMOSFET) fabricated using the different gate dielectrics of plasma nitrided oxide (PNO) and thermally nitrided oxide (TNO). The mobility and constant overdrive current of the PMOSFETs fabricated using PNO as a gate oxide material are about 30 and 23% higher than those of the devices fabricated using TNO, respectively. The core PMOSFETs fabricated using PNO show a better NBTI and HCI immunity than those fabricated using TNO owing to the lower nitrogen concentration at the SiO₂/Si-substrate interface. However, the I/O PMOSFETs fabricated using PNO show a higher HCI-induced degradation rate because of a higher oxide bulk trap density but a better NBTI than the devices fabricated using TNO at a normal stressed bias due to a low interface trap density.

Previously, a Monte Carlo simulation (MCS) was carried out to determine the Townsend's secondary ionization coefficient γ of a MgO film using the experimental values of starting voltage between the electrodes covered by the MgO film. The electrodes were mounted at the center of a chamber as a modeled plasma display panel (PDP) cell filled with Ar. The purpose of the study was to examine the effect of the energy in a nonequilibrium state of electrons on the Townsend's secondary ionization coefficient. It was confirmed that the energy nonequilibrium effect appeared and the effect strongly depended on the initial energy distribution of electrons emitted from the cathode. The values of γ considered in the nonequilibrium of electron energy were approximately 20% larger than those considered in energy equilibrium under the operating conditions of the PDP. In this study, we investigated the effect of electron reflection on both electrode surfaces on the secondary ionization coefficient and the electron transmission coefficient. The electric power injection into the gap space based on the electron transmission coefficient and the dynamic characteristics of electron flux at the anode are explained using the electron reflection coefficient obtained in our previous experiments.

The disinfection of water containing the microorganism, Escherichia coli (E. coli) by exposure to a pulsed-discharge plasma generated above the water using a multineedle electrode (plasma-exposure treatment), and by sparging the off-gas of the pulsed plasma into the water (off-gas-sparging treatment), is performed in the ambient gases of air, oxygen, and nitrogen. For the off-gas-sparging treatment, bactericidal action is observed only when oxygen is used as the ambient gas, and ozone is found to generate the bactericidal action. For the plasma-exposure treatment, the density of E. coli bacteria decreases exponentially with plasma-exposure time for all the ambient gases. It may be concluded that the main contributors to E. coli inactivation are particle species produced by the pulsed plasma. For the ambient gases of air and nitrogen, the influence of acidification of the water in the system, as a result of pulsed-plasma exposure, may also contribute to the decay of E. coli density.

Barrier discharge characteristics have been investigated for a twin needles-to-plane electrode configuration in dry air. The characteristics of barrier discharge under ac voltage application have been investigated for various distances between two needle tips (d=1.0–4.0 mm). We have found that corona discharge behavior strongly depends on needle–tip distance. In the case of a twin-needles configuration with a long needle–tip distance (d=4.0 mm), discharges from the two needle tips develop into a dielectric barrier with almost a straight path. On the contrary, the development of repulsive discharges from two needle tips in the gap between needles and a barrier was obtained for the shortest needle–tip distance investigated here (d=1.0 mm) and it was enhanced by increasing the peak voltage. From detailed time-resolved observations, development of repulsive discharge was observed only during positive polarity upon ac voltage application. Moreover, the degree of repulsion increased with increasing applied voltage of positive polarity. The observed unique discharge behavior can be interpreted as the effect of field relaxation induced not only by charge accumulation on the barrier surface, which is markedly enhanced at a short needle–tip distance, but also by space charge by coronas between two needles.

To investigate the hydrocarbon redeposition process on the graphite tile surface, we developed a modeling code that considers a complete set of collisional reactions in the plasma, energy- and species-dependent reflection coefficients, and fragmentation at the tile surface. The model calculations revealed local redeposition characteristics. The redeposition rate, which is the number of redeposited particles on the tile surface per launched CH₄ molecule, decreases with decreasing plasma temperature due to a steep decrease in the rate coefficients for electron impact ionization at temperatures of less than 10 eV. At elevated plasma temperatures, large numbers of singly or multicharged carbon ions are redeposited because of the high sticking coefficient of the multicharged ions, which is strongly accelerated by the sheath field. The hydrogen concentration of the deposited species increases because of a decrease in the number of dissociative reactions in the plasma with decreasing plasma density. Using energy- and species-dependent sticking coefficients, low-energy ion species are reflected by the tile surface where dissociation occurs and are subsequently dissociated due to transport in the plasma; accordingly, the hydrogen concentration of deposited species is low.

A neoclassical transport database for the large helical device (LHD) plasma, DCOM/NNW, is constructed using the neural network method. Monoenergetic neoclassical transport coefficients evaluated by the Monte Carlo code, DCOM, are used as training data of the neural network. The databases for two typical magnetic field configurations in LHD, namely, standard and inward-shifted configurations, are constructed and transport coefficients for thermal plasma are evaluated. The plasma parameter dependencies and the ambipolar radial electric field are investigated.

The aging characteristics of commercial deuterium lamps not subjected to a pre-aging process were measured. The evaluation of window material degradation showed that the degradation alone cannot completely account for the observed decrease in radiant flux. The variation in the plasma condition of a deuterium lamp was investigated as a possible cause of the decrease. A new measurement method using the cathode box of the deuterium lamp as a probe was used to evaluate the electron temperature of the plasma of the deuterium lamp. The electron temperature was also estimated by a spectroscopic method. The variations in the electron temperatures derived by these two methods were consistent, showing that the average energy loss of electrons exceeds 20% after a 400 h operation. These results suggest that another possible cause for the decrease is the variation in the plasma condition of the deuterium lamp.

Both optical emission spectroscopy and infrared diode laser absorption spectroscopy were applied to measurements of rotational temperatures of CF radicals in 60 MHz capacitively coupled CF₄ and CF₄/Ar plasmas. The rotational temperature of CF radicals in the excited state was determined by fitting the optical emission spectra with the calculation results. The calculation for emission spectra was performed using two different rotational constant value of A=0.76 and 4.48 for the B²Δ state, and then the constant A was evaluated to be 0.76 from the emission intensities. In the CF₄ plasma, the CF rotational temperature was increased from 300 to 380 K as the 60 MHz power was increased from 300 to 1500 W, and the radical density was increased from 1.59×10¹² to 5.05×10¹² cm^-3. On the other hand, in the CF₄/Ar plasma, the CF rotational temperature was increased by 20 K with the power, and the radical density was constant at 1.1×10¹² cm^-3. It was found that the rotational temperatures of CF radicals in the excited state were in equilibrium with those in the ground state under the present conditions.

We study the characteristics of one-photon resonant two-photon ionization of Sr through the spin-resolved detection of photoions by laser-induced fluorescence. In particular, the dependence of spin polarization on the wavelength and polarization of the ionization laser is experimentally investigated. By changing the polarization of the ionization laser from parallel linear to perpendicular linear with respect to the quantization axis defined by the circularly polarized pump laser, a significant difference is found in the degree of spin polarization, whereas the dependence on the laser wavelength at three different wavelengths (308, 266, and 248 nm) turns out to be very small. To understand the experimental results, we have also undertaken a theoretical analysis, which predicts consistent spin polarization with our experimental results for both parallel and perpendicular linear polarization for a given ratio of bound-free transition moment into the 5sks and 5skd continua. The ratio of the bound-free transition probabilities from the bound 5s5 p³P₁ state to the 5sks and 5skd continua is evaluated.

We have developed green phosphorescent organic light-emitting devices (OLEDs) with high quantum and luminous efficiencies. A green phosphorescent metal complex, fac-tris(2-phenylpyridine) iridium [Ir(ppy)₃], was used as an emitter material. Wide-energy-gap materials with high triplet excited energy levels were used as host materials for Ir(ppy)₃ and as carrier transport materials. Hole injection and electron injection from the electrodes were balanced by placing chemically doped layers at the interface between the electrodes and the organic layers. In addition, a highly reflective Ag cathode was employed as an anode, instead of a conventional Al cathode to enhance the reflectivity of the cathode metal. An optimized device exhibited an external quantum efficiency (EQE) of 27% (95 cd/A) and a high power efficiency of 97 lm/W at 100 cd/m² at 3.1 V.

In this study, we demonstrated the use of a long-period grating in photonic crystal fibers is for bending measurement, in which the loss peak of the long-period grating shifts toward the shorter-wavelength side and the loss intensity decreases as the radius of curvature of the photonic crystal fibers decreases. Bending sensitivity was determined to be 10.63 nm/cm in the curvature radius range of 8–12 cm and 1.41 nm/cm at a curvature radius larger than 12 cm.

Preventing spuriousness in a quartz surface acoustic wave (SAW) resonator is important for maintaining reliability in digital communication systems because it reduces phase noise quality of signals. For such a resonator, the in-harmonic modes, which are also undesirable responses in the direction of the lengthwise x-coordinate and the transversal y-coordinate, have been studied. We show that the governing equation of the resonator is given by a Helmholtz equation, and we obtain equations corresponding to the resonance frequencies. We solve them theoretically for transverse modes, and numerically using a T matrix for longitudinal modes. We obtain a frequency-mode chart of a one-port quartz SAW resonator and obtain adequate agreement of accuracy with in-harmonics that involve two-dimensional modes. Furthermore, we study mesa-structure-type SAW resonators to determine a method of controlling the frequency arrangement.

The "vapor transportation method," a process for doping dye into polymers, enables us to prepare a favorable doped layer in a polymer. The doped layer had both a uniform dye concentration and a smooth surface. As a further development, we expanded the present method for use in the preparation of an optical waveguide. For the preparation of the waveguide, a low-molecular-weight compound (phenyl benzoate, PB) with a high refractive index was dispersed in a matrix polymer [poly(methyl methacrylate), PMMA] through a mask. After dispersion, the mask was removed, and another PMMA plate was placed on the doped plate using a vacuum thermal press. The double-layered structure of the doped and nondoped regions was clear in the cross section. The two regions described were transparent. A beam incident onto the edge of the doped region of the prepared sample emerged from the other edge, indicating that the doped regions acted as a core. The core radius (depth of the doped region) increased with treatment time and treatment temperature. Furthermore, the refractive index of the core was controlled by the treatment temperature. The fabricated waveguide showed a propagation loss of 0.47 dB/cm at 650 nm.

A fast X-ray digital imager was developed to perform high-speed phase-contrast X-ray imaging. The imager consists of a scintillator, a transferring optical fiber, and a high-speed interlined charge-coupled device (CCD) based camera. The field of view of the imager was 50×33 mm² with 4008×2650 pixels, and the maximum frame rate was 1.6 frame/s. The performance tests of the imager were performed using synchrotron radiation, and the results showed that the detection efficiency was 100% and the modulation transfer function (MTF) was 0.6 for 10 cycle/mm. We also performed the feasibility tests of high-speed phase-contrast computed tomography with an imaging system fitted with an X-ray interferometer and the imager. A clear three-dimensional image of a rat kidney was obtained with a 10-min measurement period. The density resolution was also found to be approximately 1.7 mg/cm³.

It is essential for soft tissue cutting to precisely predict the effects of laser irradiation before treatment. The purpose of the present study was to investigate the dynamic absorption coefficients of wet gelatin around λ=6.05 µm (tuned to the OH bending and amide-I bands) during laser irradiation. Wet gelatin was irradiated by a tunable mid-infrared free electron laser within the wavelength range of 5.6–6.7 µm. The incident fluence was fixed at 3.6±0.3 J/cm². Structural changes of the irradiated gelatin were observed with an optical microscope. At λ=6.05 µm, the wet gelatin was efficiently removed due to vaporization of water, and the absorption coefficient during irradiation increased slightly by 30–40% of magnitude from that before irradiation. Thus, we showed the possibility that 6.05-µm-light can predictably remove soft tissue without unexpected effects. A laser system with λ=6.05 µm is expected to be a novel cutaneous laser.

The flow rate and fluence rate dependences of the triplet-state lifetime (τ_T) and singlet oxygen (¹O₂) luminescence intensity of a Talaporfin sodium (mono-L-aspartyl chlorin e6, Laserphyrin^®) photochemical reaction in a flowing solution were studied. The oxygen consumption rate constant (k) did not proportionally increase as the fluence rate increased. The relationship between the static oxygen concentration in the flowing solution and τ_T was estimated. τ_T at the fluence rate of 0.8×10⁴ W/m² was 16% longer than that at 0.2×10⁴ W/m² at the same oxygen concentration. The τ_T increase at the high-fluence rate is attributed to local and temporal oxygen depletion. The local and temporal oxygen depletion might cause the fluence-rate dependence nonproportionality of the measured k.

We report that the composition ratio of a silver oxide film affects the intensity of surface-enhanced raman scattering (SERS) from a film on which a focused laser beam is incident. Three different composition films (Ag_xO) of x=1.1, 1.7, and 2.4 were fabricated by rf reactive magnetron sputtering with a silver target using a gas mixture of Ar and O₂. The composition of the silver oxide films was controlled by varying the gas mixture ratio during sputtering. A He–Ne laser beam was focused on a Ag_xO film dipped in a solution of benzoic acid diluted with 2-propanol. It was found that the Ag_2.4O film generated SERS and formed silver nanoparticles at the lowest laser power of irradiation. For an Ag_1.1O film, although the laser power required the generation of SERS and formation of silver nanoparticles was highest, the film generated the strongest SERS signal at a higher laser power of irradiation since the film could form silver nanoparticles without the formation of a silver-film-like structure such as that observed in the Ag_1.7O and Ag_2.4O films.

We theoretically study the dynamical properties of an electron confined in a two-dimensional (2D) quantum dot (QD) under photon illumination, by solving the time-dependent (TD) Schrödinger equation numerically by the finite difference method in both real space and actual time. To deepen our understanding of the TD features of photon-assisted tunneling (PAT), we employ projection analysis, in which the TD wave function at a QD is decomposed into (static) resonant states by calculating the inner products among them. This analysis further enables the deduction of effective lifetime, by which one can infer the actual period of the electron confined in the QD. The wave number distribution for the transmitted electron is also discussed to examine the propagation of the electron through the system.

It is increasingly required to reduce the environmental impact and cost in the field of industrial cleaning. As a substitute for conventional degreasing technology using organic solvents, acids, and alkalis, the authors have developed a new cleaning technology that uses microbubbles having an average diameter of about 70 µm. Grease being adsorbed onto a bubble's surface and grease being separated from a solid surface by its buoyancy were captured using a high-speed microscopic video camera to demonstrate the degreasing capability of bubbles. High-density microbubbles were generated by adding a trace amount of a specific chemical (0.1% weight or less). The cleaning performance using microbubbles was found to be highly improved compared with that using normal bubbles. It was also revealed that the grease removal efficiency was strongly dependent on the viscosity of the grease. Raising the temperature of the cleaning solution is an effective method of improving cleaning performance by reducing the viscosity. Finally, the degreasing of about 150 machining metal parts at the same time was demonstrated to exceed the common target cleaning level (5–20 µg/cm²) in only 2 min because of their large surface area. Furthermore, the high degreasing performance was maintained even after repeated use of the cleaning solution because of the separation of grease due to buoyancy.