Table of contents

Hydrogenated amorphous silicon and related alloy films have attracted much attention because of the wide application of these films in devices such as thin-film transistors and solar cells. However, the degradation of these films caused by intense illumination is a serious shortcoming. In this review, various experimental results concerning this problem and various models for the photocreation of dangling bonds which is thought to be the main origin of the degradation are introduced and discussed. Degradation in the device performance, some efforts to overcome the degradation and some metastable defects other than photocreated ones are also briefly introduced.

The effects of substrate temperature on optoelectronic and structural properties of undoped microcrystalline silicon thin films have been investigated. The undoped silicon films have been deposited by the very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique using a SiH₄ and H₂ gas mixture at 105 MHz plasma excitation frequency and moderately low power density of 70 mW/cm². The effect of the systematic variation of substrate temperature (from 180°C to 370°C) on film properties has been studied, while keeping the other parameters constant. The deposition rate is considerably high (2.6 Ås^-1) at 180°C and remains almost constant over the whole temperature range. Dark conductivity for all the films lies around ∼10^-6 Scm^-1. Low subband gap absorption has been observed by photothermal deflection spectroscopy for these microcrystalline films. Increase of substrate temperature improves the microcrystallinity of the film, which is confirmed from structural studies. Crystalline grain size also increases with increase of substrate temperature and a maximum of 460 Å has been achieved at 370°C. A satisfactory correlation is observed among the results of different structural studies: Raman spectroscopy, infrared spectroscopy, X-ray diffraction, transmission electron microscopy and atomic force microscopy.

To yield an activated electrode surface on a silicon solar cell, a surface treatment was examined using a dielectric barrier discharge instead of a wet cleaning technique. After the dry cleaning process using the dielectric barrier discharge, the surface state and the fill factor of the solar cell were evaluated. The results showed that the dielectric barrier discharge plasma could effectively activate the electrode surface of the solar cell in a relatively short time. Additionally, it was found that the surface treatment on finger electrodes played an essential role in the improvement of the fill factor.

Tensile-strained Si_1-yC_y alloy films were grown on Si(001) by gas-source molecular beam epitaxy (GS-MBE). The substitutional C contents (C_s) were estimated from X-ray diffraction patterns and were found to decrease with increasing substrate temperature. The thermal stability of the Si_1-yC_y alloy films was investigated by annealing experiments. The C_s value was also reduced at annealing temperatures higher than 850°C. Metal-oxide-semiconductor (MOS) transistors were fabricated using the strained Si_1-yC_y channel layer grown by GS-MBE and the transistor characteristics were confirmed.

In this study, we propose single and double heterostructure-emitter bipolar transistors (SHEBTs and DHEBT, respectively) with undoped spacers inserted on both sides of the base. The spike-free HEBT is achieved by solving Poisson's equation. The SHEBT and DHEBT with 100 Å spacers exhibit common-emitter current gains of 200 and 120, along with offset voltages of 80 and 50 mV, respectively. Meanwhile, the current gains of the passivated SHEBT and DHEBT reach 360 and 180, respectively. The passivated SHEBT with 100 Å spacer exhibits a current gain over unity at ultralow current densities of 10^-5 A/cm². Additionally, experimental results for different spacer thicknesses demonstrate that the 100 Å spacer yields the highest current gain.

The stress in a GaAs vertical microchannel epitaxy (V-MCE) layer on Si was simulated using the finite element method. The stress in the V-MCE layer decreased with increasing distance from the heterointerface. In a thin V-MCE layer, tensile stress was produced by the difference in thermal contraction between GaAs and Si. The stress at the center of the top surface of the V-MCE layer rapidly decreased with increasing thickness of the layer (H). Also, the sign of the stress changed from tensile to compressive when H exceeded a critical value. As H increased further, the stress decreased, thus forming a peak in the compressive stress. The stress generally decreased whit increasing thickness of the V-MCE layer, but the stress canceled when the V-MCE layer reached a critical thickness in which the tensile stress was equal and opposite to the compressive stress from the bowing of the substrate. The simulation also gives the stress distribution in the V-MCE layer, which is very useful for optimizing V-MCE for device fabrication.

Polycrystalline silicon (p-Si) thin-film transistors (TFTs) were fabricated using a high-temperature process that included solid-phase crystallization (SPC) and dry thermal oxidation with excimer laser annealing (ELA). X-ray diffraction and transmission electron microscopy analyses showed that the ELA process improved the quality of p-Si films markedly. The p-Si TFTs exhibited a higher performance than the SPC and a-Si+ELA p-Si TFTs. The field-effect mobility for n-type self-aligned TFTs was 251 cm²·V^-1·s^-1. The longitudinal junction diffusion length of the p-Si TFTs was shorter than that of the SPC p-Si TFTs. This is favorable for fine design rules. This fabrication process is consistent with the high-temperature-processed p-Si TFT development trend towards using large substrates, low temperatures, and fine design rules.

A detailed investigation of the nonequilibrium occupancy of band tail states and dangling bond (DB) states in undoped amorphous silicon has been performed using the subgap-light-induced electron spin resonance (subgap LESR) technique. Measurements performed over a wide range of excitation intensities and temperatures reveal a systematic change of the LESR line-shape. Lowering the excitation intensity transforms the superposition of band-tail electron and hole absorption lines, corresponding to the creation of these carriers, into a reversed single DB line, corresponding to the annihilation of neutral DB states. The LESR behavior is reasonably well interpreted in terms of the charge neutrality requirement for band-tail carriers and charged DBs under illumination. A careful inspection of the experimental results on the basis of numerical calculation as well as analytical consideration proves that neutral DBs predominantly occur in thermal equilibrium, and that the ratio of charged to neutral defect density is not more than 10%.

In order to understand carrier statistics in phosphorus-doped n-type diamond with an ionization energy of 0.6 eV, electron statistics involving compensation and the deep-dopant effect are theoretically analyzed. For n-diamond with a compensation ratio (c) larger than 1×10^-4, the electron concentration (n) at room temperature (RT) is insensitive to the donor concentration (N_D) and decreases with increasing c value. On the other hand, for diamond with a c value smaller than 1×10^-4, the n value at RT increases with increasing N_D value and is insensitive to the c value. Correspondingly, the length of Debye tailing (λ_n) at RT decreases with increasing c value for n-diamond with c>1×10^-4 and is insensitive to the c value for n-diamond with c<1×10^-4. The n=10¹⁴ cm^-3 and λ_n=3 µm are predicted to be obtained at RT for diamond with a c value smaller than 10^-5 and N_D of 5×10¹⁸ cm^-3. However, it is found that an increase in temperature is effective in increasing the n value and reducing the λ_n value. The n value as large as 10¹⁵ cm^-3 and the λ_n value as small as 100 nm are expected to be achieved at an elevated temperature of 473 K.

We propose the concept of a variable body effect factor Fully Depleted Silicon-On-Insulator Metal Oxide Semiconductor Field Effect Transistor (FD SOI MOSFET) in which the body effect factor is varied by the substrate depletion capacitance. In this device, both higher drive current in the active mode and low leakage current in the standby mode can be obtained in the variable threshold voltage scheme. In the active mode, the body effect factor is reduced by the substrate depletion capacitance and the drive current increases. In the standby mode, the substrate is inverted or accumulated, and the depletion layer capacitance is neglected, resulting in a larger body effect factor that suppresses the standby subthreshold current. We demonstrate the validity of the proposed scheme with two-dimensional simulations and experiments.

We have investigated a mechanism for increasing the contact resistance (R_c) of the ruthenium (Ru) and the titanium nitride (TiN) barrier during the tantalum oxide (Ta₂O₅) oxidation annealing in the metal–insulator–metal (MIM) capacitors. It has been found that controlling the atomic ratio of Ti to N (Ti/N ratio) is a key to keeping the contact resistance low. Controlling the Ti/N ratio is easy for the sp-TiN, while it is difficult for the chemical-vapor-deposited TiN. On the basis of this result, we have proposed a novel Ru/TiN contact with a stacked-barrier structure fabricated by using the point-cusp magnetron (PCM) sputtering method. We have applied this structure to the MIM-Ru/Ta₂O₅/Ru capacitor in a gigabit DRAM with 0.10 µm design. In this capacitor, we have obtained the contact resistance of 10 kΩ·bit and the capacitor leakage current of 10^-17 A/bit in the range of -1 to +1 V.

In this paper, we report a uncooled infrared sensor coupled with a 3-dimensional (3D) feed-horn shape micro-electro-mechanical system (MEMS) antenna using novel UV lithography technique for fabricating a 3D feed-horn-shaped mold array, obtaining parallel light using a mirror-reflected parallel-beam illuminator (MRPBI) system and plastic micromaching. The microassembly of infrared detector and 3D feed-horn-shaped antenna arrays is difficult using the conventional MEMS bonding process. To overcome limitation, the proposed novel 3D MEMS bonding technique is mesh structure bonding (MSB) using microchannels with micromolding in capillaries by polydimethylsiloxane (PDMS). The feasibility of fabricating both a 3D feed-horn MEMS antenna and a mold array was demonstrated. As a result, it seems possible to use a 3D feed-horn-shaped MEMS antenna to improve uncooled infrared sensor performance and applications to fabricate MEMS device.

Vertically aligned carbon nanotubes (CNTs) grown in patterned areas are used as electron sources in field emission displays (FEDs), but detrimental electron beam spreading may occur in a vacuum space. In this paper, a novel emitter structure with two coaxial electrodes and vertically aligned CNTs is proposed and analyzed using three-dimensional (3D) computation of the electric field. One of the gate electrodes plays a role in electron extraction and the other one in electron beam focusing. Unlike the case of double-gated Spindt emitters, the focusing gate electrode is placed near the plane of the CNT tips while the extraction electrode is placed at some distance from it. An improved electric field uniformity within the CNT array and focusing of the electron beam are thus achieved. Electron beam confinement characteristics and field emission properties are calculated as functions of device geometry and its functional parameters.

The main purpose of this study was to evaluate ozone chemistry in NH₄OH solutions in terms of oxidizing power compared with H₂O₂-based NH₄OH solutions. The solubility of ozone in the solutions tested was almost nil at room temperature when the solution pH was higher than 9. However, the decrease in solution temperature to 10°C resulted in a dissolved ozone concentration at the ppm level in NH₄OH solutions. The slow decrease in pH and the increase in redox potential were measured as functions of ozone injection time in NH₄OH solutions at 10°C. The half-life times of peroxide were 40 min and 4 h in 1:1:5 (volume ratio) NH₄OH:H₂O₂:H₂O (SC1, standard clean 1) solution at 80 and 50°C, respectively. However, the half-life of ozone at room temperature was less than 2∼ 5 min at the concentrations investigated. The contact angles of bare silicon changed from 72° to less than 5° within 10 s in SC1 at 80°C. In ozonated solutions, change of contact angle to hydrophilic took longer than 3 min depending on the concentration of ozone in NH₄OH solutions. The addition of peroxide and ozone significantly reduced the etch rate of silicon in NH₄OH solutions. When Al₂O₃ particles were deposited on silicon wafers, ozonated NH4OH combined use with megasonic power at room temperature could remove more than over 90% of particles from the wafer surface.

Hafnium (Hf) and hafnium nitride (Hf–N) flims were deposited on silicon wafers using a magnetron sputtering system. The as-deposited Hf film has a hexagonal close packed structure and a low resistivity of 101 µΩcm. The phases form in the order of α-Hf → HfN_0.4 → ε-Hf₃N₂ → fcc-HfN with increasing nitrogen concentration in the Hf–N film. The thermal stabilities of Cu/Hf–N/Si contact systems are evaluated by thermal stressing at various annealing temperatures. In Cu/Hf/Si, a reaction between the Hf barrier layer and the Cu layer is observed, and copper–hafnium compounds form after annealing at 550°C. Moreover, highly resistive copper silicide is found after 600°C annealing. No copper–hafnium or copper silicide compounds are found in the Cu/HfN_0.47/Si contact system even after annealing at 650°C. Incorporating nitrogen into the hafnium diffusion barrier can suppress the formation of copper–hafnium compounds and copper penetration, thus improving the barrier's thermal stability.

We simulated grain growth in a damascene trench structure varying the overburden thickness, driven by the surface and the interface energy minimization. The modified Potts model based on the Monte Carlo method was implemented. To determine whether the trench evolved a bamboo microstructure or not, we analyzed the normalized number of the triple junction points per cross-section that approaches zero with completion of a bamboo. The results of both the simulation and the triple junction analysis suggest that only the trench whose depth is significantly thicker than the overburden thickness can evolve a bamboo. While the trench and the overburden evolve their microstructure independently at the initial stages, only the microstructure of the thick overburden continues to grow to the inside of the trench because of their large enough grain size. These may provide a clue to understand the dependence of the trench microstructure on the overburden counterpart.

Metal–semiconductor–metal (MSM) AlN mid-ultraviolet (mid-UV) photodetectors were fabricated. AlN layers were grown on GaN substrates by magnetron reactive sputtering deposition. The AlN photodetectors exhibited a high responsivity at wavelengths from 210 nm to 190 nm, and the response tails off at a wavelength of 220 nm. The responsivities at 200 nm at biases of 5 V and 10 V were 1.08 and 3.51 A/W, respectively. When the reverse voltage was higher than 7 V, responsivity increased almost linearly with reverse voltage. The responsivity at 25 V was calculated to be approximately 14.9 A/W.

The electronic properties of Si-doped InGaN thin films with different In compositions were investigated. The samples were grown by metalorganic vapor phase epitaxy (MOVPE), and then evaluated using photoluminescence, X-ray diffraction and variable temperature Hall effect measurements. The Si donor activation energy was found to decrease with the increase in In composition of InGaN as a result of shrinking bandbap energy, and determined to be 17 meV, 10 meV and 6 meV for 4%, 9% and 13% of In compositions through the least square fitting of experimental carrier concentrations versus temperatures. InGaN alloy with 9% of In composition exhibited the best electronic properties with the lowest compensation ratio and the highest mobilities among those three samples over the whole range of measurement temperature. The relatively high mobility of 227 cm²/Vs at room temperature was achieved in this sample. Scattering mechanism in InGaN alloy was also studied using a simple model.

The radiative recombination of a two-dimensional electron gas (2DEG) was investigated in Al_0.30Ga_0.70N/GaN single heterostructures (SHs) without intentionally doping the barrier material, i.e., where the 2DEG appears at the interface due only to polarization effects. In addition to the typical excitonic transitions and the LO-phonon replicas originating from the GaN flat-band region, the photoluminescence spectra displayed three well-defined transitions. Their small binding energies and the observed blue shift with the excitation density suggested the association of these new emissions to quasi-2D excitons. On the basis of the thermal and excitation power dependences, the transitions were assigned to interface excitonic lines. Applying a weak electric field parallel to the growth direction, which depletes the triangular well, corroborated the 2DEG nature.

Curie temperatures are evaluated using first principles in (K,Zr)₂S and (K,Nb)₂S diluted magnetic semiconductors which have been designed as half-metallic and transparent materials with a large magnetoptical effect. From the total energy differences between the ferromagnetic state and the spin-glass state, estimations of Curie temperatures are achieved by mapping to the Heisenberg model within the mean-field approximation. According to the results, it is possible to fabricate transparent, half-metallic and room-temperature ferromagnets with Zr- and Nb-concentrations of around 5 at%. Effects of additional carrier doping for (K,Mo)₂S are also evaluated and it is found that (K,Mo)₂S with hole doping (∼5 at%) exhibits transparency, is half-metallic and has room-temperature ferromagnetism.

We measured a spin-dependent luminescence from a GaAs–GaAsP strained layer superlattice and GaAs substrate to evaluate the spin polarization of conduction band electrons excited by circularly polarized light. The GaAs–GaAsP strained layer superlattice with a mixture of group-V elements, As and P, was considered as a suitable spin-polarized electron source because the discrepancy of the valence band was reported to be larger than that of the conduction band. The observed maximum circular polarizations of the luminescence from the GaAs–GaAsP strained layer superlattice and GaAs substrate were 68% and 15%, respectively. The dependence of the circular polarization of the luminescence on the excitation photon energy was well explained by the calculated band structure. The initial spin polarizations of conduction band electrons excited in the GaAs–GaAsP strained layer superlattice and GaAs substrate were estimated to be 95% and 46%, respectively, from the luminescence polarization, lifetime and spin relaxation time. The high initial spin polarization of conduction band electrons proved the high performance of a photocathode with the GaAs–GaAsP strained layer superlattice as the spin-polarized electron source.

The effect of oxygen impurity on the production of room-temperature stable metastable defects has been studied in n-type silicon implanted with hydrogen ions at 88 K. Deep-level transient spectroscopy measurements have been performed for implanted epitaxial-(Epi) and Czochralski-grown (CZ) samples. It is found that three metastable defects (E_c–0.29, 0.41 and 0.55 eV) are observed in implanted CZ samples as already reported, while no production of metastable defects is revealed in Epi samples. This indicates that metastable defects are hydrogen-related defects involving oxygen.

High-quality and large single-phase Bi2212 whiskers are grown by a new growth–melt–regrowth method. The average composition of the Bi2212 whiskers and the maximum size of single-crystal domains are Bi_2.15Sr_2.08Ca_0.90Cu_2.00O_x and 0.5 µm × 88 µm × 2 mm, respectively. The results of X-ray diffraction analysis and I–V characteristic measurement indicate that the crystallinity of the obtained Bi2212 whiskers is excellent.

We have fabricated interface-engineered junctions (IEJs) with different counterelectrode materials. YbBa₂Cu₃O_x and La_0.2Yb_0.9Ba_1.9Cu₃O_x were used as the upper layer materials, and (La,Sr)₂AlTaO₆ (LSAT) was deposited on the ramp surface prior to counterelectrode deposition to modify the interface barrier. The junction critical current density was decreased by La-doping and LSAT deposition, though all junctions exhibited resistively and capacitively shunted junction current–voltage (I–V) characteristics. Furthermore, La-doping and LSAT deposition led to increases in the junction capacitance and hysteresis in the I–V characteristics, while I_cR_n, J_c spreads, and inductances were almost the same for junctions with similar J_c values.

The diffraction spectral intensity characteristics of a time-dependent Gaussian pulse from triangular and elliptic apodized slits in the far field are studied both theoretically and numerically. The apodization for the spectrum of the Gaussian pulse for both types can be observed as well as the red or blue shift of the spectral intensity maximum of the incident pulse. Also, the formulae used to determine the temporal intensity and energy distribution of the diffracted pulse on the observation plane are provided in this work.

We propose a new method for the slice amplification and frequency expansion of a Ti:sapphire laser. A mathematical model is set up and numerically simulated on the basis of an optical parametric effect. A multiplicate mechanical laser, which can slice amplify and expand a Ti:sapphire pulse, a one nanosecond Q-switch Nd:YAG laser, pumping a narrow-bandwidth pulse Ti:sapphire tunable laser (by 532 nm) and a BBO-OPO (by 355 nm), is designed. In an experiment, the pulse-slice amplification and expansion of Ti:sapphire laser narrow linewidth (<0.1 nm), and a frequency expansion of 120 nm (560–680 nm) with an energy output of 6 times as large as that of no slice amplification are demonstrated.

The second-harmonic generations (SHGs) of nanosecond pulses using first- and second-order quasi-phase matching (QPM) were realized in a two-dimensional periodically poled LiNbO₃ with square lattice. Maximum conversion efficiency of 35% and 14% was achieved respectively at the fundamental wavelengths of 1.352 µm and 1.064 µm. In addition, the SHG of 1.064 µm picosecond laser using second-order QPM was also studied in this crystal. Based on the comparison between the SHGs excited by nanosecond and picosecond pulses, it may be concluded that if second-order QPM is used, the incident laser with higher peak power is necessary.

This paper reports the structural properties and lasing characteristics of GaInAsP/InP multiple-quantum-wire lasers fabricated by electron beam lithography, CH₄/H₂-reactive ion etching and organometallic vapor-phase-epitaxial regrowth. Good size distributions of multiple-quantum-wire structures (wire widths of 18 nm and 27 nm in a period of 80 nm) have been obtained with standard deviations less than ±2 nm. We have confirmed that low-damage etched/regrown interfaces of quantum-wire structures can be realized by using a partially strain-compensated quantum-well structure. Threshold current densities of 5-quantum-well wirelike lasers (wire widths of 43 nm and 70 nm) were found to be lower than that of the quantum-film laser, fabricated from the same initial wafer, due to a volume effect at temperatures up to 85°C. Finally, room temperature (RT)-continuous wave (CW) operation of multiple-quantum-wire lasers (wire width of 23 nm in a period of 80 nm, 5-stacked quantum-wires) was achieved, and the good reliability of this quantum-wire laser was demonstrated for the first time by means of lifetime measurement under the RT-CW condition.

Using tertiarybutylarsine (TBAs) as the arsenic precursor and the nitrogen as the carrier gas, high-quality AlGaAs/GaAs quantum well (QW) diode laser materials have been grown by metalorganic chemical vapor deposition (MOCVD). Photoluminescence and device measurement studies indicate that the quality of the grown AlGaAs/GaAs laser materials can be comparable to those grown by using AsH₃ as the arsenic precursor and hydrogen as the carrier gas. For the first time, a low threshold current density of 200 A/cm² for 1000 µm cavity length broad area AlGaAs/GaAs lasers has been achieved by this MOCVD growth method. It has been shown that TBAs and nitrogen gas can be employed in MOCVD growth of the widely used AlGaAs/GaAs laser materials, for substituting the highly toxic source gas AsH₃ and the highly explosive carrier gas H₂.

A 90°-domain structure was fabricated using electrical poling in ferroelectric birefringent KNbO₃ crystal. The refraction and reflection characteristics of the light at the boundary of the 90°-domain structure were investigated, and the novel behavior of total refraction (no reflection) has been found for the P-polarized light throughout the entire range of incident angle (0≤θ≤90°). Strong refraction of the light was observed after it exited from the crystal output surface at the incidence parallel to the domain boundary. These behaviors were explained analytically.

We fabricated a GaInNAs semiconductor optical amplifier (SOA) by applying a facet coating to a buried-ridge-stripe GaInNAs laser. Due to a low reflectivity (<0.1%) and a wide bandwidth (70 nm) coating, Fabry–Perot (FP) modes of the GaInNAs laser were suppressed sufficiently, and thus a 1.3 µm traveling-wave GaInNAs SOA was realized for the first time. Peak chip gains of more than 9.6 dB and a 3-dB-gain bandwidth above 49 nm (9 THz) were obtained simultaneously with a cavity length between 600 µm and 900 µm. In addition, on/off ratios between 20 and 30 dB were obtained by switching the current on and off, which seems sufficient for the SOA to work as a switching device. With the temperature characteristics, we found that the ASE intensity and the gain coefficient of the GaInNAs SOA were much less dependent on temperature than those of conventional InP-based SOAs. These results demonstrate the superior temperature characteristics of the GaInNAs SOA compared with conventional InP-based SOAs.

We proposed and investigated a Michelson interferometer-type wavelength converter with a multimode interference coupler (MIWC-MMIC) as one of the key devices in future DWDM photonic switching networks. The MIWC-MMIC is compact and efficient due to its Michelson interferometer-like structure, which uses an MMIC simultaneously as input and output-side couplers. The dependence of the output characteristics on structural parameters, such as the power-division ratio of the MMIC and the reflection coefficient at semiconductor optical amplifier (SOA) ends, was analyzed to optimize the structure for operation with a low excess loss and a low signal light power. The device was actually fabricated and its preliminary static characteristics were measured. The cross modulation of the converted light by 9.0 dB was attained by introducing a signal light with a power of about -5 dBm.

In this paper, an optical fiber sensor for the determination of critical micelle concentration (CMC) is described. The sensor is based on the adsorption effect. When the concentration of the surfactant solution reaches the CMC, the outputs from the fiber suddenly begin to increase due to the interaction between the evanescent wave and surfactant molecules. Using this phenomenon, the sensor is able to determine the CMC of the surfactant solution in real time. The effect of launching angle of the light and interaction length of the fiber in the sensing region on sensor sensitivity has been studied. It has been found that the selective rays launching close to the critical angle of the fiber and the long interaction length of the sensing region increase the sensor sensitivity.

We have studied a concurrent read only memory–random access memory (ROM–RAM) optical disk system without laser feedback by optimizing pit depth. When the pit depth was 47 nm (optical depth about 1/11 λ) and the pit width 0.45 µm, about 8% jitter in both pit and magneto-optical (MO) signals was obtained with a 785 nm wavelength laser diode and 0.55 NA objective lens by employing magnetic-field-modulation (MFM) MO recording. Both pit data and MO data were recorded with eight to fourteen modulation (EFM) code with a minimum mark length of 0.83 µm and a track pitch of 1.6 µm and thus the areal density is comparable to 1.3 GB for φ120 mm single sided disk. By the optimization of the pit depth, sufficient system margins for practical use were obtained without laser feed back for the simultaneous reproduction of both pit and MO signals.

Silicone ([SiO(CH₃)₂]_n) films were photochemically modified into SiO₂ by irradiation with a 157 nm F₂ laser. The dissociation of Si–CH₃ bonds of silicone simply depended on the photon number of the F₂ laser. The quantum yield of the modification was estimated to be approximately 1×10^-2. Mechanisms of oxidation and O–H production in the modified films were clarified. The depth of the modification was not limited by the absorption coefficient of silicone because SiO₂ of the modified films is transparent for the F₂ laser. A fine pattern of the 1.5-µm-thick silicone films could be fabricated by immersing the modified samples in 0.2 wt% hydrogen fluoride solution.

We have proposed an in-plane switching twisted nematic (IT) mode. The characteristics of the IT mode are the wide viewing angle, the narrow cell gap error tolerance, and the relative fast response time. However, an IT mode needs a high electric field to obtain a high contrast ratio. To improve this situation, we propose a compensation method using a twisted nematic liquid crystal (LC) film or a twisted discotic LC film. Specifically, the latter can achieve the wide viewing angle, the high contrast ratio and the decrease in the driving voltage. In this paper, a compensation method using a film is suggested and evaluated by numerical calculation.

The optical performance of the Ho:CaF₂ Q-switched Tm:YAG laser as a function of the initial population in the ground state of the Ho:CaF₂ saturable absorber, pumping rate, and the reflectivity of the output coupler are studied numerically. The results obtained numerically are in good agreement with those obtained experimentally. For a typical laser configuration, a Q-switched laser pulse of 70 mJ in 45 ns is obtained.

The fabrication of polymeric waveguides and the loss of waveguides were investigated for optical interconnection. Multimode polymeric waveguides were fabricated by hot embossing process. The replication of waveguide channels with hot embossing technology is of interest for single step processes that have to deliver a surface roughness far below the wavelength. Resulting waveguides exhibited a smooth surface profile and the square cross section of the core. The average propagation loss of these waveguides was approximately 0.2 dB/cm at 850 nm wavelength.

This paper presents an equalizer for a high-density optical disc reproducing apparatus. The equalizer ensures small bit error rate (BER) applying simple circuitry. The results of the experimental tests of the equalizer are described. The experimental comparison of the proposed equalizer with a known limit equalizer is given.

We propose and experimentally demonstrate a new fast wavelength-selectable laser technique, which is based on Fabry–Perot (FP) lasers with external light wave injection. By using different bias currents of FP lasers, wavelength tuning can be realized. In the experiment, the tuning of three different wavelengths tuning, the side-mode suppression ratio of >20 dB, and the wavelength switching time of <2 ns were attained.

Under 172 nm light excitation, energy transfer from Pr³⁺, Nd³⁺, Tb³⁺ or Tm³⁺ to Gd³⁺ resulting in strong Gd³⁺ emission at 312 nm was observed in GdPO₄ doped with one of these ions. Among them, Pr³⁺ provides the strongest Gd³⁺ emission and Tm³⁺ is the second best. A wide energy gap between the 5d state and 4f levels of Pr³⁺ resulting from a simple electron configuration of 4f² leads to energy transfer from a 5d-to-4f transition of Pr³⁺ to a 4f-to-4f absorption of Gd³⁺. Presumably, this is also the case with Tm³⁺, which has an electron configuration similar to that of Pr³⁺. The quantum output of the Gd³⁺ emission from GdPO₄:Pr³⁺ (1 mol.%) relative to the blue luminescence of BaMgAl₁₀O₁₇:Eu²⁺, a commercial phosphor for plasma display panels, is about 37% under 172 nm excitation. Reverse energy transfer from Gd³⁺ to Dy³⁺ occurs under excitation by the Gd³⁺ absorption at 276 nm.

The excitation and emission spectra of O₂^- molecular ions in KI, KBr and KCl crystals have systematically been investigated at 8.7 K. The present results for the emission spectra with zero-phonon lines were in good agreement with previous results. From the temperature dependence of their emissions, we found that the luminescence intensities of O₂^- ions still appear at room temperature (RT) and are much stronger than those of other chalcogen molecular ions particularly in a KCl crystal. On the other hand, we found vibronic structures on the low-energy sides of the excitation spectra of KI and KBr:O₂^- crystals, showing several peaks with nearly equidistant spacings. The anharmonic vibrational energies of O₂^- molecular ions in the excited state were obtained from these energy differences, depending on their lattice constants. Using spectroscopic constants calculated from the experimental data, we could construct a configurational-coordinate diagram for an O₂^- center in a KI:O₂^- crystal.

This paper presents high-performance asymmetric two-beam coupling, beam diffraction and holographic recording in polymeric composites without poling and applying an external electric field. The polymer composites are based on poly(2-(9-carbazoyl)ethyl methacrylate) (PCzEMA) and poly(N-vinyl carbazole) (PVCz) as host matrices with 2,4,7-trinitro-9-fluorenone (TNF) as a sensitizer, four kinds of plasticizer; tricresyl phosphate (TCP), n-butyl benzyl phthalate (BBP), diphenyl phthalate (DPP), and dicyclohexyl phthalate (DCP); and (s)-(-)-1-(4-nitrophenyl)-2-pyrrolidine-methanol (NPP) as a nonlinear optical dye. The gain coefficient and diffraction efficiency increased markedly with increasing TNF and NPP concentrations. The highest net gain coefficient of 101.9 cm^-1 with optical gain of 224 cm^-1 and absorption coefficient of 122.1 cm^-1 was obtained for PVCz/NPP/DDP/TNF (35/20/40/5), and the highest diffraction efficiency of 88% was achieved for PCzEMA/NPP/TCP/TNF (35/30/30/5) and PVCz/NPP/DDP/TNF (35/20/39/6) composites. The BBP plasticizer significantly enhanced the speed of two-beam coupling and diffraction grating formation for both PVCz and PCzEMA composites. Holographic images stored in the polymer composites were clearly read out using a probe beam. The key point for achieving the external-electric-field-free high performance of asymmetric energy transfer and diffraction efficiency is to have a high concentration of TNF (5 or 7 wt%).

The morphology of titanium oxide films, prepared via two different methods, oxidation following the evaporation of titanium and spin-coating a suspension of TiO₂ nanoparticles, was investigated by scanning electron micrograph (SEM) and X-ray diffraction (XRD). SEM images indicated that the surface of the TiO₂ film is rough and the pore size is large, compared with those of the TiO_x film, which results from the connected network of the TiO₂ film. Pore filling is likely to be easier in the TiO₂ film than in the TiO_x film due to its larger pore sizes. Poly(3-hexylthiophene) (PAT6) chains can be interrupted by the TiO₂ network structure, as evidenced in UV-Vis spectrum. XRD revealed better crystallinity in the TiO₂ film than in the TiO_x film. The investigation of the photoluminescence (PL) spectra revealed that PL of PAT6 is quenched when it was filled into the network pores. We prepared the photovoltaic devices using PAT6 as both sensitizer and hole conductor and titanium oxide and PV films as the electron conductor, to reveal the effect of the morphology of the titanium oxide films on the photovoltaic performance. An improvement of conversion efficiency by over twofold in the TiO₂ cells compared with that of the TiO_x cells was observed. These phenomena suggest that the photovoltaic performances of PAT-TiO₂ (or TiO_x)/PV cell were dependent on the interfacial morphology between both PAT6 and TiO_x and PAT6 and PV.

A defect-free, large memory angle, high contrast ratio and bistable surface stabilized ferroelectric liquid crystal (SSFLC) display, which has potential for electronic paper and liquid crystal on silicon (LCoS) applications, has been developed using an alignment layer of 5° obliquely evaporated SiO_x. In this paper, optimized conditions for achieving a defect free device are presented.

In this study, we consider band structures of two classes of photonic crystals with two geometric parameters. The first class has a square lattice and is studied for dielectric contrast, centered at ε/ε₀=11.4 (GaAs-air). The second class has a hexagonal lattice and is studied for dielectric contrast, centered at ε/ε₀=13 (silicon-air). These examples have the following feature: the optimal (and largest) full band gap is obtained when both band gaps for E and H polarizations have the same (simultaneous) band edges. In addition, photonic crystals with two geometric parameters typically have much larger optimal band gaps than their counterparts with one geometric parameter.

The average lattice constant of Cd_xZn_1-xS/ZnS multiple quantum wells (MQWs) can be matched to that of GaP at a cadmium (Cd) content (x) in the range of 0.2–0.35. The induced strain in the Cd_xZn_1-xS well of the Cd_xZn_1-xS/ZnS MQWs lattice-matched to GaP is smaller than that in Cd_xZn_1-xS/ZnS MQW with a ZnS buffer layer on a GaAs substrate. Effective band gap energy increases in the former compared with that in the latter.

SnO₂ thin films on three different kinds of substrates (sapphire, alumina, and Si with 1000 Å-thin oxide layer) were grown by a reactive r.f. magnetron sputter method. Epitaxial SnO₂ thin film without an apparent grain structure but with high dislocation density along lateral direction to substrate was grown on a sapphire substrate. The microstructure of the thin film was investigated, using the 3C2 beam line from a Pohang Light Source (PLS) consisting of a 2-GeV electron accelerator, 4 circle X-ray diffractometer, and AFM. It was confirmed that the thin film grew epitaxially on the sapphire substrate with variants structure. A large defect density was exhibited on the surface of the epitaxial thin film, which is related to sorption sites reacted with the gas. SnO₂ films on the polished alumina and Si substrate showed poly-crystalline structure of tetragonal structure, low resistance of about 10 Ω, and good optical transmittance. An epitaxial SnO₂ thin film exhibited the highest sensitivity to combustible gases and a particular sensitivity of 95% to alcohol at 2000 ppm and 350°C. The sensor also showed a good stability with small baseline drift and short reaction times of about 5 seconds, respectively. This experiment confirms substrate effects on characteristics of an SnO₂ thin film plus the potential for the application of epitaxial SnO₂ film in the production of stable gas sensors.

Ultrathin ZrO₂ films with a dielectric constant of 20 have been deposited at 150°C on carbon-implanted solid phase epitaxy (SPE)-grown Si_1-yC_y heterolayers by microwave plasma-enhanced chemical vapor deposition (PECVD) using zirconium tetra-tert-butoxide. The SPE-grown Si_1-yC_y heterolayers and deposited ZrO₂ films have been analyzed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) for chemical analysis. The fixed oxide charge density (Q_f/q) and interfacial trap density (D_it) of as-deposited ZrO₂ films are found to be 2.6×10¹¹ cm^-2 and 5.6×10¹¹ eV^-1cm^-2, respectively. The gate current of the ZrO₂ layers is found to decrease after 400°C annealing in N₂ for 30 min. The main conduction mechanism is dominated by Schottky emission in the ZrO₂ films deposited on Si_1-yC_y layers.

This study describes a multi-layer piezoelectric voltage and power transformer which has one direction poling, operates in a wide-frequency range and delivers both step-up and step-down voltages by inverting the electrical connections. In this design, the input and output electrodes are on the same side of the disk and are isolated from each other by a fixed gap. Investigations were performed on a disk of diameter 29.1 mm. The electrode pattern is a ring/dot structure, where a strip connects the dots. Various ratios of input to output area were studied and it was found that area ratio in the range of 2.8–3.3 or the output diameter in range of 13–15 mm yields high power and efficiency. The power density for the optimized single layer transformer was 40 W/cm³ while that for the 3-layer structure was 25 W/cm³. Though the power increased with multilayer structure, the effective power density decreased because of the interlayer constraints.

The sintering behaviors and microwave dielectric properties of V₂O₅-added and -substituted ZnNb₂O₆ ceramics with columbite structure (abbreviated as ZNV and ZVN, respectively) have been investigated. It was found that the addition or substitution of V₂O₅ to ZnNb₂O₆ ceramics lowers the sintering temperature from 1150°C to ∼900°C, but the sintering mechanisms are different. The formation of a ternary liquid phase is attributed to enhanced sintering in ZNV samples. Interaction between ZnNb₂O₆ and V₂O₅ also led to the formation of a second phase, V₃Nb₁₇O₅₀. In contrast, it has been observed that with up to 8 mol% substitution of V₂O₅ in ZnNb₂O₆, a complete solid solution is formed. The sintering temperature for the ZVN sample becomes lower due to the decreased temperature of liquidus according to the substitution of V for Nb ions. The microwave dielectric properties of ZNV samples are seriously degraded due to the presence of a V₃Nb₁₇O₅₀ second phase. This was confirmed by measuring the dielectric properties of V₃Nb₁₇O₅₀ second phase. However, V-substituted Zn(Nb_0.94V_0.06)₂O₆ samples sintered at 875°C for 2 h exhibit excellent microwave dielectric properties: Q×f of 65,000 GHz, ε_r of 24, and τ_f of -72 ppm/°C.

The effects of 2ZnO–B₂O₃ (2ZB) glass addition on the densification and dielectric properties of CaTiO₃ (CT) have been investigated. With the 2ZB glass content greater than 20 vol%, the densification temperature can be greatly reduced from 1300°C for pure CT to 875–925°C for CT+2ZB dielectric ceramics. The above result is attributed to a chemical reaction taking place at the interface of 2ZB/CT during firing. The Ca in CT dissolves into 2ZB, forming a new glass of CaO–ZnO–B₂O₃ at 840–860°C which enhances the densification kinetics of 2ZB+CT dielectric ceramics. For the samples with 20–40 vol% 2ZB, the resulting 2ZB+CT ceramics have a dielectric constant of 60-90 and dielectric loss of less than 0.15% at frequencies below 13 MHz.

Microwave dielectric properties of A₂P₂O₇ (A = Ca, Sr, Ba, Mn, Mg, Ba) ceramic materials were investigated by a network analyzer at the frequency of 10 GHz. It was found that A₂P₂O₇ ceramics could be sintered at relatively lower temperature below 1150°C, although the thortveitite type series, Mn₂P₂O₇, α-Mg₂P₂O₇ and α-Zn₂P₂O₇ with smaller ionic radii of A cations were hard to sinter to full density. The dielectric constant of A₂P₂O₇ is lower than 10. The Q×f value increased according to the sequence of δ-Ba₂P₂O₇, α-Sr₂P₂O₇ and β-Ca₂P₂O₇ in dichromatic type series, and the sequence of Mn₂P₂O₇, α-Mg₂P₂O₇ and α-Zn₂P₂O₇ in thortveitite type series, respectively. The temperature coefficient of resonant frequency τ_f for all samples exhibits negative value. Larger τ_f for α-Zn₂P₂O₇, α-Mg₂P₂O₇ and δ-Ba₂P₂O₇ is mainly due to their reversible phase transformations. The microwave dielectric properties were discussed from the point view of bond valence.

Light scattering study of ripplon (surface tension waves of thermal origin) was made at a high frequency range of more than 10 MHz on pure water surface. The observed power spectra were in very good agreement with the theoretical curves strictly derived from the fluctuation dissipation theory. The two approximations currently used for the ripplon analysis were also examined, namely, the first approximation P₁(ω) of two Lorentzian peaks and the second one P₂(ω) with two additional terms of antisymmetric components. Contrary to most expectations, P₁(ω) proved to be a much better approximation than P₂(ω) that has the higher-order terms. The possibility of surface viscosity on the pure water surface was experimentally confirmed by the wide-band frequency measurement. However, the ripplon power spectra obtained up to 40 MHz showed no such evidence.

Optical, thermal and mechanical properties of Si–O–C ternary alloy films grown by organic catalytic chemical vapor deposition (CVD) were studied in comparison with those of Si–O films grown by electron-beam evaporation and AlN grown by electron cyclotron resonance sputtering. Si–O–C with Si: 36 at.%, O: 46 at.%, and C: 18 at.%, grown using TEOS, shows a relatively high refractive index of around 1.9 and a small extinction coefficient of less than 0.01 at wavelengths between 500 nm and 1000 nm. The value of the extinction coefficient is roughly five times smaller than that of SiO films grown by electron-beam evaporation. The thermal conductivity of 0.64 W/m·K and the stress of the film are comparable with those of SiO. The results indicate that Si–O–C grown by organic catalytic CVD using TEOS is a promising material for optical applications such as laser diodes and semiconductor optical amplifiers.

Continuous single-step fabrication of cubic nanocrystalline Y₂O₃:Eu³⁺ phosphor particles using flame spray pyrolysis was successfully conducted without any post-heat treatments. The morphology of the as-prepared particles was spherical and nonaggregated. The mean size of as-prepared particles was easily controlled by adjusting the precursor concentration. On varying the overall concentration of the precursor solution from 0.01 to 0.5 M, the crystallite size and geometric mean particle diameter varied from 38.4 nm to 50.6 nm and 263 nm to 741 nm, respectively. XRD spectra of as-prepared particles indicated that all products, regardless of the precursor concentration, showed the cubic phase with high crystallinity without any post-treatments, although residence times in the flame were very short. Upon excitation with 254 nm light, all of the as-prepared particles showed bright red emission due to the 4f–4f transitions of Eu³⁺ ions, and the highest photoluminescent intensity at 611 nm was found at a Eu³⁺ content of about 12 mol%. These results indicate the possibility of the fabrication of cubic nanocrystalline Y₂O₃:Eu³⁺ phosphors with a high production rate and high purity.

The thermoelectric properties of layer-structured homologous compounds of (ZnO)_mIn₂O₃ (m is an integer) were investigated in terms of the detailed dependence of the molar ratio of ZnO to In₂O₃, n (=ZnO/In₂O₃), and of doping, such as with Ba²⁺, Ca²⁺, Sr²⁺, and Sn⁴⁺, for an In site. Except for the Ba and Sr dopings, all sintered specimens with n≥3 were found to be in the phases of (ZnO)_mIn₂O₃. The highest power factor apparently existed around n=3 while the thermal conductivity was minimum at the range from n=3.5 to 5. The Ca doping effectively reduced the thermal conductivity, resulting in a dimensionless figure of merit of 0.23 (at 1053 K) for n=3.5, which was relatively high among n-type oxides.

High-surface-area anatase titania nanoparticles are prepared by metalorganic chemical vapor deposition (MOCVD) using thermophoretic collection. Based on the dependence of X-ray linewidth (FWHM) on collection distance, a formation mechanism for the nanoparticles is proposed in which it is assumed that the relative changes in the grain size of and vacancy concentration in the nanoparticles are proportional to the velocity of the gas flow in the reactor. Three nondimensional equations that describe the dependence of the properties of the nanoparticles on collection distance are derived. This model explains well the effect of collection distance on X-ray linewidth, and it is not only in good agreement with XPS results but also consistent with TEM observations.

We introduce an annealing method performed with only Bi powders at 673 K. With this method, the carrier concentration is controlled and the conductivity type can be changed by adjusting the annealing time. Most importantly, conductivity-type transition occurs in an annealing time of 48 hours. The thermoelectric properties of the alloys are measured and described as functions of carrier concentration and annealing time. n-Type hot-pressed Bi_1.8Sb_0.2Te₃ alloys that deviated from the optimal figure-of-merit Z condition owing to high carrier concentration can be optimized by this annealing method.

We investigated the relation between internal friction and magnetism due to a random arrangement of magnetic atoms by using the Mn–Cu–Ni–Fe alloy, called M2052. Its internal friction and dc susceptibility were measured as a function of the temperature from 4.2 K to room temperature. As for the internal friction, two peaks were observed at around 70 K and 270 K; the peak at the lower temperature was shifted by changing the measurement frequency. A comparison of the temperature dependency of the susceptibility and the internal friction indicated that freezing of the magnetic moments of ferromagetic clusters could cause low-temperature internal friction. We confirmed that relaxation related to the internal friction is consistent with magnetic relaxation in random magnetism.

In in situ polymerized polypyrrole (PPy), the deposition process strongly depends on the nature of the substrate surface. That is, for a surface that is negatively charged, there is a linear correspondence between dipping time and the amount of PPy deposited on the substrate. However, in the case of a positively charged surface, there is an apparent rest period of approximately 10–20 min, during which no PPy is deposited. From optical absorption spectroscopy and photoelectron emission studies etc., it became clear that oligomers of pyrrole were adsorbed on the positively charged surface during the rest period, as a result the polymerization reaction of PPy could proceed.

We have investigated the effect of Bi on the homoepitaxial growth of Cr on Fe(100) by reflection high-energy electron diffraction (RHEED) measurements. It was found that Bi enhances the layered growth of Cr on Fe(100)-c(2× 2)O reconstruction surfaces. The dependence of the growth on Bi layer thickness suggests that there exists a suitable amount of Bi surfactant layer that enhances smoother layered growth. The surface segregation effect of Bi was studied by Auger electron spectroscopy.

With complex treatment, which includes plasma irradiation pretreatment and reactive sputtering treatment, a boron–carbon–nitrogen (B–C–N) film was deposited as an overcoat on a CoCrTa magnetic disk by RF sputtering using two semicircular targets. Nitrogen-containing carbon (C–N) and CN/BN layered films were deposited by controlling the time duration the substrate faced each of the graphite and hexagonal boron nitride (h-BN) targets. The effects of plasma irradiation produced from an argon and nitrogen (N₂+Ar) mixed gas as well as a nitrogen and helium (N₂+He) mixed gas on the mechanical properties of these films were evaluated in this work. Based on the results obtained in microwear and oscillation scratch tests, it is verified that the wear resistance of the B–C–N film formed in N₂+He was improved and this film exhibited a high lubricant performance, with a low friction of µ=0.027, due to He addition.

A new atomic force microscope (AFM) imaging has been used to study the bending of a sharpened and slim probe in the digital probing method (step-in mode) for the critical dimension (CD)-AFM technique. The bending of the AFM probe indicates a serious problem in measuring very fine patterns with a high aspect ratio with an error of less than 1 nm when we use the sharpened and slim probe. In our estimation, position errors Δr (in plane) and Δz (in perpendicular) rapidly increase with the slope angle and a controlled force. In experiments, we measured a degradation of the pattern profile as the controlled force increased in the AFM system. We have to control the probe at a force of <2 nN to be free of probe bending, when we measure very fine pit patterns with a size of <100 nm and an aspect ratio of >5 accurately.

The distributions of linear energy transfer for LET (LET_water) in front of the 80-cm-thick concrete side shield at the CERN-EU high-energy reference field (CERF) facility were measured with a Si detector telescope named real-time radiation monitoring device-III (RRMD-III) covered with and without a 1 cm-thick acrylic plate. In these measurements, a difference of about 20% in the absorbed dose between the two LET_water distributions was observed as a result of protons, deuterons and tritons recoiled by neutrons. The LET_water distribution obtained using RRMD-III without the 1-cm-thick acrylic plate is compared with lineal energy distributions obtained using the dosimetric telescope (DOSTEL) detector under the same conditions. These dose equivalents are also compared with that obtained using HANDI TEPC which is used as the standard at the CERF facility.

A proton detector for lifetime measurement of neutrons using a thin ruby scintillator which can be used under an environment of neutrons and γ-rays has been developed. The detector is almost insensitive to neutrons and γ-rays. This was confirmed by setting the detector adjacent to the ultra-cold neutron (UCN) facility installed in Kyoto University Reactor. When a single proton was injected into the scintillator, many scintillation signals were observed. The number of scintillation signals decreases with decreasing proton energy. Although the output signals generated by the scintillation and by the dark currents of a photomultiplier have approximately the same pulse heights, the proton can be detected by counting the signals within the time width corresponding to the decay time of scintillation. This neutron lifetime measurement system can be applied to the detection of particles other than protons.

The etching of contact holes of 0.1 µm size in SiO₂ is achieved using, for the first time, cyclic (c-)C₅F₈ with a small greenhouse effect in the pulse-modulated inductively coupled plasma. The shape of the cross section of the contact hole is as good as that etched using conventional c-C₄F₈. It is confirmed that Kr mixing instead of Ar in the plasma does not change the etching characteristics, although lowering of the electron temperature is expected which reduces the plasma-induced damage. Pulse modulation of the plasma is found to improve the etching selectivity of SiO₂ with respect to Si. Langmuir probe measurement of the plasma suggests that the improvement of the etching selectivity is due to the deposition of fluorocarbon film triggered by lowering of the electron temperature when the off time of the radio frequency (rf) power is extended.

The effect of driving frequency in the range of 13–50 MHz on the electron energy probability function (EEPF) in capacitively coupled discharges is studied using particle-in-cell/Monte Carlo(PIC/MC) method. The EEPFs obtained from the simulation generally agree well with the measured data of Abdel-Fattah and Sugai. Detailed comparison shows, however, that the transition from the Druyvesteyn distribution to the bi-Maxiwellian type with increasing driving frequency is not as clear in the simulation as in the experiment.

When a trapped ion is used for optical frequency standards, it is usually cooled by laser radiation and then pumped to the m=0 state. However, simple laser cooling cannot be applied to some ion species due to the formation of the dark state. This paper shows theoretically that such ions can also be cooled to the Doppler limit and can be prepared in the m=0 state by three laser beams with different polarizations and frequency detunings.

To compare the gravity field effect on copper-electroless plating with the magnetic field effect on the same reaction, the plating rates were measured under various vertical gravity fields. Consequently, considerably different results from those of the magnetic-field case, where the reaction was suppressed by the magnetic field, were obtained; the reaction was not suppressed but promoted by the gravity field. The total reaction rate increased with increasing gravitational acceleration, and followed the diffusion current equation in a vertical gravity field. The scanning electron microscope (SEM) observation also revealed the promotion by the gravity field, i.e., the increase of crystal sizes with increasing gravitational acceleration. This is because, in the magnetic field, the micro-magnetohydrodynamic (micro-MHD) flows interact with the nonequilibrium fluctuations accompanying the reaction. Therefore, it was concluded that the gravity convection cells occurring under gravity fields do not interact at least up to 170 G with the nonequilibrium fluctuations. At the same time, the density coefficients intrinsic to cathodic and anodic partial reactions were obtained by measuring current responses to sweeping gravitational acceleration, i.e., sweep gravitammetry. By comparing observed data with those calculated from the density coefficients, it was clarified that the autocatalytic process between the cathodic and anodic reactions is more accelerated by gravity convection than the intrinsic autocatalytic process without gravity convection.

In this report, organic thin film transistor (OTFT)-driven active-matrix liquid crystal display (AM-LCD) on flexible polymer substrate is demonstrated. A polymer material, poly (3-hexylthiophene) (P3HT) was used as the active layer and printed by a rubber stamp printing method using a prepatterned silicone elastomer stamp. With this method, the active layer was easily printed on the device without further patterning process. The saturation field-effect mobility of the rubber-stamp-printed TFT array was 0.025 cm²/V·s and the on/off ratio was 10⁴. From the results, a 2'' OTFT-LCD panel with 35×24 pixels was successively fabricated and operated using a polycarbonate substrate. In addition, we investigated the reliability of the OTFT device under various conditions with or without a passivation layer to realize more stable devices.

The photoluminescence (PL) of TiO₂ suspensions containing ethanol in the concentration range from 5 to 100 ppm by volume was measured at room temperature. We found that the relationship between the PL of TiO₂ in the presence of ethanol and the adsorption of ethanol onto the TiO₂ surface can be described as a simple Langmuir isotherm by assuming that the PL intensity is proportional to the surface coverage of ethanol on the TiO₂ surface.

In this paper, we propose a novel method using the surface acoustic wave (SAW) sensor for monitoring in situ the thickness of a silicon membrane during wet etching. Similar to pressure sensors and accelerometers, some micro-electro-mechanical systems (MEMS) devices require the thickness of silicon membranes to be precisely known. Precisely controlling the thickness of a silicon membrane during wet etching is important, because it strongly influences post-processing and device performance. Furthermore, the proposed surface acoustic wave sensor enables the thickness of a silicon membrane, from 50 µm to 80 µm, to be monitored in situ. In summary, the proposed method for measuring the thickness of a silicon membrane in real time from 50 µm to 80 µm, is highly accurate, is simple to implement and can be used for mass production. The principles of the method, detailed process flows, the set up for measuring thickness and simulation and experimental results are all discussed. The theoretical and measured values differ by an error of less than 2 µm; thus the experimental and theoretical values correlate well with each other.

An aluminum film with a thickness of 1500 Å has been used as a filter for the He Iα resonance line (21.2182 eV) from a microwave-driven high-flux discharging lamp to reduce the degradation of sample surfaces during photoemission spectroscopy (PES) measurements. A marked increase in the lifetime of sample surfaces, which overcomes a ∼90% intensity reduction, has been observed. The thin-film filter, if combined with a high-flux discharging lamp, provides clean vacuum ultraviolet lights for reliable PES measurements with an ultrahigh resolution.

The applicability of insensitive properties of measured equation of invariance (MEI) coefficients for the computation of scattering from modified structured bodies is presented in this letter. During scattering computation by using MEI technique (in IE-MEI or SIE-MEI method), the MEI coefficients of the whole scatterer is calculated in the conventional method. In contrast, using the insensitive properties of the MEI coefficients, the new method calculates the MEI coefficients only around the modified area if some portion of the scatterer is modified and reuse those for the other portion of the scatterer. Thus CPU time for solving the modified problem can be saved by using the new method. The numerical results verified the validity of the new technique which is compared with the available numerical solutions.

A simple model for reproducing temperature recalescence behaviour in spherical undercooled liquid metallic samples, undergoing crystallization transformations, is presented. The model is applied to constant heat extraction rate, uniform but time dependent temperature distribution inside the sample (even after the start of crystallization), a classical temperature dependent rate of nucleation (including contributions from different specific heats for different phases and also a catalytic factor to model the possibility of heterogeneous distributed impurities) and the solidified grain interface velocity is taken proportional to the temperature undercooling. Different assumptions are considered for the sample transformed fraction as function of the extended volume of nuclei, like the classical Kolmogoroff, Johnson–Mehl, Avrami one (corresponding to random distribution of nuclei), the Austin–Rickett one (corresponding to some kind of clusterized distribution) and also an empirical one corresponding to some ordering in the distribution of nuclei. As an example of application, a published experimental temperature curve for a zirconium sample in the electromagnetic containerless facility TEMPUS, during the 2nd International Microgravity Laboratory Mission in 1994, is modeled. Some thermo-physical parameters of interest for Zr are discussed.

The behaviors of proteins and nanoparticles coupling with the cell membrane were analyzed using an external mechanical vibration model. This model was based on a one-dimensional seismic vibration system. A simple equation was derived for the relationship between the amplitude of cell vibration and the amplitude of mobile protein or nanoparticle vibration in the cell membrane. Using this equation, the optimal frequency for the efficient vibration of mobile proteins or nanoparticles was found in the applications of in vivo and in vitro cell treatments.

Multiwalled carbon nanotubes were formed on Fe–Ni–Co alloy-coated glass substrates by infrared-radiation-heated thermal chemical vapor deposition using CO and H₂ gases at temperatures as low as 480–580°C. Growth of the carbon nanotubes was strongly affected by Ar or N₂ gas introduced during the heat-up stage prior to the growth, which markedly increased the growth rate of carbon nanotubes by an order of magnitude and yielded the carbon nanotubes with better crystallinity and less amount of carbonaceous impurity particles, in comparison with those grown at the same condition but heated in vacuum to the growth temperature. It is proposed that gas-phase energy transfer enhances the synthesis of highly crystalline carbon nanotubes while suppressing the formation of carbonaceous impurity particles.

We have developed a novel method for the purification of single-wall carbon nanotubes (SWNTs) that involves annealing in air and dispersing the SWNTs in an aqueous solution of carboxymethylcellulose (CMC). The purity of the resulting SWNTs was evaluated by analytical techniques such as electron microscopy, Raman spectroscopy, and thermogravimetric analysis (TGA). As a result, it was revealed that CMC functioned as an effective dispersion reagent in the exfoliation of the SWNT bundles and thereby, SWNTs with appreciably high quality were prepared.

The molecular orientation of a flavin Langmuir–Blodgett film was investigated by Stark spectroscopy. The first-harmonic Stark spectrum was found to be close to the first derivative of the absorbance, indicating that the flavin (isoalloxazine) ring took a specific orientation toward the direction of the applied electric field instead of a random orientation. From the analysis of the Stark spectrum, it was deduced that difference dipole moments for the S₀ → S₁ and S₀ → S₂ transitions were almost parallel to the substrate in the direction of approximately 35° from the long axis of the isoalloxazine ring.

The optical properties of two-dimensional photonic crystals (PhCs) in anodic aluminum oxide (AAO) films obtained using a simple and low-cost pre-patterning procedure are described. The prepatterning of the initial Al film surface was carried out by imprinting with an optical diffraction grating; the anodization of the prepatterned sample led to the formation of a good quality, large-area PhC with a triangular lattice of air holes (lattice period a=0.48 µm, hole radius r=0.2 µm) in an AAO film. The optical transmission spectra of the sample were measured at visible wavelengths in the range of 0.4–1.0 µm for various incidence angles and linear polarizations of the probing light. The detailed analysis of the transmission data indicates a photonic band gap in the 0.9–1.0 µm wavelength range for light waves linearly polarized in the direction perpendicular to the axes of PhC pores.

A microsensor with a picogram mass sensitivity has been researched using the resonance frequency shift of an atomic force microscope (AFM) cantilever. The mass change of the water molecules adsorbed on the cantilever was measured by analyzing the resonance frequency shift using a laser beam deflection detection system. As experimental results, a sensitivity of about 2 pg/Hz was obtained. The mass change due to increasing humidity showed that the mechanism of water molecular growth changed from an island growth to a layer growth. The critical point of the mechanism change was a humidity of about 60%. The adsorbed mass corresponds to a water layer of about 12 monolayers.