Table of contents

Four diffusion models based on the pair diffusion models of vacancy and interstitial mechanisms are adopted for the simulation of six experimental profiles of P surface concentration, CP+s, from 3×1020 to 2.5×1018 cm-3 at 900°C. Values of fitting parameters are determined to simulate the profiles of CP+s=3×1020 and 2.5×1018 cm-3 well. Changing only CP+s, other profiles are simulated. At high CP+s, a large amount of excess I is generated. For the simulation of CP+s=3×1020 cm-3, it is necessary to control excess I. For the simulation of CP+s<3×1020 cm-3, the effect of a main parameter upon the control of excess I should decrease with decreasing CP+s. Based on this, the decrease in quasi self-interstitial formation energy or the ratio of the diffusion coefficient of a negatively charged P–V pair to that of a neutral one is suitable for the main parameter. To decide the suitable main parameter, it is necessary to obtain a more accurate experimental profile, paying attention to whether or not the profile has a plateau.

Field effect of photoluminescence due to excitons bound to nitrogen atom pairs in GaAs has been investigated for uniformly doped and atomic-layer-doped samples grown on (001) GaAs substrates. The intensities of excitonic photoluminescence lines due to distant nitrogen atom pairs decrease much more rapidly than those from closer pairs when the electric field is increased. In addition, photoluminescence due to the nearest neighbor pairs in atomic-layer-doped samples exhibits much more stable characteristics than that of uniformly doped samples against an applied electric field. This stability is observed only when the electric field is applied in either the [110] or [110] direction. This anomalous field effect can be explained by considering the electron trapping process to the isoelectric N traps modulated by the electric field.

The growth characteristics and microstructure of AlN thin films grown by plasma assisted molecular beam epitaxy on Si substrates were investigated by comparing structure differences between AlN/Si(100) and AlN/Si(111). A model for the growth of AlN crystals on Si(100) and Si(111) substrate is proposed and the growth behavior of AlN film on single crystalline silicon substrate has been characterized. The difference in morphologies and microstructures between AlN/Si(100) and AlN/Si(111) can be explained by crystalline coherency at the interface between the AlN film and the Si substrate. While the c-axis direction of the wurtzite AlN [0001] on silicon substrates are the same, the coincidence of the radial direction of each of the AlN crystallites is dependent on the coherency of the interface of AlN/Si(100) and AlN/Si(111). Thus, although each AlN column on the Si(100) has a (0002) basal plane as a bottom of the column, their radial directions do not coincide and show a columnar growth. However on Si(111), each AlN column has directional coherency and therefore are able to combine together to form a single crystallite, and show epitaxial growth. The difference in surface morphology between AlN/Si(100) and AlN/Si(111) is clearly the result of the difference of the interfacial structures.

Large crystalline grain growth was demonstrated for 60-nm-thick silicon films using the electrical-current-induced joule heating method. Tapered electrodes were used in order to ensure distribution of the joule heating intensity in the lateral direction along the surface in silicon strips. Melting of silicon for 17 µs caused by the joule heating resulted in the formation of 4–8-µm-long crystalline grains. The change in the film thickness was at most 6 nm in the crystallized region. There was a tensile stress of 5.6 ×10⁸ Pa in the film. The heat flow simulation demonstrated that the solidification occurred in the lateral direction according to the temperature gradient and that the solid/liquid interface moved in the lateral direction at the velocity of about 1–2 m/s.

The instability mechanisms of the hydrogenated n-channel low-temperature polycrystalline silicon thin film transistors under on-state stress were investigated with various bias stress conditions and device channel widths. It was found that hot carrier degradation which originated from a high drain electric field and self-heating during high current operation were the two dominant mechanisms responsible for device degradation. An electrically reversible depassivation/passivation phenomenon was also found in devices under high current stress, but not in those under hot carrier stress. It was inferred that the self-heating effect would accelerate the bond breakage and diffusion of hydrogen ions, thus enhancing the rate of depassivation/passivation. Moreover, when the current in the hot carrier stress mode was sufficiently high, self-heating became the dominant degradation mechanism and hot carrier degradation phenomenon was also suppressed for devices with large channel width. Meanwhile, the electrically reversible depassivation/passivation phenomenon also occurred in this case.

Ultra-violet-light-induced states in amorphous polymethylphenylsilane have been investigated by a time-of-flight technique for transient photocurrent measurements. It is found that the photo-induced change is reversible below 320 K, while irreversible above 320 K. The finding is attributable to the formation of two photocreated dangling bond states having different metastabilities. It is shown that the experimental results are successfully explained in terms of the configurational-coordinate potential-energy diagram representing the ground-state and two different metastable-dangling-bond-state configurations. Origins of the two metastable dangling bond states are discussed.

ZnO ultrafine particles were produced by dropping Zn powder into a nichrome boat heated above 1000°C in a mixture gas of argon and oxygen. Cubic ZnO particles were predominantly produced in the mixture gas of oxygen at 5 Torr and argon at 95 Torr. The well-known hexagonal smoke particles were predominantly produced in the mixture gas of oxygen partial pressure of more than 20 Torr in the total pressure of 100 Torr. The characteristic infrared (IR) spectra due to the cubic and hexagonal phase were observed experimentally. The IR spectra of samples embedded in KBr pellets exhibited a peak at 20.3 µm wavelength for the cubic phase, and 18.3 µm and 23.0 µm wavelength for the hexagonal phase. The existence of cubic nuclei at the center of the tetrapod shape has been confirmed from the IR spectra.

In this work, we give the first report on the synthesis of GaN fine particles from gallium oxide hydroxide (GaOOH) powders and on their structural and photoluminescence (PL) properties. Simple heat treatment of GaOOH in NH₃ gas flow leads to the formation of submicron-sized hexagonal GaN powders, even at the low reaction temperature of 800°C, through intermediate conversion to the metastable gallium oxide, α-Ga₂O₃. X-ray diffraction measurements show that the powders obtained are of pure single phase GaN without any impurity phases or structural defects. However, energy dispersive spectroscopy, Fourier transform infrared, and PL measurements indicate oxygen-related characteristics. The results obtained demonstrate that submicron-sized GaN powders can be synthesized from GaOOH powders. However, there is a need to minimize the oxygen incorporation during the reaction process.

Photocurrent was measured as a function of wavelength for Cl-doped semi-insulating CdTe specimens with evaporated Au electrodes. It is found that the photocurrent decreased with decreasing temperature. This behavior of the photocurrent is different from that usually observed in other semiconductor specimens. Employing the theory, which was proposed for the amorphous semiconductor, we attempted to explain this phenomenon. From the photocurrent spectral peak at various temperatures, the band gap of CdTe was deduced and an empirical equation for the temperature dependence of the band gap E_G(T) was obtained as E_G(T)=E_G(0)-αT²/(T+β), α=5.21×10^-4 eV/K, β=37.5 K.

The effects of N₂O plasma treatment on the performance of excimer-laser-annealed (ELA) polycrystalline silicon thin film transistors (poly-Si TFTs) were investigated. The N₂O plasma treatment was conducted following the deposition of the low-temperature gate oxide, resulting in an obvious improvement in the performance of the ELA poly-Si TFTs. This improvement is presumably due to the smoothed oxide/poly-Si interface, the improved gate-oxide quality, and the reduced trap states at the interface and in the poly-Si channel, resulting from the incorporation and passivation reaction of the N₂O-plasma-generated nitrogen and oxygen radicals. Moreover, the N₂O plasma treatment also improved the stability of the ELA poly-Si TFTs under dc voltage stress.

Reliability tests of N-channel metal–oxide–semiconductor field-effect transistors (NMOSFET's) with oxide thickness ranging from 3.3 nm to 1.7 nm are performed and analyzed in this work. New device failure mechanism due to gate-to-drain leakage path formation is observed, and it severely degrades the off-state performance of devices with sub 2 nm gate oxides. Among the device parameters monitored, on-state conduction current and off-state drain leakage are the two most decisive parameters which dominate NMOSFET's functional reliability. A new unified functional reliability model is proposed, and lifetime predictions due to respective device parameters can be achieved.

Films of carbon nanotubes (CNTs) have recently being shown to be efficient field emission electron sources. In this paper, we propose and model a dual-gate structure having a nanotube-on-emitter structure as a cold electron source suitable for X-ray generation and other applications. The electrons are emitted from the confined region of the nanotube apex, the electron beam angular aperture being controlled by the focusing gate electrode. The electric field distribution in the structure has been computed using the commercial software package Simion 3D 7.0. The CNT emission current has been computed using a recently developed model that takes into account the low dimensionality of the CNT electronic system. The device characteristics have been calculated as a function of the device geometry and its functional parameters.

The band-gap energy and band-gap bowing parameter of the wurtzite AlInN alloys are investigated numerically with the CASTEP simulation program. The simulation results suggest that the unstrained band-gap bowing parameter of the wurtzite AlInN alloys is b=3.326 ±0.072 eV. The simulation results also show that the width of the Al_xIn_1-xN top valence band at the Γ point has a maximum value of about 6.57 eV when the aluminum composition is near 0.53. A summary of the band-gap energies, the width of the top valence band at the Γ point, and the band-gap energy versus lattice constant relationship of the ternary In_xGa_1-xN alloys, Al_xGa_1-xN alloys, and Al_xIn_1-xN alloys is also provided.

Monte Carlo based calculations of the impulse photoresponse in bulk InAs p–i–n structures at the 2.0 µm wavelength are reported. The predicted results look promising with effective turn-off times of less than 5 ps. These results are much better than the response reported for GaAs photodetectors at their bandedge.

Liquid-phase deposition of SiO₂ (LPD-SiO₂) is used for the deposition of silicon dioxide (∼40 Å) on GaAs substrate during GaAs metal–oxide–semiconductor field effect transistors (MOSFET) fabrication with an 8 µm gate length and 40 µm channel width, thereby providing the advantage of a process temperature lower than 60°C. LPD-SiO₂ quality can be improved significantly by annealing at 400°C in N₂ for 33 min. This occurs automatically, however, during source (drain) ohmic contact deposition/alloying, which also requires annealing at 400°C in N₂ for 33 min. A normalized transconductance was obtained in the vicinity of 280 mS/mm. High-quality MOSFET fabrication using LPD-SiO₂ is proven feasible, and involves fewer fabrication steps than other MOSFET fabrication technologies.

AlGaN/GaN heterojunction field-effect transistors (HJFETs) employing an AlN spacer layer have been fabricated. By employing the AlN spacer layer, the two-dimensional electron gas (2DEG) mobility increased from 650 cm²/(V·s) to 950 cm²/(V·s). With regard to DC operating characteristics, the maximum transconductance g_mmax increased from 100 mS/mm to 125 mS/mm. In addition, the Schottky barrier at the gate electrode improved, and the saturation current I_s decreased from 1.0×10^-9 A to 6×10^-11 A.

Hall effect, photocurrent (PC) and photoluminescence (PL) measurements are carried out to study the impurity levels of Sn-doped n-InSe. From the temperature dependence of electron concentration and PC spectra, we found that the donor level in Sn-doped samples is located at about 0.06 eV below the conduction band. Moreover, the 1.275 eV emission band observed in the PL spectra is probably associated with the transition between the donor level at 0.06 eV below the conduction band and the valence band or the shallow acceptor level.

Ba_xSr_1-xTiO₃ (BST)/YBa₂Cu₃O_x (YBCO)/SrTiO₃ (STO) structures were deposited, and the microstructure, orientation and electrical characteristics were investigated. (00l) oriented YBCO thin films were deposited on STO substrates using pulsed laser deposition, and (h00) oriented BST thin films were deposited on YBCO/STO substrates using electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapor deposition (MOCVD). A new phase was formed at the interface between YBCO and BST films and was speculated to be (Ba_xY_1-x)(Ti_yY_1-y)O₃. Ba-rich BST films showed a higher dielectric loss than Sr-rich BST films did, which indicates that Sr-rich BST films are more suited for application to microwave devices. The dielectric loss of the films was reduced as temperature decreased, which may be due to the conductivity change of YBCO film and the formation of a conduction path rather than a dielectric property change of the BST film itself. The capacitance vs voltage and the dielectric loss vs bias voltage curves of BST film showed a polarity dependence, which may be speculated to be because of the barrier height difference between the interfaces.

We report on the well-characterized properties of a-axis oriented trilayer Josephson junctions made of NdBa₂Cu₃O_7-δ and PrBa₂(Cu,Co)₃O_7-δ films, and c-axis oriented trilayer Josephson junctions made of NdBa₂Cu₃O_7-δ and PrBa₂Cu₃O_7-δ films with smooth surface morphology and good crystallinity. a-Axis oriented NdBa₂Cu₃O_7-δ/PrBa₂(Cu,Co)₃O_7-δ/NdBa₂Cu₃O_7-δ trilayers and c-axis oriented NdBa₂Cu₃O_7-δ/PrBa₂Cu₃O_7-δ/NdBa₂Cu₃O_7-δ trilayers were prepared on (100) SrTiO₃ substrates to obtain planar junctions. Their current–voltage characteristics are of the resistively-shunted-junction type at 4.2 K. They showed well-developed Shapiro steps corresponding to 5–20 GHz microwave irradiation. Moreover, the power dependences of the maximum amplitudes of the Shapiro steps were clearly obtained and consistent with the theoretical values expressed as J_n(2eV/hf). The magnetic field dependence of the Josephson current for a-axis oriented trilayer Josephson junctions showed a Fraunhofer-like pattern, suggesting the spatial uniformity of the critical current flowing over the PrBa₂(Cu,Co)₃O_7-δ barrier layer.

A digital search technique based on the flip–flop method was applied to design a broadband antireflection coating using very thin high-, middle- and low-index layers. The optical performance of the average reflectivity over the visible region (from 400 to 750 nm) was 0.19%, which yielded a better result than the design using only very thin high- and low-index layers.

We propose and study all-optical probe switching using a control signal in a nonlinear interferometer configuration. In our proposed device, we can have a power- or a phase-controlled switching function with a control signal that is much weaker than the probe signal. Since the control signal and the probe have the same wavelengths and polarizations, the pulse walk-off associated with the dispersion does not take place, and thus the speed of operation is not limited by dispersion. We have experimentally demonstrated power-controlled switching with a control signal whose power is 10 times weaker than the probe power.

We propose a new scheme of trace gas detection by the use of a Fabry–Perot cavity (FPC) and the wavelength modulation technique. Optical propagation length is enhanced using a 25 cm FPC with a finesse of ∼100. By applying the same modulation to both the laser and cavity frequency, we observe the first derivative signal of acetylene absorption at 1.5 µm. It is found that a sample-and-hold circuit serves well for restoring the signal level, which otherwise is degraded because of the pulsation of the detected laser intensity due to a feedback loop required for scanning the laser and cavity frequency simultaneously. Compared with the signal intensity observed with a 20 cm Brewster cell, this experiment yields the improvement of signal intensity by a factor of 81.2 with an acetylene pressure of 2.6 Pa.

GdPO₄:Tb phosphor particles with spherical shape and high photoluminescence were prepared by spray pyrolysis. The brightness of the prepared GdPO₄:Tb under vacuum ultraviolet (VUV) illumination was comparable with that of commercial Zn₂SiO₄:Mn phosphor particles. The spherical morphology of prepared GdPO₄:Tb particles was completely maintained even after post treatment up to 1100°C. When the post treatment temperature was over 1100°C, the particles did not maintain the spherical shape. However, given that the highest photoluminescence was obtained at 1050°C, the GdPO₄:Tb phosphor particles with spherical shape prepared by spray pyrolysis are a promising candidate as a green phosphor for plasma display panels (PDPs). By changing the content of the activator (Tb) and phosphorous, the optimal composition giving the highest photoluminescence intensity was found. Under the optimal condition, the decay time of prepared spherical GdPO₄:Tb phosphor particles was approximately 6.9 ms, which is appropriate for application to PDPs.

High-resolution multiple-crystal multiple-reflection X-ray diffractometry is used for the structural characterization of nonlinear optical single crystals of K₃Li₂Nb₅O₁₅ (KLN) grown by the micro-pulling-down (µ-PD) method. The combination of high-resolution X-ray diffractometry and topography shows that the lattice parameters along the c-axis (c-parameters) decrease towards the seed crystals, because of the decrease in the K content and increase in the Nb content. However, the KLN single crystals exhibit multi domain structures in which discontinuous changes in the c-parameters are periodically observed along the growth direction, despite the compositional change being continuous. Large mosaic structures due to discontinuous tilt in the lattice planes are also observed at the boundaries between the domains.

A novel blue light-emitting material, di-spiro-9,9^'-di-fluorene-9^'',9^'''-(9,10-dihydro-anthracene), has been synthesized and fully characterized. Organic electroluminescent (EL) cells have been fabricated using this spiro-annulated compound as the emitting layer with N,N^'-di(α-naphthyl)-N,N^'-diphenyl-(1,1^'-biphenyl)-4,4^'-diamine (NPB) and/or 4,4^',4^''-tris(3-methylphenyl-phenylamino)-triphenylamine (m-MTDATA) as the hole transport layer. Pure blue emission with a maximum luminous efficiency up to 4.73 lm/W (15.1 cd/A) has been achieved, demonstrating that this compound might be a suitable blue light-emitter for fabricating blue organic EL devices.

We fabricated layered structures of SiO₂ films with different refractive indices by pulsed laser deposition with silicone targets. The refractive index of SiO₂ films could be controlled by the deposition rate. Lowering of the deposition rate helped to make a dense film, showing higher refractive index. A 0.4-µm-thick SiO₂ cladding film deposited at 0.1 nm/pulse was first formed on the entire surface of a Si wafer, and then a 1-µm-thick SiO₂ core film was deposited at 0.05 nm/pulse in a line of 1 mm width on the sample. The deposited films were free of impurities such as H₂O and carbon. Transparent, tightly layered structures were obtained. The layered structures could also be fabricated on a flexible substrate consisting of a 100-µm-thick polyester sheet. Both samples functioned as an optical waveguide for a 633-nm He–Ne laser. The single-mode propagations were observed as designed.

We present the fabrication and the characterization of a hollow optical waveguide with an etched groove substrate. The propagation characteristics of a slab hollow waveguide were measured. The propagation losses were 1–2 dB/cm and 3–4 dB/cm for TE and TM modes, respectively. We also propose and demonstrate a novel three-dimensional (3D) hollow waveguide with a lateral confinement caused by a step in an etched groove.

In this study, the Cu_xS conductive layer is coated on the particle surface of ZnS:Ag, Cl by a wet chemical reaction and using Cu(CH₃COO)₂·H₂O as the coating source. The low-voltage phosphor film is prepared with In₂O₃ coprecipitation. From the analyses of X-ray diffraction (XRD) patterns, a preferential orientation phenomenon of the phosphor film is observed. Electron probe microanalysis (EPMA) reveals that Cu ions in the Cu_xS-coated ZnS:Ag, Cl are homogeneously distributed. After 4 h of coating at room temperature, the Cu and O concentrations in the Cu_xS-coated ZnS:Ag, Cl phosphor are 2.41 and 0.125 mol%, respectively. The luminance of the phosphor increases with coating time and coating solution concentration. However, the luminance of phosphor film is degraded due to the oxidized phosphor surface. In₂O₃ coprecipitated with the prepared phosphor film enhances the luminance and stabilizes the luminance efficiency of the phosphor.

Polycrystalline ZnO films both exhibiting strong ultraviolet (UV) photoluminescence (PL) and having smooth surfaces applicable to electronic devices have been obtained by rf-sputter deposition and subsequent heat treatment. The peak of UV PL was located at 3.05 eV and exhibited a linewidth as narrow as 70 meV, along with a strong intensity comparable to that observed for ZnO epitaxial film grown on sapphire under the same conditions. The UV PL intensity was found to be complementary to that of the red PL emerging at around 2 eV, which is caused by the crystal imperfection of the films along the c-axis. The increased film-growth temperature and subsequent heat treatment at low temperatures prominently reduced the red PL, which resulted in the above excellent features of the polycrystalline ZnO films.

The effects of annealing in reactive gases (H₂, N₂, O₂) upon the optoelectric properties of nanophased titanium dioxide (TiO₂) prepared by chemical vapour deposition (CVD) were investigated. The nanocrystalline structure containing nanosize grains and pores was analyzed by grazing-incidence small-angle scattering of synchrotron radiation (GISAX). The annealing (up to 1073 K) in H₂ and N₂ generally proved detrimental to photoconductivity due to the overall increase of the electrical conductivity of the samples. In this work, the result of UV (248–404 nm) photoconductivity measurements on TiO₂ films annealed in O₂ at 773 K and 1073 K are presented. A rather long illumination time (typically 2 h) enabled us to clearly distinguish two types of nonequilibrium photoconductivity variations with time. A fast exponential photoconductivity increase occurred during the initial stage of irradiation, while a slow power–type increase was observed in the later stage. A nonlinear combination of both functions was used in a numerical fitting procedure, which allowed precise determination of the asymptotic value of exponential photoconductivity increase. A relative quantum efficiency for both as-prepared and annealed samples exhibits a nonmonotonic variation with photon energy. Such wavelength-dependence variation might be due to the electronic density function structure at the valence-band edge, or near-valence-band levels in the gap. Generally, the samples annealed at higher temperatures exhibit a higher quantum efficiency and shorter time constants of the excitation processes, in the examined UV range.

Cd₂GeSe₄ single crystal was grown by a modified Bridgman method. The optical energy band gap obtained from the optical absorption measurement was approximately 1.922 ±0.002 eV at 10 K and 1.707 ±0.002 eV at 298 K. In the photoluminescence (PL) spectra measured at temperatures below 70 K, two peaks were distinguished. One corresponds to the ground state (n=1) and the other corresponds to the excited state (n=2) of the free exciton. The binding energy of the exciton was about 5.2 meV. The energy band gap obtained from the PL measurements was 1.920 eV at 10 K.

We report the mobility in organic electron transport materials determined from current–voltage characteristics in the regime of space charge limited current. The electron mobilities obtained are highly dependent on applied electric field, similar to the cases using a conventional time-of-flight method. The electron mobilities of phenanthroline derivatives are high and comparable to hole mobilities of conventional hole transport materials. Two parameters, zero-field mobility and electric field activation parameter are discussed from the viewpoint of oxidation and reduction reactions. The electric field activation parameter increases gradually with the increase of ionization potential. These facts suggest that there is a good possibility for realizing low driving voltage in organic light-emitting diodes (OLEDs).

We present numerical results on the current mirror effect in a single-electron turnstile capacitively coupled with a one-dimensional (1D) array of small tunnel junctions. Contrary to conventional operation with a sinusoidal signal source, the single-electron turnstile is driven by charge solitons (and anti-solitons) transferred through the 1D array. Then, the current through the turnstile can be locked to the current through the 1D array; this is the current mirror effect. We numerically demonstrate the current mirror effect in our circuit, where a 4-junction turnstile and a 20-junction 1D array are coupled at their middle nodes via a coupling capacitor. We introduce a coupling parameter, Q_c, to define the strength of coupling between the 1D array and the turnstile. We also introduce a current mirror index, CMI, to evaluate the quality of the current mirror effect. The dependence of CMI upon the soliton length, the current through the 1D array, and Q_c is discussed.

We have studied an oxidation effect of multiwalled carbon nanotubes (MWCNTs) grown by thermal chemical vapor deposition (CVD) using ultraviolet photoelectron spectroscopy (UPS) and transmission electron microscopy (TEM). With an increasing oxygen exposure, the carbon 2p-π states at ∼3 eV below the Fermi level in the UPS spectra almost disappear, whereas the 2p-σ states around 6 eV are significantly increased. Annealing above 1000 K results in an increase of the density of states (DOSs) near the Fermi level, although a complete recovery of the 2p-π electron states is not observed. We also observe a mode around 23 eV that is associated with the collective σ+π plasmon excitation and chemisorbed C–O bonds, which is confirmed by the density functional calculations.

Initial growth stage of TiO₂ on a silicon substrate was studied by a plasma-enhanced chemical vapor deposition system with in-situ observation equipment using laser Raman spectroscopy. The TiO₂ film on the substrate was grown laterally at the early stage of the growth. It was found, via in-situ observation, that titanium silicide was formed simultaneously. Furthermore, the growth mode changed suddenly from lateral to vertical and the titanium silicide disappeared with the progression of growth time. The titanium silicide plays an important role in the formation process of TiO₂ and determines the growth mode, structure, stress and surface roughness of TiO₂ grown on the Si substrate.

The Pt/SBT/ZrO₂/Si structure was proposed for metal–ferroelectric-insulator–semiconductor field-effect-transistor applications. A SrBi_2.4Ta₂O₉ (SBT) thin film was prepared using liquid source misted chemical deposition (LSMCD) on a Si substrate with ZrO₂ buffer layer deposited by reactive sputtering. The LSMCD-derived SBT film exhibited 2P_r of 16.6 µC/cm² and E_c of 25 kV/cm at ±5 V. Interdiffusion between SBT and Si was suppressed with a ZrO₂ layer thicker than 20 nm. The memory window of the Pt/SBT (400 nm)/ZrO₂/Si with 20–50 nm ZrO₂ became larger with increasing the gate voltage and decreasing ZrO₂ thickness. The Pt/SBT (400 nm)/ZrO₂ (20 nm)/Si exhibited memory windows of 0.83 V at ±5 V and 1.26 V at ±7 V.

The microwave dielectric properties and microstructures of (1-y)Ca_1-xNd_2x/3TiO₃–yLi_1/2Nd_1/2TiO₃ ceramics, prepared by a mixed oxide route, have been investigated. A maximum quality factor Q×f=8600 GHz (where f is the resonant frequency) was achieved for samples with y=0 and x=0.39, although the dielectric properties varied with sintering temperature. The Q×f value of (1-y)Ca_1-xNd_2x/3TiO₃–yLi_1/2Nd_1/2TiO₃ increased up to 1400°C, after which it decreased. The decrease in dielectric properties was coincident with the onset of rapid grain growth. In the (1-y)Ca_1-xNd_2x/3TiO₃–yLi_1/2Nd_1/2TiO₃ system, as y increased, the temperature coefficient of resonant frequency (τ_f) decreased from 800 to 8 ppm/°C for y=0.52 (x=0.39). However, the optimum combination of microwave dielectric properties was achieved at 1400°C for samples where y=0.45 (x=0.39) with a dielectric constant ε_r of 101, a Q×f value of 5300 (at 7.2 GHz) and a τ_f value of +13 ppm/°C.

Particle formation was investigated during laser ablation of strontium bismuth tantalate (SBT) with a background of pure oxygen (O₂). For an O₂ pressure, P_O2, varying from 210 to 1300 Pa, the mean particle size ranged from 9 to 22 nm, and the particle concentration ranged from about 10¹² to 10⁸ cm^-3. For P_O2=210 Pa, the particle size ranged from 5 to 30 nm, and for P_O2=1300 Pa, the particle size ranged from 10 to 80 nm. Transmission electron microscopy measurement of particles size-classified at 10 and 20 nm showed that some particles were spherical and others were irregularly shaped. Electron diffraction of the particles showed that the spherical particles were partially crystallized whereas the irregularly shaped particles were amorphous. The formation of these two different morphologies is attributed to different particle cooling rates stemming from spatially nonuniform gas temperatures induced by laser ablation. Regardless of their shape, the particles were composed of strontium, bismuth, tantalum, and oxygen.

In this paper the population of the excited levels in a high frequency surface-wave-produced and -sustained argon plasma, has been measured in the pressure range 0.2–2.8 Torr. The experimental procedure is based on different techniques; for the radiative transitions between 4p–4s argon excited levels a self-absorption method has been implemented, whereas for the rest of the transitions (involving 5d, 5p, 6d and 6s levels) the plasma has been assumed optically thin and an optical emission spectroscopy technique has been used. The results show that the plasma remains very far from thermodynamic equilibrium. The excited states present an overpopulation when compared to those obtained through equilibrium relations (to an order of magnitude of 10⁵, or even higher). The plasma is, therefore, an ionizing plasma; so a classification of the excited levels according to the dominant collisional processes has been established. The dependence of these populations on the effective quantum number, p, is proportional to p^-6 and their overpopulation is proportional to p^-5.

The effects of rare-earth oxides, e.g., La, Nd, Sm, Dy and Yb, on the reliability of multilayer capacitors (MLCs) with X7R dielectrics and Ni electrodes were investigated. Microstructures of the dielectrics were analyzed by transmission electron microscopy (TEM) and electron probe microanalysis (EPMA) in order to characterize the rare-earth ions. Incorporation of rare-earth ions to BaTiO₃ ceramics depended on their ionic radius, resulting in different microstructures and electric performances of dielectrics. Dy ions provided BaTiO₃ ceramics with ideal X7R characteristics and high reliability. The mechanism governing leakage current was discussed in terms of the voltage dependence of leakage current. Electric properties and related reliability of the capacitors were attributed to solubility, distribution of rare-earth oxides and their occupation site in BaTiO₃.

The electronic structure of lightly La-doped SrTiO₃ (La_xSr_1-xTiO₃) has been investigated by resonant-photoemission spectroscopy (RPES). The RPES spectra show that the Ti 3d partial density of states in the valence band decreases with increasing La dopant concentration. This finding indicates that the hybridization effect between the Ti 3d and O 2p states decreases with La³⁺ dopant concentration.

In general, deducing the switching time of twisted nematic liquid crystal displays by only using the optical response curves is difficult unless the cell's parameters are optimized. The difficulty is increased in the case of reflective displays which are asymmetric and then exhibit fluctuations in their optical response when driven with an AC voltage. A new method is proposed to determine the dynamic response optically, independent of the shape of the reflectance-time curve. The experimentally found values for different cell gaps and driving voltages are in good agreement with theoretical expectations.

A rigid organic compound possessing two photoreactive groups, N,N^'-di(2-anthryl)pyromellitimide (DAPI), has been synthesized, and the structure of its thin films formed on alkali halides by vacuum evaporation was investigated by transmission electron microscopy, electron diffraction, and atomic force microscopy. The thin films of DAPI were composed of many rod-like crystallites with preferred orientation of the longer axis in the direction parallel or perpendicular to the [100] steps of the alkali halides. The electron diffraction pattern showed a four fold symmetry. The spacings of electron diffraction spots coincided with those observed for a bulk crystal by the wide angle X-ray diffraction measurement. The obtained results revealed that the heterogeneous nucleation at the steps plays an important role in the observed epitaxial growth for the present DAPI thin films.

The 3rd-order nonlinear piezoelectric constants of relaxor-type perovskite ceramics, 0.5Pb(Ni_1/3Nb_2/3)O₃–0.35PbTiO₃–0.15PbZrO₃ (50PNN–35PT–15PZ) and 0.64Pb(Ni_1/3Nb_2/3)O₃–0.36PbTiO₃ (64PNN–36PT), were estimated by the dynamic measuring of velocity variation under an alternating electric field. Their nonlinearity was much larger than that of the various types of current lead zirconate titanate (PZT) ceramics. We have succeeded in the generation of acoustic phase conjugate waves through the nonlinear properties of PZT ceramics and obtained an efficiency over 100%, the efficiency being defined as the intensity ratio of the phase conjugate wave to the incident wave. We theoretically calculated the phase conjugate efficiencies in both 50PNN–35PT–15PZ and 64PNN–36PT ceramics from the measured 3rd-order nonlinear piezoelectric constants, and found very large values that could yield a phase conjugator with 300% to 500% efficiency.

A numerical method was used to study the second-harmonic generation (SHG) in ferroelectric liquid crystals with a helical structure distorted by an electric field, where a fundamental wave propagates nearly directly along the helical axis and the electric field is applied normal to the helical axis. It is shown that SHG can be enhanced when the wavelength of the fundamental wave is close to one of the edges of the field-induced full-pitch band.

The thickness profile of a silicon epitaxial film formed using a horizontal single-wafer epitaxial reactor in a trichlorosilane–hydrogen system is evaluated using numerical calculations, taking into account the details of the entire gas inlet geometry for the first time. The characteristic thickness profile is mainly due to the nonuniform temperature distribution above the silicon substrate formed by the gas inlet, consisting of inlet plates, a step and three adjustable inlet sections. The authors conclude that the gas inlet is responsible for the nonuniform thickness profile of the silicon epitaxial film.

We report a new second-harmonic generation blue laser using a K₃Li_2-xNb_5+xO_15+2x single crystal film waveguide on a K₃Li_2-x(Nb_0.98Ta_0.02)_5+xO_15+2x crystal substrate by the metalorganic chemical vapor deposition method. Second-harmonic blue light with output power of 2 mW at 487 nm was successfully generated. The phase-matched wavelength bandwidth of the device was 1.3 nm, and the temperature coefficient of the phase-matched wavelength was 0.36 nm/°C. Crystallographic evaluation was also performed for the KLN thin film crystal. The (001) plane of KLN crystal film was well orientated to the (001) plane of the KLNT substrate, and the surface morphology of the film was very smooth. Moreover, it was revealed that an as-deposited KLN film crystal has a single domain structure.

A hybrid electroluminescent (EL) device structure was developed, consisting of a screen printed Pt/Ag conductor and high-k BaTiO₃ dielectric, on which a phosphor, a thin insulator and a transparent conductor were deposited by atomic layer deposition (ALD). The use of the hybrid EL structure results in more than a doubling of brightness compared with the thin-film EL alternative structure. While hybrid EL devices with ALD-grown thin-film stack deposited directly on top of a rough dielectric yield a uniform light emission, the aging stability is determined largely by the occurrence of local breakdown events due to electric field inhomogeneities originating from the combination of the rough BaTiO₃/ZnS:Mn interface and the high dielectric constant of BaTiO₃. Nevertheless, lifetimes of more than 600 h at 1 kHz could be obtained.

We attempted the nanometer-scale mechanical processing of materials with a layered crystal structure by tip sliding with an atomic force microscope, based on the anisotropy of the crystal structures. By mechanically operating a sharp tip, processing mainly occurs to depths equivalent to multiples of the period of the multilayered crystal structures, corresponding to the depth from the surface of one cleavage plane to the surface of the cleavage plane beneath it. By applying this mechanism in the mechanical processing of molybdenum disulfide and muscovite mica, high-precision cutting processing of lines and cross grooves can be performed in a layer-period unit of a multilayered crystal material that has periodic weak van der Waals bonds. However, in the processing of graphite, the bond strength of the basal plane is very high, making it difficult to perform the essential nanometer-scale cutting processing. Therefore, to utilize the high bond strength of its basal plane, the bending processing of the graphite basal plane on the nanometer scale was attempted and realized.

We investigated the morphology of Fe films grown on self-organized SrTiO₃(001) substrates with inclined angles. The Fe films are grown in two parts on the inclined substrate; one is a continuous film in the lower part and the other features cluster coagulation in the upper part. We clarified the step structure of the Fe, the shape of the Fe clusters, the distribution of the Fe cluster sizes and height, and their dependence on inclined angle. We discussed the differences according to inclined angle in terms of Fe atom mobility on the SrTiO₃ substrate. The growth of Fe films on the inclined SrTiO₃ substrates influences the features of substrates and their morphologies are affected by the inclined angle of the substrates. We also determined the crystalline orientational relationship between Fe and SrTiO₃ to be Fe(001)[110]∥SrTiO₃(001)[100].

We studied the surface structure of self-organized sapphire (0001) substrates with various inclined angles, using an atomic force microscope (AFM) in UHV. The self-organized surface structure strongly depended on annealing condition, inclined angle and inclined direction. We could successfully produce a highly self-organized step structure by choosing suitable values of these parameters. The surface of the self-organized inclined substrates was characterized by step and terraces. The morphology of step edges depends on the inclined direction of the substrate. In the case of the <100 > inclined direction, the step edges were faceted, and the faceted plane was the {20} plane. On the other hand, in the case of the <110 > inclined direction, the step edges were straight. The distribution of step heights and terrace widths measured from AFM images are presented. The distribution of step heights had peaks corresponding to the unit cell of the sapphire crystal, while the terrace widths followed a normal distribution.

Monodispersed Co clusters with mean cluster diameter d=13 nm have been deposited on a stepped graphite surface and a lithography-patterned Si wafer using a plasma-gas-condensation cluster beam deposition apparatus. High-resolution scanning electron microscope observation indicates that 1) cluster aggregation is much more limited at the steps than on the flat terrace regions of the graphite surface, and 2) cluster density is much higher in the grooves than on the flat top of the lithography-patterned Si wafers. These results suggest the possibility of the regular arrangement of monodispersed Co clusters if the pattern size (the width of grooves and tops) is comparable with the cluster size.

With the aim of evaluating the properties of diamond-like carbon (DLC) films, a comparison is made between tetrahedral amorphous carbon (ta-C) films fabricated by the double-bend-filtered cathodic vacuum arc (FCVA) method using no material gas and hydrogenerated amorphous carbon (a-C:H) films fabricated by the chemical vapor deposition (CVD) method using a hydrocarbon gas. It was found that the ta-C films are superior to the a-C:H films in terms of both wear resistance and combustion resistance. It was also determined that this superiority applies for ultra thin films as well.

Amorphous hydrogenated silicon carbide (a-SiC:H) films were deposited from a mixture of silane and methane gases using the plasma-enhanced chemical vapor deposition (PECVD) process. The properties of the film, following ammonia plasma treatment, are reported. A lower silane flow rate reduces the refractive index, but increases the carbon content and the optical band gap. Increasing the carbon concentration of the a-SiC:H films reduces the dielectric constant. The films were treated with ammonia plasma for various treatment periods. The original film has a smooth surface with a roughness of 0.231 nm, but increasing the ammonia plasma treatment period gradually roughens the surface. The chemical bonding nature of the a-SiC:H films with higher silicon content was investigated by X-ray photoelectron spectroscopy. Various nitrogen ionization species reacted with Si to promote the formation of silicon nitride. As a result, although the dielectric constant of the a-SiC:H films increased slightly, the leakage current density declined as the ammonia plasma treatment time increased.

We have investigated the chemical reaction of Si nanoparticles with H₂ and O₂ gases in gas phase after laser ablation of Si targets in Ar and Ne gases. First, we observed time-resolved photoluminescence (PL) from Si nanoparticles in pure Ar gas. The formation of Si nanoparticles begins after the thermalization of Si plasma on a time scale of 1 ms. The energy dissipation of electronic system govern the formation of Si nanoparticles. It was clearly observed that Si nanoparticles grow up to 1.8 ms. Based on the formation dynamics, we observed chemically modified Si nanoparticles using the time-resolved PL method. We found that Si nanoparticles react with hydrogen and oxygen atoms dissociated in the laser plasma. The hydrogenation results in PL at 550 nm and vibronic lines in the wavelength range of 650–800 nm disappear. Oxidation results in PL quenching when O₂ partial pressure is higher than 1 Pa. Thus, we have demonstrated chemical modification of Si nanoparticles.

Fully vacuum-sealed triode-type active-matrix field emission display (AMFED) having an active-matrix cathode on soda-lime glass substrate was designed and fabricated. Each pixel in the active-matrix cathode has the monolithically integrated structure of an amorphous–silicon thin-film transistor (a-Si TFT) and triode-type field emitter array with conical Mo-tips just on the drain of the a-Si TFT. Experimental data indicate that the emission currents of the fabricated active-matrix cathode could be successfully controlled by the a-Si TFT gate voltage. We demonstrated that an emitting image of a moving picture from the fully vacuum-sealed 2-inch AMFEDs could be achieved by switching the low bias-voltage of the a-Si TFT gate to a value below 25 V.

A nucleation enhancement technique with defined ion-bombardment energies has been developed for diamond deposition on mirror-polished Si wafers. The substrate was negatively biased at several tens of volts in an electron cyclotron resonance methane-hydrogen plasma at 0.13 Pa. The nucleation density was significantly increased to ∼10⁸ nuclei/cm² for the bias voltage range of -20 to -50 V. The highest density was obtained with a mean ion energy of around 50 eV. The mechanism of nucleation enhancement was correlated with the formation of sp³ bonds as nucleation sites by energetic ion bombardment.

High-reflection mirrors of fluoride multilayers were developed for a F₂ excimer laser, using the ion beam sputtering method. Fluoride multilayer mirrors deposited by ion beam sputtering method are known to have good morphology and low scattering loss, but it was rather difficult to reduce their absorption loss. In this work, the reflectance of the mirror composed of AlF₃/LaF₃ layers was improved to 93.6% at a wavelength of 157 nm with an incidence angle of 45° by the optimization of deposition conditions. This value of reflectance is almost equivalent to that of mirrors deposited by the conventional deposition method.

An overload test of a new type of ceramic field emitter, ZnO:Al whisker covered with amorphous hydrogenated carbon nitride film, was performed. The aim of this study is to investigate surface damage of the whisker-type cold emitter under overload conditions. The morphologies of the emitter surface before and after operation were compared using scanning electron microscopy. The emission was terminated after the generation of surge current that severely damaged the emission surface.

The influence of oxygen on field emission properties of single-walled carbon nanotubes (SWCNTs) was studied experimentally. Field emission images and current–voltage curves acquired using a field emission microscope (FEM) showed that exposure to oxygen resulted in an increased work function of SWCNTs. Oxidation etching at high temperature sharpened the SWCNT ends and field emission was therefore enhanced.

The objective of this study is the determination of the distribution of the activity of radio-elements contained in radioactive waste packages by means of single photon emission computed tomography (SPECT). A three- dimensional (3D) projector simulator for a parallel hole collimator and NaI(Tl) scintillator, based on the point kernel integration method, is proposed. The model takes into account the attenuation and scatter of gamma rays. Primary scattered photons are treated by the Compton process and Klein-Nishina formula, and the multiple scattering is accounted for by means of the dose buildup factor normally used in shielding problems. An advantage of the proposed model is that it offers the possibility of generating a full two-dimensional point-spread function (PSF) that can be used for 3D reconstruction. The developed model is convenient in those situations where more exact techniques (such as Monte Carlo simulation) are not economical. The model has been evaluated for the package having homogenous density with the Cs-137 point source inside.

We have developed a down-flow ashing system for microprocessing of large substrates. The system is equipped with a surface-wave-plasma source of which the "slot-type" antenna was specially designed to generate a uniform and high-density plasma. In this work, the oxygen-plasma-induced damage to the GaAs surface was investigated as a function of the plasma-substrate distance D and exposure time T. These samples were evaluated by X-ray photoelectron spectroscopy (XPS), ellipsometry, photoluminescence (PL), deep level transient spectroscopy (DLTS) and current–voltage (I–V) measurements. XPS results showed that the part of the oxide layer near the surface consists mainly of Ga₂O₃ and As₂O₃ while deeper in the oxide layer, Ga₂O₃ predominantly exists. Ellipsometry results showed that the thickness of the oxide layers increases up to 100 Å with decreasing D and increasing T. PL intensity of free exciton (FE) and (e,A⁰) observed in GaAs decreased with decreasing D and increasing T. The origin of this decrease in PL intensity was confirmed by DLTS measurements to be due to an increase in EL2 (0.73 eV) defect level density. I–V measurement showed that the effective barrier height decreases with decreasing D. This is probably due to the creation of surface states and to an increase in EL2 density, which lead to an increase in the recombination current at the interface or depletion layers. These results demonstrate that a low amount of damage can be ensured at D≧157 mm. The developed ashing system and condition is currently being used for the mass production of actual semiconductor devices.

The mechanism of microtrench generation in SiO₂ trench etching in fluorocarbon gas chemistry is presented using the magnetron etch system under a 40–80 mTorr pressure condition. In the previous study, we pointed out that the microtrench is caused by the etch rate increase at the trench bottom edge where the fluorocarbon film is thin, because the thicker fluorocarbon film was formed more easily at the center of the trench bottom where the solid angle is larger than at the edge of the trench bottom. In this study, the experimental condition is extended to lower pressures. The microtrench ratio becomes higher in accordance with a larger pattern size at pressures higher than 40 mTorr. However, the pattern dependence of the microtrench ratio is reversed at 20 mTorr. This is explained by the effect of a constant residence time, the dilute gas effect, and the inverse-reactive ion etching (RIE) lag which is observed at 20 mTorr. In conclusion, the microtrench formed by the shadowing effect for fluorocarbon radicals is offset by increasing the bombarded ions at the trench bottom with the decrease of pressure to a condition such as 20 mTorr pressure.

The etching of an organic low-dielectric-constant (low-k) material, FLARE, with gas mixtures of CH₄/N₂ and H₂/N₂ was investigated in a magnetic neutral loop discharge (NLD) plasma system. The hole-etching profile of FLARE with a SiO₂ hard mask and reactive ion etching (RIE) lag characteristics (the etch rate depends on the hole size) were studied for hole diameters from 0.16 to 0.4 µm. We discuss the role of CH₄ in organic low-k etching and consider the etching mechanism in a CH₄/N₂ plasma in comparison with that in a H₂/N₂ plasma. Etching with no RIE lag was achieved at a CH₄ concentration of about 30% with a total flow of 100 sccm, pressure of 0.4 Pa, source power of 1000 W, and bias power of 200 W in a CH₄/N₂ plasma. FLARE etching profiles with a perpendicular or normal taper and no microtrenching were obtained with CH₄ concentrations below about 70%. We used X-ray photoelectron spectroscopy (XPS) to evaluate films deposited on a Si substrate during etching under several plasma conditions to clarify the mechanism of the organic low-k material etching.

The etch characteristics of hydrido-organo-siloxane-polymer (HOSP), a typical silsesquioxane-based low-dielectric material, were compared with those of silicon dioxide in CF₄ and CHF₃ plasmas. The etch-rate ratios of the two materials are more significantly affected by the types and pressure of plasma gases than by plasma bias voltage, indicating that the relative etch rates are determined largely by the density of radicals than by the energy of ions incident on the substrate surface. The etching of silsesquioxane is accompanied by an increase in the CF₂ radical density and a significant decrease in F radical density, indicating that silsesquioxane is etched via the sequential dissociation of Si–CH₃ and cage-like Si–O bonds by reaction with F radicals. Based on the findings herein, we propose that the relative amounts of cage-like and network Si–O bonds remaining in silsesquioxane after etching can be controlled by adjusting the parameter, (F radical density)²/(CF₂ radical density).

A simple experimental technique to measure the axial average gas temperature in a surface-wave-produced and -sustained plasma has been developed. This experimental method is based on the assumption of a viscous laminar gas regime, and evaluates the gas temperature through the changes in the upstream and downstream pressures when the plasma is switched on and off. Two time scales have been found in the heating and cooling processes, a faster one related to the gas, and a slower one related to the vessel. In addition, the axial average gas temperature has been evaluated as a function of the gas pressure and the incident microwave power at the gap.

Collisional quenching of laser-excited C₂(d³Π_g) and C₃(\tildeA¹Π_u) has been investigated experimentally in carbon plumes produced by laser ablation of a graphite target in ambient He gas. The radiative lifetime of C₂(d³Π_g) was evaluated to be 115 ns. Collision with He did not affect the lifetime of C₂(d³Π_g) at pressures less than 5 Torr. On the other hand, collision with He reduced the lifetime of C₃(\tildeA¹Π_u) at pressures higher than 0.5 Torr. The radiative lifetime of C₃(\tildeA¹Π_u) and the rate coefficient for the collisional quenching were evaluated to be 210 ns and 3.0 ×10^-11 cm³/s, respectively. Several microseconds after the irradiation of the ablation laser pulse, collision with particles ejected from the target reduced the lifetimes of both C₂(d³Π_g) and C₃(\tildeA¹Π_u). From the reduced lifetime of C₃(\tildeA¹Π_u), we estimated the absolute particle density in the plume.

Atmospheric pressure micro-plasma jet (µ-PJ) was generated at the tip of a stainless steel surgical needle with an inner diameter of 0.4–0.5 mm and with a length of 19–25 mm using RF (13.56 MHz) corona discharge. The He µ-PJ spouted to a free space at a power of less than 10 W. The He atomic excitation temperature (T_exc) estimated by means of an optical emission spectrum was 3270 K at a gas flow rate of 350 sccm and T_exc decreased with increasing gas flow rate. The O₂ µ-PJ was also generated at a power of 12 W and it was applied to the localized removal of a photoresist.

The plasma light emitted from a pulse discharge of 0.2 and 1 Torr neon gas inside a high-T_c superconducting tube was revealed to have a decay time of two times longer than that without the tube, using a high-sensitivity charge coupled device (CCD) streak camera. Thus, the additional superconducting tube clearly improved the confinement of plasma particles and/or energy.

The excited state behavior of dye molecules under intense pulsed laser excitation appears to differ from that under low-power cw Xenon lamp excitation. In the latter case molecules absorb photons (from the lamp), go to the excited state and produce normal fluorescence. This is a one photon–one molecule process. But in the former case, two excited dye molecules combine together to form `superexciplex' and produce fluorescence and also amplified spontaneous emission (ASE) under intense, sharp, laser pulse excitation. This paper gives sufficient evidence verifying the existence of this new molecular species.

We use a first-principles discrete variational (DV)-Xα method to investigate the electronic structure of chromium aluminum oxynitride. When nitrogen is substituted for oxygen in the Cr–Al–O system, the N2p level appears in the energy range between O2p and Cr3d levels. Consequently, the valence band of chromium aluminum oxynitride becomes broader and the band gap becomes smaller than that of chromium aluminum oxide, which is consistent with the photoelectron spectra for the valence band using X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). We expect that this valence band structure of chromium aluminum oxynitride will modify the transmittance slope which is a requirement for photomask application.

The characteristics of a hydrogen bond and the stability of Iβ-phase crystalline cellulose in sub/super-critical water (up to 750 K) were investigated by molecular dynamics (MD) simulations with the GROMOS87 force field and the flexible SPC model. The population of hydrogen bonds between cellulose chains decreases as the temperature or the water density increases. The increase of the temperature also decreases the lifetime of the hydrogen bond between cellulose and water and between celluloses, where the lifetimes are shorter than that between water molecules. The fluctuation of the crystalline structure was observed and it degraded with chains leaving due to the breaking of hydrogen bonds. A model estimating the break-period of a chain link by hydrogen bonds is proposed. The break-period estimated by this model based on probability and lifetime of hydrogen bonds between chains agrees to with that obtained by molecular dynamical calculation.

A microwave (Li_0.5Fe_0.5)_0.4Ni_0.3Zn_0.3Fe₂O₄ (LNZ) ferrite was prepared by a conventional sintering method in air. Thermoplastic natural rubber (TPNR) was prepared from polypropylene (PP) and natural rubber (NR) in the ratios of 80:20, 70:30, 60:40, 50:50 and 40:60 with liquid natural rubber as a compatibilizer by a melt blending technique. LNZ ferrite-TPNR composites with 20 wt% ferrite filler were prepared using a Brabender plasticorder internal mixer. The microwave electromagnetic properties of the composites were studied in the frequency range of 0.3–13.5 GHz using a microwave vector network analyzer (MVNA). The real and imaginary components of the relative complex dielectric permittivity (ε_r^*=ε_r^'-jε_r^'') and magnetic permeability (µ_r^*=µ_r^'-jµ_r^'') were calculated from the measured complex scattering parameters (S₁₁^* and S₁₂^*) using the Nicolson–Ross model. The dielectric and magnetic properties were found to depend on the NR and PP content in the composites. The minimum reflection loss (R_L) under the matching conditions increases with increasing NR content.

A new power source, able to generate high-frequency, up to 20 kHz, and high-peak pulse current, up to 500 A, has been developed. By using the new power source, arc pressure and bead depth 3 times as high and twice as deep as those obtained from the DC power source were obtained. The new power source achieved a stable arc in a narrow groove with high aspect ratio due to high constriction. Welding speeds using the new power source are twice as fast as the DC arc.

We have employed a mesh experiment for back-illuminated (BI) charge-coupled devices (CCDs). BI CCDs possess the same structure as front-illuminated (FI) CCDs. Since X-ray photons enter from the back surface of the CCD, a primary charge cloud is formed far from the electrodes. The primary charge cloud expands through a diffusion process until it reaches the potential well that is just below the electrodes. Therefore, the diffusion time for the charge cloud produced is longer than that in the FI CCD, yielding a larger charge cloud size than expected. The mesh experiment enables us to specify the X-ray point of interaction with subpixel resolution. We measured a charge cloud shape produced in the BI CCD. We found that there are two components of the charge cloud shape having different sizes: a narrow component and a broad component. The size of the narrow component is 2.8–5.7 µm in units of standard deviation and strongly depends on the attenuation length of incident X-rays in Si. The shorter the attenuation length of the X-rays, the larger the charge cloud. This result is qualitatively consistent with a diffusion model inside the CCD. On the other hand, the size of the broad component is roughly constant at ≃13 µm and does not depend on X-ray energies. Judging from the design value of the CCD and the fraction of each component, we conclude that the narrow component has its origin in the depletion region whereas the broad component originates in the field-free region.

An in-situ measurement system for particles in an electron beam (EB) writer is developed to improve mask yield management. The system has satisfied the required installation specifications for a mask blank inspection system for the EB writer, and the results of an experiment using the system prove that particles added from the mask handling system in our EB writer satisfy the total particle count specification (<1.25 counts/cycle for 6 inch mask). The investigation of particle increase after repeated mask movement has been carried out in each segmented mask handling route. It has been clarified that the segmentation test using this system is helpful for investigation of the origin of particle production on a mask. Effective application of information such as particle position and size obtained by this system will be very useful for improving mask yield management in the mask fabrication process in terms of pattern inspection and repair system.

A Monte-Carlo code for calculating secondary electron emission from carbon induced by H₂⁺ ion has been developed. The projectile H₂⁺ splits into cluster H⁺ ion and e^- at a certain depth in the solid. H₂⁺, cluster H⁺+H⁺ and e^- make different contributions to the total backward electron yield, and the contribution fractions are calculated using the code. The calculated molecular effect [R(Y_b)] in the backward electron emission is from 0.85 to 1.09 in the energy range from 400 keV to 3000 keV. The calculated ratios of forward to backward electron yield increase with energy and decease with target thickness. The molecular effect [R(Y_f)] in the forward electron emission decreases with target thickness for a given energy. When the projectile energy is greater than 3700 keV, ratio R(Y_f) in the forward electron emission will be greater than one [R(Y_f)>1] for the target thickness of 1000 Å.

In order to increase the beam intensity of a laser ion source extracted from laser photoionized plasma, a pair of semispherical electrodes was set outside the conventional parallel plate electrodes, and the obtained intensity distributions were measured by scanning a multichannel Faraday cup. The vertical and horizontal widths of the ion beam at the position of the detector were reduced by the concentric electric field formed with these electrodes. The central ion beam intensity increased about 36 times compared with that in the case without the additional electric field. The ion trajectories as a function of the potential applied to the electrodes and the initial emergent position on the electrode were studied by simulations using SIMION 3D 7.0 software package.

An 850-nm vertical-cavity surface-emitting laser (VCSEL) with a Au/AuBe/TaN/Ta/Si mirror substrate has been realized by low-temperature wafer bonding. It is found that the mirror substrate can be used as the bottom reflector to enhance the reflectivity of a bottom distributed Bragg reflector. The metal mirrors also served as the adhesive layers and ohmic contact layers to bond the Si substrate and the VCSEL epilayers. When the mirror-substrate-bonded VCSELs are excited by continuous-wave current at room temperature, they exhibit lower threshold current density and differential resistance (22 A/cm², 35 Ω) as compared with the original VCSELs on GaAs substrates (77 A/cm², 60 Ω). This feature is attributed to the finding that the Si substrate provides a good heat sink.

To use a scanning mirror for laser display, the size of the mirror must be larger than that of the laser beam and the laser beam must be scanned linearly with analog operation to produce an undistorted image. A 1500 µm×1200 µm silicon scanning mirror having vertical comb fingers, which satisfies such requirements for laser display, has been fabricated and characterized. The open loop responses were measured using a laser doppler vibrometer (LDV) according to the input signal wave forms and the deflection angle was measured according to the control voltage with dc bias voltages. This scanning mirror showed a very linear actuating performance and it could be used for laser display as a galvanometric vertical scanner.

This paper describes the development of the nonresonant ultrasonic motor (NRUSM) applied to a 300-mm-stroke ultra-precision stage for future LSI manufacturing, in particular electron beam based technologies. Advantages of the NRUSM are high resolution, no magnetic noise generation, high servo rigidity and high retention. It is confirmed that the NRUSM is suitable for ultra-precision positioning, and slow- and high-velocity feeding at closed-loop controls. The performance of the NRUSM-driven stage includes; (1) 85 mm/s feed velocity with average acceleration 375 mm/s² over the 300 mm stroke at open-loop control; (2) ±0.69 nm positioning accuracy at step and repeat response, 17 ms average positioning time for ±30 nm positioning accuracy, positional error during constant velocity feeding below ±1.5 nm for 100 nm/s and ±40 nm for 20 mm/s, and velocity ripple at 36 mm/s is below 0.04% at closed-loop control.

Extreme ultraviolet (EUV) lithography is a promising candidate for the fabrication of semiconductors with feature sizes of 50 nm and below. In order to fabricate a fine pattern in a single-layer resist process, the development of resist materials with small absorption is required. To date, we have developed a method of measuring resist transmittance at an EUV wavelength using EUV reflectometer. We found that measured resist transmittance is in good agreement with calculated resist transmittance and that this method is very effective for measuring actual transmittance at EUV wavelength. In this paper, using the developed method of EUV transmittance, we report the study of transmittance of various kinds of polymers for resists and commercial resists and the influence of a photoacid generator (PAG) on resist transmittance. Our transmittance measurement by the EUV reflectometer is quantitatively useful for these studies. Polymers with carbon and silicon atoms show higher transmittance. On the other hand, polymers with fluorine atoms show lower transmittance. Photoacid generators have a negligible affect on transmittance.

We acquired a two-dimensional (2D) laser vector graphic video image using 1500 µm×1200 µm silicon scanning mirrors with vertical comb fingers. Vector image signals from the graphic board were applied to two scanning mirrors, and a SHG green laser was directly modulated to shape independent graphic images. These scanning mirrors were originally designed for laser raster video display as a galvanometric vertical scanner, and are controlled perfectly by the ramp waveform of 60 Hz with the duty cycle of 90%.

Improvement in the selectivity of semiconducting resistive-type NO₂ sensors has been achieved by numerical compensation derived from the output of calorimetric hydrocarbon sensors. The electrical resistance of resistive-type sensors using thick-film SnO₂ increases due to exposure to NO₂, whereas its resistance is decreased by i-C₄H₁₀. Oxidizing gases such as O₂ and NO₂ which are electronegative are adsorbed on the surface of n-type semiconductors, whereas reducing gases such as hydrocarbons and carbon monoxide react with these adsorbed oxidizing gases, causing electrons to return to the semiconductor. Calorimetric sensors are based on the principle of catalytic combustion between reducing gases and atmospheric oxygen on the surface of gas-detecting materials, therefore they are sensitive to reducing gases such as hydrocarbons, but are insensitive to oxidizing gases. It was found that the resistance of NO₂ sensors in the range from 0 to 100 ppm NO₂ was unaffected by the co-existence of 0 to 300 ppm i-C₄H₁₀ using a semiconducting NO₂ sensor, a calorimetric sensor and numerical compensation.

Optically stimulated luminescence (OSL) and thermoluminescence (TL) for γ-irradiated ice samples have been investigated as future dating techniques for icy bodies in the solar system. The OSL around 400 nm lasted more than 600 s for γ-irradiated H₂O ice and D₂O ice under 623-nm-light stimulation at 90 K; the latter was used to study the migration of hydrogen atoms. A defect containing trapped electrons is the most suitable explanation of the OSL emissions. The intensity of the TL peak at 120 K increased linearly with γ-dosage increasing up to 15 kGy for both D₂O ice and H₂O ice. Intensities of both OSL and TL for D₂O ice were larger than those for H₂O ice. The TL peak related to H₂O was observed but its thermal characteristics did not agree with those of OH and HO₂ radicals measured by ESR. The OSL method should be employed in future surveys in the solar system.