We have studied the photoluminescence (PL) of titanium dioxide nanocrystalline powders (TiO2) synthesized by the thermal hydrolysis in the form of anatase (A), whose surface has been modified by the adsorption of chromium ions (Cr3+). The samples are characterized by X-ray diffraction, X-ray fluorescence, and Raman spectroscopy. PL spectra were excited by a nitrogen UV laser. The Cr3+ ion doping in А/TiO2 leads to short-wave and long-wave shifts of the PL peaks due to the Burstein–Moss effect and due to the contribution of radiation "tails" of the electron density of states, respectively. The PL intensity of Cr3+-doped A/TiO2 at low concentration of Cr3+ (up to 0.5 at.%) increases in comparison with the undoped A/TiO2 due to the formation of additional centers of radiative recombination of carriers. With increasing the concentration of Cr 3+ (∼1.0 at.%), the A/TiO2 PL intensity decreases due to the concentration quenching.

The present study deals with rapid, automatic, estimation of some earthquake parameters (location, focal depth, and magnitude) in a region of rather high seismic activity, in quasi-real time, through the analysis of incoming broadband records. The method can be applied, in particular, in poorly instrumented countries with high seismic-risk potential. It can also be applied when the analysis of a very important flow of data requires rapid, sophisticated, preferably automatic, data processing. The method requires, as a minimum, a three-component broadband seismographic station and a sufficiently populated database, that is, an instrument operating for a time long enough to have accumulated an appropriate data set, used to construct the knowledge base. The more extensive the knowledge base, the better the accuracy of the method. We proceed in several steps. First, applying the spars algorithm to the only vertical component, available waveforms are classified according to the source location taken from National Earthquake Information Center (neic) catalog; it results in the sorting out of a subset of waveforms/events which will not be included in the knowledge base. Second, each element of the knowledge base is validated according to the epicentral distance with respect to the reference station (and eventually the azimuth of the corresponding source). Third, new input waveforms are analyzed and compared with one or more elements of the knowledge base to estimate their source location and size. The method can be used to search for doublets (or multiplets); if multiplets are found, their location and focal depth can be determined by using a fuzzy event relocation method. We have tested the capability of the proposed algorithms, processing (broadband) waveforms collected during four and half years at the geoscope broadband station pvc, operated by Institut de Recherche pour le Developpement, formerly ORSTOM (ird) at Port Vila, Vanuatu. Among 650 events recorded at this station, 254 ones, meeting a good criterion of quality, have been sorted. The results show that, in a range of distances up to 1000 km, the method is capable of yielding, in a very short time, the location of the input event, the accuracy depending on the local density of known events in the vicinity. We also obtain a reliable estimation of the energy by measuring the maximum surface wave (or S -wave) amplitude, related to the classical magnitude msz.

Sub-50 nm junction depth p+n and n+p diodes are formed by excimer laser annealing (ELA) of BF2 + and As+ implants, respectively, performed directly in the contact windows. The latter are etched through a stack composed of a reflective Al masking layer deposited on a silicon oxide isolation layer. The etching process, the laser anneal energy and the implantation parameters are optimized for low surface roughness at the silicon surface of the contact with respect to the final junction depth and good edge coverage of the diodes. In this manner near-ideal diode characteristics with ideality factors of 1.06-1.16 and low contact resistances are achieved in the laser energy processing window of 800-1000 mJ/cm2 . Moreover, the uniformity and reproducibility over the wafer is excellent

Laser-induced surface roughness and damage formation in ultra-shallow n+–p and p+–n junctions, formed by low energy (5keV) As+ and BF2+ implantations in Si, respectively, with a dose of 1 × 1015cm−2 have been investigated by atomic force microscopy (AFM) and Positron Annihilation Doppler Broadening (PADB) technique. The Si surface roughness is found to increase with laser energy density, and reaches a value of 3.5nm after excimer-laser annealing (ELA) at 1100mJ/cm2. However, anomalous behavior is witnessed for BF2+-implanted Si sample at 800mJ/cm2, at which energy very high surface protrusions up to 9nm high are observed. By PADB this behavior is correlated to extensive deep microcavity formation in the Si whereby the volatile F2 fraction can accumulate and evaporate/out-diffuse, leading to Si surface roughening. The consequences for the diode characteristics and contact resistivity are examined.

This paper reviews advanced excimer-laser crystallization techniques, developed by our group, enabling precise location-control of the individual Si grains. Combined microstructure and time-resolved optical reflectivity investigations during conventional excimer-laser crystallization showed that explosive crystallization occurs during excimer-laser irradiation. The location-control methods use local structural modification in the underlying materials (substrate) using a conventional photolithography. With the developed process, the large grains having a diameter of 6 μm can be set precisely at predetermined positions. We will also discuss the performance of the single-crystalline Si TFTs that are formed within the location-controlled Si grains. The field-effect mobility for electrons is 430 cm2/Vs on average, which is well comparable to that of TFTs made with silicon-on-insulator wafers.

A 2D phase-field model was applied to simulate the phase-transition kinetics and the thermal field distribution during the lateral crystallization of a-Si induced by single pulse excimer laser. The higher tilt of solid/liquid interface increases the supercooling temperature in the melt due to the fast latent heat extraction at the solid/liquid interface. The lateral growth velocity is in average four times faster than the vertical one. When the lateral growth velocity exceeds the critical value of 19 m/s, amorphization of Si can be initiated because of unstable growth front. Therefore, thickness of Si film and the thermal properties of underlying layer play a crucial role not only in ultra-large grain fabrication but also in defect-free crystal growth.

The processing energy density window of the location controlled Si (LC Si) grains has been studied experimentally. These Si grains were fabricated by dual-beam excimer laser irradiation in an a-Si/SiO2/metal stack with an array of bumps in the oxide. The influence of the bump diameter and the bump height on the lower and upper laser energy bounds has been investigated for the entire energy density range, where LC Si grains were formed. The widest obtained processing window, where location-controlled single grains as large as 4.2–4.7 μm were observed, had a width of 6.8%. The experimental results were also found to be in a very good agreement with the numerical simulation, based on the resolution of the two-dimensional heat flow equation.

This paper reviews advanced excimer-laser crystallization techniques and its application to crystal-Si thin film transistors (TFTs). Combined microstructure and time- resolved optical reflectivity investigations during conventional excimer-laser crystallization showed that explosive crystallization occurs during excimer-laser irradiation. Two methods enabling location-control of large silicon islands will be reviewed. One of the methods uses local thermal relief by modifying locally the heat extraction rate towards the substrate. A small unmolten region remains at the center of high heat extraction part which then acts as a seed for radially grown Si grain with a diameter of 6 micrometers . One of the other methods use geometric selection through a vertical narrow constriction. In this method, upon laser irradiation, a small unmolten Si region remains at the bottom of narrow holes etched in the underlying isolation layer. During vertical regrowth, a single grain is filtered out which subsequently seeds the lateral growth of large grains. We will also discuss the performance of crystal-silicon TFTs that are formed in the location-controlled Si grains. The field-effect mobility for electrons is 450 cm2Vs, which is very close to that of TFTs made with silicon-on-insulator wafers.

An array of large Si grains was placed at a predetermined position by dual excimer-laser irradiation of a multi-layer structure of silicon (Si), silicon dioxide (SiO2) with an array of bumps and metal on a glass substrate. We have investigated the effects of irradiating energy density and the topology of the structure on the grain size and crystallographic structure by scanning electron microscopy (SEM) and electron back-scattering pattern (EBSP) analysis. In the low-energy-density regime, numerous small grains and petal shaped grains formed on top of the SiO2 bumps. The number of small grains on the bumps decreased with increasing irradiating energy density. At sufficiently high energy densities, one single Si grain as large as 3.5 µm was positioned at the center of the bumps. Although most of the area of the large Si grain has a single crystallographic orientation, twins and low-angle grain boundaries are often formed at the periphery of the grain. There was no preferred crystallographic orientation in the center of the location-controlled Si grain. Numerical analysis of the temperature profile showed that a temperature drop occurs at the center of the bump, during and immediately after laser irradiation. The diameter of the location-controlled Si grain increased with total thickness of the intermediate SiO2 layer, and took the maximum value of 6.2 µm.

The effect of thickness variation of an intermediate insulator layer on the grain size of a recrystallized large Si grain in an a-Si/SiO2/metal stack with an array of bumps in the oxide has been investigated. Increased thickness of the intermediate oxide portion and bump height resulted in grain size enlargement of the Si grain. Si crystal grains as large as 5.1 μm were obtained located exactly at the desired position on the oxide. The explanation of the growth-enhanced mechanism by the solidification rate behavior, based on numerical simulation in terms of temperature gradient arguments is given.

We propose a method to locate a large silicon (Si) crystal grain at a predetermined position on a glass substrate following excimer-laser melting of Si thin-film. The thickness of part of the intermediate insulator of the amorphous-Si (a-Si)/insulator/metal/glass structure was increased. After the irradiation by dual-beam light to both the back and front sides of the structure, a Si crystal grain as large as 4 µm was located exactly at the center of the predetermined position, for wide range of diameter of the thick portion and irradiated light energy density.

Anisotropic etching of silicon has been studied in SF6/O2/He plasma using a multivariable experimental design. It has been found that the main monitored responses of the etching process such as silicon etch rate, selectivity of silicon over oxide, etch uniformity and etch anisotropy were influenced by a combination of independent variables. The most important variables were RF power, chamber pressure, total gas flow and oxygen content (i.e., percentage of the O2 flow in the total gas flow). The physical and chemical explanations have been based upon the etching models obtained with the Response Surface Methodology (RSM). The models were subsequently used to optimise the etching process for trench isolation applications. The optimal values of process parameters for U-shaped 4 μm trench etching with anisotropy of 0.97 have been found. Applications of the trenches obtained have been tested at low/high doped multilayer structures.

gated with new line focusing systems. Also double pass amplification with use of a soft x-ray mirror was tested. Based on these results, two curved targets were placed in series to double the gain length. Two opposing laser beams irradiated the double targets with a suitable time difference for traveling wave pumping in an arrangement shown in Fig. 1. The on-axis spectra ofthe x-ray laser emission were measured with two grazing-incidence spectrometers placed on opposite sides with a soft x-ray CCD on one side and a streak camera on another side for angle resolved (but timeintegrated) and time-resolved measurements, respectively. The double target amplification was successfully demonstrated with two-beam irradiation. The separation between the two slabs transverse to the on-axis was varied from 210 to 320 pm. The maximum x-ray laser output was observed at 320 p m separation. The x-ray laser intensity amplified along the traveling wave has increased over an order of magnitude in comparison to that against the traveling wave, as shown in Fig. 2. With a single curved slab, x-ray lasing occurred at the latter three pumping pulses with comparable intensities, whereas with the double curved targets, the last pulse gave the strongest lasing. These results indicate the better condition for coupling of the x-ray laser beam between the two targets at the later part of the pulse train. Further analyses are going on. *Osaka National Research Institute, Ikeda Osaka 563 Japan **National Laboratory for High Power Lasers and Physics, P.0. Box 800-21 1 Shanghai, China ?Institute for Applied Physics and Computational Mathematics, P.O. Box 8009, Belling 100088, China THUk

The feasibility of a solid-state laser driver pumping by Nd lasers with flashlamps is examined. At the pulse train mode operation Nd-laser 1.06-mu m radiation may be effectively transformed by SRS to the absorption bands of several rare-earth and transition metal activator ions in crystals. 0.94- and 1.33-mu m free-running Nd3+:garnet lasers are to be useful for Yb3+:YAG and Co2+:MgF2 active media pumping. Stored energy efficiencies of 2-4% are expected under Nd-laser pumping of driver's amplifier modules.

It is showned in this paper, that computing of Accident Prevention System (APS) control signals in real time is only possible on the basis of parallel processing of power flow in the electrical grid and computing of the control signals in parallel for groups of specified types of perturbations. High-speed hardware and software for parallel systems produced by leading manufacturers and fiber-optic communication lines provide the basis for the creation fo hierarchical distributed APS employing the principles of functional (cybernetic) modeling.

In connection with an elaboration of selective pumping techniques for solid-state laser-drivers a stored energy formation in solid state media under absorption of a narrow-band pumping radiation has been considered. The calculations demonstrate the possibility of the inversion profile smoothing in the slab-like Nd- and Yb-doped active elements pumped from excited levels of activator's or sensitizer's ions. A possibility of the Nd:glass and iodine lasers usage to carry out modelling experiments on selective pumping at several kJ energy level is discussed.

In this study the surface roughness of the contact windows in which the laser annealed shallow junctions are formed is investigated. The contact windows are etched through a stack of an aluminium reflective masking layer on a silicon dioxide surface isolation layer. Comparisons are made between different types of Al and oxide layers, as well as different layer thicknesses. Various combinations of dry and wet etching are examined and the preliminary results show that the etch procedure can be tuned so that the resulting surface roughness is minimal.