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1.
The unsaturated losses , and the saturation intensityI
s, were measured in an uv-preionized KrCl laser for optimized He and Ne based laser gas mixtures. The measurements were made as a function of the specific power loading and of the total pressure of the laser mixtures. Higher values for andI
s
were found for the Ne-based laser mixture than for the He-based mixture. At 45 kV charging voltage and at 355 kPa of total pressure we measured =0.053 cm–1 andI
s
=9.4MW/cm2 for the Ne based mixture, and =0.035 cm–1 andI
s
=5.1MW/cm2 for the He based mixture. 相似文献
2.
E. D'Anna S. Luby A. Luches E. Majkova M. Martino 《Applied Physics A: Materials Science & Processing》1993,56(5):429-436
Interdiffusion phenomena, thermal damage and ablation of W/Si and Si/W bilayers and multilayers under XeCl-excimer laser (=308 nm) irradiation at fluences of 0.15, 0.3 and 0.6 J/cm2 were studied. Samples were prepared by UHV e-beam evaporation onto oxidized Si. The thickness of W and Si layers and the total thickness of the structures were 1–20 nm and 40–100 nm, respectively. 1 to 300 laser pulses were directed to the same irradiation site. At 0.6 J/cm2 the samples were damaged even by a single laser pulse. At 0.3 J/cm2 WSi2 silicide formation, surface roughening and ablation were observed. The threshold for significant changes depends on the number of pulses: it was between 3–10 pulses and 10–30 pulses for bilayers with W and Si surfaces, respectively, and more than 100 pulses for multilayers with the same total thickness of tungsten. At 0.15 J/cm2 the periodicity of the multilayers was preserved. Temperature profiles in layered structures were obtained by numerical simulations. The observed differences of the resistance of various bilayers and multilayers against UV irradiation are discussed. 相似文献
3.
Poly(9,9-dioctylfluorene) (PF8) thin films have been deposited by matrix-assisted pulsed laser evaporation (MAPLE) using a KrF excimer laser. The influence of the laser fluence (50-500 mJ/cm2) and the nature of the solvent (chloroform, toluene, tetrahydrofuran) on the films properties have been studied. The chemical composition of the deposited films was investigated by Fourier transform infrared (FTIR) spectroscopy and compared with the one of spin coated films. To investigate the effect of the deposition parameters on the optical properties of the films, photoluminescence (PL) measurements were performed. Poor structural and optical properties were observed for films deposited starting from chloroform solutions. When using toluene as solvent, the spectra characteristics improved with increasing laser fluence, while wide PL spectra were observed. The characteristic emission bands of the PF8 polymer were nicely detected for films deposited starting from a tetrahydrofuran (THF) solution. Moreover, in this last case, the PF8 structure is preserved at high laser fluences, too. 相似文献
4.
A. P. Caricato A. Cretí A. Luches M. Lomascolo M. Martino R. Rella D. Valerini 《Laser Physics》2011,21(3):588-597
Various kinds of zinc oxide (ZnO) nanostructures, such as columns, pencils, hexagonal pyramids, hexagonal hierarchical structures,
as well as smooth and rough films, were grown by pulsed laser deposition using KrF and ArF excimer lasers, without use of
any catalyst. ZnO films were deposited at substrate temperatures from 500 to 700°C and oxygen background pressures of 1, 5,
50, and 100 Pa. Quite different morphologies of the deposited films were observed using scanning electron microscopy when
different laser wavelengths (248 or 193 nm) were used to ablate the bulk ZnO target. Photoluminescence studies were performed
at different temperatures (down to 7 K). The gas sensing properties of the different nanostructures were tested against low
concentrations of NO2. The variation in the photoluminescence emission of the films when exposed to NO2 was used as transduction mechanism to reveal the presence of the gas. The nanostructured films with higher surface-to-volume
ratio and higher total surface available for gas adsorption presented higher responses, detecting NO2 concentrations down to 3 ppm at room temperature. 相似文献
5.
S. Acquaviva M. Fernández G. Leggieri A. Luches M. Martino A. Perrone 《Applied Physics A: Materials Science & Processing》1999,69(7):S471-S474
We have designed and built an ultra-high vacuum chamber which allows thin film deposition on large area (up to 100 mm diameter) flat substrates and on three-dimensional substrates (e.g. 100 mm long, 50 mm diameter cylinders) by the pulsed laser deposition and reactive pulsed laser deposition techniques. Heating of substrates during and after film deposition is possible using either resistive heaters or a lamp array. Metal (Cu) and metal nitride (TiN) and carbide (TiC) films were deposited on Si wafers (60 and 100 mm diameter), three-dimensional steel substrates (steel cylinders and screws), Teflon plates, and paper sheets. 相似文献
6.
The small-signal net gain of the KrCl laser, excited in an UV-preionized transverse discharge, was measured using the passive absorption cell method. A maximum net gain of 0.13 cm-1 was measured in a 0.09% HCl/10.1% Kr/1.5% He/ 88.3% Ne mixture at a total pressure of 355 kPa and at a specific power loading of about 23 MW/cm3. Smaller gains were measured when He was used instead of Ne in the lasing mixture. 相似文献
7.
E. D'Anna G. Leggieri A. Luches 《Applied Physics A: Materials Science & Processing》1988,45(4):325-335
The relevant results obtained in the field of laser synthesis of metal silicides are reviewed. Particular emphasis is given to the work using a pulsed laser in the nanosecond regime and to the results obtained in our laboratory. Formation of stable and metastable compounds, their structure and the surface morphology of the irradiated materials are discussed. The reaction kinetics is investigated through a comparison of the experimental results with the heat flow and temperature calculations. 相似文献
8.
Plasma bursts were produced by focusing excimer-laser (XeCl, 308 nm) pulses on Ge and Si targets. At moderate laser fluences (30 MW/cm2) high-intensity Ge3+ and Si3+ ion pulses were extracted from the laser-produced plasma. A peculiar electrical circuit allows a self-bunching of the beam. By time-of-flight method, the currents produced by the ions of different charge number were measured. Peak currents of 620 mA and 800 mA were recorded for Ge3+ and Si3+ ions, respectively, with an extraction voltage of only 400 V. 相似文献
9.
E. D'Anna G. Leggieri A. Luches M. Martino P. Mengucci I. N. Mihailescu J. Zemek 《Progress in Surface Science》1990,35(1-4):129-142
A review is presented of the results obtained on the formation of nitride surface layers on semiconductor (Si) and metal (Ti) samples by multipulse (up to 2500) XeCl excimer laser (λ=308 nm) irradiation in N2 and NH3 atmosphere through a collaboration of Italian, Czechoslovak and Romanian laboratories. Different diagnostic techniques (optical and electron microscopy, Rutherford backscattering spectroscopy, nuclear reaction analysis, Auger and x-ray photoelectron spectroscopy) were used to positively identify the formed compounds. Silicon nitride formation was obtained only when laser irradiation was performed in ammonia atmosphere. In contrast, when titanium samples were irradiated the nitridation process resulted very efficient in both atmospheres. The characteristics of laser synthesized nitride layers are illustrated and discussed as a function of the kind of irradiated materials, the number of subsequent laser pulses and the nature of the ambient gas. 相似文献
10.
V.S. Teodorescu A. Luches R. Dinu A. Zocco M.F. Ciobanu M. Martino V. Sandu M. Dinescu 《Applied Physics A: Materials Science & Processing》1999,69(7):S667-S670
The influence of substrate temperature on the composition and crystallinity of boron carbonitride (BCN) thin films deposited on (100) Si substrates by sequential pulsed laser deposition (PLD) has been investigated. A correlation between the target composition, the nitrogen pressure involved in the process, and the amount of B, C, and N elements (at % ) in the deposited films is established from energy dispersive spectroscopy (EDS) analysis. Electron microscopy studies show that the films deposited on heated substrates are mainly amorphous. Fourier-transform infrared spectroscopy (FTIR) analysis confirms the BCN-compound formation: the peak of C-BN and the peaks from B-N-B bending vibrations and C-N C-bond vibrations are present in the spectra. SEM studies show that the deposited films have a smooth surface, with no cracks and few droplets. Results were compared with those obtained on films deposited at room temperature under similar experimental conditions. 相似文献