We present in this paper a comparison of the photodissociation processes of SiH 4 and Si 2 H 6 under pulsed excimer laser at 193 nm. The experimental curves of the gas composition as a function of laser energy density show that the dissociation of Si 2 H 6 results from both one and two-photon absorption whereas SiH 4 only absorbs two photons. The deposition yield of Si 2 H 6 has also been determined as a function of the number of laser pulses or initial pressure. These experimental results show the establishment of a stationary state in the gas phase and prove the existence of reverse reactions in the disilane kinetic model. The photodissociation of Si 2 H 6 under UV laser excitation (193 nm) presents, therefore, similar properties to those of SiH 4 .

The C 1s and N 1s core levels of carbon nitrides are composed of several contributions whose assignment is controversial due to the lack of appropriate reference materials and the great variety of configurations of carbon and nitrogen. From the comparison of nitrogen-containing polymeric compounds and solid carbon references an assignment of the individual lines of the C 1s and N 1s core levels is given. Nitrogen-containing polymeric compounds are used as reference materials as they provide a more adequate account of the screening of the ionized states in the photoemission process than molecular references. This screening effect is even more pronounced in case of aromatic or cyanogen-type bonds where delocalized pi electrons strongly affect the screening of the core hole. In the second part of the paper these assignments are used to interpret the changes of the chemical environment in pulsed laser deposited carbon nitride films as a result of systematic changes in laser fluence, nitrogen pressure, and target-to-substrate distance. The effect of subsequent annealing and sputtering by argon ions is also discussed. The chemical structure of the films is dominated by nitrile, N(pyramidal)-C(trigonal) and nitrogen in sp(2) hybridization (with the electron doublet out of plane) inserted into carbon graphitic network at high laser fluence, and nitrile and pyridinic sp(2)-hybridized configurations at low laser fluence, in good line with the fact that sp(3) and sp(2) hybridization states around carbon and nitrile configuration with nitrogen, are preferred.

Amorphous carbon nitride films are deposited at room temperature on silicon substrates by ArF excimer laser (193nm) ablation of a graphite target in nitrogen atmosphere. By tuning the process parameters, fine control of the carbon–carbon and carbon–nitrogen bond configuration is achieved in a broad range as followed by X-ray photoelectron spectroscopy (XPS) and infrared (IR) absorption spectroscopy. Based on the comparative and quantitative analysis of changes in measured IR versus XPS spectra as a function of reactive gas pressure, laser fluence and target-to-substrate distance, and on a critical review of the existing interpretation of IR data, an assignment of the components of the broad band extending from 900 to 1900cm−1 in the IR spectra to specific carbon–carbon and carbon–nitrogen bond configurations is proposed.

Laser energy is able to ablate, coagulate, and vaporize tissues. Its transmissibility in thin optical fibers makes it an ideal tool for use in percutaneous procedures. This article describes two applications in interventional musculoskeletal radiology. In percutaneous laser disc decompression the laser source is used to vaporize a small portion of the nucleus pulposus. In interstitial laser photocoagulation of osteoid osteoma the laser energy is used to coagulate and destroy the tumor by direct heating.

L'analyse spectroscopique, de 110 à 600 nm, de l'émission des plasmas créés lors de l'ablation par laser à excimères (KrF, A.=248 nm) de cibles monoatomiques de Ge et de Si et diatomiques de SiGe a été entreprise dans le but d'identifier les espèces radiatives présentes dans le panache.L'analyse spectroscopique (intégrée dans le temps) de l'émission des plasmas se fait perpendiculairement à la cible tournante, irradiée sous une incidence de 90 e , par un monochromateur McPherson 218 isolé de la cellule d'ablation par une fenêtre en FLi, un filtre passe-haut (300 nm) amovible permettant d'éliminer les ordres supérieurs.Les photons sont détectés par un photomultiplicateur RTC à fenêtre en FLi relié à un système de comptage de photons suivi d'un enregistreur graphique.Les spectres d'émission, non corrigés par la réponse spectrale de l'ensemble du système optique et représentés sur la figure 1, sont constitués d'un fond continu non structuré dont l'intensité décroît vers le visible, sur lequel se superpose un nombre élevé de raies identifiées à partir des tables de raies spectrales des éléments Ge et Si [1].Les transitions auxquelles elles correspondent ont été déterminées d'après les valeurs connues des niveaux d'énergie de leurs états excités [2].La plupart des 73 et 35 raies respectivement identifiées dans les plasmas de Ge et de Si ont été attribuées à la désexcitation radiative d'atomes excités: Ge* [...4s 2 4p ns (n = 5,6,7,8), ...4s 2 4p nd (n = 4,5,6) et ...4s 4p 3 ] et Si* [...3s 2 3p ns (n = 4,5,6,7), ...3s 2 3p nd (n = 3,4,5,6,7) et ...3s 3p 3 ] vers leur niveau fondamental Seules les raies Ge I (n° 72-73) et Si I (n° 30-35) avaient été observées par d'autres auteurs lors d'études similaires sur des domaines spectraux plus restreints : au-delà de 400 nm dans le cas du Ge [3] et de 250-300 nm en ce qui concerne Si [4,5], ainsi qu'un certain nombre de raies ioniques dont nous ne relevons pas la présence.Cependant, les raies n° 4, 29, 43 et 46 dans le cas de Ge et la raie n° 23 de Si, émises endessous de 220 nm, pourraient provenir d'une désactivation d'espèces ioniques.Il semblerait que, dans nos conditions expérimentales, les ions présents dans le plasma disparaissent essentiellement par recombinaison radiative.La nature et la pression du milieu gazeux environnant : 7,5.IO' 2 et 2.10 -5 Torr d'air ou 7,5.IO" 2 Torr d'hélium n'affectent en rien la structure de ces spectres.Le seuil d'apparition du plasma avec émission lumineuse est de 1,2 à 1,3 J/cm 2 .L'augmentation de la fluence jusque 4 J/cm 2 n'entraîne pas l'apparition de nouvelles émissions atomiques ou ioniques mais uniquement une augmentation de l'intensité : uniforme et de l'ordre de quelques % pour Si, elle varie de 20 à plus de 100 % selon le domaine d'émission dans le cas de Ge.Dans les spectres d'émission déterminés pour une cible de SiGe, on retrouve la plupart des raies atomiques correspondant à chacun de ses éléments, à l'exception de 23 raies assignées à Ge et 5 à Si.Aucune nouvelle émission pouvant provenir de la désexcitation d'agrégats SiGe formés en phase gazeuse n'est décelée.

A study of the pulsed laser evaporation process of thin superconducting films using both Nd:YAG and ArF eximer lasers is presented. Nuclear reaction analysis, Rutherford backscattering spectrometry (RBS) and scanning electron microscopy were used to characterize composition, thickness and surface morphology of the deposited films. The influence on the properties of the films, of the various parameters of the method such as photon wavelength, laser power density and geometrical conditions are presented and discussed.

The gas immersion laser doping (GILD) technique requires the measurement of the fraction of incident light absorbed in the gas phase during the irradiation with a pulsed laser. Here we report the absorption of boron trichloride (BCl3) gas at the wavelength of a pulsed ArF excimer laser (λ=193 nm). We have determined the one-photon (σ1) and two-photon (σ) absorption cross sections of this dopant gas for 193 nm. The values of σ1 and σ are 3.6×10−20 cm2 and 9×10−45 cm4·s, respectively. However, the distinction between simultaneous and sequential absorption has not been possible. Based on these results, we have established a relationship which allows the calculation of the fraction of incident light absorbed as a function of incident intensity and gas pressure.

We have prepared BiSrCaCuO superconducting thin films by the pulsed laser evaporation method, using a YAG or an ArF excimer laser. The as-deposited films, which were enriched in Cu with respect to the bulk target composition Bi2Sr2Ca1Cu2O8 (i.e., the “2212” phase), were converted into the superconducting phase by a subsequent high temperature annealing in oxygen. Resistivity measurements showed superconducting transitions near 90 K, and the highest zero resistivity temperature was 83 K. The influence of the deposition parameters (photon wavelength) and annealing conditions (temperature, duration, and atmosphere) have been studied. The composition and in-depth distribution of the various elements were determined by Rutherford backscattering spectrometry (RBS), and the surface morphology was studied by scanning electron microscopy (SEM).

The deposition of YBaCuO and BiSrCaCuO thin films by laser evaporation in a clean environment has been performed using a pulsed ArF excimer laser. The as-deposited thin films were successfully converted into the superconducting phase by a subsequent anneal in oxygen in the 850–900°C temperature range. The onset critical temperatures were respectively 85 and 92 K with a zero resistance at 83 K for BiSrCaCuO.

Several groups have recently observed a specific influence of ultraviolet laser light on the oxidation of silicon and silicon monoxide. Thermodynamic calculations suggest that these results must be interpreted by carefully taking into account the possible laser-induced temperature rise of the irradiated surfaces, especially when silicon monoxide is photo-oxidized into silicon dioxide with a pulsed excimer laser.

We have determined for the first time, the two-photon absorption cross-section of silane at 193 nm, by measuring directly the fraction of incident light absorbed in the gas phase during the irradiation with a pulsed ArF excimer laser.