Maria-Antoaneta Bratescu

Electron and excited particle densities in a carbon ablation plume

Abstract In a plume produced by excimer ArF laser, the number densities of excited atoms and electrons, and the expansion velocity of ablated carbon atoms in an Ar gas were measured and compared with those obtained in vacuum. A saturation in C( 3 1 P 1 0 ) density was observed as the laser fluence increased. This saturation was shown to be closely related to the electron density saturation. The excitation of Ar(4s′[1/2]10) and C( 3 1 P 1 0 ) was interpreted by electron collisions and was dependent on gas pressure and excimer laser fluence.

Evanescent wave absorption by Xe(1s5) lying on a discharge tube wall

A simple and sensitive detection method of Xe(1s5) excited atoms in the vicinity of a discharge wall with laser-collision induced fluorescence (LCIF) produced by evanescent wave absorption is proposed. The signal to noise (S/N) ratio was 102. The hyperfine structure (hfs) in the Xe LCIF spectra induced by resonant absorption of Xe(1s5→2p6) was confirmed to be identical with the hfs in laser absorption spectra, although the detection point (xPD) on the discharge wall was chosen independently of the position of the EW absorption (xEW). The insignificantly large fluorescence, which appeared for incident light angles to a prism larger than 4.8°, is explained by the fact that the refracted light emerged in a plasma. The Xe(1s5) number density in a dc Xe discharge, although roughly estimated, on the tube wall between the electrodes is presented.

Application of perfluorocarbon liquids for a-C:F film production on electrodes by plasma enhanced chemical vapor deposition

Application of dielectric liquids for production of thin films on substrates was presented. In our studies, taking a perfluorooctane C/sub 8/F/sub 18/ monomer liquid, an amorphous fluorocarbon thin film (a-C:F) was deposited on substrates in radio-frequency C/sub 8/F/sub 18/ vapor plasma. The decomposed species in the plasma were observed as C, C/sub 2/, CF, CF/sub 2/ and CF/sub 3/. The chemical and electrical properties of a-C:F films were examined. The breakdown voltage (V/sub s/) of N/sub 2/, Ar and He gases between the a-C:F film coated Al sphere-sphere electrodes for a gas pressure (p) times gap length (d), 0.1-100 Torr cm, was measured. It was found that the a-C:F film coated electrodes enhanced V/sub s/ values by a several times higher than the Al electrode case.

Carbon nanotube growth on metal-catalyzed substrates in a laser oven apparatus

Carbon nanotubes (CNTs) were grown on Ni- and Fe-coated SiO 2 /Si substrates in a laser oven apparatus. The grown CNTs were analyzed by scanning electron microscopy. It is speculated that the CNTs grow out from the metal nanoparticle after laser-ablated carbon clusters have been dissolved in it. In a range of oven temperatures between 800 and 1100°C, growth of CNTs was achieved at a temperature ≥ 1000°C. The thickness of the Ni film controlled the CNTs diameter.

Excited xenon(1s4) atom detection by modulation laser absorption spectroscopy

A study on the space distribution of the excited xenon atoms on level 1s4 in a d.c. discharge in neon-xenon mixture is presented in this paper. The relative density of the excited xenon atoms was measured using diode laser absorption at 828.239 nm, corresponding to the xenon transition between 1s4 and 2p5 levels. A comparative analysis of the laser absorption signal and corresponding optogalvanic signal, permitted us to define a new parameter, namely optogalvanic effect efficiency, EffOG, as the size of the optogalvanic signal corresponding to an atom optically pumped by laser.