LASER-ABLATED CARBON PLASMAS - EMISSION-SPECTROSCOPY AND THIN-FILM GROWTH

The effect of the ambient gas pressure on thin films of carbon deposit ed by laser ablation using third harmonics at 355 nm of an Nd:YAG lase r is reported. Scanning electron microscopy, X-ray diffraction and Ram an spectroscopy have been used to characterize the deposited films. Th e nucleation density and morphology of the films and microcrystals are strongly affected by the pressure of the ambient gas. It is found tha t there is an optimum pressure at which nucleation is more pronounced. The optical emission spectra of C-2, recorded as a function of the la ser energy and background gas pressures, is used to estimate the vibra tional temperature of the species. The vibrational temperature of the molecular C-2 species is estimated using Swan bands. The intensity of the Swan bands increased as the pressure of the background gas (argon) was increased. The vibrational temperature depends on the laser energ y, and on the choice of the ambient gas and its pressure. The correlat ion of the vibrational temperature with characteristics of the deposit ed film and with plasma plume parameters is discussed.