Laser-ablated carbon plasmas: emission spectroscopy and thin film growth

Abstract

The effect of the ambient gas pressure on thin films of carbon deposited by laser ablation using third harmonics at 355 nm of an Nd: YAG laser is reported. Scanning electron microscopy, X-ray diffraction and Raman spectroscopy have been used to characterize the deposited films. The nucleation density and morphology of the films and microcrystals are strongly affected by the pressure of the ambient gas. It is found that there is an optimum pressure at which nucleation is more pronounced. The optical emission spectra of C 2, recorded as a function of the laser energy and background gas pressures, is used to estimate the vibrational 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 energy, and on the choice of the ambient gas and its pressure. The correlation of the vibrational temperature with characteristics of the deposited film and with plasma plume parameters is discussed.