Study of diamond thin-film growth mechanism in a filament-assisted excimer laser ablation system

Abstract

Diamond and amorphous carbon films have been deposited on silicon (100) substrates by filament-assisted XeCl excimer laser ablation of graphite targets. The influence of process parameters on the growth mechanism of diamond were studied by depositing films over a wide range of gas pressures and substrate temperatures. The surface morphology and bonding of the deposited films were characterized by scanning electron microscopy, and Raman and electron-energy-loss spectroscopy. In these experiments, microcrystalline diamond films with growth rates comparable to conventional chemical-vapor-deposition and plasma-enhanced chemical-vapor-deposition techniques could only be obtained at substrate temperatures and hydrogen pressures greater than 700 °C and 1.3 mbar, respectively. Conversely, the best conditions for growing carbon films with predominately sp3-type bonding structures were at temperatures and pressures less than 300 °C and 0.3 mbar, respectively. These results suggest that carbon-hydrogen gas phase reactions as well as gas-surface reactions are both necessary for the formation of diamond.