Gas pressure effects on the structure of CNx thin films deposited by laser ablation

Carbon nitride thin films with different nitrogen concentration have been deposited at different N₂ and N₂/Ar mixed partial pressures. Time-integrated optical emission spectroscopy measurements have been performed to gather information on the nature of the chemical species present in the plasma. Both the CN and C₂ molecular species have been observed. Fast photography imaging of the expanding plume revealed the change of the dynamics from a free expansion at low pressure to a shock wave formation followed then by the plume stopping upon increasing the gas pressure values. Raman and XPS spectroscopy measurements performed on the deposited thin films revealed that the films, structure strongly depends on the dynamics of the expansion plasma regime rather than on the partial pressure at which the deposition takes place.