Effect of ambient gas ionisation on the morphology of a pulsed laser deposited carbon film

The paper reports a study of the mechanism of ambient gas ionisation and its effects on a growing carbon film. Such an ionisation occurs during the expansion through an inert gas of an ablation plume generated by laser irradiation of a target. Charge transfer reactions between ablated ions and inert gas atoms lead to the formation of a charged layer in contact with plume front. The energy lost by fast ablated ions associated with plume slowing down is calculated. In the case of carbon ablated in helium and argon atmospheres, where ionisation plays a very different role, we discuss the microstructure changes observed in the deposited films in terms of dramatic differences of plume dynamics.