Plasma study in laser ablation process for deposition.

In order to get a better inside in the reactive Pulsed Laser Deposition (PLD) of nitride thin films, we performed time- and space-resolved plasma diagnostics during ablation of Ti, Al and C targets in low pressure nitrogen containing atmospheres using pulsed nanosecond UV lasers. In the case of carbon, thin films of CxNy were deposited on silicon substrates and characterized by Rutherford Backscattering Spectroscopy (RBS) and Nuclear Reaction Analysis (NRA). With respect to irradiation of metal targets, during which a dense and highly ionized plasma was induced for laser intensities greater than or equal to 100 MWcm(-2), much higher values greater than or equal to 1 GWcm(-2) were necessary to induce significant plasma ionization on carbon. To increase the plasma reactivity in the case of carbon ablation, a radiofrequency discharge was added to excite and preionize the ambient gas. From correlation between the plasma characteristics and thin film analyses, conclusions could be made about the CxNy deposition process.