Surface nitridation processes and non-linear behaviour of the reactive magnetron discharge with titanium target

Recently, a model was proposed to explain the non-linearity of the V-I char acteristics of the reactive magnetron discharge with a Ti-cathode in an Ar- N-2 gas mixture. It accounts for the rapid development of an additional (lo wer impedance) metal-target discharge, which is coupled in parallel to the existent one, after outrunning a current threshold. Here, we employed vario us surface science techniques to confirm the connection between mentioned n on-linearity and target nitridation-versus-sputtering processes. Surface at omic N/Ti ratios were measured for different N-2, pressures, and ion curren t densities using X-ray photoelectron spectroscopy, Auger electron spectros copy and low-energy ion scattering spectroscopy. Systematic experiments sho wed that while the nitridation enhancement process plays a significant role at lower current densities, the sputtering process becomes predominant aft er outrunning a critical current density. Taking into account the checked s caling effect of pressure and ion beam density, we were able to correlate t he mentioned critical current density with the threshold currents in the V- I plots. (C) 2001 Elsevier Science Ltd. All rights reserved.