NITRIDATION INDUCED ON METAL-SURFACE BY AR+-ION IMPACT UNDER N2 ATMOSPHERE

Nitridation of surfaces has been examined by bombarding transition metals with 0.3-8 keV Ar+-ions (4 μ A cm-2) under a nitrogen atmosphere (1 × 10-3 Pa) at room temperature. The surface N:Metal ratio determined by XPS increased with irradiation time at lower fluences and reached a plateau at higher fluences. Using reaction kinetics for the nitridation of a Ti target allows the rate of nitride formation, defined as the number of TiN molecules produced by one incident ion, to be determined. For this procedure it is estimated to be about 17. The saturation value of the N:Me ratio for various metal targets increased with decreasing Gibbs free energy for the thermochemical formation of a nitride. This suggests that the dominant mechanisms for ion-induced nitridation are the thermochemical processes which occur at the bombardment area of the target surface. © 1990 Pergamon Press plc.