Phase variation and properties of (Ti, Al)N films prepared by ion beam assisted deposition

(Ti, Al)N films were prepared using ion beam assisted deposition (IBAD), in which the films were formed by vapour deposition of Ti and Al under simultaneous bombardment with nitrogen ions in the energy range 0.2-20 keV. Detailed investigations on the phase variation of (Ti, AI)N films as a function of Al content were carried out using selected area electron diffraction. The structural analysis showed the formation of a single-phase NaCl structure in the films with Al content up to 67 at.%. With increasing Al content, the films exhibited a double phase mixture consisting of NaCl and wurtzite structure phases. With Al content above 84 at.%, the phase was observed to transform into a single-phase wurtzite structure. The critical Al content for the phase transition from NaCl to wurtzite structure (67 at.% Al)was in excellent agreement with the value (65.3 at.% Al) theoretically predicted using the two band parameters; i.e. the hybrid function and the gap reduction parameter. High-temperature oxidation tests of the (Ti0.7Al0.3)N film did not show appreciable oxidation up to similar to 900 degrees C, whereas the TiN films began to show significant weight gain at temperatures as low as similar to 700 degrees C. (C) 1997 Elsevier Science S.A.