Phase stability and decomposition products of Ti–Al–Ta–N thin films

Abstract

Ab initio calculations of quaternary alloys were used to predict the phase stability of (Ti1−xAlx)1−yTayN. Experimental observation of a dual phase structure containing wurtzite AlN and cubic Ti1−yTayN after thermal decomposition of sputter deposited thin films by vacuum annealing to 1400 °C is in excellent agreement with the calculated phase stabilities of the investigated compositions. We found positive mixing enthalpies for Ti1−xAlxN and Al1−yTayN, with maximum values of 0.25 eV/atom and 0.30 eV/atom, respectively, but negative values for Ti1−yTayN over the whole composition range. The difference in lattice parameters obtained from experiments and ab initio calculations is within ∼1%.