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

Ab initio calculations of quaternary alloys were used to predict the phase stability of (Ti1-xAlx)(1-y)TayN. 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 degrees 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 similar to 1%. (C) 2010 American Institute of Physics. [doi:10.1063/1.3495783]