Compositional and structural evolution of sputtered Ti-Al-N

The compositional and structural evolution of Ti-Al-N thin films as a function of the total working gas pressure (p(T)), the N-2-to-total pressure ratio (p(N2)/p(T)), the substrate-to-target distance (ST), the substrate position,the magnetron power current (I-m), the externally applied magnetic field, and the energy and the ion-to-metal flux ratio of the ion bombardment during reactive sputtering of a Ti0.5Al0.5 target is investigated in detail. Based on this variation we propose that the different poisoning states of the Ti and At particles of the powder-metallurgically prepared Ti0.5Al0.5 target in addition to scattering and angular losses of the sputter flux cause a significant modification in the Al/Ti ratio of the deposited thin films ranging from similar to 1.05 to 2.15. The compositional variation induces a corresponding structural modification between single-phase cubic, mixed cubic-hexagonal and single-phase hexagonal. However, the maximum At content for single-phase cubic Ti1-xAlxN strongly depends on the deposition conditions and was obtained with x = 0.66, for the coating deposited at 500 degrees C, p(T) = 0.4 Pa, ST = 85 mm, and p(N2)/p(T) = 17%. Our results show, that in particular, the N-2-to-total pressure ratio in combination with the sputtering power density of the Ti0.5Al0.5 compound target has a pronounced effect on the Al/Ti ratio and the structure development of the coatings prepared. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.