Compositional and structural evolution of sputtered Ti-Al-N

Abstract The compositional and structural evolution of Ti-Al-N thin films as a function of the total working gas pressure (pT), the N2-to-total pressure ratio (pN2/pT), the substrate-to-target distance (ST), the substrate position, the magnetron power current (Im), 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 Al 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 ~ 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 Al 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 °C, pT = 0.4 Pa, ST = 85 mm, and pN2/pT = 17%. Our results show, that in particular, the N2-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.