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 ( 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 Ti 0.5Al 0.5 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 Ti 0.5Al 0.5 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 Ti 1−xAl xN strongly depends on the deposition conditions and was obtained with x = 0.66, for the coating deposited at 500 °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 Ti 0.5Al 0.5 compound target has a pronounced effect on the Al/Ti ratio and the structure development of the coatings prepared.