Linear surface smoothening of (Ti0.48Al0.52)N thin films grown on rough substrates

The evolution of surface roughness during the growth of sputter-deposited solid solution (Ti0.48Al0.52)N films on rough high-speed-steel (HSS) substrates has been studied by atomic force microscopy. It has been revealed that the growing (Ti0.48Al0.52)N∕HSS film experiences a continuous surface smoothening. Scaling analyses along with surface power spectra calculation of the (Ti0.48Al0.52)N films grown on smooth Si(100) substrates under the same deposition conditions indicate that this surface smoothening is linear and can be explained by a simple linear equation with surface diffusion as the smoothening mechanism and shot noise as the roughening effect. The observed linear surface smoothening in (Ti0.48Al0.52)N∕HSS films has also been confirmed by our numerical simulations of the film growth using real HSS and Si(100) substrates as their initial growth conditions and can be understood in terms of the competition between the surface-diffusion-induced decrease in substrate roughness contribution and the noise-driven roughening effect.