Deposition process, microstructure and mechanical behaviours of RF magnetron sputtered (Ti,Al)N thin films

Abstract

Thin films of (Ti,Al)N with different Al contents were co-deposited using one Ti and one Al targets by radio frequency (RF) pulsed magnetron sputtering. Their composition, microstructure, nanohardness, surface morphology and deposition process were investigated by energy dispersive spectrometer system, X-ray diffraction, nanoindentation, atomic force microscopy and optical emission spectrum. A face cubic centred (fcc) TiN (B1) structure was found in the thin films when Al target power was low. When Al target power was increased, an additional hexagonal AlN (B4) structure appeared. With increasing Al content, the resulting films gradually changed from B1 structure to that of B4, accompanying with decrease of the lattice constant of B1 structure. Simultaneously, the preferred orientation of B4 structural thin films gradually transformed from (111) to (200). The mode of thin films transformed from island to fibre, subsequently to column with increasing Al target power. Optical emission spectrum analysis indicated that Al target surface reached non-metal sputtering mode earlier than that of Ti target under the same deposition parameters, which resulted in a lower sputtering rate of Al target than Ti target and loss of Al content in (Ti,Al)N thin films.