Plasma enhanced atomic layer deposition of titanium nitride-molybdenum nitride solid solutions

Abstract

As part of improving the tribological properties of TiN-based coatings, researchers have introduced additional elements to the binary TiN system. Addition of a self-lubricating and oxide-forming substitutional element such as Mo to the rock salt TiN system deposited by sputtering has been widely studied. But, the TiN-MoN solid solution system grown by atomic layer deposition (ALD) is yet to be reported. Our current work is motivated by the need to understand and probe the structure of TixMo1−xN solid solutions with respect to the ALD growth process. In this work, thin films of TixMo1−xN (0 ≤ x ≤ 1) were deposited by plasma enhanced atomic layer deposition (PEALD) at 250 °C. Tetrakis(dimethylamido) titanium, bis(tert-butylimido)bis(dimethylamido) molybdenum, and N2 plasma were used as sources for Ti, Mo, and N, respectively. X-ray diffraction revealed nanocrystalline films with a rock salt crystal structure for all compositions of TixMo1−xN except for MoNx, which consisted of multiple phases with cubic MoN being the dominant phase. The elemental composition determined by x-ray photoelectron spectroscopy deviated from the pulse ratio of TiN:MoN. This study revealed that nearly the whole solid solution of the TiN-MoN system can be accessed by PEALD.