Effects of bias on surface properties of TiN films fabricated by hollow cathode discharge

Titanium nitride (TiN) films have been deposited on AISI 304 stainless steel substrates using hollow cathode reactive plasma vapor deposition. Titanium is introduced by sputtering the Ti cathode nozzle and TiN is formed in the presence of a nitrogen plasma excited by radio frequency. The substrate bias voltage is varied from $0to−300V$ to investigate its effect on the mechanical and structural properties of the films. X-ray diffraction results show the formation of TiN (111) and $Ti2N$ (220) phases in the films. The sample bias has a critical influence on the thickness of the deposited films. The bias of $−200V$ leads to the thickest films (about $1680nm$⁠) and the deposition rate is $18.7nm∕min$⁠. The microhardness, root-mean-square (rms) roughness values, and tribological properties also exhibit nonlinear relationship with increasing bias voltages. The highest hardness of about 1027 hardness vickers and best wear resistance are achieved at a bias voltage of $−100V$⁠. Atomic force microscopy results reveal the lowest rms surface roughness of $3.19nm$ when the bias voltage is $−200V$⁠.