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.