Microstructure and composition of titanium nitride formed by ion beam enhanced nitrogen sorption of evaporated titanium under argon ion irradiation

Deposition of titanium nitride by ion beam-assisted evaporation (IBAD) is possible by two methods. One is evaporation of the metal under bombardment with nitrogen ions at a low gas pressure. The metal is converted to the nitride by implantation of the ions. The other method is evaporation of the metal in an atmosphere of nitrogen gas under bombardment with rare gas ions. The metal reacts with gas molecules from the ambient atmosphere. The features of the obtained TiN films strongly depend on the process mode. In the present study, TiN films prepared by gas sorption under argon ion bombardment are dealt with. The ion energies were in the medium-to-high energy regime of IBAD (> 10 keV). Owing to the high mass of the bombarding species and a comparatively high energy, the TiN films are subject to heavy radiation damaging during deposition. This influences the microstructure and composition of the films. Argon ion irradiation leads to a reduction in contamination by residual gas. The oxygen content is reduced from 10-20 at.% down to below 5 at.%. On the other hand, argon is incorporated up to 6 at.%. The crystal orientation changes from [111] to [100], and a fiber texture develops. The grain size increases from approximate to 10 nm without ion bombardment up to 300 nm at high ion current densities. Without ion bombardment and at very low irradiation intensities, the material develops a fine-grained structure. With increasing ion irradiation intensity, the grains grow as large columns. (C) 1998 Elsevier Science S.A. All rights reserved.