The formation of chromium/nitrogen phases by nitrogen ion implantation during chromium deposition as a function of ion-to-atom arrival ratio

Abstract

Nitrogen-containing phases of chromium can be formed when chromium films deposited from the vapor phase are bombarded with an intense beam of nitrogen ions. In the present paper, formation of Cr/N-phases with ion bombardment with a comparatively high ion energy is discussed. Chromium was electron beam evaporated onto silicon during bombardment with 30 keV nitrogen ions. Ion flux and atom deposition rate were varied over a wide range. At low I/A (ion-to-atom) arrival ratio, nitrogen-containing chromium films were formed. At high I/A-ratios, monophase CrN was obtained. In the transition between these phases, phase mixtures of Cr(N), Cr 2N and CrN were formed. The results show that phase formation is mainly due to ion implantation. By contrast to titanium nitride, reactions with adsorbed gases do not play a role. It turns out that phase formation follows the equilibrium phase diagrams and is a direct function of the I/A-ratio. The regions of existence of the different phases in the deposition rate / ion current density diagram are separated by iso-I/A-lines.