Comparative study of anneal-induced modifications of amorphous carbon films deposited by dc magnetron sputtering at different argon plasma pressures

This work investigates the evolution of the structural, mechanical and trib ological properties of amorphous carbon films (a-C) undergoing thermal anne aling. Two different types of a-C film were studied: hard, stressed and den se films, henceforth called 'diamond-like', and soft, more relaxed and less dense films, called 'polymer-like'. The two sets of films were deposited b y de magnetron sputtering at 0.36 and 1.4Pa argon plasma pressures, respect ively, and both were annealed in vacuum for Ih at temperatures between 300 and 700 degrees C. Raman results provided indications of a remarkable incre ase of the sp(2) hybridized domains, that occurs mainly at temperatures hig her than 400 degrees C for the diamond-like films and in a continuous way f or the polymer-like films. The friction coefficient of both types of film a pproaches the same value with increasing temperature, whereas the surface r oughness is nearly constant. For diamond-like films, the hardness and compr essive internal stress are nearly constant up to 500 degrees C, and then un dergo a fast decrease. In contrast, the hardness of the polymer-like film c ontinuously decreases with temperature, whereas the compressive stress rema ins constant. (C) 2000 Elsevier Science S.A. All rights reserved.