Elastic constants of diamond-like amorphous carbon films: the effect of internal stresses

The extreme wear resistance and chemical inertness of tetrahedral, or
diamond-like, amorphous carbon (ta-C) make it a promising material for
wear-resistive mechanical coatings. The unique mechanical behaviour of ta-C
is related to the atomic structure of amorphous carbon and atomic scale
modeling becomes a valuable tool to study both growth mechanisms of ta-C
films and their mechanical properties. Here we report results of atomistic
calculations of elastic constants in ta-C films grown by a realistic
computer simulation of ion-beam deposition. The dependence of the elastic
constants on the ion energy is presented. Similar to the real as-grown
nonequilibrium (not annealed) ta-C films, the simulated structures possess
the high internal compressive stress, which can considerably effect on
elastic constants. An approach employed allows for the stress dependence of
elastic constants to be analysed. We demonstrate the variation of elastic
constants as a function of the internal stress, and therefore the
importance of nonlinear elastic properties in amorphous carbon.