Mechanical and thermophysical properties of diamond-like carbon (DLC) films with different sp3/sp2 ratios

In this paper we present the results of a study of the mechanical and thermal properties of hydrogenated amorphous carbon (a-C:H) films. The hardness and Young's modulus of the films show a rough dependence on the ratio, while the thermal expansion coefficient of the films is a definite function of the ratio. In fact, it is shown that the thermal expansion coefficient at low temperature (below 130 K) increases with decreasing ratio. In turn, the thermal conductivity depends on the number of sp3 sites, although further investigations are needed to detail this dependence. The mechanical properties are indirectly correlated with the thermal ones, since both are sensitive to the sp3 amount.