Rheological analysis of creep in hydrogenated amorphous carbon films

We present a nanoindentation study to detect time-dependent deformations in non-polymeric hydrogenated amorphous carbon films. When the bonded hydrogen content increases from 18 to 36 at.%, as measured by Fourier transform infrared spectroscopy, we find that the film becomes less graphitic and softer. Moreover, its hardness shows a larger sensitivity to strain rate and the film with the higher hydrogen content also exhibits a larger and slower creep deformation when subjected to a step-loading experiment. The creep data compares well to the Burgess model and we discuss the influence of Van der Waals bonds on the deformation of the carbon network.