A new process for the development of hard and stable sputtered amorphous carbon films

We have developed a new process for building up thick and stable amorphous carbon films (a-C) rich in sp(3) bonds with high hardness and controllable values of internal stress. The films were prepared by rf magnetron sputteri ng in multilayers (sequential thin layers with alternating positive and neg ative substrate bias voltage, V-b). Detailed analysis of in situ spectrosco pic ellipsometry data, obtained in the energy range 1.5-5.5 eV, based on di fferent models and the study of density and stress within the individual la yers, provide valuable information about the growth and stress relaxation m echanisms in these systems. In addition, nanoindentation measurements show an improvement in the elastic properties of the multilayered a-C films comp ared with the a-C films developed solely with negative V-b(rich in sp(3) bo nds). In view of the obtained results, possible explanations on the origin of the stress relaxation and the enhancement of the elastic properties in m ultilayer a-C films are proposed and discussed. (C) 1999 Elsevier Science L td. All rights reserved.