Substrate temperature effects on the microhardness and adhesion of diamond-like thin films

Diamond-like films were deposited on silicon substrates by r.f. plasma-enhanced chemical vapor deposition from gas methane. In this study, the substrate temperature, T-s, was varied in a wide range from 20 to 370 degrees C while maintaining fixed other important process parameters such as r.f. power (70 W) or pressure (2.5 Pa). The increase of T-s causes an increase of the sp(2)/(sp(2) + sp(3)) bonded carbon ratio and a decrease of the hydrogen content. These changes produce a great modification of the mechanical properties: microhardness, friction coefficient and adhesion. The variations of mechanical properties with T-s correlate well with the sp(2)/(sp(2) + sp(3)) bonded carbon ratio and the hydrogen content in the films showing a gradual transformation of the diamondlike structure into a more sp(2)-rich one. (C) 1999 Elsevier Science S.A. All rights reserved.