Ž . Diamond and Related Materials 10 2001 10701075 A study of microstructure and nanomechanical properties of silicon incorporated DLC films deposited on silicon substrates J.F. Zhao a, , P. Lemoine a , Z.H. Liu b , J.P. Quinn a , P. Maguire a , J.A. McLaughlin a a NIBEC, School of Electrical and Mechanical Engineering, Uni ersity of Ulster, Shore Road, Newtownabbey, County Antrim, BT37 0QB, Northern Ireland, UK b MXT Inc., 1744 William Street, Suite 104, Montreal, Quebec H3J 1R4, Canada Abstract Ž . Silicon incorporation into DLC films prepared by plasma enhanced chemical vapour deposition PECVD was studied by a combination of surface analysis methods and nanomechanical measurements; namely XPS, Raman spectroscopy and nanoinden- tation. Addition of silicon into the films leads to an increase in the sp 3 contribution, as measured from XPS analysis, and a decrease in the Raman band intensity ratio I I . These changes are consistent with an evolving C C bond network. The D G mechanical properties were first studied as a function of film thickness and indentation depth to assess the effect of substrate proximity. Silicon incorporation produces films with lower hardness and Young’s modulus. It is suggested that, for such a PECVD process, the weakening of the mechanical properties is caused by the increased hydrogen content in the doped films, as shown by the increased Raman background slope. These tendencies are attributable to the development of polymer-like chains, which weakens the inter-molecular structure of the films. 2001 Elsevier Science B.V. All rights reserved. Keywords: DLC film; Silicon incorporation; XPS; Nanoindentation 1. Introduction Ž . Diamond-like carbon DLC thin films can display high hardness with high wear resistance 1 , chemical inertness with corrosive resistance 2,3 and low surface energy 4 with potential applications in the field of protective coatings. However, examples of practical ap- plications remain few since DLC presents a relatively high coefficient of friction at atmospheric ambient and internal stresses, of approximately 3 GPa 5 , that can Corresponding author. Tel.: 44-28-90368997; fax: 44-28- 90366863. Ž . E-mail address: junfu@nibec-s1.nibec.ulst.ac.uk J.F. Zhao . lead to adhesive failure. These problems can be par- tially overcome by doping DLC 6 8 , particularly with silicon which has been shown to reduce the internal stress below 1 GPa 9 . However, the effect of silicon on the mechanical properties of DLC has not been firmly established 7,9 11 and seems to depend on the silicon concentration and preparing techniques. In a previous work 12 , we have found that a small amount of silicon incorporation decreased the hardness and elastic modulus of films deposited on ceramic sub- strates. We also measured the silicon-induced stress- relief for ultra-thin films deposited on silicon can- tilevers 13 . In this study, we studied the effects of high Ž . silicon content up to 20.23 at.% incorporation on the microstructure and nanomechanical properties of DLC 0925-963501$ - see front matter 2001 Elsevier Science B.V. All rights reserved. Ž . PII: S 0 9 2 5 - 9 6 3 5 00 00544-6