Structure and properties of Si incorporated tetrahedral amorphous carbon films prepared by hybrid filtered vacuum arc process

Abstract

The mechanical properties and atomic bond structure of Si incorporated into tetrahedral amorphous carbon (ta-C) films were investigated. The films were deposited by a filtered vacuum are of graphite with simultaneous sputtering of Si. The Si concentration in the film could be controlled by changing the flow rate of the Ar sputtering gas, It was observed that the incorporated Si preferentially substituted sp(3) bonded carbon when the Si concentration was less than 2.5 at.%. Since the Si-C bond generated by the substitution was weaker than C-C bond, the Si incorporation could cause the relaxation of nearby distorted C-C bonds by inducing large strain in the Si-C bond. This structural change resulted in a significant decrease in the residual compressive stress in this Si concentration range. In contrast, the incorporated Si which has only sp3 hybridization, generated the weaker Si-C bonds-without breaking the three-dimensional interlinks of the atomic bond structure. Hence, the hardness and the plane strain modulus gradually decreased with Si incorporation. The saturated mechanical properties observed when the Si concentration was higher than approximately 10 at.% are due to the formation of a large amount of SiC phase in the deposited film. (C) 2002 Elsevier Science B.V. All rights reserved.