Mechanical characterisation and properties of DLC films

Abstract

This chapter reviews the mechanical characteristics of diamond-like carbon (DLC) materials. It examines the motivations behind such studies, presents the experimental methods used to characterise them and discusses the main findings. DLC usually present wide-ranging mechanical properties, with the best specimen being tetrahedrally bonded in some cases approaching the performances of diamond. The chapter also discusses the effect of internal stress, doping and layering. However, we note a number of remaining issues, which concern mainly the nanoindentation protocols for ultra-thin layers, a significant aspect of the problem being the simultaneous effect of substrate deformations and tip blunting. To that end, a new analytical method was designed which extracts the intrinsic film's hardness HF. Surveying a variety of DLC layers, we find that the HF value tends to increase with thickness, at least up to 50 nm. This result is supported by complementary non-mechanical analysis. It is also observed elsewhere and is consistent with current growth models. Such independent correlation of the intrinsic characteristics of very thin DLC layers is a difficult task. It is, however, of importance to improve our understanding of the growth and bonding structure of DLC. © 2008 Springer Science + Business Media, LLC.