Temperature dependence of single-asperity friction for a diamond on diamondlike carbon interface

A variable temperature, ultrahigh vacuum atomic force microscope (AFM) was used to characterize interfacial friction for a single-asperity diamond contact on a diamondlike carbon (DLC) substrate over a nominal substrate temperature range of 90 to 275 K. Calibrated friction force measurements were obtained by analyzing lateral force hysteresis loops as a function of normal force. For sufficiently large normal forces, the lateral force was proportional to the normal force, and a friction coefficient mu could be identified. mu varied approximately linearly with substrate temperature, with mu=0.28 at T=90 K and mu=0.38 at 275 K. These results are compared to other recent variable temperature AFM friction measurements and to theoretical calculations based on the Tomlinson model. This comparison is obscured by large, experimentally uncontrolled temperature differences between the tip and the substrate which inevitably exist in conventional, variable temperature AFMs. A thermal model which can be used to quantitatively estimate these temperature differences is presented. (C) 2010 American Institute of Physics. [doi:10.1063/1.3436564]