Nanotribological and Nanomechanical Properties of Ultrathin Amorphous Carbon Films Synthesized by Radio Frequency Sputtering

Abstract

The dependence of the nanotribological properties of ultrathin amorphous carbon (a-C) films, deposited on Si(100) substrates by radio frequency sputtering, on their nanomechanical properties was investigated using surface force microscopy. The thickness and nanohardness of the a-C films were found to be in the range of 7–95 nm and 9–44 GPa, respectively. Sharp conical diamond tips with a 90 deg included angle and radius of curvature of about 20 μm and 100 nm were used to perform friction and wear experiments, respectively. The effect of the substrate compliance on the nanomechanical and nanotribological properties of the a-C films is interpreted in terms of the indentation depth and the film thickness. The coefficient of friction and wear rate of the a-C films are related to their nanomechanical properties, thickness, and surface roughness. The dependence of the coefficient of friction on contact load and the dominant friction mechanisms of elastically and plastically deformed films are discussed in light of friction force and surface imaging results. High effective hardness-to-elastic modulus ratio and low surface roughness characterize high wear resistance a-C films. Below a critical load, the steady-state removal rate of the film material is insignificantly small, revealing a predominantly elastic behavior.