Effects of Surface Contamination Layers and Roughness on the Determination of Mechanical Properties of Thin Films Using Nanoindentation

Nanoindentation measurements on TiAlN, CrN, a-C:H:Me, and TiN, deposited on steel substrates have been performed. It was found that the resulting surface roughness/morphology after deposition significantly affects the measurements of nanomechanical properties, while measurements of these properties on the surface may be significantly different than the bulk portion of the coating, exhibiting a lower nanohardness due to the existence of a surface contamination layer. A simple method is proposed for accurately measuring the nanomechanical properties of coatings alleviating the need for excessive statistical analysis and the issues that arise from surface topography and the presence of surface and contamination layers on thin films.