Relation between delamination of thin flims and backward deviation of load–displacement curves under repeating nanoindentation

Abstract The delamination behavior of sputter coated TiN and AlN films have been examined from the load–displacement curves under repeated nanoindentation loading. When the penetration depth is either much larger or much smaller than the film thickness, the curve progresses in forward direction that represents the deformation of the substrate or film. On the other hand, a backward deviation is observed when the penetration depth is comparable with the film thickness. Observation of the indents by a scanning electron microscope (SEM) and an atomic force microscope (AFM) shows that cracking and extrusion of the film occur when the backward deviation appears. It suggests that the partially delaminated film releases the compressive residual stress and causes an upward bending due to the elongation of the delamintated film, which resists the penetration of the indenter in the consecutive cycle.