Evaluating the interfacial toughness of GaN-on-diamond with an improved analysis using nanoindentation

An improved analysis of the interfacial toughness using nanoindentation induced blistering of thin films on stiff substrates is demonstrated on GaN-on-diamond. The Hutchinson-Suo analysis requires accurate measurement of blister dimensions, conventionally measured using 2-D line-scans from 3-D topographical maps. The new meteorology overcomes shortcomings of this technique by fitting the 3-D analytical solution of a clamped Kicrchoff plate to the topological map of the blister. This allowed for quantification of interfacial toughness of smaller blisters in GaN-on-diamond, previously assumed invalid for analysis due to inadequacies of the line-scan analysis. Three samples were investigated and found to have interfacial toughness ranging from 0.6–1 J m −2 . Additionally, the relationship between residual stress in the GaN and interfacial toughness was investigated using photoluminescence spectroscopy . In all cases, the GaN was found to be under increased compression at the diamond interface by up to -0.81 GPa, although no correlation with interfacial toughness was observed.