MICROSCRATCH ANALYSIS OF THE WORK OF ADHESION FOR PT THIN-FILMS ON NIO

The adhesion of as-sputtered Pt thin films to NiO single crystals has been characterized by a continuous microscratch technique. In these experiments, a conical indenter was driven into a 1.2-mu-m thick Pt film at a rate of 15 nm/s, and across the sample surface at a rate of 0.5-mu-m/s, until a load drop was observed indicating that the film had delaminated. Using the width of the scratch track at the point at which the film delaminated from the substrate, the critical load required for delamination, and the area of the delaminated region, a model has been developed to determine the work of adhesion of the Pt/NiO system. This model uses an elastic contact mechanics approach to relate the stresses acting in a scratch experiment to the strain energy released during film delamination. Using this model, the work of adhesion and hence the interfacial fracture toughness have been determined to be 0.023-0.06 J/m2 and 0.07-0.11 MPa square-root M, respectively. These values are in reasonable agreement with those determined by other methods for metal-ceramic systems.