Principle and application of the constant strain rate tensile test with in situ scanning electron microscopy for evaluation of the adhesion of films

Based on the theory of mechanics of materials, a constant strain rate tensile test with in situ scanning electron microscopy (SEM) for measuring the adhesion of PVD films was developed, and the adhesion of a film to a substrate was determined in terms of the shear strain energy of the film during the elongation of the film/substrate combination, i.e. the adhesion depends on the elongation ΔL of the film/substrate combination. The adhesion of three different TiN films prepared by different processes was evaluated by the constant strain rate tensile test with in situ SEM and the conventional scratch test. The results of the two tests show that (1) when the films are thin the adhesion values are in good agreement, but for the thick films with increasing thickness the adhesion decreases in the tensile test while the adhesion first increases and then decreases in the scratch test and (2) for three different TiN films of the same thickness, the identical adhesion order was obtained in the two tests.