ANALYSIS OF THE MECHANICAL RESPONSE OF FILM ON SUBSTRATE SYSTEMS PRESENTING ROUGH INTERFACES

The effect of the mechanical polishing of the substrate surface on whi ch thin films were deposited was investigated by 'in situ' tensile tes ts. These tests, performed in a Scanning Electron Microscope, showed d ifferent responses through cracking and debonding behaviour of the fil ms, which could be related to the roughness of the substrate surfaces fixed by the granulometry of the polishing paste. The rougher surfaces produced an activation of film cracking and debonding earlier than th e smoother ones. We also observed that the crack activation was depend ent on the direction of the scratches which were produced before the d eposition on the samples surfaces. Two directions of scratches were in vestigated, perpendicular and parallel to the sample tensile axis. A s imple energy balance gave apparent values of the critical cracking ene rgy of the film/substrate inter-faces. (C) 1998 Elsevier Science S.A.