Dewetting at the edge of a thin NiO-film on Si by swift heavy ion irradiation

We have investigated dewetting along a straight edge of a thin NiO-film on a Si-wafer induced by irradiation with 4.8 MeV/u Au-ions at room temperature. Both, the retreat of the edge as well as the opening and growth of circular holes in the film were monitored using our in-situ high resolution scanning electron microscope at the UNILAC accelerator at the Helmholtz Centre for Heavy Ion Research in Darmstadt. The “dewetting kinetics” (dependence of the retreated length and the hole radius on the ion fluence) are compared to previously published results on dewetting of poly-crystalline (Au) and glassy (polymer) films. In the present case the dewetting kinetics compare well with those observed for isothermal dewetting of the highly viscous polymer films, presumed that the role of time in thermally induced dewetting is taken over by the ion fluence in ion induced dewetting. Both, from the dewetting kinetics and the shape of the remaining NiO-traces in the dewetted area in front of the retreating edge, we conclude that the presently observed swift heavy ion induced dewetting occurs by interfacial slipping. It occurs in spatially and timely separated steps in the transiently molten single ion tracks, where the required reduction of the viscosity of NiO is achieved.