In-situ investigation of swift heavy ion beam induced dewetting of thin oxide films

Recently we have reported dewetting of thin oxide films on Si during irradiation with swift heavy ions. The dewetting patterns compared surprisingly well with those observed when melting polymer films on Si, although the irradiation was performed at 80 K, far below the melting point of the oxides. Hence, the dewetting processes and driving forces must be similar. In fact, we could identify the same hole nucleation mechanisms as reported for the polymers: heterogeneous nucleation at interfacial defects and spontaneous (homogeneous) nucleation due to (thermal) film density fluctuations. Using our new in-situ high resolution scanning electron microscope at the UNILAC accelerator of GSI, we are now able to follow the history of individual holes and determine their growth kinetics. In our first experiments we could show, that ion induced dewetting exhibits hole growth with rim formation, with the hole area being proportional to the applied ion fluence after the hole has fully evolved. This points at a growth mechanism which is controlled by the dissipation of the material removed from the hole. Capillary forces dominated growth (exponential increase with fluence) could be identified in the early stages of dewetting.