In this dissertation, the out-of-equilibrium dynamics of crystalline surfaces have been studied.We have emphasized on solid state dewetting of single crystalline thin films and morphological instabilities induced by electromigration. On an experimental viewpoint, Low Energy Electron Microscopy and Grazing Incidence Small Angle X-ray Scattering provide real time and in situ information. In particular we show that solid state dewetting of Silicon and Germanium thin films onto Silica give rise to dendritic like instabilities driven by the gain of surface/interface energies and kinetically limited by ad-atoms surface diffusion mechanisms. The central role of dewetting front faceting on morphological instabilities is highlighted ; in particular some crystallographic orientations reduce the dewetting front speed and favour stable and straight fronts. The morphological instabilities induced by electromigration on vicinal surfaces of Silicon provide the opportunity to study mono-atomic step-step interactions. We show that these repulsive interactions favour the successive development of a step density wave then a faceting of the whole surface at long times. At last, the self-organized growth of Pd nanostructures onto an oxidized surface of Ni3Al is presented. We end up with some perspectives concerning the dynamics of the solid-solid-vapor triple line as well as the technique of Low Energy Electron Microscopy.
