Electric field induced surface diffusion and micro/nano-scale island growth

An experimental study of electric field induced surface diffusion is presented. A stability analysis of conductive surfaces subjected to a normal uniform electric field shows that sufficiently strong electric fields can destabilize a flat surface, similar to strain induced surface evolution in strain mismatched semiconductor thin films. Further, electric field gradients such as those under a sharp electrode or in the fringe field in a capacitor can drive surface diffusion, leading to nano-scale and micro-scale surface structure growth. Experiments are conducted on gold surfaces at elevated temperatures around 250–350 C, subjected to electric fields of the order of 108–109 V=m. Growth of islands as ridges was observed, the height of which was as high as 200 nm. A description of the initial surface normal velocity is developed by using the Maxwell– Rowgoski solution for the fringe field at the edge of a parallel plate capacitor.