An explicit expression for the elastic potential energy, Wp, stored in a thin foil by a dissociated dislocation running parallel to the free surface was obtained assuming isotropic elasticity. It was used to explain the metastable elastic equilibrium of a 60° dislocation in an ultra-thin Si foil when the fault plane was slightly inclined with respect to the free surface. The energy, Wp, depended in particular upon the positions of the two partials in the foil and upon the thickness, h; a situation not previously fully considered. For such ultra-thin foils, optimising the observation of partial dislocation cores at near-atomic resolution, the theory predicted rapid changes, with h, of the separation distance, S. This result was in accord with previous experimental observations of S, obtained using the so-called forbidden-reflection lattice imaging technique.

The Elastic Potential Energy of a Thin Foil Deformed by an In-Plane 60° Dislocation. S.Youssef, R.Bonnet: Philosophical Magazine, 2007, 87[31], 4935-48