A Surface Effect Associated with Dislocation Ribbons

A new surface effect associated with extended dislocations, in materials with small stacking-fault energy, and which consists in a widening of the ribbons at the surface, is discussed from a theoretical point of view and illustrated with observations in graphite and molybdenum sulphide. The effect leads to a method for estimating surface energies. The surface energy of graphite as deduced from the widening effect is in fair agreement with the value found by other methods.