Misfit dislocation networks at the Ag/MgO(001) interface were investigated by applying grazing-incidence X-ray diffraction to Ag films of various thicknesses between 10 and 150nm. The latter were deposited onto MgO(001) surfaces with various step densities, at room temperature, by means of molecular beam epitaxy. They were analyzed after growth and after annealing at increasing temperatures. A square network of edge dislocations was found to relieve the 3% lattice misfit between Ag and MgO. The dislocation lines were found to be oriented along <110> directions, with an a/2[110] Burgers vector. Quantitative analysis showed that the substrate deformed according to elasticity theory. The as-grown Ag films contained stacking faults and twins, in numbers that increased with increasing substrate surface-step density. Annealing the films at 300C eliminated the stacking faults. Annealing at higher temperatures led to recrystallization of the Ag epilayers, as well as to an improved ordering of the dislocation network. With increasing temperature, the period of the dislocation network instantaneously adapted to suit the actual lattice parameter misfit. After cooling, a large residual deformation was found in the Ag, and this was smaller when the substrate step-density was greater. This was explained in terms of an energy barrier to the nucleation of misfit dislocations.

Misfit Dislocation Network at the Ag/MgO(001) Interface: a Grazing-Incidence X-Ray Scattering Study. G.Renaud, P.Guénard, A.Barbier: Physical Review B, 1998, 58[11], 7310-8