Misfit relaxation by dislocations in perovskite SrRuO3/SrTiO3 (001) heterostructure with low lattice mismatch (f = 0.64%) was studied. Pure edge misfit dislocations with a Burgers vector of the a<011> type were found to be the major interfacial defects responsible for the misfit relief. They were introduced by half-loops expansion from the film surface as well as by extension of pre-existing dislocations in the substrate. These 45° misfit dislocations formed along the <100> directions in a rectangular grid pattern, preferentially at surface steps of the TiO2-terminated SrTiO3 substrate. At film thicknesses much higher than the critical film thickness (hc), however, the misfit dislocation spacing was not reduced but saturated in a nearly constant value far above the equilibrium prediction (~61.4nm). The saturated spacing of misfit dislocations corresponds to roughly the ledge distances on the SrTiO3 surface (120–150nm). It was suggested that difficulties in the multiplication of misfit dislocations by the already-formed ones lead to the abnormally high residual strain. Further accumulation of residual strain resulted in microstructural modifications such as surface undulations and the two-layered structure along the growth direction.

Misfit Strain Relaxation by Dislocations in SrRuO3/SrTiO3 (001) Hetero-Epitaxy. S.H.Oh, C.G.Park: Journal of Applied Physics, 2004, 95[9], 4691-704