High-resolution transmission electron microscopy imaging of misfit-dislocation networks at Cu-MgO and Cu-MnO interfaces

Misfit dislocation networks at Cu-MgO and Cu-MnO {111}(metal)//{111}(oxide) interfaces were studied with high-resolution transmission electron microscopy. Experimental results were compared with image simulations of tentative atomic structures of the interface region derived from lattice statics calculations. The calculations take into account the two-dimensional misfit at the interface, which is necessary given the high misfit and short repeat distances at the interfaces. The lattice statics calculations use simplified potentials across the interface which capture essential characteristics that have emerged from recent experimental results and ab-initio calculations. Trigonal networks of edge misfit locations with Burgers vectors 1/6[112] and line direction [110] follow from these calculations. These misfit-dislocation networks have associated strain fields in the metal, stretching out from the interface with approximately the repeat distance along the interface. These strain fields show up in image simulations (along [110] and [112] directions) by characteristic but subtle periodic changes in contrast and brightness as well as small displacements of spots. The experimental images, also along [110] and [112] directions, showed similar characteristics but they were difficult to detect, especially along [112] for the Cu-MnO interface, and may easily be missed. Judging from this evidence we conclude that the proposed misfit-dislocation structure is in fact present at these interfaces.