Structural relaxation at the Ag/MgO (001) interface measured by grazing incidence x-ray diffraction

Abstract

Metal/ceramic interfaces are used in various technologically important areas such as thin film technology, electronic packaging, composites, protective coatings, catalysis and the glass industry. The mechanical properties of these systems strongly depend on the defects at the interface such as misfit dislocations. The Ag/MgO interface has been chosen as a model of such interfaces. If one assumes first that Ag atoms preferentially bond with only one type of ion Mg or O, the 0-lattice theory predicts a misfit dislocation network which is a square array of edge dislocations 9.5 nm apart and aligned along (110) directions with 1/2 (110) Burgers vectors. Another geometry might be expected in the case of similar bond strength of Ag-O and Ag-Mg. In this case the points of best match produce a square array of 6.7 nm parallel to (100) directions with 1/2 (100) Burgers vectors. Recently Trampert et al. have observed dislocations at the Ag/MgO interface by High Resolution Transmission Microscopy (HRTEM). From observations at (100) cross sections they claim that the dislocation network is of the latter type (dislocation lines along (100)), arguing that the observed dislocations are equally spaced in this direction. But lattice images show only weakly localized end-on dislocations whichmore » could be the result of sample preparation. The (100) project of the Burgers vector is found to be 1/2(100), from which they infer that the misfit dislocations separate the regions where Ag is on O from those where Ag is on Mg. However the (100) Burgers vector projection is the same for the two networks. Therefore there is not yet clear evidence for the orientation of the dislocation network in this system. In an attempt to determine unambiguously the network orientation and Burgers vector, the authors present here a first study of the dislocation network at this interface using grazing incidence X-ray diffraction.« less