Reflectivity Studies of Thin Au Films and Au Bicrystals with Grain Boundaries

X-ray reflectivity is an ideal method to get information on buried interfaces and, therefore, well suited for the study of artificial grain boundaries in bicrystals. Such bicrystals with (001) twist grain boundaries are produced by hotpressing two thin single-crystal films, one of 25nm thickness and the other of 400nm thickness, in air at 523K for 1–2 hours. The single-crystals are epitaxially grown onto single-crystal NaCl substrates. Our reflectivity studies of the single-crystal films either still on the substrate or dissolved and mounted on a Siwafer and the bicrystals themselves revealed in each case strong diffuse non-specular intensity. The existence of this non-specular intensity can be explained by lateral correlations of atoms which are detected because of an additional component of the scattering vector parallel to the surface. Contributions in the diffuse non-specular intensity originating from the artificial grain boundary could be identified by performing experiments with its in situ formation and destruction through annealing. The non-specular reflectivity is observed to be dependent on the twist angle of the grain boundary.