Mosaic and facet structures of epitaxial MnO films on Au (110)

Growth and annealing behavior of epitaxial MnO films on an Au (110)–(1 × 2) substrate have been studied by means of Auger electron spectroscopy, low energy electron diffraction, and scanning tunneling microscopy. MnO (110) films have been successfully grown by Mn evaporation in an oxygen atmosphere at room temperature with subsequent annealing to 750 K. Instead of the expected (110)-like diffraction pattern complex mosaic and facet structures are found depending on annealing conditions. The mosaics are misfit-induced and display along [001] directions a misorientation of ± 1.5°. At temperatures around 850 K, mosaics gradually vanish and simultaneously a saw-tooth-like film morphology develops which is formed by ribbons of narrow (100) and (010) MnO facets. At temperatures above 850 K the film partially dewets from the substrate, and the film transforms to three-dimensional MnO islands that have a roof-like shape where large roof sides and small end sides are composed by {100} and by {111} facets, respectively. The experiments corroborate the theoretical predicted tendency of facet formation of MnO (110) surfaces.