Epitaxial stabilization of MnO(111) overlayers on a Pd(100) surface

The growth of epitaxial MnO(100) and MnO(111) layers on Pd(100) surface has been investigated by spot-profile analysis low-energy electron diffraction, dynamic atomic force microscopy, photoemission and high-resolution electron energy loss spectroscopy, and density functional theory. We have found that despite the large lattice mismatch to the Pd(100) substrate, the MnO(100) layers are kinetically stabilized at low temperatures (⩽350°C) and at oxygen pressures between 2×10⁻⁷ and 5×10⁻⁷mbar. Annealing in ultrahigh vacuum at 650°C or, alternatively, deposition of manganese metal in oxygen pressure <1×10⁻⁷mbar causes the transformation of the MnO(100) to a polar MnO(111) surface, which is decorated by triangular pyramids with (100) side facets. It is suggested that the growth of MnO(111) layers is energetically preferred over MnO(100) due to the epitaxial stabilization at the metal-oxide interface.