Stabilization of the pristine reconstructed and unreconstructed MgO(111) polar surface

MgO in the (111) direction shows alternating polar planes of Mg²⁺ and O^2- forming a hexagonal two-dimensional unit cell at the surface. The stabilization of its polar surface as been achieved via (2 x 2), (√3 x √3)R30° and (2√3 x 2√3)R30° reconstruction or hydrogen adatoms. However, alternative surface structure with lower surface roughness is required to use MgO(111) as substrate for thin films deposition. In this work, we present a method to prepare such stable and smooth surface in MgO(111) substrates. We first produce single crystal  (√3 x √3)R30° reconstructed MgO(111) surface by face-to-face annealing in O² environment. We then use dissolution of the top layers in acid to achieve a hydroxylated unreconstructed surface. The structure and stoichiometry of the resulting surfaces are characterized using electron and X-ray diffraction, atomic force microscopy and X-ray photoelectron spectroscopy.