POLAR SURFACES OF OXIDES - REACTIVITY AND RECONSTRUCTION

Polar oxide (111) surfaces are prepared on thin films of NiO, CoO and FeO. In the limit of completely ionic rock salt type crystal structure s these (111) surfaces, whether they are oxygen or metal terminated, s how a tendency for reconstruction. We show that the unreconstructed po lar surfaces are OH covered, and, after OH removal, the surface recons tructs. We show that this is true for NiO(111). For CoO(111) the stabi lity of the oxide film does not allow the removal of OH, so that the r econstruction cannot be observed. The FeO(111) surface is permanently reconstructed and we show that for FeO(111) grown on Fe(110) the surfa ce is not of Fe3O4(111) type.