SCANNING-TUNNELING-MICROSCOPY ON THE GROWTH OF ORDERED NIO LAYERS ON AU(111)

Experiments are described, where by deposition of Ni from a Knudsen-type effusion cell in an O2 atmosphere onto an Au(111) substrate epitaxial and ordered NiO layers are formed. By analyzing the surfaces with scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) it is found for room temperature condensation a three-domain NiO(100) film, while for deposition on a heated (300-degrees-C) substrate NiO(111) is obtained. In the latter case three-dimensional NiO(111) crystallites and a thin smooth NiO(111) structure showing a p(2 x 2) reconstruction is observed. A p(2 x 2) reconstruction is theoretically expected, if the surface is composed of octopolar subunits ((NiO)4), which overcomes the problem of Madelung instability of a polar surface.