Growth and surface morphology: epitaxial MgO films and the Ag(1,1,19) substrate

The morphology of Ag(1,1,19) and the growth of thin MgO layers on it, mostly at room temperature, was investigated by LEED spot profile analysis. These measurements have been supplemented by UPS, XPS and EELS data in order to clarify the electronic structure of the films. Our LEED analysis shows that only steps of monoatomic height are formed on the vicinal Ag surface with a geometric terrace width distribution. The 2 monolayer (ML) thick MgO film does not completely cover the substrate. It forms pyramidal clusters on the surface. Thicker films are closed, and the coexistence of a stepped MgO film with the formation of mosaics is observed. At 5 ML about half of the MgO film consists of mosaics and of non-tilted MgO-crystallites. Their steps are mostly one atom high, with edges that point on average both in non-polar and in polar directions. The influence of the substrate structure on the morphology of the MgO films is discussed.