Scanning tunneling microscopy imaging of NiO(100)(1 × 1) islands embedded in Ag(100)

The imaging of NiO(100)(1 × 1) islands embedded in Ag(100) by scanning tunneling microscopy is addressed. As a function of tunneling conditions and tip termination it is possible to resolve the NiO-vacuum interface, the second oxide layer as well as the NiO-substrate interface with atomic contrast. We find that for sub-monolayer coverages of NiO the oxide islands consist of an essentially defect-free surface layer at the vacuum interface with a number of NiO second layer patches incorporated into the Ag substrate underneath. The oxide layer is surrounded by a rim of a NiO bilayer of monoatomic width. A reduction of the density of states between a NiO monolayer and local NiO bilayer stackings is suggested to be responsible for the observed appearance of mosaic patches at the island surface.

► The three-dimensional structure of the NiO islands is disclosed for coverages < 1ML. ► The first layer at the vacuum interface is defect-free. ► 20-30% of NiO units are incorporated into the Ag substrate below the first layer. ► The oxide layer is surrounded by a rim of a NiO bilayer of monoatomic width.