Noncontact atomic force microscopy imaging of ultrathin ${\mathrm{Al}}_2{\mathrm{O}}_3$ on NiAl(110)

Noncontact atomic force microscopy (NC-AFM) has been used to image ultrathin film ${\mathrm{Al}}_2{\mathrm{O}}_3$ on NiAl(110). Atomic scale rows were observed with a 9 Å periodicity. This provides support for a previous scanning tunneling microscopy study that concluded that the rows arise from the oxide rather than the underlying substrate. NC-AFM data image domain boundaries in the oxide film as either trenches or ridges, depending on the state of the tip. This suggests that NC-AFM does not simply trace the topography of the surface.