Imaging of atomic-scale structure of oxide surfaces and adsorbed molecules by noncontact atomic force microscopy

Atom-resolved images of a TiO2 110.- 1=1.surface and individual formate and acetate ions adsorbed on the surface were obtained by noncontact atomic force microscopy NC-AFM.in ultrahigh vacuum. In contrast to previous scanning tunneling microscopic studies imaging five-fold coordinated Ti atoms, outermost atoms of bridge-bound oxygen ridges of the surface were resolved as protruding rows by NC-AFM. High-resolution image of the surface revealed that the bridging oxygen atoms on terraces ordered in a 1=1.periodicity. Randomly distributed point and multiple defects of oxygen atoms were also imaged as dark spots. The 2=1.overlayer of formate and acetate ions were resolved as ordered bright spots. Dispersed formate ions at a low coverage were also observed as bright spots between the bridging oxygen ridges along the w001xdirection. q1999 Elsevier Science B.V. All rights reserved.