Models of atomic scale contrast in dissipation images of binary ionic surfaces in non-contact atomic force microscopy.

Using model ionic systems and the recently proposed theory of dynamical response at close approach (Kantorovich and Trevethan 2004 Phys. Rev. Lett. 93 236102) in non-contact atomic force microscopy (NC-AFM), we present the results of calculations performed to investigate the formation of atomic scale contrast in dissipation images. The accessible energy states and barriers of the microscopic tip-surface system are determined as a function of tip position above the surface. These are then used along with typical experimental parameters to investigate the dynamical response of the system and mechanisms of atomic scale contrast. We show how the damping signal contrast can appear either correlated or anti-correlated with the topography depending on the distance of closest approach and the system temperature. The dependence of the dissipated energy, and the reversibility of a structural change, on the tip frequency and system temperature is investigated and the relevance of this to single-atom manipulation with the NC-AFM is discussed.