Imaging problems on insulators: What can be learnt from NC-AFM modelling on CaF2?

Abstract.

By combining theoretical modelling with experimental data on CaF₂, we studied the interactions responsible for atomic resolution in this system; we discuss the general significance of these results for imaging other insulators. Theoretical modelling was used to calculate the tip–surface interactions in noncontact atomic force microscopy (NC-AFM) imaging of a charged and neutral CaF₂ (111) surface. The modelling predicts that both the Ca and F sublattices can be imaged depending on the nature of potential from the tip. However, the theoretical scanlines of the surface are characteristic for each sublattice, and a method for determining the sublattice imaged in future experiments is suggested. It was found that atomic resolution was independent of the nature of the background force, and imaging problems with other insulators are likely to be due to surface roughness.