Phase contrast and attraction–repulsion transition in tapping mode atomic force microscopy

Abstract

The origin of phase contrast in tapping mode (TM) atomic force microscopy (AFM) images has been a persistent issue of concern to many TM-AFM users. In the present study, it is revealed experimentally that phase contrast relates principally to large phase differences between regions of attractive and repulsive dominated probe–sample interactions at the attraction–repulsion transition point rather than variations in energy dissipation due to shifting probe–sample interactions. To provide a rational basis for characterizing phase contrast we demonstrate that the length of the attractive-dominated region in amplitude–phase-distance (apd) data can not only help to determine whether a reliable phase image can be obtained on a particular sample surface, but also provide a quantitative “fingerprint” for a sample surface. We term this quantity the attraction-dominated region length.