We investigated insulating Cu2N islands grown on Cu(100) by means of combined scanning tunneling microscopy and atomic force microscopy with two vastly different tips: a bare metal tip and a CO-terminated tip. We use scanning tunneling microscopy data as proposed by Choi et al. [T. Choi et al., PRB 78, 035430 (2008).] to unambiguously identify atomic positions. Atomic force microscopy images taken with the two different tips show an inverted contrast over Cu2N. The observed force contrast can be explained with an electrostatic model, where the two tips have dipole moments of opposite directions. This highlights the importance of short-range electrostatic forces in the formation of atomic contrast on polar surfaces in non-contact atomic force microscopy.
Cite
@article{arxiv.1402.5246,
title = {CO Tip Functionalization Inverts Atomic Force Microscopy Contrast via Short-Range Electrostatic Forces},
author = {Maximilian Schneiderbauer and Matthias Emmrich and Alfred J. Weymouth and Franz J. Giessibl},
journal= {arXiv preprint arXiv:1402.5246},
year = {2015}
}