Identification of multiple oscillation states of carbon nanotube tipped cantilevers interacting with surfaces in dynamic atomic force microscopy

摘要

Carbon nanotubes (CNTs) have gained increased interest in dynamic atomic force microscopy (dAFM) as sharp, flexible, conducting, nonreactive tips for high-resolution imaging, oxidation lithography, and electrostatic force microscopy. By means of theory and experiments we lay out a map of several distinct tapping mode AFM oscillation states for CNT tipped AFM cantilevers: namely, noncontact attractive regime oscillation, intermittent contact with CNT slipping or pinning, or permanent contact with the CNT in point or line contact with the surface while the cantilever oscillates with large amplitude. Each state represents fundamentally different origins of CNT-surface interactions, CNT tip-substrate dissipation, and phase contrast and has major implications for the use of these probes for imaging, compositional contrast, and lithography. In particular, we present a method that uses energy-dissipation spectroscopy to identify if the CNT slips laterally on the surface or remains pinned in the intermittent contact regime. By comparing phase contrast images and energy dissipation on graphite, graphene oxide, and silicon oxide surfaces, we demonstrate the utility of the method in identifying pinning or slipping of the CNT on the surface in the intermittent contact regime.