Distinguishing Elastic Shear Deformation from Friction on the Surfaces of Molecular Crystals
Vivek Kalihari,1 Greg Haugstad2 and C. Daniel Frisbie1
1Department of Chemical Engineering and Materials
Science, University of Minnesota, 421 Washington Avenue SE and 2Characterization
Facility, Institute of Technology, University of Minnesota, 100 Union Street SE,
Minneapolis, Minnesota 55455
Elastic deformation on the surfaces of molecular crystals can be imaged using a variant of lateral force microscopy in which the tip is scanned parallel to the cantilever axis. The shear force transverse to this direction has a distinctly different origin than the friction force as determined by the tip velocity and temperature dependence of the cantilever torque. An elastic deformation model for the tip-sample interaction predicts the crystallographic anisotropy of the transverse shear contrast, establishing its connection with the relative magnitude of the in-plane elastic tensor components.