Scanning tunneling microscope-induced molecular motion and its effect on the image formation

The effect of tip-induced molecular motion on the appearance of scanning tunneling microscope (STM) images of anthracene on Ag(110) was investigated for various tunneling parameters and at various temperatures. At 50 K, isolated molecules can be imaged at a high tunneling resistance. For an increased tip-molecule interaction at a decreased resistance, apparent one-dimensional and two-dimensional molecular superstructures arise in the STM images that are due to an interplay between tip-induced motion, transient binding at specific substrate sites and repeated imaging of a molecule. At an even higher tip-molecule interaction strength, molecules can be dragged over the surface such that an atomically resolved substrate lattice is discernible. The slid molecule acts as an amplifier of the charge corrugation of the metallic surface. (C) 1998 Elsevier Science B.V. All rights reserved.