Influence of the local adsorption environment on the intramolecular contrast of organic molecules in noncontact atomic force microscopy

摘要

Thin epitaxial layers of the organic molecule 3,4,9,10-perylenetetracarboxylic dianhydrite on a Cu(111) surface were imaged using noncontact atomic force microscopy in ultrahigh vacuum. The second layer molecules show a distinct intramolecular structure, which is compared to the internal charge distribution of the molecule. The molecules in the first layer, though, exhibit no detectable intramolecular features. This effect is discussed with respect to the presence of the metallic substrate for the first layer molecules, which demonstrates the strong influence of the local adsorption environment on the internal electronic properties of organic molecules.