Dynamic force microscopy study of 3,4,9,10-perylenetetracarboxylic dianhydride on KBr(001)

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Abstract
A scanning force microscope operated in the dynamic force mode has been used to analyze the arrangement of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) molecules on a KBr(001) surface. The molecules do not form a close-packed layer but crystallites with the shape of truncated pyramids. Even after depositing only 0.3 molecular layers of PTCDA, these crystallites have a height of 20–30 molecular layers. We have been able to resolve individual molecules of the top layer and on some of the crystallites facets. The results agree with the known “herringbone” structure of the bulk. A comparison of the experimentally observed contrast to a simple force field calculation based on semiempirical interaction potentials is given.