Imaging Benzene Molecules and Phenyl Radicals on Cu111

In two sets of experiments built on the work of Brian Bent, we imaged benzene molecules and phenyl radicals on the Cu111 surface at low coverage and low temperature. 1 The experiments allowed us to see how mobile molecules on surfaces probe the electronic structure of the surface. Bare terraces of the Cu111 surface appear extremely flat in scanning tunneling microscope images. We are thus able to image the perturbations to the electronic structure caused by steps, defects, and adsorbates. These perturbations determine the structure and dynamics of the adsorbates. Benzene forms ordered structures along step edges at even very low coverages. Adsorbed phenyl radicals form complex pairs, aligned so as to be able to couple to form biphenyl at higher temperature. We discuss the chemical consequences of such substrate-mediated interactions.