Strong electronic perturbation of the Cu{111} surface by 7,7′,8,8′-tetracyanoquinonedimethane

We have imaged 7,7',8,8'-tetracyanoquinonedimethane (TCNQ) on the Cu{111} surface at 77 K; using scanning tunneling microscopy. TCNQ forms molecular chains along the steps at extremely low surface coverages. Oriented adsorption of TCNQ occurs along both the top and the bottom of the Cu steps in which the long molecular axis is parallel to the steps. Monolayer films on the terraces nucleate from TCNQ adsorbed at the steps. Ordered domains of TCNQ coexist with regions of disorder within the monolayer. We find that TCNQ strongly and anisotropically perturbs the local density of electronic states on the Cu{111} surface. These molecular perturbations of the surface determine the ordering of TCNQ on the Cu terraces. (C) 1998 Published by Elsevier Science B.V. All rights reserved.