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} s urface at 77 K; using scanning tunneling microscopy. TCNQ forms molecular c hains along the steps at extremely low surface coverages. Oriented adsorpti on of TCNQ occurs along both the top and the bottom of the Cu steps in whic h 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 st rongly and anisotropically perturbs the local density of electronic states on the Cu{111} surface. These molecular perturbations of the surface determ ine the ordering of TCNQ on the Cu terraces. (C) 1998 Published by Elsevier Science B.V. All rights reserved.