Impact of Bidirectional Charge Transfer and Molecular Distortions on the Electronic Structure of a Metal-Organic Interface

(Received 31 August 2007; published 18 December 2007)Interface energetics are of fundamental importance in organic and molecular electronics. By combiningcomplementary experimental techniques and first-principles calculations, we resolve the complex inter-play among several interfacial phenomena that collectively determine the electronic structure of the strongelectron acceptor tetrafluoro-tetracyanoquinodimethane chemisorbed on copper. The combination ofadsorption-induced geometric distortion of the molecules, metal-to-molecule charge transfer, andmolecule-to-metal back transfer leads to a net increase of the metal work function.