title: Postadsorption Work Function Tuning via Hydrogen Pressure Control.
abstract: The work function of metal substrates can be easily tuned, for instance, by adsorbing layers of molecular electron donors and acceptors. In this work, we discuss the possibility of changing the donor/acceptor mixing ratio reversiblyafteradsorption by choosing a donor/acceptor pair that is coupled via a redox reaction and that is in equilibrium with a surrounding gas phase. We discuss such a situation for the example of tetrafluoro-1,4-benzenediol (TFBD)/tetrafluoro-1,4-benzoquinone (TFBQ), adsorbed on Cu(111) and Ag(111) surfaces. We use density functional theory andab initiothermodynamics to show that arbitrary TFBD/TFBQ mixing ratios can be set using hydrogen pressures attainable in low to ultrahigh vacuum. Adjusting the mixing ratio allows modifying the work function over a range of about 1 eV. Finally, we contrast single-species submonolayers with mixed layers to discuss why the resulting inhomogeneities in the electrostatic energy above the surface have different impacts on the interfacial level alignment and the work function.
authors.affiliation: Institute for Solid State Physics, NAWI Graz, Graz University of Technology , 8010 Graz, Austria.
authors.forename: Hermann
authors.initials: H
authors.lastname: Edlbauer
authors.affiliation: Institute for Solid State Physics, NAWI Graz, Graz University of Technology , 8010 Graz, Austria.
authors.forename: Egbert
authors.initials: E
authors.lastname: Zojer
authors.affiliation: Institute for Solid State Physics, NAWI Graz, Graz University of Technology , 8010 Graz, Austria.
authors.forename: Oliver T
authors.initials: OT
authors.lastname: Hofmann