title: Work Function of Oxide Ultrathin Films on the Ag(100) Surface.
abstract: Theoretical calculations of the work function of monolayer (ML) and bilayer (BL) oxide films on the Ag(100) surface are reported and analyzed as a function of the nature of the oxide for first-row transition metals. The contributions due to charge compression, charge transfer and rumpling are singled out. It is found that the presence of empty d-orbitals in the oxide metal can entail a charge flow from the Ag(100) surface to the oxide film which counteracts the decrease in the work function due to charge compression. This flow can also depend on the thickness of the film and be reduced in passing from ML to BL systems. A regular trend is observed along first-row transition metals, exhibiting a maximum for CuO, in which the charge flow to the oxide is so strong as to reverse the direction of rumpling. A simple protocol to estimate separately the contribution due to charge compression is discussed, and the difference between the work function of the bare metal surface and a Pauling-like electronegativity of the free oxide slabs is used as a descriptor quantity to predict the direction of charge transfer.
authors.affiliation: CNR-IPCF, Istituto per i Processi Chimico-Fisici of the Consiglio Nazionale delle Ricerche , Molecular Modeling Laboratory, I-56124 Pisa, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Sementa
authors.affiliation: CNR-IPCF, Istituto per i Processi Chimico-Fisici of the Consiglio Nazionale delle Ricerche , Molecular Modeling Laboratory, I-56124 Pisa, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Barcaro
authors.affiliation: CNR-IPCF, Istituto per i Processi Chimico-Fisici of the Consiglio Nazionale delle Ricerche , Molecular Modeling Laboratory, I-56124 Pisa, Italy.
authors.forename: Fabio R
authors.initials: FR
authors.lastname: Negreiros
authors.affiliation: CNR-IPCF, Istituto per i Processi Chimico-Fisici of the Consiglio Nazionale delle Ricerche , Molecular Modeling Laboratory, I-56124 Pisa, Italy.
authors.forename: Iorwerth O
authors.initials: IO
authors.lastname: Thomas
authors.affiliation: Surface and Interface Physics, Institute of Physics, Karl-Franzens University Graz , A-8010 Graz, Austria.
authors.forename: Falko P
authors.initials: FP
authors.lastname: Netzer
authors.affiliation: Dipartimento di Chimica e IFM, Università di Torino , I-10125, Turin, Italy.
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Ferrari
authors.affiliation: CNR-IPCF, Istituto per i Processi Chimico-Fisici of the Consiglio Nazionale delle Ricerche , Molecular Modeling Laboratory, I-56124 Pisa, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Fortunelli