title: Stabilization principles for polar surfaces of ZnO.
abstract: ZnO is a wide band gap metal oxide with a very interesting combination of semiconducting, transparent optical and catalytic properties. Recently, an amplified interest in ZnO has appeared due to the impressive progress made in nanofabrication of tailored ZnO nanostructures and functional surfaces. However, the fundamental principles governing the structure of even the clean low-index ZnO surfaces have not been adequately explained. From an interplay of high-resolution scanning probe microscopy (SPM), X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption fine structure (NEXAFS) spectroscopy experiments, and density functional theory (DFT) calculations, we identify here a group of hitherto unresolved surface structures which stabilize the clean polar O-terminated ZnO(0001) surface. The found honeycomb structures are truly remarkable since their existence deviates from expectations using a conventional electrostatic model which applies to the opposite Zn-terminated (0001) surface. As a common principle, the differences for the clean polar ZnO surfaces are explained by a higher bonding flexibility of the exposed 3-fold coordinated surface Zn atoms as compared to O atoms.
authors.affiliation: Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, Aarhus University, Denmark. jvang@inano.au.dk
authors.forename: Jeppe V
authors.initials: JV
authors.lastname: Lauritsen
authors.forename: Soeren
authors.initials: S
authors.lastname: Porsgaard
authors.forename: Morten K
authors.initials: MK
authors.lastname: Rasmussen
authors.forename: Mona C R
authors.initials: MC
authors.lastname: Jensen
authors.forename: Ralf
authors.initials: R
authors.lastname: Bechstein
authors.forename: Kristoffer
authors.initials: K
authors.lastname: Meinander
authors.forename: Bjerne S
authors.initials: BS
authors.lastname: Clausen
authors.forename: Stig
authors.initials: S
authors.lastname: Helveg
authors.forename: Roman
authors.initials: R
authors.lastname: Wahl
authors.forename: Georg
authors.initials: G
authors.lastname: Kresse
authors.forename: Flemming
authors.initials: F
authors.lastname: Besenbacher