title: Impact of defects on the surface chemistry of ZnO(0001 macro)-O.
abstract: Scanning tunneling microscopy and core level photoelectron spectroscopy measurements have been used to investigate the morphology of ZnO(0001 macro)-O, and its reactivity with carbon monoxide and carbon dioxide, as a function of surface preparation. Real space images of the surface indicate that increasing the substrate anneal temperature during preparation significantly reduces the surface step density. Surface defect concentration is also monitored by employing formic acid as a chemical probe, which is shown to adsorb dissociatively (HCOOH --> [HCOO](-) + H(+)) only on zinc cations at step edges. Carbon 1s X-ray photoelectron spectra show that carbon monoxide and carbon dioxide both react to form surface carbonate species. Spectra, recorded both as a function of surface preparation and following coadsorption, demonstrate that the carbonate formed from either reactant molecule is located at oxygen vacancies at step edges, evidencing the significant role that defects can play in the surface chemistry of ZnO(0001 macro)-O.
authors.affiliation: Surface Science Research Centre and Chemistry Department, Manchester University, Manchester M13 9PL, UK. ryl@ssci.liv.ac.uk
authors.forename: Robert
authors.initials: R
authors.lastname: Lindsay
authors.forename: Ela
authors.initials: E
authors.lastname: Michelangeli
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Daniels
authors.forename: Timothy V
authors.initials: TV
authors.lastname: Ashworth
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Limb
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Thornton
authors.forename: Aurora
authors.initials: A
authors.lastname: Gutiérrez-Sosa
authors.forename: Alessandro
authors.initials: A
authors.lastname: Baraldi
authors.forename: Rosanna
authors.initials: R
authors.lastname: Larciprete
authors.forename: Silvano
authors.initials: S
authors.lastname: Lizzit