title: The (111) surface of NaAu2: structure, composition, and stability.
abstract: The (111) surface of single-crystal NaAu(2) is a model for catalytically active, powdered NaAu(2). We prepare and characterize this surface with a broad suite of techniques. Preparation in ultrahigh vacuum consists of the traditional approach of ion bombardment (to remove impurities) and thermal annealing (to restore surface order). Both of these steps, however, cause loss of sodium (Na), and repeated treatments eventually trigger conversion of the surface and near-surface regions to crystalline gold. The bulk has a limited ability to repopulate the surface Na. Under conditions where Na depletion is minimized, electron diffraction patterns are consistent with the bulk-terminated structure, and scanning tunneling microscopy reveals mesa-like features with lateral dimensions of a few tens of nanometers. The tops of the mesas do not possess fine structure characteristic of a periodic lattice, suggesting that the surface layer is disordered under the conditions of these experiments.
authors.affiliation: Department of Chemistry and ∥Department of Materials Science & Engineering, Iowa State University , Ames, Iowa 50011, United States.
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Kwolek
authors.forename: Roland
authors.initials: R
authors.lastname: Widmer
authors.forename: Oliver
authors.initials: O
authors.lastname: Gröning
authors.forename: Okan
authors.initials: O
authors.lastname: Deniz
authors.forename: Holly
authors.initials: H
authors.lastname: Walen
authors.forename: Chad D
authors.initials: CD
authors.lastname: Yuen
authors.forename: Wenyu
authors.initials: W
authors.lastname: Huang
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Schlagel
authors.forename: Mark
authors.initials: M
authors.lastname: Wallingford
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Thiel