title: The two-dimensional cobalt oxide (9 × 2) phase on Pd(100).
abstract: The two-dimensional (2D) Co oxide monolayer phase with (9 × 2) structure on Pd(100) has been investigated experimentally by scanning tunneling microscopy (STM) and theoretically by density functional theory (DFT). The high-resolution STM images reveal a complex pattern which on the basis of DFT calculations is interpreted in terms of a coincidence lattice, consisting of a CoO(111)-type bilayer with significant symmetry relaxation and height modulations to reduce the polarity in the overlayer. The most stable structure displays an unusual zig-zag type of antiferromagnetic ordering. The (9 × 2) Co oxide monolayer is energetically almost degenerate with the c(4 × 2) monolayer phase, which is derived from a single CoO(100)-type layer with a Co(3)O(4) vacancy structure. Under specific preparation conditions, the (9 × 2) and c(4 × 2) structures can be observed in coexistence on the Pd(100) surface and the two phases are separated by a smooth interfacial boundary line, which has been analyzed at the atomic level by STM and DFT. The here described 2D Co oxide nanolayer systems are characterized by a delicate interplay of chemical, electronic, and interfacial strain interactions and the associated complexities in the theoretical description are emphasized and discussed.
authors.affiliation: Institute of Physics, Karl-Franzens University Graz, Graz, Austria.
authors.forename: L
authors.initials: L
authors.lastname: Gragnaniello
authors.forename: G
authors.initials: G
authors.lastname: Barcaro
authors.forename: L
authors.initials: L
authors.lastname: Sementa
authors.forename: F
authors.initials: F
authors.lastname: Allegretti
authors.forename: G
authors.initials: G
authors.lastname: Parteder
authors.forename: S
authors.initials: S
authors.lastname: Surnev
authors.forename: W
authors.initials: W
authors.lastname: Steurer
authors.forename: A
authors.initials: A
authors.lastname: Fortunelli
authors.forename: F P
authors.initials: FP
authors.lastname: Netzer