Structural phases formed by NO2/CO co-adsorption on Au{111} surfaces

Exposing a Au{111} surface to NO2 and then to CO at temperatures around 120 K in ultra-high vacuum gives rise to molecular overlayers in which the two species are co-adsorbed, which we have investigated using low-temperature scanning tunnelling microscopy. Under NO2-rich conditions, a (root 7 x root 7)R19.1 degrees phase with 3:1 NO2:CO stoichiometry forms. Under CO-rich conditions, this phase co-exists with other phases having 2:1 and 1:1 NO2:CO stoichiometries and different symmetries, and with bare Au surface. Structural models for these phases are discussed. Individual domains of the (root 7 x root 7)R19.1 degrees phase are chiral, by virtue of the arrangement of their achiral components, an observation that may have more general implications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4743901]