title: Adsorption site determination for Au-octanethiolate on Au(111).
abstract: Self-assembled monolayers (SAMs) of Au-octanethiolate on Au(111) have been studied using scanning tunneling microscopy (STM). Thermal annealing of the dense (square root(3) x square root(3))R30 degrees layer at 353 K for 1 h leads to the formation of a (5 square root(3) x square root(3))R30 degrees striped phase coexisting with the (square root(3) x square root(3))R30 degrees phase. High-resolution STM imaging shows that the unit cell of the (5 square root(3) x square root(3))R30 degrees phase consists of four adsorbed Au-thiolate species giving rise to an adsorbate coverage of 0.27 ML. The four Au-thiolate species take the standing-up orientation and occupy inequivalent adsorption sites: one on a bridge site and three on the hollow sites. By drawing connections between the (5 square root(3) x square root(3))R30 degrees and the (square root(3) x square root(3))R30 degrees phases, it is found that the adsorption site for Au-thiolate inside the (square root(3)3 x square root(3))R30 degrees phase must be either the fcc hollow or the hcp hollow site.
authors.affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China.
authors.forename: Fangsen
authors.initials: F
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Tang
authors.forename: Wancheng
authors.initials: W
authors.lastname: Zhou
authors.forename: Quanmin
authors.initials: Q
authors.lastname: Guo