Molecularly induced step faceting on Cu(110) surfaces

Scanning tunneling microscopy (STM) has been used to study structures formed by adsorbed formate and benzoate species on Cu(110) surfaces. Partially oxygen-precovered and clean surfaces were exposed to formic and benzoic acids, respectively. STM images show that both adsorbed formate and benzoate result in a tendency for bunched steps to align along [1(1) over bar2$] directions and to become equidistant effectively creating small facet planes on the surface. In the case of benzoate, these planes can be described as (11 13 1) and (11 13 (1) over bar) planes. In the case of formate, ordered arrays of facet planes can form on step edges giving the steps a ''sawtooth'' appearance. Under some conditions adsorbed formate also appears to stabilize finger-like islands and pits.