Monolayer structure of phenoxy species on Cu(110): an STM study

The monolayer structure of phenoxy species (PhO) on a metal surface has been studied for the first time with scanning tunneling microscopy (STM). The phenoxy species was produced by exposing the Cu(110) surface to phenol at room temperature. The monolayer exhibits a c(4 × 2) LEED pattern; however, molecular resolution STM imaging of the monolayer reveals three types of overlayer structures: (1) a densely packed c(4 × 2) or 4002 structure with a coverage of 0.25 PhO per surface copper atom, (2) more densely packed phenoxy chains separating the c(4 × 2) regions with a local coverage of 0.33 PhO per Cu, and (3) a distorted c(4 × 2) or 4102 structure consisting of phenoxy chains. Structural models are proposed for each case based on the real dimensions measured with STM. These structures exhibit a constant binding site for the phenoxy species with different orientations (from nearly parallel to almost normal) with respect to the surface plane. The “15°–20° tilts” measured by other techniques on Pd(110) and Ni(110) may be affected by the sum of different structures.