Induced Growth from a Ag Gas on Cu(111)

We investigate the induced growth of a Ag layer on a Cu(111) surface by variable low-temperature scanning tunneling microscopy between 100 and 140 K at submonolayer coverage. Without any interference by the scanning process, the Ag atoms form a two-dimensional gas on the Cu(111) surface. Imaging the surface at elevated voltage induces nucleation and growth of one-dimensional Ag stripes of monolayer height, eventually filling the surface of the imaged area completely. The stripes consist of rods of atoms with a preferential length of (1.88 ± 0.10) nm, corresponding to approx. seven or eight Ag atoms on eight to nine Cu hollow sites. At a ratio of approximately 1:3, rods of double length are the second most observed species. The rods stack in the ⟨112⟩ directions at the √3 distance of Cu(111). Although all equivalent three surface directions are observed, their abundance is not equally distributed, such that the rod direction aligned with the fast scanning direction predominates. At slow growth rates, it is possible to create a striped pattern with one surface direction only.