Two-dimensional vacancy islands induced by the growth of Cr on Cu(111)

Surface structures induced by the growth of Cr on Cu(111) at room temperature are studied with scanning tunneling microscopy. At sub-monolayer Cr coverage, islands and vacancy islands with lateral sizes of about 10 nm in length are observed. The islands show one- or two-monolayer heights with irregular shapes, while vacancy islands have one-monolayer depth and hexagonal shapes with openings. Atomic structures inside and near the vacancy islands are the same as those of bare Cu(111), implying that Cu atoms detach from the vacancy islands and attach to other step edges and islands. Possible origins and atomic processes for the observed structures are discussed.