title: Alloying at surfaces by the migration of reactive two-dimensional islands.
abstract: We have studied the formation kinetics of the copper-tin alloy bronze when tin is deposited on the (111) surface of copper at room temperature. Low-energy electron microscopy and atomic-resolution scanning tunneling microscopy reveal that bronze forms on the surface by a complicated, unanticipated cooperative mechanism: Ordered two-dimensional tin islands containing several hundred thousand atoms spontaneously sweep across the surface, leaving bronze alloys in their tracks. We propose that this process, driven by surface free energy, is a version of the "camphor dance" observed on liquid surfaces, and should be a general mechanism of surface alloying when surface diffusion is faster than exchange into the substrate.
authors.affiliation: Sandia National Laboratories, Livermore, CA 94551, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Schmid
authors.forename: N C
authors.initials: NC
authors.lastname: Bartelt
authors.forename: R Q
authors.initials: RQ
authors.lastname: Hwang