Array of double Au-Ag chains on the Si(5Â 5Â 7) surface

Using scanning tunneling microscopy we study the topographic properties of Ag structure on the Au induced, highly ordered Si(5 5 7) surface. Topography measurements show that a small amount of Ag (0.25 ML) deposited on that surface leads to considerable modifications of the one-dimensional structure induced by Au atoms. In particular, we observe two different chains on each terrace, which are identified as Si adatoms and Ag chain structures. The STM topography of those chains strongly depends on the bias voltage, indicating an important role of electronic effects in this system.