Initial growth of silver on Ge(111) studied by scanning tunneling microscopy

Scanning tunneling microscopy (STM) has been used to study the Ge(111) surface after submonolayer depositions of Ag. At the lowest coverages a (4×{}4) reconstruction, with small insets of a (3×{}1) edge structure, is observed. Based on the STM images we propose a mixed Ag and Ge adatom structure for the (4×{}4) reconstruction, in which the adatoms have local (1×{}1) and (2×{}2) arrangements corresponding to a Ag coverage of 6/16 monolayers. The (3×{}1) structure appears to have a configuration similar to the Si(111)/Ag-(3×{}1) reconstruction, although in this case it has a much more limited extension, restricted to a few unit cells in the near vicinity of step edges and phase boundaries. At higher coverages, after the completion of a full (4×{}4)/(3×{}1) surface, a ({}3 ×{} {}3 )R30^∘{} structure appears showing STM images similar to those previously published for the Si(111)/Ag system.