Surface studied by scanning tunneling microscopy

The Na- and K-induced (3 x 1) reconstructions of the Ge(111) surface have b een studied using scanning tunneling microscopy. For Na/Ge(111)-(3 x 1), th e filled-state image reveals a zigzag chain structure similar to those repo rted for alkali-metal-induced Si(111)-(3 x 1). The empty-state image also c onsists of double-width rows separated by dark channels. This is distinctiv ely different from the single-width rows for Si(111)-(3 x 1) and must be pa rtly interpreted as being from the unoccupied states localized on the Ge at oms. The filled-state image of K/Ge(111)-(3 x 1) is similar to that of Na/G e(111)-(3 x 1) but contains more vacancy defects, presumably because of the large lattice mismatch between K and Ge.