Sb-induced GaAs(111)B surface reconstructions: Success and failure of the electron-counting rule

Deposition of antimony on the GaAs(111)B-(2 x 2) surface, followed by annealing in the 300-525 degrees C range, results in reconstructions having Sb trimers and Sb chains as their basic structural units. Scanning tunnelling microscopy data illustrates that a transition from a complex surface terminated by a number of local arrangements of Sb chain pairs and trimers to a (1 x 3) reconstruction having a high degree of long-range order occurs as the annealing temperature is increased. While the various unit cells formed by the combination of chain pairs and trimers satisfy the electron-counting rule, the unit cell of the (Ix 3) structure formed at higher annealing temperatures has partially filled dangling bonds. Some possible reasons for this observed breakdown of the electron-counting model are discussed.