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 h aving Sb trimers and Sb chains as their basic structural units. Scanni ng tunnelling microscopy data illustrates that a transition from a com plex 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. Whi le 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 fil led dangling bonds. Some possible reasons for this observed breakdown of the electron-counting model are discussed.