A study was made of the equilibrium structure of an (001) surface with a single dimer vacancy, and of the migration of the dimer vacancy, by using a tight-binding total energy scheme. The calculated (001) surface exhibited p(2 x 2) ordering, in good agreement with experiment. For a single dimer vacancy, 3 equilibrium structures were found: non-bonding, re-bonding, and weak bonding. The local electronic density of states revealed that the non-bonding model did not exhibit deep gap states; in good agreement with experiment. A study was also made of the migration of a single dimer vacancy. The bond-breaking mechanism and the place-exchange mechanism were compared. The energy barriers for the place-exchange and bond-breaking mechanisms were found to be equal to 1.90 and 1.18eV, respectively. This was contrary to the general belief that the place-exchange mechanism was favored over the bond-breaking mechanism.

M.S.Jeong, Y.H.Lee, Y.G.Hwang: Physical Review B, 1995, 51[23], 17151-7