A steric interaction model was presented that described roughening and reorganization on halogen-terminated Si(100)-2x1 surfaces. This model was based upon parameters derived from density-functional theory total-energy calculations. Using these parameters together with the requirements for re-bonding and atom conservation, it was possible to explain the types of reorganization events that could occur and the different steady-state morphologies observed in the presence of different halogen terminations. Using scanning-tunneling microscopy, it was shown that dimer vacancy string elongation could occur by a process termed primary roughening, i.e., the removal of pairs of dimers from the terrace and the formation/elongation of terrace islands. It was shown that experimentally and within the confines of the steric interaction model end-on coalescence of dimer vacancy strings was unfavorable but side-on coalescence could result in the formation of wider vacancy pits. The steric interaction model thus explained why elongated vacancy pits were formed in the case of Br termination, whereas short wider structures were observed with Cl. The model was also used to explain the nucleation of terrace islands and the attachment of dimers at islands and surface steps. The model predicted larger numbers of islands and enhanced roughness at SB-type steps on the Br surface; in excellent agreement with experiment.

Steric Interaction Model of Roughening and Vacancy Reorganization on Halogen-Terminated Si(100)-2x1 Surfaces. D.Chen, J.J.Boland: Physical Review B, 2003, 67[18], 184302 (6pp)