Vacancy diffusion mediated dynamics of domain boundaries on Ge(111)- c(2×8)

Domain boundaries often play a pivotal role in surface dynamics and surface phase transitions. In this study we scrutinize the dynamics of domain boundaries on the Ge(111)-c(2×8) surface using scanning tunneling microscopy. The dynamics of these domain boundaries, which are aligned along the (1-10) directions, is governed by the diffusion of vacancies. The hop rate of a vacancy at a domain boundary is more than one order of magnitude larger than the hop rate of a vacancy in a pristine c(2×8) domain. The diffusion pathway of a single vacancy along the domain boundary involves the formation of two, more mobile, semivacancies. The probability that these two semivacancies rejoin is very likely, but there is also a chance that the two semivacancies diffuse away from each other. This scenario provides a logical explanation of why single vacancies occasionally exhibit unusually long displacements along the domain boundary.