July 2013 – In this study, we find that isolated heavy dopants behave entirely different at the surface compared to the bulk and to lighter dopants. The common light impurity P replaces individual Si atoms and maintains the integrity of the dimer superstructure of the Si(001) surface, but loses its valence electrons to surface states. In contrast, we find that Bi atoms form pairs with Si vacancies, retain their electrons, and have highly localized, half-filled orbitals. This result strikingly shows that the basic properties of dopants at surfaces and interfaces are not solely governed by their column of origin as they are in the bulk.
Collaboration with UCL/LCN.