The atomic and electronic structures of positively charged P vacancies on (110) surfaces was determined by combining scanning tunnelling microscopy, photo-electron spectroscopy and density-functional theoretical calculations. The vacancy exhibited an asymmetrical rebonded atomic configuration, with a charge transfer level which was 0.75eV above the valence-band maximum. The scanning tunnelling microscopic images revealed only a time average of 2 degenerate geometries, due to a thermal flip motion between mirror configurations. This led to an apparently symmetrical scanning tunnelling microscopic image, even though the ground-state atomic structure was asymmetrical.

Symmetrical versus Non-Symmetrical Structure of the Phosphorus Vacancy on InP(110). P.Ebert, K.Urban, L.Aballe, C.H.Chen, K.Horn, G.Schwarz, J.Neugebauer, M.Scheffler: Physical Review Letters, 2000, 84[25], 5816-9