Symmetric versus nonsymmetric structure of the phosphorus vacancy on InP(110)

The atomic and electronic structure of positively charged P vacancies on In P(101) surfaces is determined by combining scanning tunneling microscopy, p hotoelectron spectroscopy, and density-functional theory calculations. The vacancy exhibits a nonsymmetric rebonded atomic configuration with a charge transfer level 0.75 +/- 0.1 eV above the valence band maximum. The scannin g tunneling microscopy (STM) images show only a time average of two degener ate geometries, due to a thermal nip motion between the mirror configuratio ns. This leads to an apparently symmetric STM image, although the ground st ate atomic structure is nonsymmetric.