Chemical surface analysis by Raman spectroscopy utilizing dimer vibrations

We report on the investigation of reconstructed semiconductor surfaces by Raman spectroscopy from dimer vibrations. Localized modes of Te dimers on the (100) surface of the zinc blende II-VI semiconductor BeTe allow the analysis of Te- and Be-rich surface structures, as well as oxidation effects. The Te-rich surface exhibits one dimer-vibration mode at 165 cm(-1), while two modes appear at the Be-rich surface (157 and 188 cm(-1)). The mode assignment as dimer vibrations is underscored by their symmetry properties and by frozen phonon calculations, yielding mode frequencies and eigenvectors. This approach opens up a new field of surface chemistry analysis by dimer-vibration spectroscopy.