ELECTRONIC-STRUCTURE OF SURFACE-DEFECTS IN K0.3MOO3

The nature of defects on the cleavage surface of the quasi-one-dimensional oxide conductor K0.3MoO3 has been studied by angle-resolved photoemission and Auger electron spectroscopy. Defects were created on the (201BAR) surface by Ne+ ion bombardment and by photon-stimulated desorption (PSD). The crystal cleaves to expose K atoms on the surface. Initial sputtering of the cleaved surface leads to the disappearance of emission from the Mo 4d states at the Fermi level (E(F)) and the growth of a well-defined emission feature 2 eV below E(F). Continued sputtering leads to the reappearance of emission at E(F). We explain this behavior by the sequential removal of K and O, respectively, from the surface, and verify this model by using PSD to selectively create only 0 vacancies. This model is further verified by measuring work function changes during surface modifications and by the use of Auger spectroscopy.