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

The nature of defects on the cleavage surface of the quasi-one-dimensi onal oxide conductor K0.3MoO3 has been studied by angle-resolved photo emission and Auger electron spectroscopy. Defects were created on the (201BAR) surface by Ne+ ion bombardment and by photon-stimulated desor ption (PSD). The crystal cleaves to expose K atoms on the surface. Ini tial sputtering of the cleaved surface leads to the disappearance of e mission 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 sputter ing leads to the reappearance of emission at E(F). We explain this beh avior by the sequential removal of K and O, respectively, from the sur face, and verify this model by using PSD to selectively create only 0 vacancies. This model is further verified by measuring work function c hanges during surface modifications and by the use of Auger spectrosco py.