A RESONANT PHOTOEMISSION-STUDY OF THE ZRO2 VALENCE-BAND

Valence band photoemission spectra have been measured from in situ the rmally grown ZrO2 using synchrotron radiation. Resonant photoemission was observed at photon energies hnu almost-equal-to 39 eV, well above the Zr4p --> 4d threshold. The phenomenon has been used to identify th e Zr4d derived valence states and good agreement was found with valenc e band structure calculations. Ar+ bombardment of ZrO2 causes the grow th of an emission feature in the band gap at a binding energy of 1.5 e V associated with oxygen vacancies as well as a second band at 3.5 eV and other changes in the 0 2p band, all of which are clearly associate d with the formation of a highly oxygen deficient surface layer. Reson ant photoemission of the bombarded oxide not only demonstrates the d-c haracter of the states in the band gap but also shows a significant in crease of the Zr contribution to the O 2p band.