AN EFFECT OF THE ZN3D-STATES ON UV AND X-RAY-SPECTRA IN ZNO

The present study deals with ZnO photoelectronic spectra (PES) recorde d at 1253.6 eV as well as within a wide photon energy range of 30-150 eV. It has been shown that the shape of the 02p valence band PES depen ds on the incident photon energy. On the basis of SCF X alpha-scattere d waves (X alpha-SW) cluster approximation, the O2p valence band PES h ave been calculated in the given photon energy range. The changes in t he O2p PES shape are proved to be caused by Zn3d electrons, which part icipate in the covalent binding along with Zn4s electrons. The percent age of the Zn3d-states was obtained on the basis of the quantum-chemic al calculations and using the photon energy dependence of the integral intensity ratio I-O2p/I-Zn3d. Based on this result, the ZnO stoichiom etry and the concentration ratio profile [O]/[Zn] as a function of the escape depth have been calculated. The weight of Zn3d-states, as eval uated from the photon energy dependence, is 9%. A theoretical predicti on for this weight is 7%, which is very close to the experimental valu e. (C) 1998 Elsevier Science B.V. All rights reserved.