ELECTRONIC-STRUCTURE OF ZNO(0001) STUDIED BY ANGLE-RESOLVED PHOTOELECTRON-SPECTROSCOPY

The electronic structure of the ZnO(0001) surface was studied by angle -resolved photoelectron spectroscopy. The recorded normal emission spe ctra give information about the Valence band states as well as the Zn 3d states. The dispersions of the four valence bands observed in the ( 0001) direction were compared with theory and are in good agreement wi th recent calculations which consider the Zn 3d electrons as part of t he valence band. The Zn 3d states are seen to separate into two groups of four and six bands, which show dispersion with k(perpendicular to) . This is in agreement with theoretical results but the location of th ese states were not accurately predicted. The present photoemission re sults show that they lie around 10.5 eV below E(F). Two surface states were observed on the (0001) surface. One, at 7.5 eV binding energy, w as predicted by theory and is interpreted as arising from the ''back-b ondings'' of the Zn 4s-O 2p mixed bulk states. The other one at 4.5 eV below E(F), most likely Zn 4p-0 2p derived, was not predicted by theo retical calculations and this is discussed further in the text. (C) 19 97 Elsevier Science B.V.