Photoemission study of In2O3 thin films on NiIn(0001): valence bands and indium 4d levels of a model for ITO

Ultraviolet photoemission has been used to study the growth of ultrathin fi lms of In2O3 on NiIn(0001), a model material for technologically important indium-tin-oxide (ITO). He II excited In 4d spectra are shown to be an exce llent monitor of the indium oxidation, which allows an interface layer to b e discerned between the alloy and In2O3 film. The growth of the second laye r begins before the completion of this layer. Valence band spectra show tha t the electronic structure of the films is consistent with photoemission da ta from bulk In2O3 and In2O3 grown on Si(111), and with published density o f states calculations. From a comparison of He I and He II excited valence band spectra we suggest that the valence band contains a finite contributio n from In 4d antibonding states, as seen in the published calculations. Wit h the exception of oxygen plasma treated ITO, which also shows significant differences to the calculations, the In2O3/NiIn(0001) valence band spectra are in good agreement with spectra from differently treated ITO samples. (C ) 2000 Elsevier Science B.V. All rights reserved.