Photoemission spectroscopy analysis of ZnO:Ga films for display applications

We report the physical properties of ZnO:Ga-based films prepared by metalorganic chemical vapor deposition (MOCVD) using ultraviolet and x-ray photoemission spectroscopy (UPS and XPS). In addition, the surface characteristics of the films are modified with a series of cleaning and etching steps. The films were produced in an argon-oxygen atmosphere using metalorganic precursors at low pressure in a rotating disk reactor. The XPS results show a gallium oxide rich layer more than 20 Angstrom on the surface of the as-received MOCVD films, with a small fraction of Zn. This oxide layer is removed by a cleaning and plasma treatment, which enhances the conductivity of the ZnO:Ga films. From UPS, the work function is 4.23 eV after an O-2 plasma treatment. Finally, we report on the surface morphology of the ZnO:Ga films after the cleaning process. The post-deposition treatment of these MOCVD films is important for the improved conductivity that is vital to display applications. (C) 1999 American Vacuum Society.