XPS AND X-RAY-DIFFRACTION STUDIES OF ALUMINUM-DOPED ZINC-OXIDE TRANSPARENT CONDUCTING FILMS

Aluminum-doped zinc oxide transparent conducting films are prepared by spray pyrolysis at different dopant concentrations. These films are s ubsequently characterized by X-ray diffractometric and X-ray photoelec tron spectroscopic (XPS) techniques. The results are compared with tho se obtained from pure zinc oxide films prepared under identical condit ions. X-ray diffraction measurements show an increase in lattice param eters (c and a) for aluminum-doped films while their ratio remains the same. This study also indicates that within the XPS detection limit t he films are chemically identical to pure zinc oxide. However, a diffe rence in the core-electron line shape of the Zn 2p(3/2) photoelectron peaks is predicted. An asymmetry in Zn 2p(3/2) photoelectron peaks has been observed for aluminum-doped films. The asymmetry parameters eval uated from core-electron line-shape analysis yield a value of the orde r of 0.04 +/- 0.01. The value is found to lie between those obtained f or pure zinc oxide and has been attributed to the presence of excess z inc in the films.