XPS investigations of surface segregation of doping elements in SnO2

Various doped tin oxide (dopants Sb, Nb, In) were prepared. By means of X-r ay photoelectron spectroscopy (XPS) the dependence of the surface concentra tion on doping element, doping concentration and preparation technique was determined. Simultaneously, the electrical and morphological properties are strongly influenced even by low doping concentration. The dopant distribut ion was studied by XPS and SIMS depth profiling. A model for dopant distrib ution in the fine powders was proposed. At low concentrations, the doping e lement is build into the lattice of SnO2 partially and the residue substitu tes Sn atoms in the topmost layer. Particles of the second phase are found at higher doping concentrations. Additionally, the analysis of Sb 3d(3/2) p eak position and shape in Sb doped samples shows a decrease of oxidation st ate of antimony with increasing doping concentration. (C) 2001 Elsevier Sci ence B.V. All rights reserved.