Calibration of XPS - energy scale for determination of the oxidation states of doping elements in SnO 2 powders.
X-ray photoelectron spectroscopy (XPS) has been used to investigate the oxidation states of doping elements in doped SnO(2) powders. Because of low conductivity, however, charging and resulting peak shift is observed. To obtain the real peak position a suitable reference peak must be found in the XPS spectrum. In this study both internal (Sn3d(5/2) peak) and external references (Au4f(7/2) and C1 s) were examined. When external references were used a shift of all the peaks studied was observed; the extent of this depended on the doping element and the doping concentration. By doping with an element of valence >4 (Nb and Sb) we obtained peaks at binding energy (BE); doping with a trivalent element (In) led to peaks at values of the BE. This peak shift is connected with changes of Fermi level. In contrast, by using Sn3d(5/2) as reference we obtained results which enabled, for example, observation of the dependence of changes of the oxidation state of Sb on doping concentration.
Dobler
D
D
Leibniz-Institute of Solid State and Materials Research Dresden, Postfach 270016, 01171 Dresden, Germany.
Oswald
S
S
Wetzig
K
K