Sb 0 -the product of reduction of Sb 2 O 3 by carbon of the graphite heater -is, in fact, responsible for the appearance of Sb +5 states in the surface layers. In 32 , it was demonstrated that atmospheric oxygen gradually oxidizes metallic Sb, which results in Sb +5 signal in XPS spectra. Note, that the Sb +5 /Sb +3 intensity ratio is higher for ZSb01_3 in the initial spectrum than for ZSb01_1 (Fig. ) due to the availability of excess metallic Sb while in the case of ZSb01_1 the only source of Sb 0 is a relatively small amount of reduced antimony, which is below detection limit of XRD. Therefore, Sb +5 states are created via atmospheric oxidation of metallic Sb while Sb +3 states stabilized both in ZnO lattice and in excess Sb 2 O 3 are not susceptible to such oxidation. Interestingly, the binding energy of Sb(III) component of the Sb3d3/2 peak on the surface is 539.5 eV, which precisely corresponds to Sb 2 O 3 while after Ar + etching this energy increases to 539.7 eV (Fig. ). This observation indirectly proves incorporation of Sb in ZnO lattice where it forms impurity centers with oxygen coordination differing from its native oxide.