Structural and optical properties of ZnO and manganese-doped ZnO

Abstract

The structural, morphological and optical properties of manganese oxides supported on commercial ZnO,prepared by impregnation with manganese nitrate, were investigated. The nominal compositions of Mnin the samples were 5, 10, 15 and 20%w/w.The X-ray diffraction (XRD) experiments revealed the presenceof the ZnO wurtzite phase in all the samples, and ZnMnO3 was also found in the samples with 15 wt% and20 wt% of Mn. X-ray photoelectron spectroscopy (XPS) showed the presence of Mn2þ and Mn4þ in thexMnZnO samples. The results showed that the Mn2þ ions had substituted the Zn2þ ions withoutchanging the wurtzite structure of ZnO, while Mn4þ might be assigned to the ZnMnO3 impurity phase.The optical band gap was found to be 3.3 eV for undoped ZnO samples and 3.10 eV for Mn-dopedsamples. The lattice defect distribution was investigated using the positron annihilation method. Theresults revealed that the average lifetime is a function of the Mn concentration and the formation of theZnMnO3 phase