Optical properties of Mn doped ZnO films and wires synthesized by thermal oxidation of ZnMn alloy

Abstract

Mn doped ZnO films and wires, having different manganese concentrations were synthesized by thermal oxidation of the corresponding ZnMn alloy films and wires electrodeposited on a gold substrate. Structural and optical properties were addressed with scanning electron microscopy, X-ray diffraction (XRD), Raman scattering and photoluminescence (PL). To estimate the manganese concentration in Mn doped ZnO films, X-ray photoelectron spectroscopy was used. XRD patterns indicate that the incorporation of Mn2+ ions into the Zn2+ site of ZnO lattice takes place. Quenching of the ZnO PL appears due to Mn2+ ions in the ZnO lattice. Moreover, a significant decrease in the green emission of ZnO is reported in the case of the Mn doped ZnO wire array with a Mn concentration of 1.45%. The wurtzite ZnO has a total of 12 phonon modes, namely, one longitudinal acoustic (LA), two transverse acoustic (TA), three longitudinal optical (LO), and six transverse optical branches. Compared to the undoped ZnO, a gradual up-shift of the Raman lines assigned to the 2LA and A1 (LO) vibrational modes, from 482 and 567cm−1 to 532 and 580cm−1, respectively, takes place for the Mn doped ZnO films having a Mn concentration between 2 and 15%. Additionally, in the case of the Mn doped ZnO films with 7 and 15% Mn concentration, Raman spectra show the appearance and increase in the relative intensity of the ZnO Raman line assigned to the TA+LO vibrational mode in the 600–750cm−1 spectral range. For the Mn-doped ZnO wires, the presence of the Raman line peaking at 527cm−1 confirms the insertion of Mn2+ ions in ZnO lattice.