Raman scattering studies of Mn-doped ZnO thin films deposited under pure Ar or Ar + N2 sputtering atmosphere

This paper investigates the anomalous and specific Raman modes present in Mn-doped ZnO thin films deposited using the magnetron co-sputtering method. To trace these peaks, we prepared Mn-doped ZnO films with different Mn concentrations by altering the sputtering power of the Mn target in a pure Ar or Ar + N2 sputtering atmosphere. A broad band observed in the Raman spectra of heavily Mn-doped ZnO films ranges from 500 to 590 cm− 1. This band involves the enhanced A1 longitudinal mode and activated silent modes of ZnO, as well as a characteristic mode of Mn2O3. Four anomalous Raman peaks at approximately 276, 510, 645 and 585 cm− 1 are present in pure and Mn-doped ZnO films deposited under the Ar + N2 sputtering atmosphere. The peaks at 276 cm− 1 and 510 cm− 1 may originate from the complex defects of Zni–NO and Zni–Oi, respectively, while the peak at approximately 645 cm− 1 could be due to a complex defect of Zni coupled with both the N and Mn dopants. The results of this study suggest classifying the origins of anomalous and specific Raman peaks in Mn-doped ZnO films into three major types: structural disorder and morphological changes caused by the Mn dopant, Mn-related oxides and intrinsic host-lattice defects coupled with/without the N dopant.