Optical properties of (Mn, Co) co-doped ZnO films prepared by dual-radio frequency magnetron sputtering

Dual-radio frequency magnetron sputtering was employed to prepare (Mn, Co) co-doped ZnO films on sapphire (0001). X-ray diffraction and X-ray photoelectron spectroscopy results indicate that the films are highly c-axis oriented and the doped Mn and Co ions in films are both in the divalent states. A dominant photoluminescence peak was observed at the wavelength of 405 nm. Ultraviolet-Visible absorption spectra show band gaps of 2.80, 2.90, 3.27, and 3.22 eV for (Mn-0.02, Co-0.04) Zn0.94O, Zn0.90Co0.10, Zn0.97Mn0.03O and ZnO films, respectively. A red-shift more than 500 meV was observed in a (Mn, Co) co-doped ZnO film. The Raman spectra measurement of (Mn, Co)ZnO films revealed additional vibrational modes at 276.6, 525.6, 634.6, and 643.9 cm(-1) compared to the host phonons of ZnO. (c) 2006 Elsevier B.V. All rights reserved.