Photoluminescence of ZnO and Mn-Doped ZnO Polycrystalline Films Prepared by Plasma Enhanced Chemical Vapour Deposition

ZnO and Mn-doped ZnO polycrystalline films are prepared by plasma
enhanced chemical vapour deposition at low temperature (220°C), and
room-temperature photoluminescence of the films is systematically investigated. Analysis from x-ray diffraction reveals that all the prepared films
exhibit the wurtzite structure of ZnO, and Mn-doping does not induce the
second phase in the films. X-ray photoelectron spectroscopy confirms the
existence of Mn²⁺ ions in the films rather than metallic Mn or Mn⁴⁺ ions. The emission efficiency of the ZnO film is found to be dependent strongly on the post-treatment and to degrade with increasing temperature either in air or in nitrogen ambient. However, the enhancement of near band edge (NBE) emission is observed after hydrogenation in ammonia plasma, companied with more defect-related emission. Furthermore, the position of NBE shifts towards to high-energy legion with increasing Mn-doped concentration due to Mn incorporation into ZnO lattice.