Charge trapping processes in hydrothermally grown Er-doped ZnO

Abstract

Influence of X-ray irradiation on luminescence properties and defects creation was studied in the erbium doped hydrothermally grown ZnO by using the combination of photo- and radioluminescence (PL and RL), thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR). The photoluminescence properties of the ZnO:Er appeared affected by the X-ray irradiation – the intensity of the zinc vacancy-related red band and exciton-related ultraviolet band were weakened. The irradiation also evoked charge trapping and new centers creation whose type and number depended on Er doping. The X-ray induced defects were oxygen-based hole and electron trapping centers, O− and O2−, respectively. The X-ray irradiation had also influence on shallow donors in the bulk and at the surface of the ZnO nano- and microrods. TSL glow curves consisted of one broad peak with the maximum at about 110 K, its intensity was varying with the changing Er content. The glow peak was correlated with the thermal destruction of the unstable O2− electron trapping centers. Zinc vacancies-based defects participated in the thermally stimulated luminescence as recombination centers for the electrons released from the O2−.