Structural, morphological, photoluminescence and photocatalytic properties of Gd-doped ZnO films

Abstract

Nanostructured Gd-doped ZnO films were deposited at 600°C using RF magnetron sputtering technique. The effects of Gd concentration varying from 0 to 2.0at.% on structure as well as morphology and subsequent changes in optical and photocatalytic properties were studied using X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), optical absorption spectra and photoluminescence (PL) spectroscopy. XRD and selected area diffraction results indicated that all Gd-doped ZnO films were of highly (002) preferred orientation and possessed the hexagonal wurtzite structure. SEM images revealed that ZnO nanowires/film structures were grown with a lower Gd content or pure ZnO, and the film crystalline sizes were decreased with Gd doping. XPS results confirmed that the Gd ion was +3 valence states. PL spectroscopy demonstrated an immense enhanced deep-level emission which attributes to the increase in defects concentration due to Gd doping. With a critical doping concentration of 1.6at.% Gd, the ratio of the deep-level emission and the near band edge emission increases by a factor of almost five as compared with pure ZnO. The photocatalytic activities of the films were evaluated by the degradation of methylene blue in aqueous solutions under UV light. The photocatalytic results indicated that the 0.7at.% Gd-doped ZnO nanowires/film structure performed the hightest photocatalytic activity.