Surface analysis of Ga-doped 3D urchin-like ZnO structure and density functional theory investigation of the quenching in photoluminescence property

Ga-doped 3D urchin-like ZnO structures with different morphologies have been synthesized by thermal evaporation with different molar ratio gallium oxide as the dopant source. The morphology, microstructure and chemical state were determined by field emission scanning electron microscopy, X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS). The investigation confirmed that the morphologies of the 3D urchin-like ZnO structure had a significant transform with the increase of the dopant. The XPS result indicates that Ga is incorporated into the ZnO lattice. photoluminescence emission peak has been found to be quenched remarkably caused by 5 mol% Ga2O3 dopant. The reason of the emission quench is discussed by means of density functional theory calculations. It is found that O-2p states slightly hybridize with Zn-3d and Ga-4s, Ga-4p states giving rise to the conduction band downward and introduction of the correlative impurity levels, which will result in the increase of non-radiative transition.