Composition dependent cation distribution in ZnxGa2O3+x nanocrystals

Abstract Zn x Ga 2 O 3+x (0.8 ≤ x ≤ 1.1) nanocrystals with the size of 15–30 nm were prepared by the sol-gel method. The effect of composition (Zn/Ga ratio) on the distribution of Zn 2+ and Ga 3+ ions was studied using X-ray photoelectron spectroscopy (XPS). Both of these cations occupied tetrahedral sites as well as octahedral sites of spinel structure in the studied samples. Octahedral Ga 3+ ions are dominant and the as-synthesized samples are partially inverse spinel-structure. The fraction of tetrahedral Ga 3+ ions was calculated to be 0.07–0.16, and increased with Zn/Ga ratio increasing. The inverse parameter (two times the fraction of Ga 3+ in the tetrahedral sites) increases from 0.14 to 0.32 when x value increases from 0.8 to 1.1. The EPR and emission spectra indicated that oxygen vacancies formed in the nanocrystals. The emission intensity of the peak due to oxygen vacancies decreased with increasing Zn/Ga ratio, indicating the decreasing of the concentration of oxygen vacancy.