ZnxGa2O3+x (0 ≤ x ≤ 1) solid solution nanocrystals: tunable composition and optical properties

Abstract

Homogenous Zn_xGa₂O_3+x (0 ≤ x ≤ 1) solid solution nanocrystals were successfully prepared by a solvothermal approach and characterized by X-ray powder diffraction (XRD), X-ray spectra in fluorescence (XRF), transmission electron microscopy (TEM), UV-vis spectroscopy, and X-ray photoelectron spectrum (XPS). XRD pattern analysis revealed that the lattice parameters of Zn_xGa₂O_3+x (0 ≤ x ≤ 1) solid solution nanocrystals increased linearly with the increase of ZnGa₂O₄ ratio according to Vegard's law, which confirmed the homogenous structures of these solid solution nanocrystals. UV-vis absorption spectra demonstrated that the band gap of the obtained Zn_xGa₂O_3+x solid solution nanocrystals could be precisely tuned in the range of 4.43 to 3.70 eV by elaborately controlling the content of zinc. The emission of Zn_xGa₂O_3+x solid solution nanocrystals strengthened and red-shifted gradually with the increase of x value, and ZnGa₂O₄ nanocrystals showed an intense blue emission. XPS results revealed that Zn_xGa₂O_3+x binding energy of O²⁻ 1s increased with the increase of the x value, indicating the decrease of the oxygen vacancies (V_o*) of O_h sites and the increase of the symmetry of the Ga–O octahedron, which resulted in the emission red-shift of Zn_xGa₂O_3+x solid solution.