Experimental and theoretical insights on the structural and optical properties of GeOx thin films deposited via RF magnetron sputtering under varying oxygen percentage

In this study, GeOx films were produced by radio frequency magnetron sputtering (RFMS) under varying oxygen percentages. The structural and optical properties of films grown have been studied experimentally and theoretical calculations have been presented using density functional theory (DFT). Considering the x-ray diffraction (XRD) analysis, Ge (111) peak was observed in the as-deposited film produced only at 2% oxygen percentage. In order to emerge crystal phases, all the amorphous films were annealed at 900 °C under atmospheric conditions. It was found that the intensity of the (101) peak increased as the oxygen percentage increased. At the same time, film grown at 2% oxygen percentage was annealed at different annealing temperatures sequentially at 850, 900, and 950 °C. As a result, the polycrystalline properties changed as the annealing temperature increased. It was found that the optical properties of the films grown are strongly dependent on the oxygen percentage. As the oxygen percentage has changed, the energy band gap has increased to the values 2.30, 2.31, 2.58, and 6.28 eV. There are Ge-O-Ge antisymmetric stretching peaks appeared at 861.51 cm−1, 949.94 cm−1 and symmetric stretching of hexagonal peaks at 516.34 cm−1, 546.29 cm−1, 581.95 cm−1. The energy band gap results of the density functional theory (DFT) calculations are in good agreement with the experimental observations.