Strong near band edge emission of (Ce, Yb) co-doped ZnO thin films after high temperature annealing

We studied the photoluminescence (PL) properties of (Ce + Yb) co-doped ZnO thin films as a function of high temperature annealing. The films were fabricated by magnetron sputtering. After 1000-1100°C annealing, the near band edge (NBE) emissions of the films were dozens to a hundred times stronger than that of undoped ZnO, while the Yb³⁺ emission (~980 nm) was quite weak, indicating that energy transfers from the ZnO host to Yb³⁺ ions in the films were not efficient. X-ray diffraction analysis and scanning electron microscopy observations demonstrated that the (Ce + Yb) co-doping had a large effect on the morphology and crystallinity of the films. The crystallinity enhancement of the films is considered to be the main reason for the strong NBE enhancements of the co-doped ZnO films.