Preparation and optical properties of high-quality oriented of Al and Er co-doped ZnO thin films

High-quality c-axis oriented Al and Er co-doped ZnO films were prepared on the quartz glasses by sol–gel method. In order to obtain the optimal processing parameters for the growth of the oriented film, an L₁₆ (4⁵) orthogonal experimental design was chosen. The experimental results show the rank of 5-factors as follows: Er at.% > the number of coating layer > annealing temperature > Al at.% > the concentration of the sol. The Al and Er co-doped film prepared using the optimal parameters exhibits the preferential orientation along the c-axis perpendicular to the substrate surface. In addition, the structural, morphological and optical properties of the films were studied by X-ray diffraction, scanning electron microscopy, and UV–visible spectrophotometer, respectively. The photoluminescence spectra were also used to characterize the luminescence properties of the samples. It is found that when ZnO was co-doped with 7 % Al and 1.5 % Er, the blue emission centered at 465 nm disappears and the green emission centered at 547 nm increases with a blue shift, resulted from the rapid reducing of the interstitial Zn defect, and increasing of the oxygen defects and vacancies caused by Al³⁺ and Er³⁺ dopants.