Influence of substrate temperature on the structural and optoelectronic properties of ZnMgO:Al coatings deposited by radio frequency magnetron sputtering

Abstract

ZnMgO:Al coatings were prepared by radio frequency (RF) magnetron sputtering on glass substrates, and the effects of the substrate temperature on the structural, electrical, and optical properties of ZnMgO:Al coatings were studied. The ZnMgO:Al coatings had a hexagonal wurtzite crystal structure oriented along the c-axis, regardless of the substrate temperature. Increasing the substrate temperature increased the grain sizes of the coatings and thus their Hall mobilities. The high substrate temperature also promoted the doping concentration efficiency of Al³⁺ ions, leading to enhanced carrier concentration. The optimal deposition was obtained at 400 °C, which led to the lowest resistivity (2.82 × 10⁻³ Ω cm) and 91 % transmission in the visible range. The optical bandgap increased to 3.632 eV as the substrate temperature increased to 400 °C. Wide bandgap, highly transparent, and conductive ZnMgO:Al coatings can be used as electrodes for ultraviolet photovoltaic applications.