Influence of the substrate temperature on the microstructure and electron-induced secondary electron emission properties of MgO/Au composite film

•MgO/Au film was prepared by magnetron sputtering of individual Mg and Au targets.•A higher substrate temperature (Ts) is conducive to the growth of MgO grains.•The surface roughness firstly rises and then decreases with Ts increasing.•The increase of Ts greatly enhances the SEE coefficient of the composite film.