Effects of Cu doping on the structure, electronic and optical properties of SnO2 thin films by spray pyrolysis: An experimental and density functional study

Cu doped SnO2 thin films have been prepared by spray pyrolysis methods. The optical band gap increases with the concentration of Cu dopants while the crystallite size of SnO2 decreases with the Cu doping concentration. X-ray diffraction analysis shows that Cu doped SnO2 thin films display the preferred growth along (110) plane at a high Cu concentration. X-ray photoelectron spectroscopy shows that Cu2 + is observed in the SnO2 thin films at a low Cu doped concentration and transforms into Cu+ at a high Cu concentration and that oxygen vacancies decrease with the Cu doping concentration. Density functional theory calculation reveals that the crystal lattice constant of Cu doped SnO2 is smaller than the principle SnO2 leading to the increase in the band gap. Our results give a significant basic theory on the Cu doped SnO2 thin films which will be promising materials for optoelectronic devices due to the remarkable photoelectrical properties.