Investigations on the structural and optical properties of band gap engineered Zn 1−x (Cd, Mg) x O thin films deposited by sol–gel technique

Cadmium and magnesium co-doped zinc oxide (ZnO) thin films have been deposited on sapphire substrates using the sol–gel method and the spin coating technique. X-ray diffraction studies confirmed that the deposited films exhibit a hexagonal wurtzite ZnO structure. A strong ultraviolet near-band-edge emission and a deep level emission were observed in the room temperature photoluminescence (PL) spectra of all the films. The PL spectra were also investigated as a function of temperature to examine the emission mechanism of the deposited films. The ability to vary the band gap energy from 3.1 to 3.6 eV was realised by adjusting the cadmium and magnesium concentration in the co-doped ZnO films. X-ray photoelectron spectroscopy studies revealed the successful incorporation of cadmium and magnesium in the ZnO films.