Production of high-transparent MgO films by radio-frequency sputtering method

Magnesium oxide (MgO) thin films were deposited on silicon and glass substrates by the radio frequency (RF) sputtering method. The MgO films were annealed at 400 ⁰C for 4h. The effect of working pressure on the structure and optical properties of MgO films was investigated. Structural characterization of thin films was determined using the X-ray diffraction (XRD) method. XRD results showed the presence of dominant peaks corresponding to the (200) and (220) lattice planes of MgO. However, peaks corresponding to (111), (311) and (222) lattice planes of the MgO also appeared in the films deposited at low pressure. It was determined that the average crystal size decreased as the working pressure reduced, while the deposition rate increased. SEM analysis showed that the microstructure of the nano-spherical MgO film transformed into a coarse-grained nano-pyramidal shape after annealing. The optical properties of MgO films were investigated by UV-Vis spectroscopy. Accordingly, it was determined that the absorption threshold of the films was around 310 nm wavelength and the optical band gap of the films varied between 4.07 and 4.14 eV. As a result, MgO films with high transmittance reaching an average of 95% in the visible region were obtained.