Influence of oxygen pressure on the structural and optical properties of DC magnetron reactive sputtered cadmium oxide films

Cadmium oxide thin films were prepared onto glass substrates by a DC magnetron reactive sputtering method from a metallic cadmium target in an argon and oxygen atmosphere. A systematic study has been made on the influence of oxygen partial pressure, ranging from 2 x 10(-4)mbar to 5 x 10(-3) mbar, on the film structure and optical properties. The films were polycrystalline in nature with cubic structure. The grain size of the films was in the range 40-80nm. The optical transmittance of the films was in the range 65-85% in the wavelength region 600-1600nm. The optical band gap and refractive index of the films increased from 2.46 eV to 2.54 eV and 2.33 to 2.42 with increase in the partial pressure of oxygen ranging from 5 x 10(-4)mbar to 5 x 10(-3) mbar respectively.