Investigation of the optical and dielectric behaviour of SnO2-CuO mixed oxides thin films

Abstract

The effects of CuO on the optical and dielectric properties of SnO2 thin film were studied to achieve improved light photon absorption and conversion. The films were deposited using airblast chemical spray pyrolysis. Rutherford Backscattering Spectrometric analysis using the Windows SIMNRA software gave the compositions of as-deposited and annealed films and their thicknesses. The optical and dielectric parameters were evaluated from the transmittance data obtained from UV – Visible spectrophotometer. The optical band gap of as-deposited SnO2-CuO film was evaluated to be 3.4 eV. The value of Urbach tail width of the as-deposited mixed oxide is higher (296 meV) compared to that of the annealed (252 meV) indicating the presence of more disordered states in the as-deposited film. The analysis also showed that the presence of CuO in the matrix of SnO2 led to a decrease in optical bandgap, refractive index, and by extension dielectric constants of SnO2. Our investigation led to the conclusion that the addition of CuO into SnO2 increased its electromagnetic photon absorption and also delay its speed thereby enhancing photon interaction with free charge carriers in the mixed oxide film. We opined that the mixed oxide will perform better in photocatalysis, photodegradation of pollutants and other light harvesting applications since the CuO inclusion has extended its absorption edge towards the visible light range.