Widening of the optical band gap of CdO_2(1-X)Al_(X) thin films prepared by pulsed laser deposition

Abstract

In this study, doped thin cadmium peroxide films were prepared by pulsed laser deposition with different doping concentrations of aluminium of 0.0, 0.1, 0.3, and 0.5 wt.% for CdO_2(1-X)Al_(X) and thicknesses in the range of 200 nm. XRD patterns suggest the presence of cubic CdO₂ and the texture factor confirms that the (111) plane was the preferential growth plane, where the texture factor and the grain size decreased from 2.02 to 9.75 nm, respectively, in the pure sample to 1.88 and 5.65 nm, respectively, at a concentration of 0.5 wt%. For the predominant growth plane, the deviation of the diffraction angle Δθ and interplanar distance Δd from the standard magnitudes was 2.774° and 0.318 Å, respectively, for the pure sample decreased to − 2.633° and 0.301 Å for the largest doping concentration. The optical absorption was found to decrease with increasing doping concentration, where the changes in threshold wavelengths from the standard λ = 496 nm were blue shifted by Δλ = 142, 133, 128, and 152 nm, respectively, for the concentrations used. The occurrence of such blue shifts points to a widening of the band gap to Eg = 3.5, 3.4, 3.35, and 3.6 eV for concentrations of 0.0, 0.1, 0.3, and 0.5 wt%, respectively.