Role of Al in engineering the optical band gap and PL emission intensity properties of CdO thin films grown by SILAR method

Abstract

Herein, we report on synthesizing pure and aluminum (Al) doped cadmium oxide (CdO) thin films onto glass slides by successive ionic layer adsorption and reaction (SILAR) method. The optical, electrical, structural, and morphological evaluations were conducted for the produced samples after the grown thin films heat treated in a convection ashing furnace at 200 °C. X-ray diffraction (XRD) results disclosed that the prepared samples posses the polycrystalline cubic phase of CdO material and the (1 1 1) plane was the preferred growth orientation. Besides, the XRD analysis strongly suggested that the integration of aluminum into the CdO lattices completed as no other phases, such as Cd, Al, or related oxides, were present in the diffraction patterns. From the field emission scanning electron microscope (FE-SEM) images, it was noticed that Al doping concentration changed the surface morphologies. Energy dispersive X-ray analysis (EDAX) confidently proves the presence of Al as a result of the SILAR process. The optical properties were assessed by performing Ultraviolet–visible spectroscopy (Uv–vis), and it was observed that the optical bandgap increased from 2.5 eV to 3 eV due to the increased percentages of Al content in the Al:CdO nanostructures. The Photoluminescence (PL) spectrum evidently showed that the PL emission intensity of prepared samples was directly influenced over varying Al content in the CdO nanostructures. The electrical features of the SILAR derived CdO thin films uncovered that the resistivity of samples showed increment with the Al doping, thus the electrical conductivity of the grown samples decreased in return.