Enhancement in optical and electrical properties of ZnO thin films via Co doping for photodetector applications

Abstract

Co doped ZnO thin films were developed by cost effective Successive ionic layer adsorption and reaction (SILAR) method. The Co doping concentration was varied from 0, 2, 4, 6 and 8% in the ZnO and their corresponding physical, morphological, structural, optical, and photo sensing properties were carried out. The XRD studies confirmed the phase purity, structure of ZnO lattice as hexagonal wurtzite and the crystallite size increases from 43 to 52 nm due to the substitutional replacement of Co doping concentration. The morphology of the thin films by FESEM revealed that inclusion of Co over the ZnO lattice doesn’t affect the morphology but increment of grain size which is desired for UV Photo detectors. From the optical studies, maximum absorbance in UV region and minimum optical bandgap for ZnO:Co4% sample was observed. Photoluminescence intensity was high for 4% Co doped ZnO sample with near band edge (NBE) emission at 392 nm. Responsivity (R), External Quantum Efficiency (EQE) and Detectivity (D*) were carried out and found to be 9.35 × 10−1 AW−1, 218% and 9.32 × 1010 Jones respectively for ZnO:Co 4% sample. The entire work concludes that inclusion of 4% Co in the ZnO thin film made it as a potential candidate for photo sensing applications in UV region.