The effect of magnesium doping concentration on the structural and optical properties of zinc oxide nanoparticles

Abstract

In this study, the optical and structural properties of Magnesium doped Zinc Oxide (Zn1-xMgxO) nanoparticles (x = 1%, 3%, and 5%) were examined. The synthesis was carried out at 300 oC by using a simple co-precipitation method. The structural samples were used to characterize the synthesized nanoparticles by using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Energy Dispersive X-Ray spectroscopy (EDX) was used to determine the chemical composition of the samples. Furthermore, UV-Vis spectroscopy was conducted to study our samples’ optical characteristics. As per XRD analysis, both pure and Mg doped ZnO samples possess wurtzite structure. The particle size was revealed to decrease significantly with Mg concentration, from 36 nm for pure sample to 23.87 nm with 5% Mg. In comparison to ZnO, the XRD pattern of Mg-doped ZnO shows a peak shift towards lower 2θ values. As a result of deformation of crystal structure caused by integrated Mg+2 ions onto Zn+2 sites. SEM images of synthesized samples reveal that the nanoparticles possess sheet, spherical and rod like morphologies for different values of x. The EDX analysis verifies the purity of samples within the detection limits. According to optical absorption spectra obtained from UV-Visible spectroscopy in the 200nm to 1000nm range affirmed that as Mg concentration increased, the band gap increased from 3.37 eV for pure sample to 3.74 eV with 5% Mg. The UV-Visible spectra of pure ZnO and Mg-doped ZnO samples also exhibit distinct peaks in the UV region at 335 nm, 311 nm, 310.6 nm, and 310 nm. Across the spectra of pure and Mg-doped ZnO samples, the UV peak is attributed to free exciton transitions, whereas, in the spectra of Mg-doped ZnO UV absorbance peak in the visible region is attributed to the radiative transitions of electrons captured at oxygen vacant sites with holes trapped at singly ionized oxygen vacancies.