Effect of Co/Y co-doping concentrations on the tailoring structure and optical properties of ZnO nanostructures

Abstract

Undoped and 0.01, 0.03 and 0.05 mol% concentrations of Co/Y co-doped ZnO nanostructures were attempted by solid-state method. In this study, to investigate experimentally how Co/Y co-doping concentrations impact the crystalline structure, surface particle dimension, and optical characteristics of ZnO nanostructures. Hexagonal structure was found in the XRD pattern of undoped ZnO. However, distortion in the hexagonal structure were noticed in the ZnO by introducing co-dopant concentrations (Co/Y) from 0.01 to 0.05 mol% in the XRD pattern. Non-uniform size with agglomerated spherical, coalescence with spherical, porous structure with smaller size spherical, and highly porous with well dispersed spherical particles were noticed for the undoped, 0.01, 0.03 and 0.05 mol% of Co/Y co-doped ZnO in the SEM studies. FT-IR spectra indicate that the Zn-O vibrational shift towards to the lower wavenumber with an increasing Co/Y dopant concentrations in the ZnO. Raman spectra were studied to understand the structural confirmation of the synthesized compounds. The molecular elements, chemical composition, elemental oxidation states and its corresponding binding energy of the synthesized undoped ZnO and Co/Y-doped ZnO were recorded from the EDX/mapping and XPS studies. Optical absorption spectra were evaluated for the synthesized compounds and their optical band gap (Eg = 1.76 to 1.46 eV) results narrowing in the ZnO by increasing co-dopant concentrations from 0.01 to 0.05 mol% when compared to the undoped ZnO (Eg = 3.16 eV). The PL emission bands (UV and visible portion) and colour coordinates (x, y) position values were slightly tuned under the impact of co-dopant concentrations in the synthesized ZnO nanostructures.