Synthesis of Er doped ZnO cone-like nanostructures with enhanced structural, optical and magnetic properties

Abstract

In this report, undoped ZnO and Er doped ZnO nanostructures [Zn_1−xEr_xO, where x = 1, 3, 5 and 7 at.%] were synthesized by chemical precipitation technique. The chemical precipitation route for the preparation of undoped ZnO and Er doped ZnO nanostructures at different concentrations represents an easy, fast and efficient method. The synthesized nanostructures were characterized to analyze their crystal structure, crystal morphology, optical and magnetic properties using X-ray diffraction (XRD), Energy dispersive X-ray (EDX), High resolution scanning electron microscopy (HRSEM), Ultraviolet–Visible spectroscopy (UV–Visible), Photoluminescence spectroscopy (PL) and Vibrating sample magnetometer (VSM) respectively. The XRD studies exposed that undoped ZnO and all Er doped ZnO samples have a hexagonal wurtzite crystal structure. The XRD results showed that Er³⁺ ions were successfully doped into ZnO nanostructures as no diffraction peaks of Er or erbium oxide were observed in the pattern. EDX results also confirmed that Er ions were successfully incorporated into the lattice position of Zn ions in ZnO. HRSEM characterization showed that presence of Er³⁺ ions in crystal structure of ZnO can change the morphology i.e. the transformation of nanorods to nanocones. Nanorods-like structure obtained with 1 at.% Er extend to nanocones-like for 3–7 at.% Er doped ZnO with changes in length and thickness in nm range. In UV–Visible absorbance spectra, a red shift was observed in the band gap of undoped ZnO and Er doped nanostructures with increasing Er concentration. PL measurements also revealed that the undoped ZnO and Er doped ZnO nanostructures had an UV emission, a defect emission and the Er ions doping induced a red shift in the UV emission with a small enhancement in the defect emission. The VSM study revealed that the undoped ZnO and Er doped ZnO nanostructures exhibit paramagnetic and ferromagnetic behaviour at room temperature respectively.