Lithium ion assisted luminescence and ferromagnetism in europium doped zinc oxide

Abstract

We have investigated the influence of different lithium concentrations (0.25–1.0%) on Eu(1%) doped zinc oxide nanoparticles synthesized by sol gel method. The results of XRD, TEM, EDS, FTIR and Raman analysis authenticate the crystalline structure and incorporation of europium and lithium in hexagonal crystal structure of zinc oxide without any impurity phase. The XPS spectra of lithium confirm the existence of Li substitutional and Li interstitial. The local structure has been investigated by X-ray absorption spectroscopy analysis. The results ascertain oxidation state of elements in samples. The variation in bond length observed by EXAFS fitting supports XPS data and indicates the presence of dopant in the host. The position of Li plays an important role in defect mediated ferromagnetism of zinc oxide. The photoluminescence study demonstrates the enhancement in europium related peak for small lithium concentration. We found that the ferromagnetism in zinc oxide reduces after europium doping, while incorporation of lithium (0.5–1.0%) in europium doped zinc oxide significantly enhances the ferromagnetic property of zinc oxide. Li substitutions contribute to ferromagnetic property of zinc oxide by stabilizing Zn vacancy and other magnetic defects. The existence of enhanced luminescence coupled with RTFM makes this material suitable for optoelectronics devices.