Density Functional Theory Studies of Zn12O12 Clusters Doped with Mg/Eu and Defect Complexes

S Assa Aravindh,Hussain Alawadhi,Iman S Roqan

doi:10.1007/s10876-020-01758-y

Abstract

We report a density functional theory study of ZnO cluster doped with Eu and Mg along with native point defects using the generalized gradient approximation including the Hubbard parameter. The Zn atomic positions are found to be energetically more favorable doping sites than O. The Eu has a lower formation energy than Zn and O vacancies, helps in lowering the formation energy of point defects and induces spin polarization. Mg is less favorable dopant energetically and is not inducing any magnetism in the cluster. Presence of Eu and point defects along with Mg can help in sustaining spin polarization, implying that transition metal and rare earth dopant is a favorable combination to invoke desirable properties in ZnO based materials. Eu–Eu doping pair prefers ferromagnetic orientation and a spin flip is induced by Eu in the Eu–Mg configuration. Further, Eu doping increases the value of static refractive index and optical absorption in the UV region compared to the undoped ZnO cluster.

Highlights

Cluster science is an interesting area in materials research, as clusters are often envisaged as building blocks for nanoscale materials, starting ‘‘from the bottom up’’ wherein the properties can be tuned by varying the size and composition [1]
We report a density functional theory study of ZnO cluster doped with Eu and Mg along with native point defects using the generalized gradient approximation including the Hubbard parameter
The coordination number of each atom is 3, and the atomic rings consist of 4 and 6 atoms. The uniqueness of this cluster geometry stems from all the atoms being located on the surface, which is effectively equivalent to ZnO nanoparticle or quantum dots (QDs) structures synthesized experimentally [19]

Summary

Introduction

Cluster science is an interesting area in materials research, as clusters are often envisaged as building blocks for nanoscale materials, starting ‘‘from the bottom up’’ wherein the properties can be tuned by varying the size and composition [1]. ZnO nanoparticles continue to attract significant attention from both academic and industrial researchers due to their unique properties, such as high exciton binding energy (60 meV), wide band gap, and cost-effective synthesis methods These properties can be harnessed in a variety of applications such as environmental sensors, photodetectors and transistors based on ZnO quantum dots (QDs) [4,5,6]. We report the findings yielded by a density functional theory (DFT) study of Eu-doped Zn12O12 clusters with and without native point defects, such as Zn and O vacancies (VZn and VO) As part of this investigation, we conducted co-doping in the cluster with Eu and Mg, in presence of native defects, to understand the changes in structural, magnetic, and electronic properties of the ZnO cluster

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