Oxygen vacancies induced photoluminescence in hbox {SrZnO}_2 nanophosphors probed by theoretical and experimental analysis

Manju Manju,Anup Thakur,Pargam Vashishtha,Kemal Özdoğan,Saibabu Madas,Megha Jain,Ankush Vij,Govind Gupta,Mousumi Upadhyay Kahaly,Parasmani Rajput

doi:10.1038/s41598-020-74436-8

Abstract

We report, for the first time, the influence of oxygen vacancies on band structure and local electronic structure of hbox {SrZnO}_2 (SZO) nanophosphors by combined first principle calculations based on density functional theory and full multiple scattering theory, correlated with experimental results obtained from X-ray absorption and photoluminescence spectroscopies. The band structure analysis from density functional theory revealed the formation of new energy states in the forbidden gap due to introduction of oxygen vacancies in the system, thereby causing disruption in intrinsic symmetry and altering bond lengths in SZO system. These defect states are anticipated as origin of observed photoluminescence in SZO nanophosphors. The experimental X-ray absorption near edge structure (XANES) at Zn and Sr K-edges were successfully imitated by simulated XANES obtained after removing oxygen atoms around Zn and Sr cores, which affirmed the presence and signature of oxygen vacancies on near edge structure.

Highlights

We report, for the first time, the influence of oxygen vacancies on band structure and local electronic structure of SrZnO2 (SZO) nanophosphors by combined first principle calculations based on density functional theory and full multiple scattering theory, correlated with experimental results obtained from X-ray absorption and photoluminescence spectroscopies
Having no band to band transition peak but broad spectrum indicated about presence of defect states in forbidden gap, which is confirmed by the band structure and densities of states analyses, as calculated using density functional theory
The band structure for bulk pristine SZO obtained within generalized gradient approximation estimated the direct band gap of 1.95 eV, while for SZO with oxygen vacancy concentrations 3.125% and 12.5%, the band gaps conceived indirect nature and are substantially reduced

Summary

Introduction

For the first time, the influence of oxygen vacancies on band structure and local electronic structure of SrZnO2 (SZO) nanophosphors by combined first principle calculations based on density functional theory and full multiple scattering theory, correlated with experimental results obtained from X-ray absorption and photoluminescence spectroscopies. The band structure analysis from density functional theory revealed the formation of new energy states in the forbidden gap due to introduction of oxygen vacancies in the system, thereby causing disruption in intrinsic symmetry and altering bond lengths in SZO system. These defect states are anticipated as origin of observed photoluminescence in SZO nanophosphors. The consequence of oxygen vacancies in the system is seen as broad band PL spectrum, centred at ∼510 nm, exhibited by SZO nanophosphors

Methods

Results

Conclusion