The local atomic structure and thermoelectric properties of Ir-doped ZnO: hybrid DFT calculations and XAS experiments

Andrea Zitolo,Denis Gryaznov,Natalia V Skorodumova,Juris Purans,Andris Anspoks,Alexei Kuzmin,Andrei Chesnokov,Eugene A Kotomin,Martins Zubkins

doi:10.1039/d1tc00223f

Abstract

We combined the hybrid density functional theory (DFT) calculations and X-ray absorption spectroscopy (XAS) experiments in the study of the local atomic structure around Ir ions in ZnO thin films with different iridium content.

Highlights

To date, there has been room for more details on a study of the behaviour of intrinsic and impurity defects in Zinc oxide (ZnO)
A decrease of the iridium concentration leads to the appearance of the shoulder at 11 240 eV, visible in the extended X-ray absorption fine structure (EXAFS) spectra at 2.5 ÅÀ1; it is due to the damped highfrequency contribution originating from peaks at 2–4 Å in FTs
The analysis of EXAFS spectra using the reverse Monte Carlo simulations revealed that iridium ions are predominantly octahedrally coordinated by oxygens

Summary

Introduction

There has been room for more details on a study of the behaviour of intrinsic and impurity defects in ZnO. In ZnO electronic donors are formed spontaneously leading to intrinsic doping asymmetry.[8] Even though the oxygen vacancy possesses the lowest formation energy under Zn and O-rich conditions in most theoretical studies on bulk material, understanding conditions for the growth of the thin films plays a very important role. The Mn-doped ZnO thin films required theoretical computations to explain discrepancies in the interpretation of XANES (X-ray absorption near edge structure) spectra.[9] It was established that neither O nor Zn vacancies are detectable in the XANES spectra. Their presence is less important than local structure changes induced by the Mn impurity. The results section is divided into several subsections to discuss the results of the extended X-ray absorption fine structure (EXAFS) spectra analysis using reverse Monte Carlo (RMC) simulations, the calculated structural properties of IrOx complexes in ZnO and those of the parent compounds, the electronic structure properties of IrOx complexes in ZnO, and the main results of thermoelectric property calculations

Methods

Results and discussion

Conclusions