Epitaxial stabilization of ultra thin films of high entropy perovskite

TL;DR

This paper demonstrates the successful epitaxial growth of high entropy perovskite thin films, specifically (LaPrNdSmEu)NiO3, and investigates their structural and electronic properties, revealing a first order metal-insulator transition similar to NdNiO3.

Contribution

It introduces a method for layer-by-layer growth of high entropy oxide thin films and analyzes their structural and electronic behaviors, highlighting the influence of the average tolerance factor.

Findings

High-quality epitaxial thin films were grown successfully.

The films exhibit a first order metal-insulator transition.

Electronic behavior is primarily governed by the average tolerance factor.

Abstract

High entropy oxides (HEOs) are a class of materials, containing equimolar portions of five or more transition metal and/or rare-earth elements. We report here about the layer-by-layer growth of HEO [(La$_{0.2}$Pr$_{0.2}$Nd$_{0.2}$Sm$_{0.2}$Eu$_{0.2}$)NiO$_3$] thin films on NdGaO$_3$ substrates by pulsed laser deposition. The combined characterizations with in-situ reflection high energy electron diffraction, atomic force microscopy, and X-ray diffraction affirm the single crystalline nature of the film with smooth surface morphology. The desired +3 oxidation of Ni has been confirmed by an element sensitive X-ray absorption spectroscopy measurement. Temperature dependent electrical transport measurements revealed a first order metal-insulator transition with the transition temperature very similar to the undoped NdNiO$_3$. Since both of these systems have a comparable tolerance factor, this work demonstrates that the electronic behaviors of $A$-site disordered perovskite-HEOs are primarily controlled by the average tolerance factor.