Giant Tuning of Electronic and Thermoelectric Properties by Epitaxial Strain in p-Type Sr-Doped LaCrO3 Transparent Thin Films

TL;DR

This study demonstrates that epitaxial strain in Sr-doped LaCrO3 thin films can significantly tune their electronic and thermoelectric properties, enabling enhanced performance for energy and electronic devices.

Contribution

The paper shows how epitaxial strain can be used to control and enhance the thermoelectric and electronic properties of p-type LaCrO3 thin films, a novel approach for material optimization.

Findings

Electrical conductivity varies over 2 orders of magnitude with strain.

Seebeck coefficient can be tuned by almost a factor of 2.

Thermoelectric power factor can be enhanced by nearly 2 orders of magnitude.

Abstract

The impact of epitaxial strain on the structural, electronic, and thermoelectric properties of p-type transparent Sr-doped LaCrO3 thin films has been investigated. For this purpose, high-quality fully strained La0.75Sr0.25CrO3 (LSCO) epitaxial thin films were grown by molecular beam epitaxy on three different (pseudo)cubic (001)-oriented perovskite oxide substrates: LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, and DyScO3. The lattice mismatch between the LSCO films and the substrates induces in-plane strain ranging from -2.06% (compressive) to +1.75% (tensile). The electric conductivity can be controlled over 2 orders of magnitude, ranging from 0.5 S/cm (tensile strain) to 35 S/cm (compressive strain). Consistently, the Seebeck coefficient S can be finely tuned by a factor of almost 2 from 127 microV/K (compressive strain) to 208 microV/K (tensile strain). Interestingly, we show that the thermoelectric power factor can consequently be tuned by almost 2 orders of magnitude. The compressive strain yields a remarkable enhancement by a factor of 3 for 2% compressive strain with respect to almost relaxed films. These results demonstrate that epitaxial strain is a powerful lever to control the electric properties of LSCO and enhance its thermoelectric properties, which is of high interest for various devices and key applications such as thermal energy harvesters, coolers, transparent conductors, photocatalyzers, and spintronic memories.