Bending strain induced thermal conductivity suppression in freestanding BaTiO3 and SrTiO3 membranes

TL;DR

This study demonstrates that inhomogeneous strain in freestanding BaTiO3 and SrTiO3 membranes significantly suppresses thermal conductivity locally, revealing a new approach for dynamic thermal management via strain engineering.

Contribution

It introduces the use of crease-induced inhomogeneous strain to control thermal conductivity in freestanding perovskite membranes, supported by experimental and first-principles analysis.

Findings

Thermal conductivity is sharply reduced at high-curvature regions.

Strain gradients cause symmetry breaking, broadening phonon dispersion.

Inhomogeneous strain fields can be used to design thermal switches.

Abstract

Freestanding perovskite oxide membranes provide a novel platform for elastic strain engineering, enabling the manipulation of phonon transport free from substrate clamping. In this work, we investigate the thermal transport properties of strontium titanate (SrTiO3) and barium titanate (BaTiO3) membranes subjected to self-formed crease induced inhomogeneous strain. By integrating spatially resolved Frequency-Domain Thermoreflectance (FDTR) with micro-Raman spectroscopy, we observe a sharp, localized suppression of thermal conductivity (k) in high-curvature regions. Specifically, k is reduced from 4.43 to 3.62 W/(m K) in SrTiO3 and from 2.27 to 1.81 W/(m K) in BaTiO3 at the crease centers, directly correlating with the local strain distribution. First-principles calculations reveal that, unlike uniform strain, the symmetry breaking induced by strain gradients significantly broadens phonon dispersion and enhances scattering rates. These findings not only elucidate the microscopic mechanisms governing phonon-strain coupling but also demonstrate the potential of inhomogeneous strain fields as a potent tool for designing dynamic solid-state thermal switches and active thermal management devices.