Deconvolution of Phonon Scattering by Ferroelectric Domain Walls and Point Defects in a PbTiO₃ Thin Film Deposited in a Composition-Spread Geometry

Abstract

We present a detailed analysis of the temperature dependence of the thermal conductivity of a ferroelectric PbTiO3 thin film deposited in a composition-spread geometry enabling a continuous range of compositions from ∼25% titanium deficient to ∼20% titanium rich to be studied. By fitting the experimental results to the Debye model we deconvolute and quantify the two main phonon-scattering sources in the system: ferroelectric domain walls (DWs) and point defects. Our results prove that ferroelectric DWs are the main agent limiting the thermal conductivity in this system, not only in the stoichiometric region of the thin film ([Pb]/[Ti] ≈ 1) but also when the concentration of the cation point defects is significant (up to ∼15%). Hence, DWs in ferroelectric materials are a source of phonon scattering at least as effective as point defects. Our results demonstrate the viability and effectiveness of using reconfigurable DWs to control the thermal conductivity in solid-state devices.

Real-Space Infrared Spectroscopy of Ferroelectric Domain Walls in Multiferroic h-(Lu,Sc)FeO3

“…Looking ahead, ferroelectric domain walls of the type discussed in this work will find application in emerging logic and memory technologies. Naturally, properties like thermal conductivity and heat capacity are key to effective heat management, and useful microscopic models of dissipation require information about the fundamental excitations of the lattice at the wall in addition to wall-induced scattering . These findings open the door to phononic engineering of domain-wall-based device architectures, where strategies to create bespoke behavior by altering the local chemistry significantly extend the complexity of these efforts.…”

“…Naturally, properties like thermal conductivity and heat capacity are key to effective heat management, and useful microscopic models of dissipation require information about the fundamental excitations of the lattice at the wall in addition to wall-induced scattering. 64 These findings open the door to phononic engineering of ■ METHODS Crystal Growth, Characterization, and Mapping. High-quality h-Lu 0.6 Sc 0.4 FeO 3 single crystals were grown using optical floating zone techniques as described previously.…”

Ferroelectric Domain Wall Engineering Enables Thermal Modulation in PMN–PT Single Crystals

“…Interestingly, DW engineering has also been applied in the field of thermal science, to modulate thermal conductivity (k) for achieving better control of solidstate heat transfer. [31][32][33][34][35][36][37][38][39] Thermal conductivity decreases by introducing DWs that act as thermal resistances inhibiting thermal transport. [31][32][33][34][35][36][37][38][39] The ease in manipulating ferroelectric DW density by electrical input has opened novel possibilities in thermal transport engi neering, which led to developments in ferroelectric thermal switches to enable dynamic control over heat flux in a mate rial.…”

“…[31][32][33][34][35][36][37][38][39] Thermal conductivity decreases by introducing DWs that act as thermal resistances inhibiting thermal transport. [31][32][33][34][35][36][37][38][39] The ease in manipulating ferroelectric DW density by electrical input has opened novel possibilities in thermal transport engi neering, which led to developments in ferroelectric thermal switches to enable dynamic control over heat flux in a mate rial. Thermal switches modulate thermal conductivity between two states (k high and k low ), where the high thermal conductivity state (k high ) is a result of lower ferroelectric DW density and vice versa.…”

“…Several ferroelectric DWbased thermal switches have been reported, attempting to achieve maximum contrast in DW density to obtain a high thermal conductivity switching ratio (k high / k low ). [31][32][33][34][35][36][37][38][39] Thus, utilizing this wellestablished relation between thermal conductivity and DW density, thermal conduc tivity characterization can serve as an alternative approach to assess the bulk DW density in relaxorferroelectrics.…”