Thermal Transport Mechanisms in Emergent Ferroelectric Materials 90 views

This dissertation investigates heat transport in emergent ferroelectric and metallic thin films to uncover how atomic composition, lattice symmetry, and defect dynamics govern energy flow at the nanoscale. As electronic and memory devices reach extreme miniaturization, achieving stable and predictable thermal behavior becomes vital for reliability and efficiency. Using advanced thermoreflectance and spectroscopic methods, this work builds an experimental and analytical foundation for quantifying phonon and electron transport across wurtzite, fluorite, and metallic systems. In wurtzite Al1-xBxN exceptionally high thermal conductivities are found to arise from the suppression of optical phonon scattering and preservation of lattice coherence. A direct relationship between phonon lifetime and measured conductivity in wurtzite Al1-xBxN and Al1-x-yBxScyN is established, revealing how substitutional alloying transitions heat transport from phonon-phonon to impurity-limited regimes. Complementary studies on Hf0.5Zr0.5O2 and Al0.92B0.08N under electric field cycling demonstrate that despite charge migration and structural wake-up, thermal conductivity remains invariant, indicating that polarization switching and phonon transport are largely decoupled. At the device-integration level, dilute Al0.995Cu0.005 thin films exhibit measurable deviations from the Wiedemann–Franz law, signifying the breakdown of bulk electronic transport assumptions in ultrathin metals. Together, these findings reveal that both ferroelectric and metallic thin films maintain remarkable electrothermal stability while offering tunable transport characteristics through compositional design. The results provide a framework for engineering materials that combine ferroelectric functionality with thermal reliability, guiding the development of high-density, energy-efficient computing architectures where control of heat is as critical as control of charge.

PHD (Doctor of Philosophy)

English

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2025-12-11