The lattice thermal conductivity of hafnia: The influence of high-order scatterings and phonon coherence

Abstract

Hafnia (HfO2) is a potential candidate for the high-k gate dielectrics in next-generation high-power electronics. Its thermal transport properties, which determine the performance of these related high-power electronics, are critical while rarely investigated. Here, the thermal transport properties of HfO2 in a wide temperature range of 300–2000 K with a phase transition between monoclinic and tetragonal phases at ∼1765 K, are systematically studied based on the temperature-dependent effective potential landscapes with both propagating and coherence thermal transport considered. It is found that the cage-like structure of monoclinic HfO2 results in the avoid crossing in the phonon band structures, which increases the three-phonon scattering largely. Some phonon modes with significant scattering matrix can have relatively larger 3ph and 4ph scattering rates in tetragonal HfO2. Consequently, the thermal conductivity of HfO2 is only 11.95–1.72 W/mK at 300–2000 K. Our results further show that propagating phonon channels dominate the thermal transport in HfO2 and contribute at least 70% to the total thermal conductivity. The rest of the thermal conductivity of HfO2 results from the coherence thermal transport channels, which is caused by the overlap of phonons. Four-phonon scatterings are found to be significant for the thermal transport in tetragonal HfO2, which can result in a thermal conductivity reduction of ∼50%. Our results here advance the understanding of the thermal transport in HfO2, which may benefit the performance optimization of HfO2-related electronics.