Tunability of thermal conductivity in lead chalcogenide nanowire heterostrutures by strain or alloying*

In the past few years, work on lead chalcogenide alloys of PbSe, and PbTe has shown interesting tunability of electronic properties. PbTe-based materials have shown enhanced phonon scattering driven by a near ferroelectric phase transition mediated by strain or alloying. The thermal properties of such materials are of interest for thermoelectric applications. We consider a low-dimensionality heterostructure, the nanowire, which generally has a lower thermal conductivity compared to bulk. We consider a computationally efficient shell model to find the phonon dispersion of bulk, and approximate the nanowire phonon dispersion. Phonon transport is modeled with an energy deviational Monte Carlo formulation of the Boltzmann transport equation. We further consider layered alloys, with three different transition types between layers: abrupt, linear, and exponential. The considered phonon scattering mechanisms are phonon-phonon, boundary, defect, interface, alloy, and strain. We will report on the further tunability of thermal conductivity by manipulating nanowire heterostructures of these lead chalcogenide alloys.