Ultralow Thermal Conductivity in Disordered, Layered WSe ₂ Crystals

Abstract

The cross-plane thermal conductivity of thin films of WSe 2 grown from alternating W and Se layers is as small as 0.05 watts per meter per degree kelvin at room temperature, 30 times smaller than the c -axis thermal conductivity of single-crystal WSe 2 and a factor of 6 smaller than the predicted minimum thermal conductivity for this material. We attribute the ultralow thermal conductivity of these disordered, layered crystals to the localization of lattice vibrations induced by the random stacking of two-dimensional crystalline WSe 2 sheets. Disordering of the layered structure by ion bombardment increases the thermal conductivity.