Engineering Thermal Conductivity Enhancement in Nanostructures

The ability to manipulate thermal transport at nanoscale has been restricted to reducing the thermal conductivity via diffuse scattering of phonons at interfaces. Rational material design has consequently been limited to applications such as thermoelectrics. On the other hand, enhancing thermal conduction at nanoscales which holds significant potential to develop efficient electronic, and optoelectronic devices has been largely unexplored. In this talk, we will present a novel approach to enhance the thermal conductivity of semiconductor thin-films in layered nanostructures. Specifically, we will show that the thermal conductivity enhancement can be achieved in germanium films cladded by silicon. The observed enhancement is a consequence of the coupling of the phonon spectrum of germanium and silicon materials through the interfaces. We will also present the effect of various structural conditions such as layer thicknesses and surface roughnesses on the phonon spectral coupling effect and their influence on the resultant thermal conductivities, establishing a new method to control the flow of thermal energy at the nanoscale beyond the current limits.