Reduction of solid-solid thermal boundary resistance by inserting an interlayer

An effective method is proposed to greatly improve the thermal transport across the interface between two solids with dissimilar phonon spectra. If the two solids have similar crystal structure and lattice constant, it is predicted from the molecular dynamics modeling that an over 50% reduction of the thermal boundary resistance can be achieved by inserting a 3-unit-cell-thick interlayer whose Debye temperature is approximately the square root of the product of the Debye temperatures of the two solids. On the other hand, if the two solids have a large difference in lattice constant, it is found the interfacial atomic restructuring plays an important role in thermal transport. In order to effectively reduce the thermal boundary resistance, the interlayer should have a lattice constant near the average of the lattice constants of the two solids. For this case, an over 60% reduction of the thermal boundary resistance can be achieved if the Debye temperature of the interlayer is equal to or slightly higher than the square root of the product of the Debye temperatures of the two solids. The enhancement of thermal transport is found mainly due to more phonon states participating in the boundary transport by inserting an interlayer.