Reduction of the thermal conductivity in a 1D superlattice


Many technological applications require solids having very low thermal conductivity. This work demonstrates that this can be achieved for specific layer parameters in a superlattice. The phonon dispersion for thick or uneven layered superlattices is modeled using the harmonic approximation in one dimension (1D). The dispersion curves for superlattices with uneven thickness in layers are characterized by the disappearance of forbidden regions. These gaps are usually found in superlattices having uniform thickness. From these results and assuming a constant phonon mean free path, a marked decrease in the lattice contribution to the thermal conductivity is obtained as a function of layer thickness, mass ratio between the layers or asymmetry in its structure.