Lattice Thermal Conductivity Crossovers in Semiconductor Nanowires

For binary compound semiconductor nanowires, we find a striking relationship between the nanowire's thermal conductivity ₍ₖ₈ₑ₄, the bulk material's thermal conductivity ₁ₔ₋₊, and the mass ratio of the material's constituent atoms, r, as ₁ₔ₋₊/₍ₖ₈ₑ₄ (1+1/r) ^-3/2. A significant consequence is the presence of crossovers in which a material with higher bulk thermal conductivity than the rest is no longer the best nanowire thermal conductor. We show that this behavior stems from a change in the dominant phonon scattering mechanism with decreasing nanowire size. The results have important implications for nanoscale heat dissipation, thermoelectricity, and thermal conductivity of nanocomposites.