Efficient phonon blocking in SiC antiphase superlattice nanowires
Résumé
The high thermal conductivity of SiC prevents the improvement of its thermoelectric figure of merit, although excellent power factor has been achieved. Here we propose a different type of SiC superlattice, i.e., antiphase superlattice (APSL) nanowires (NWs), composed of only SiC components but with different stacking sequences. Our molecular dynamics simulations show that the thermal conductivity of period modulated APSL NWs can be significantly reduced by up to a factor of two at room temperature compared to the one of pristine NWs. The phonon density of states reveals that new vibrational modes emerge on the interfaces due to the formation of Si-Si and C-C bonds. We identify the increased phonon interfacial scattering as the predominant factor that hinders the thermal transport along the wires with period Lp>6 nm. Phonon coherent transport is also observed in the structures with period Lp<6 nm, which leads to a minimum thermal conductivity at the period of 6 nm. These results provide clear guidelines to design structures with minimal thermal conductivity and possibly promote SiC as a competitive thermoelectric material.