The thermal conductivity of silicon nanowires (SiNWs) is investigated bymolecular dynamics (MD) simulation. It is found that the thermal conductivityof SiNWs can be reduced exponentially by isotopic defects at room temperature.The thermal conductivity reaches the minimum, which is about 27% of that ofpure 28Si NW, when doped with fifty percent isotope atoms. The thermalconductivity of isotopic-superlattice structured SiNWs depends clearly on theperiod of superlattice. At a critical period of 1.09 nm, the thermalconductivity is only 25% of the value of pure Si NW. An anomalous enhancementof thermal conductivity is observed when the superlattice period is smallerthan this critical length. The ultra-low thermal conductivity of superlatticestructured SiNWs is explained with phonon spectrum theory.
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