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Weperform molecular dynamics simulations to investigate the reductionof the thermal conductivity by kinks in silicon nanowires. The reductionpercentage can be as high as 70% at room temperature. The temperaturedependence of the reduction is also calculated. By calculating phononpolarization vectors, two mechanisms are found to be responsible forthe reduced thermal conductivity: (1) the interchanging effect betweenthe longitudinal and transverse phonon modes and (2) the pinchingeffect, that is, a new type of localization, for the twisting andtransverse phonon modes in the kinked silicon nanowires. Our workdemonstrates that the phonon interchanging and pinching effects, inducedby kinking, are brand-new and effective ways in modulating heat transferin nanowires, which enables the kinked silicon nanowires to be a promisingcandidate for thermoelectric materials. [ABSTRACT FROM AUTHOR]

The thermal conductivity of silicon nanowires (SiNWs) is investigated by molecular dynamics (MD) simulation. It is found that the thermal conductivity of SiNWs can be reduced exponentially by isotopic defects at room temperature. The thermal conductivity reaches the minimum, which is about 27% of that of pure 28Si NW, when doped with 50% isotope atoms. The thermal conductivity of isotopic-superlattice structured SiNWs depends clearly on the period of superlattice. At a critical period of 1.09 nm, the thermal conductivity is only 25% of the value of pure Si NW. An anomalous enhancement of thermal conductivity is observed when the superlattice period is smaller than this critical length. The ultralow thermal conductivity of superlattice structured SiNWs is explained with phonon spectrum theory.