  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 fifty percent 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 ultra-low thermal conductivity of superlattice
structured SiNWs is explained with phonon spectrum theory.

Materials Science;Other Condensed Matter