Anomalous heat conduction behavior in thin finite-size silicon nanowires

Abstract

Anomalous heat conduction behavior is observed for the first time usingnon-equilibrium molecular dynamics (NEMD) simulations to obtain thethermal conductivity of thin finite-size silicon nanowires (NWs) in the⟨001⟩ lattice direction. In the series of simulations, the length dependence of thermal conductivityof thin silicon nanowires (NWs) ranging from 6 to 434 nm is analyzed. It is found that atransition occurs in the thermal conductivity versus length curve after the initialconvergence trend appears near the mean free path of bulk silicon. Because noexperimental measurements of thermal conductivity are available for sub-10 nmdiameter silicon NWs, different NEMD methods are used to test and analyze thisanomalous thermal behavior of thin Si NWs with different boundary conditions. Theunderlying mechanism of the observed behavior is inferred from MD simulationswith different boundary conditions so that the anomalous behavior is mainlycaused by border restriction and boundary scattering of the thin silicon NWs.