Estimation of Phonon Mean Free Path in Small-Scaled Si Wire by Monte Carlo Simulation

A phonon transport in Si wire structures were simulated based on a Monte Carlo method to clarify the influence of the wire geometry and the surface roughness on thermal conductivity and the phonon-drag component of Seebeck coefficient. The mean free path (MFP) spectrum was estimated by tracing the simulated phonons. The MFPs of 1 THz phonons which mainly contribute to Seebeck coefficient become shorter with a decrease of the wire width for rough surfaces. This agrees with experimental observation of Seebeck coefficient. The MFPs of 3 THz phonons which mainly contribute to thermal conductivity were influenced even by small-roughness surfaces.