As one of the efforts to enhance the thermoelectric conversion efficiency, phonon transport through elastically dissimilar barriers embedded in Si nanowires is investigated. Using a Green's function method based on an elastic wave equation, the transmission function is calculated for various barrier materials with different acoustic impedance. It is found that the insertion of suicide (especially PtSi) layers into the Si nanowire substantially suppresses the phonon transmission function and, thus, is promising alternative to enhance the efficiency of thermoelectric devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3694043]