LAUSR

..Abstract In this work, we fabricated nanocomposite thin films of MnSiγ and SiGe, both of which are promising thermoelectric materials, and studied the dependence of their crystal structures and thermoelectric properties on the Ge content. The addition of Si1-xGex caused a reduction in the grain size of the MnSiγ matrix to the scale of the phonon mean free path of MnSiγ, which is essential for phonon scattering to reduce the lattice thermal conductivity. In addition, increasing the Ge ratio in the additive SiGe of the nanocomposite caused both a reduction at x = 0.2 ratio in the thermal conductivity and a monotonical reduction of the electrical resistivity with negligible change in the thermopower. The former of these two phenomena may be attributed to both a reduction in the thermal conductivity of SiGe as a result of heavier element (Ge) substitutions than Si and an increase in the thermal boundary resistance between MnSiγ and SiGe. In the case of the latter, introduction of carriers caused by the decrease in γ, which is the atomic ratio between Si and Mn, would be responsible. As a result, the estimated thermoelectric dimensionless figure-of-merit ZT increased to reach a maximum of 0.43 at 459 °C, which is larger than that of the single phase MnSiγ film, without any doping into the MnSiγ matrix with heavy elements.