Modeling of interface roughness in thermoelectric composite materials

Abstract

We use a network model to calculate the influence of the mesoscopic interface structure onthe thermoelectric properties of superlattice structures consisting of alternating layers ofmaterials A and B. The thermoelectric figure of merit of such a composite material dependson the layer thickness, if interface resistances are accounted for, and can be increased byproper interface design. In general, interface roughness reduces the figure of merit, againcompared to the case of ideal interfaces. However, the strength of this reduction dependsstrongly on the type of interface roughness. Smooth atomic surface diffusion leading toalloying of materials A and B causes the largest reduction of the figure of merit.Consequently, in real structures, it is important not only to minimize interfaceroughness, but also to control the type of roughness. Although the microscopiceffects of interfaces are only empirically accounted for, using a network modelcan yield useful information about the dependence of the macroscopic transportcoefficients on the mesoscopic disorder in structured thermoelectric materials.