Enhanced Thermoelectric Properties of SrSi₂ Composite Films with Cubic and Layered Polymorphs

Abstract

SrSi2 composite films exhibit a significant improvement in thermoelectric performance through the mixture of the stable cubic phase with a metastable layered phase. The phase fraction of the cubic and layered phases in SrSi2 films is controlled by changing the deposition temperature. The film deposited at 700 °C, which is composed of a semimetallic cubic phase and a small portion of a metallic layered phase, shows a high figure of merit, ZT, beyond 0.4 at around room temperature. This value is eight times larger than the previously reported one for cubic SrSi2 bulk polycrystals. These large values originate from the microstructures of the films, which reduce thermal conductivity without deterioration of the power factor.