Effect of Stacking Faults on the Thermoelectric Figure of Merit of Si Nanowires

The efficiency of converting waste heat to electricity requires a large value of the thermoelectric Figure of merit (ZT). This can be achieved by patterning bulk material into nanostructures like nanowires (NWs). Further improvement results from an increased surface roughness (SR) of such NWs [1]. In this work, Si NWs with stacking faults (SFs) are studied. It is shown that SFs can significantly reduce the lattice thermal conductivity as compared to ideal NWs [2]. A recent derivation of the phonon relaxation time for SF scattering [3] is adapted to the electronic case. It turns out that in most cases the thermoelectric power factor (PF) decreases to a lesser extent than the thermal conductivity. This can double ZT provided that SR scattering of electrons is negligible.