Impact of Ge clustering on the thermal conductivity of SiGe nanowires: atomistic simulation study

Using non-equilibrium molecular dynamics simulations, we demonstrate that the thermal conductivity of SiGe alloy nanowires is remarkably sensitive to inhomogeneous composition distributions. Specifically, the effects of Ge clustering on the thermal conductivity of SiGe nanowires are studied. The results showed that clustering Ge atoms can improve the thermal conductivity of SiGe alloy nanowires due to the reduction of random alloy scattering centers. When the number of Ge atoms in the nanocluster increases, the thermal conductivity of such nanowires grows monotonically compared with that of random alloy nanowires. To reveal the role of inhomogeneous Ge distributions on the thermal conductivity, we performed vibrational eigenmode analyses and found the remarkable delocalization of phonon modes after Ge clustering. Through such analyses, we found that the increase in thermal conductivity was correlated with the phonon delocalization in the SiGe nanowires, where stronger delocalization indicates a better thermal performance of the nanowires. Our results are helpful not only in understanding the clustering effects on heat transport but also in modulating the thermal conductivity of SiGe nanowires.