Thermal conductivity of hybrid graphene/silicon heterostructures

YH Jing and M Hu and LC Guo, JOURNAL OF APPLIED PHYSICS, 114, 153518 (2013).

DOI: 10.1063/1.4826492

The success of fabricating single layer graphene and silicon nanofilm (could be as thin as single layer so far) has triggered enormous interest in exploring their unique physics and novel applications. An intuitive idea is to investigate what happens if we construct a heterostructure composed of these two sheets. In this paper, we perform nonequilibrium molecular dynamics simulations to systematically investigate the in-plane thermal transport in graphene/silicon/graphene (Gr/Si/Gr) heterostructures. The effects of Si film thickness, interfacial interaction strength, and length on the thermal conductivity of the Gr/Si/Gr heterostructures are explicitly considered. Our simulations identify a unified scaling law for thickness dependence of thermal conductivity of the Gr/Si/Gr heterostructures, despite different interfacial interaction forms are used (weak van der Waals interaction and strong covalent bonding). By quantifying relative contribution from phonon polarizations and defining heat flux onto single atom, we reveal and fully understand the different mechanisms governing the phonon transport in the Gr/Si/Gr heterostructures for the two different interfacial interaction forms. We also found that the thermal conductivity of Gr/Si/Gr heterostructure is nonmonotonically dependent on the van der Waals interaction strength between graphene and Si, but monotonically dependent on the graphene-silicon covalent bonding strength. Moreover, length dependence study shows that phonon transport in Gr/Si/Gr heterostructure becomes diffusive at much shorter length as compared with single layer graphene and bilayer graphene. Comparing to single and double graphene layers, the thermal conductivity of the Gr/Si/Gr heterostructure can be reduced with more than one order of magnitude for very long structures. These results suggest that Gr/Si/Gr heterostructures are promising for nanoscale devices due to their unique thermal transport properties. (C) 2013 AIP Publishing LLC.

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