Abstract:
The compatibility of the silicene, a silicon analogue of graphene, with the current semiconductor technology and the realized low thermal conductivity in the silicene nanostructures indicate the appealing prospect of silicene based nanostructures in thermoelectric applications. In this context, we have proposed and modeled silicene based nanoribbon structures namely silicene/germanene, silicene/graphene and silicene/stanene heterobilayers as well as bilayer silicene and subsequently characterized their thermal transport by using equilibrium molecular dynamics simulation. In addition, the thermal transport in bilayer stanene is also studied and compared. Our modeled heterobilayer and bilayer nanoribbon structures depict good thermal stability within the temperature range of 200 K to 600 K. Our calculated room temperature (300 K) thermal conductivities for the 10 nm x 3nm sized pristine silicene/germanene heterobilayer nanoribbon and silicene bilayer nanoribbon are 2.94 ± 0.01 W/m-K and 5.85 ± 0.22 W/m-K respectively which are considerably smaller than the thermal conductivities of monolayer silicene, germanene, graphene and some other 2D materials. Again, the room temperature thermal conductivities of pristine 10 nm x 3 nm silicene/stanene hetero-bilayer and stanene bilayer are estimated to be 3.63± 0.27 W/m-K and 1.31 ± 0.34 W/m-K, respectively, The obtained low thermal conductivity in our considered silicene supported group IV heterobilayer and bilayer nanostructures can further be lowered using bilayer stanene nanoribbons. On the other hand, our estimated thermal conductivity of 10 nm x 3 nm silicene/graphene nanoribbon at room temperature is 118.43 ± 1.26 W/m-K, which is significantly smaller than the thermal conductivity of similar sized graphene nanoribbon. The thermal conductivity of our investigated nanoribbon structures shows a decreasing trend with the increase in temperature within a range of 200 K to 600 K due to increased phonon-phonon Umklapp scattering. Furthermore, we have investigated the size dependence (both length and width) of thermal conductivity for our considered silicene supported nanoribbon structures. The thermal conductivities of our studied nanoribbons are found to increase with the increase in the sample size (either length or width). In support of our obtained results, phonon density of states (PDOS) of the concerned structures have been analyzed. Our realized low thermal conductivity in the silicene supported bilayer nanoribbons and the possibility of further lowering the thermal conductivity values by nanostructuring would promote the potential applications of silicene based nanostructures in the thermoelectric applications.
