The thermoelectric performance of dumbbell silicene nanoribbons

Abstract

ABSTRACTDumbbell silicene, a stable allotrope of low-buckled (LB) silicene containing both sp2 and sp3 hybridized states, is a new topic in current graphene-derived material research community. In this paper, we performed a comprehensive study on the thermoelectric property of dumbbell silicene nanoribbons (DB-SNRs) via utilizing nonequilibrium Green's function (NEGF) method as implemented in the density functional based tight-binding (DFTB) framework. Our results show that DB-SNRs present superb electronic transport properties, e.g., the room temperature Seebeck coefficient could approach 2.11 mV/K (about 80% larger than that of LB silicene). A unique step-like width dependence of phononic thermal conductance is also observed in Z-DB-SNRs, which mainly attributes to localized phonon modes raised from the edged sp3 Si atoms. Based on the electronic and phononic transport coefficient, the thermoelectric performance of DB-SNRs is predicted and the stable ZT value at room temperature is found to be about 0.7(0.3) and 0.6(0.2) for A-DN-SNRs and Z-DB-SNRs with p(n)-type doping. Such thermoelectric performance could be further improved by increasing the temperature. The findings presented in this work shed light on the thermoelectric property of DB-SNRs and could provide helpful guideline for designing and fabricating of future Si-based thermoelectric devices.