Effect of electric fields on the electronic and thermoelectric properties of zigzag buckling silicene nanoribbons

Thi-Kim-Quyen Nguyen, Nguyen-Huu-Hanh Pham, Loan- Phan Thi Kim, Thanh-Tra Vu and Van-Truong Tran

Abstract

We investigate the electronic structure and the thermoelectric transport properties of zigzag buckling silicene nanoribbons (BSiNRs) under the effect of external electric fields by means of atomistic simulations. The obtained results show that thanks to the buckling feature, zigzag BSiNRs have a stronger response to a vertical electric field compared to its flat form structure and also single-layer and bi-layer graphene nanoribbons with zigzag edges (GNRs & BGNRs). An inverse is observed in the case of a transverse electric field. Interestingly, the mutual effect when applying simultaneously the vertical and transverse fields induces a larger bandgap compared to individual ones. The mutual effect observed with zigzag BSiNRs is much more pronounced compared to that in zigzag BGNRs since the vertical field has a modest effect on zigzag BGNRs stemming from weak van der Waals interactions between graphene layers. Thermoelectric performance of zigzag BSiNRs is enhanced remarkably with electric fields in which the figure of merit ZT can be tuned to exceed 1. Interestingly, although the mutual impact of two external fields induces the largest Seebeck coefficient, it unveils that the vertical electric field is overall more efficient in enhancing the thermoelectric performance of zigzag BSiNRs. In addition, the enhancement of ZT is demonstrated to stem mainly from a dramatical degradation of the electron thermal conductance around the Fermi level. This study shows that zigzag BSiNRs in combination with external electric fields have favourable advantages for different electronic and thermoelectric applications.