Structural and electronic properties of germanene/MoS2 monolayer and silicene/MoS2 monolayer superlattices

Abstract

Superlattice provides a new approach to enrich the class of materials with novel properties. Here, we report the structural and electronic properties of superlattices made with alternate stacking of two-dimensional hexagonal germanene (or silicene) and a MoS2 monolayer using the first principles approach. The results are compared with those of graphene/MoS2 superlattice. The distortions of the geometry of germanene, silicene, and MoS2 layers due to the formation of the superlattices are all relatively small, resulting from the relatively weak interactions between the stacking layers. Our results show that both the germanene/MoS2 and silicene/MoS2 superlattices are manifestly metallic, with the linear bands around the Dirac points of the pristine germanene and silicene seem to be preserved. However, small band gaps are opened up at the Dirac points for both the superlattices due to the symmetry breaking in the germanene and silicene layers caused by the introduction of the MoS2 sheets. Moreover, charge transfer happened mainly within the germanene (or silicene) and the MoS2 layers (intra-layer transfer), as well as some part of the intermediate regions between the germanene (or silicene) and the MoS2 layers (inter-layer transfer), suggesting more than just the van der Waals interactions between the stacking sheets in the superlattices.

Band gap control and transformation of monolayer-MoS2-based hetero-bilayers

“…52 As for the geometric structures, we find that the value of the buckling of silicene/germanene in hetero-bilayers is less than that in the superlattices. 52 As for the geometric structures, we find that the value of the buckling of silicene/germanene in hetero-bilayers is less than that in the superlattices.…”

Silicene on Other Two-dimensional Materials: Formation of Heterostructure

“…The most stable configuration in silicene/MoS 2 heterostructure is one Si atom is directly on S atom, and other Si atom is located above the hollow site of MoS 2 (Li et al, 2014c). In this heterostructure, binding energy (E b ) is 120.32 meV per Si atom, which is enough to hold silicene stably .…”

“…6C shows the effect of MoS 2 substrate on silicene, compared to pristine silicene and MoS 2 monolayer in Fig. 6A and B, respectively (Li et al, 2014c). The band structure of silicene on MoS 2 is like a simple sum of each band structure due to no effect each other.…”

“…Because MoS 2 is a semiconductor with a considerable band gap, researchers pay attention to MoS 2 as a substrate for silicene Li et al, 2013b;Chiappe et al, 2014;Gao et al, 2014aGao et al, , 2014bJose & Datta, 2014;Li & Zhao, 2014;Li et al, 2014c). The most stable configuration in silicene/MoS 2 heterostructure is one Si atom is directly on S atom, and other Si atom is located above the hollow site of MoS 2 (Li et al, 2014c).…”

“…heterostructure, graphene/MoS 2 has much stronger inter-layer charge transfer, which means silicene/MoS 2 has much more than the vdW interactions between stacking layers (Li et al, 2014c). According to Gao et al (2014b), induced band gap of silicene/MoS 2 is considerable 70 meV compared to the room temperature thermal scale (26 meV) and graphene/MoS 2 (nearly zero) (Ma et al, 2011), which result in improved onoff ratio.…”