Silicene beyond mono-layers—different stacking configurations and their properties

Abstract

We carry out a computational study on the geometric and electronic properties of multi-layers of silicene in different stacking configurations using a state-of-art abinitio density functional theory based calculations. In this work we investigate the evolution of these properties with increasing number of layers (n) ranging from 1 to 10. Though, mono-layer of silicene possesses properties similar to those of graphene, our results show that the geometric and electronic properties of multilayers of silicene are strikingly different from those of multi-layers of graphene. We observe that there exist strong inter-layer covalent bondings between the layers in multi-layers of silicene as opposed to weak van der Waal's bonding which exists between the graphene layers. The inter-layer bonding strongly influences the geometric and electronic structures of these multi-layers. Like bilayers of graphene, silicene with two different stacking configurations AA and AB exhibits linear and parabolic dispersions around the Fermi level, respectively. However, unlike graphene, for bi-layers of silicene, these dispersion curves are shifted in band diagram; this is due to the strong inter-layer bonding present in the latter. For n > 3, we study the geometric and electronic properties of multi-layers with four different stacking configurations namely, AAAA, AABB, ABAB and ABC. Our results on cohesive energy show that all the multi-layers considered are energetically stable. Furthermore, we find that the three stacking configurations (AAAA, AABB and ABC) containing tetrahedral coordination have much higher cohesive energy than that of Bernal (ABAB) stacking configuration. This is in contrast to the case of multi-layers of graphene where ABAB is reported to be the lowest energy configuration. We also observe that bands near the Fermi level in lower energy stacking configurations AAAA, AABB and ABC correspond to the surface atoms and these surface states are responsible for the semi-metallic character of these multi-layers.

Electrical Transport Model of Silicene as a Channel of Field Effect Transistor

“…This buckling has been reported in the range of 0.36Å to 0.75Å [26][27][28] by DFT calculation which predicts the band gap up to 800meV [26] too. The gap depends on the external perpendicular electric field and the amount of the buckling [26] which could be modified by the epitaxial strain [22].…”

Direct band gaps in group IV-VI monolayer materials: Binary counterparts of phosphorene

“…However, the major disadvantage with graphene is that it has no electronic band gap and hence it is difficult to use graphene in semiconductor device applications. Recently, the other group IV 2D materials such as silicene, germanene and stanene have attracted great interest [3][4][5][6][7][8][9][10][11] , but it is also difficult to use them as semiconductor devices. Phosphorene, a monolayer of phosphorus, has opened up the field of group V based 2D monolayer materials [12][13][14][15][16][17] .…”

Exceptional Optoelectronic Properties of Hydrogenated Bilayer Silicene

“…The freestanding bilayer silicene (BS), which is more stable than single-layer silicene, has been predicted to be an ideal material for topological insulators or superconductors [35,36] and Li-ion storage [37]. Although bilayer silicene has been synthesized in several experiments [24,26,[28][29][30][31][32], the ground-state structure of bilayer silicene, even in its freestanding form, is still under debate [35,[37][38][39].…”