Abstract
Silicene, a two-dimensional honeycomb network of silicon atoms like graphene, holds great potential as a key material in the next generation of electronics; however, its use in more demanding applications is prevented because of its instability under ambient conditions. Here we report three types of bilayer silicenes that form after treating calcium-intercalated monolayer silicene (CaSi2) with a BF4− -based ionic liquid. The bilayer silicenes that are obtained are sandwiched between planar crystals of CaF2 and/or CaSi2, with one of the bilayer silicenes being a new allotrope of silicon, containing four-, five- and six-membered sp3 silicon rings. The number of unsaturated silicon bonds in the structure is reduced compared with monolayer silicene. Additionally, the bandgap opens to 1.08 eV and is indirect; this is in contrast to monolayer silicene which is a zero-gap semiconductor.
Highlights
Silicene, a two-dimensional honeycomb network of silicon atoms like graphene, holds great potential as a key material in the generation of electronics; its use in more demanding applications is prevented because of its instability under ambient conditions
The existence of a bilayer silicene structure, whose density of unsaturated silicon bonds is reduced in comparison with monolayer silicene, has been predicted by molecular dynamics (MD) calculations[20,21,22,23,24,25,26,27]
We focused on calcium-intercalated silicene (CaSi2) and discovered a strategy for transforming monolayer silicene into a novel bilayer silicene (w-BLSi)
Summary
A two-dimensional honeycomb network of silicon atoms like graphene, holds great potential as a key material in the generation of electronics; its use in more demanding applications is prevented because of its instability under ambient conditions. Because of the electron transfer from the calcium cation, the monolayer silicene in CaSi2 is a formally anionic layer[17]: when the calcium cation becomes electrically neutral, the silicene will not retain its honeycomb structure and will reconstruct to form a more stable structure Under this supposition, we attempted to segregate the Ca and Si phases while maintaining the layer structures by diffusing fluoride (F) atoms, which are more electronegative than Si, into CaSi2; the goal was to form an ionic bond (or interaction) between Ca and F. BF4 anion based ionic liquid was used for the origin of fluoride anion
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