A new study has gained a better understanding of the fundamental properties of the two-dimensional material silicene; which is produced from single, honeycomb-shaped layers of silicon of only an atom’s thickness. An international team based in Italy and France has for the first time demonstrated that silicene can remain stable in the presence of oxygen for up to 24 hours.
Previous research has shown that silicene layers are intrinsically unstable and always revert back to silicon when more layers are added to a stack due to the regular crystal structure of silicon being more favorable than the honeycomb structure of silicene. However, this research, as reported in 2D Materials [De Padova et al. 2D Mater. (2014) DOI: 10.1088/2053-1583/1/2/021003], found that thick, multilayers of silicene can be isolated from its parent material silicon and stay intact when exposed to air for at least 24 hours, a breakthrough that could lead to the material finding uses in a new generation of electronics
Silicene, first introduced in 2010, may not have the global focus of graphene, but it was not possible to obtain a silicon-based 2D material until recently. Although it is currently fabricated in a vacuum so that no oxygen comes into contact with it, this ruins the formation of single layers. It is key that silicene is also “grown” on a surface that matches its natural structure, such as silver. To make the multilayers of silicene – transforming it from a 2D into a 3D material – a wafer of silicon was heated at a high temperature, forcing single silicon atoms to evaporate and land on the silver substrate, producing single layers.
Once fabricated, it was found that an extremely thin layer of oxidation had formed on top of the multilayered stack of monolayers. It was this that protected and preserved the integrity of the stack. While the stack of monolayers was being preserved in the open air, the team used x-ray diffraction and Raman spectroscopy measurements to confirm the material had the unique fingerprint of silicene rather than silicon.
As lead author, Paola De Padova, pointed out: “Our present study shows that multi-layered silicene is more conductive than single-layered silicene, and therefore opens up the possibility of using it throughout the silicon microelectronics industry.” The team is now exploring the prospect of growing multilayered silicene directly onto semiconductor substrates to discover more about the joint superconducting properties.