In the expanding universe of two-dimensional materials, perhaps none have been more tempting than silicon and its 2D version, known as silicene. The attraction is obvious: Silicon is the boat on which the computer age has floated for more than 50 years. And its proximity on the periodic table to carbon, whose 2D version is the wonder material graphene, has led researchers to investigate whether it might have the same attractive properties.
If researchers can overcome more of the obstacles standing in the way of silicene production, it has some pretty attractive qualities. First, unlike graphene, it has an intrinsic bandgap, which makes it attractive for digital electronics to stop and start the flow of electrons. Its semiconductor nature also comes with many of the same properties that make graphene so attractive—including, potentially, superconductivity.
While silicene is indeed tempting, it has proven frustratingly difficult to produce. Now researchers at the University of Wollongong, in Australia, have overcome one of the main obstacles: separating it from its substrate.
In research described in the journal Science Advances, they developed a technique for reliably separating the silicene from the metal surface it is grown on. The trick is to get oxygen molecules to intercalate between the underlayer of silicene, effectively isolating the upper layer of silicene from the metal substrate. (Intercalation is the reversible inclusion of a molecule or ions between two other molecules in multilayered structures or compounds.)
“We know silicene crystals prefer to firmly attach on the metallic substrate, and because they are too thin to be peeled off by any mechanical tools, it’s impossible to remove them from the substrate,” according to Yi Du, who led the research.