Since the isolation of graphene, a one-atom-thick sheet of carbon, researchers have developed a number of other two-dimensional materials. (Yes, they are really three-dimensional; it's just one of the dimensions is only an atom thick, and therefore negligible.) Knowledge of the periodic table would suggest that elements from the same column as carbon would have similar chemical properties, and therefore be excellent candidates for forming two-dimensional sheets. So, why hasn't more been done with silicon, the next element down the column from carbon?
People have actually made silicene, the silicon version of graphene. But they've only managed to make tiny patches of it on silver surfaces; under just about any other conditions, it rapidly reacts with the oxygen in air and disintegrates.
On Monday, however, researchers announced that they'd managed to create the first device—a field effect transistor—using silicene. Since interactions with silver protected the silicon sheet, the authors fabricated a large sheet on a thin silver surface. They then capped this with aluminum oxide, which also protected the silicene. At this point, they could etch off some of the aluminum, and use the remaining metal as source and drain contacts. By depositing the alumina on a silicon dioxide surface, the resulting device acted as a field effect transistor.
This allowed them to explore the flow of electrons through the silicene, which turned out to be... disappointing. While theoretical predictions had suggested electron mobilities in line with what's seen in graphene, the silicene device saw mobilities about ten times smaller than expected. The authors aren't sure why this is—whether it's silicene itself or simply their production techniques isn't clear.
Still, now that we know how to make some, it should be possible to study its properties more thoroughly. Because silicon has a larger and more complex electronic structure than carbon, it's thought that silicene can be readily manipulated either through chemical reactions or simply by placing other materials in close proximity. So, it's possible that further study could get silicene behave more in line with what researchers were hoping for.