All That Matters

Move over graphene, there is competition in town. A new type of two-dimensional materials – with the far less appealing family name, transition metal dichalcogenides –  are increasingly gaining attention. Well, at least they’re giving it a shot. Graphene, a sheet of carbon atoms only one atomic layer thick, still has plenty going for itself in terms of electronic, optical and mechanical properties. There seems nothing that graphene can’t do.

On the other hand, there are also limits. When it comes to its electronic properties graphene is not a semiconductor in the same was as silicon is. It is lacking a bandgap, a gap in its electronic states that is important for light emitters and for some electronic devices.

Schematic model of transition metal dichalcogenide atomic layers. The yellow balls represent the chalcogenide atoms, the blue ones the transition metals. Reprinted by permission from Macmillan Publishers Ltd. Nature Nanotechnology (2012). doi:10.1038/nnano.2012.193

Transition metal dichalcogenides offer an advantage there. They are semiconductors, and they can have a bandgap. And as their name says, they are formed by a combination of chalcogens such as sulphur or selenium and transition metals such as molybdenum or tungsten. Typical examples are MoS₂ or MoSe₂. These materials have become such hot stuff now that their properties have been reviewed in this month’s issue of Nature Nanotechnology. And even though the field is still young, there is plenty to review. […]