Stacking thin layers of graphene and related materials (GRMs) leads to heterostructure devices which can be tailored by design of the stack. The researchers use the molecular monolayers to create controllable periodic potentials on the surface of graphene.
“The mechanical superposition of different layered crystals has been proven to be a route towards the fabrication of heterostructures featuring 2D periodic potentials,” said Paolo Samorì from the University of Strasbourg.
The researchers used organic molecules that self-assembled into ordered structures on the surface of graphene.
The molecules consist of a long-chain tail and a reactive head with a small electric field caused by unequal distribution of the electrons in the head. The electric field of the heads influences the underlying graphene, while the regions covered by tails remain unaffected.
The presence of the molecules is said to lead to a periodic variation in the electric field in 1D, which can alter the behaviour of electric current in the graphene.
The properties of the molecule determine the specifics of the periodic potential. Using three different molecules, the researchers showed that the potentials can be controlled, with the size and orientation of the electric field in the head of the molecule determining the strength and type of effect in the graphene.
This new approach to device design could be extended to other GRMs, enabling more complex multilayer heterostructures with new properties. For example, in semiconductor transition metal dichalcogenides, the periodic potentials could lead to a series of nanoscale junctions with distinct optical properties.