Nanoscale fabrication techniques enable creation of “artificial graphene”

The research, at the engineering department of Columbia University in New York City, centred around an attempt to reproduce the electronic structure of graphene in a synthetic semiconductor device.

Graphene’s potential is derived from the way its electrons behave; carbon has four electrons available for bonding, and in graphene, three of them bind each carbon atom strongly to its neighbours to form the characteristic flat hexagonal lattice, but the fourth is free to move along the plane, giving the material its outstanding electrical conductivity. But one problem engineers have encountered in exploiting this property is that the properties depend on this specific configuration of carbon; it cannot be altered to create different conductive effects.

The Columbia team, led by physicist Prof Aron Pinczuk, used the technology normally employed to manufacture microprocessors to engineer graphene-like behaviour in gallium arsenide, a common industrial semiconductor.

Working with colleagues at Princeton and Purdue Universities and the Italian Institute Of Technology in Genoa, they devised a method using nanothithography and etching to create a hexagonal pattern of “quantum wells", which confine the movement of electrons to a lateral direction, onto a sheet of GaAs. The dots were placed about 50nm apart, which is much further than the atoms in graphene but close enough for them to interact quantum mechanically, effectively sharing their electrons like atoms do in solids.