The voltage-flow curve is almost a straight line, and operation at 1MHz has been demonstrated.
“Precision control of how heat flows through materials has been a long-held but elusive dream for physicists and engineers,” said engineering professor Yongjie Hu (pictured). “This design principle takes a big leap toward that, as it manages the heat movement with the on-off switching of an electric field, just like how it has been done with electrical transistors for decades.”
It is a nano-scale device, built starting with an atomically-flat gold coating on a substrate.
A self-assembling mono-layer comes next, of ‘carboranethiol cage’ molecules (9-SH-o-C2B10H11
(O9).
Physically, these are like multifaceted cages that stand up on the gold surface, attached by a single leg to the surface via a sulphur atom.
Across the top of this forest of cages is draped sheet of single-layer graphene, which is held ~1nm from the gold by the cage molecules.
The controlling potential bias is applied between the gold surface and a top contact above the graphene.
In operation (and please forgive Electronics Weekly for the following hand-waving explanation…), atoms shared by the sulphur and gold atoms to form their covalent bond, shift under the influence of the applied electric control field, which weakens or strengthens the bond, consequently changing local thermal conductivity. Something similar happens at the graphene interface, but based on Van der Waals attraction rather than covalent bonding.
Conductivity varies from below 10MW/m2/K to above 130MW/m2/K.
For a proper explanation of operation, the work is described in ‘Electrically gated molecular thermal switch‘, published in Science (abstract available without payment).
