PORTLAND, Ore.Graphene quantum dots could enable single-molecule sensors and could lead to ultra-small transistors and on-chip communications with semiconductor lasers, according to Rice University researchers who recently revealed their plans to create these ultra-small wells.
Quantum dots are vacancies (wells) that can confine excitonsbound electron-hole pairsin a semiconductor to achieve properties that are superior to those of bulk materials. The Rice University researchers have added a new twistleaving a single layer of carbon in the bottom of the well.
Graphene sheets are often bonded to a monolayer of hydrogencalled graphanewhich converts the material from a conductor to an insulator. The researchers reasoned that by removing islands of hydrogen from both sides of the sheets, tiny wells of conductive graphene, surrounded by the graphane insulator, will be left behind that could be used as quantum dots.
The theoretical work, supervised by professor Boris Yakobson but performed by post doctoral researchers Abhishek Singh and Evgeni Penev, shows that when the hydrogen sublattice is removed, a precise hexagonal well is left behind with sharp interface boundaries between the graphene and graphane. As a result, the quantum dots should have uniform characteristics and very little charge leakageboth desirable characteristics for producing working devices.
|Evgeni Penev, left, and Abhishek Singh, postdoctoral researchers in the lab of Rice's Boris Yakobson, theorize that removing hydrogen atoms from graphane to reveal clusters of graphene would create vacancies that act as quantum dots. CREDIT: JEFF FITLOW/RICE UNIVERSITY|
Next the researchers want to study techniques for removing the hydrogen atoms that enable them to adjust the band gap of devices by changing the size of the dot, thereby tuning its properties for specific applications such as chemical sensors, solar cells, medical imagers and nanoscale circuits.
Funding for the Rice University project was provided by the Office of Naval Research with assistance from the U.S. Department of Defense Supercomputing Resource Center at the Air Force Research Laboratory.
|Artist's rendering of quantum dots produced in graphane by removing islands of its bonded hydrogen, leaving behind wells with graphene at the bottom. CREDIT: EVGENI PENEV/ABHISHEK SINGH|