Coal-derived carbon dots help grow ultrathin insulating layers on graphene and MoS2 chips

The carbon dots are 1-5 nanometers wide and one atomic layer thick, and are derived from coal. The team assembled them into a closely packed monolayer about 0.4 nanometers thick on the surface of the 2D material, using a Langmuir-Schaefer method in which the dots are spread on water, compressed and transferred. The dots bind to the graphene or MoS2 through weak van der Waals forces without hybridizing with it, while chemical groups at their edges give atomic layer deposition a place to start growing hafnium oxide (HfO2). Without the carbon dots, the HfO2 forms rough, porous islands. With them, it forms a smooth film as thin as about 1.6 nanometers. “[Carbon nanodots] act as a primer coat for growing thin, high-quality dielectrics on 2D materials,” said Qing Cao, a professor at Illinois.

Researchers at the University of Illinois Urbana-Champaign, the US Department of Energy’s National Energy Technology Laboratory (NETL), Argonne National Laboratory and Monash University have used graphene-like carbon dots made from coal to solve a long-standing problem in 2D electronics: how to grow a high-quality, ultrathin insulating layer on top of a 2D semiconductor. The atomically smooth, bond-free surfaces of 2D materials such as graphene and molybdenum disulfide (MoS2) give them little for a gate dielectric to attach to, and the alternatives, transferring a pre-made film or seeding with organic molecules or metal oxide particles, bring problems of their own, such as residues, rough films and low thermal stability.The carbon dots are 1-5 nanometers wide and one atomic layer thick, and are derived from coal. The team assembled them into a closely packed monolayer about 0.4 nanometers thick on the surface of the 2D material, using a Langmuir-Schaefer method in which the dots are spread on water, compressed and transferred. The dots bind to the graphene or MoS2 through weak van der Waals forces without hybridizing with it, while chemical groups at their edges give atomic layer deposition a place to start growing hafnium oxide (HfO2). Without the carbon dots, the HfO2 forms rough, porous islands. With them, it forms a smooth film as thin as about 1.6 nanometers. “[Carbon nanodots] act as a primer coat for growing thin, high-quality dielectrics on 2D materials,” said Qing Cao, a professor at Illinois.

Read More Graphene-Info – Graphene industry portal