Researchers from Manchester University demonstrated synchronized use of in-plane and van der Waals hetero-structures to engineer vertical single electron tunnelling transistors
Graphene quantum dots (GQDs) and graphene nanowires follow linear spectrum in quasiparticles and have excellent chemical stability, the ability to support high currents, and small spin-orbit interaction. Moreover, the transport properties GQDs are under the influence of localized edge states. It is also challenging to arrange tunnelling contacts to GQDs with the specific, reproducible conductivity. Now, a team of researchers from the Higher School of Economics, Manchester University, the Ulsan National Institute of Science & Technology, and the Korea Institute of Science and Technology used planarand vertical hetero-structures to overcome the issues with the localized states both at the edges of the GQDs and at the edges of the contacts.
The team used catalytic-assisted substitution of boron and nitrogen atoms by carbon to form GQDs inside the hexagonal boron nitride (hBN) matrix. Therefore, the new technique collects graphene-based single-electron transistors of exceptional quality. According to the researchers, the new approach can facilitate development of two-dimensional materials. This can further be achieved by using a larger platform to study various devices and physical phenomena. The team found that high-quality GQDs can be synthesized in a matrix of monolayer hBN. The advantage of the approach is that it does not rely on the order of arrangement in the lattice.
The team found that the growth of GQDs within the layer of hBN was catalytically reinforced by the platinum (Pt) nanoparticles distributed in-between the hBN. This in turn maintained oxidized silicon (SiO2) slice, when the entire structure was under the influence of heat in the methane gas (CH4). The hexagonal structure of lattice in hBN and small lattice structure of graphene lead to a mismatch that allows graphene islands to grow in the hBN with passive state of the edges. This in turn promotes formation of quantum dots with no defects that are embedded in the hBN monolayer. Such planar hetero-structures can be used to develop future electronics. The research was published in the journal Nature Communications on January 16, 2019.