(July 15, 2015) Graphene
Week 2015 was buzzing with activity throughout the University of Manchester
venue, with more than 600 delegates presenting and discussing their work,
networking and making plans for the future. Each morning of the conference was
given over to plenary sessions, with keynote presentations from invited
speakers. Here we report on the Tuesday plenary, which was devoted to the
electronic properties of graphene and related layered materials.
Electronic transport
in the ultraclean limit
James Hone of Columbia University in New York began with a
discussion of electronic transport in 2d materials in the ultraclean limit.
With electronics applications, graphene is generally laid on
a substrate made of a bulk material. The problem is that, owing to the presence
of dangling chemical bonds, 3d materials tend to be poor substrates for 2d
materials such as graphene. One solution is to use hexagonal boron nitride
(hBN), which is both an insulator and 2d material, and so does not have the
problematic bonds.
How to create such hBN-graphene heterostructures? Graphene
may be transferred onto boron nitride films with the aid of polymers. That is,
graphene flakes are exfoliated onto polymers, aligned with a mask, and the
flakes stacked on top of each other. Such a heterostructure displays enhanced
charge carrier mobility, a lower degree of disorder, and improved field-effect
transistor performance.
Looking beyond graphene, few 2d materials have so far been
studied, and we have a long way to go before they are fully understood. One 2d
material of interest is molybdenum disulphide, with the heterostructure formed
with silicon dioxide.