Researchers lead by a team at the University of Arizona have demonstrated that mounting graphene on boron nitride instead of silicon oxide dramatically improves its electronic properties. Graphene, commonly found in pencil lead, is a sheet of carbon atoms linked in a hexagonal, chicken wire structure. It is only one atom thick and highly conductive. According to University of Arizona physicists, graphene could eventually replace conventional silicon microchips. Graphene can make devices smaller, faster and more energy-efficient.
Researchers at the University of Arizona, Massachusetts Institute of Technology and the National Materials Science Institute (Japan) discovered that by placing the graphene layer on a material almost identical in structure, instead of the commonly used silicon oxide found in microchips, they could significantly improve its electronic properties. The team was able to measure the topography and electrical properties of a smooth graphene layer with atomic resolution by substituting silicon wafers with boron nitride, which is a graphene-like structure consisting of boron and nitrogen atoms in place of the carbon atoms.
Graphene has honeycomb structure made up of rings of carbon atom, visible as small hexagons. The larger hexagons result from an interference process occurring between the graphene and the underlying boron nitride. The scale bar measures one nanometer, or one billionth of a meter. (Photo: University of Arizona)
The research results are published in Nature Materials:
Here we use scanning tunnelling microscopy to show that graphene conforms to hBN, as evidenced by the presence of Moiré patterns. However, contrary to predictions, this conformation does not lead to a sizeable band gap because of the misalignment of the lattices. Moreover, local spectroscopy measurements demonstrate that the electron-hole charge fluctuations are reduced by two orders of magnitude as compared with those on silicon oxide. This leads to charge fluctuations that are as small as in suspended graphene6, opening up Dirac point physics to more diverse experiments.