Thursday 28 Nov 2013: Electronic properties of epitaxial and functionalised graphene in simulation and experiment
Dr Peter Brommer - Department of Physics, University of Warwick
HAR/170 (3D Visualisation Suite) 14:00-15:00
Graphene in its pristine form is a zero-gap semiconductor with a linear dispersion relation E(k) at the Dirac point in reciprocal space responsible for the high electron mobility observed in graphene films. This can be deduced from the band structure, which intuitively represents some electronic properties of a system. For perfect graphene, the band structure is routinely calculated using first-principles methods implemented in codes like CASTEP. This is however no longer the case for more complex systems such as graphene in contact with a Cu substrate or functionalised by oxygen or nitrogen to modify electronic properties. Here, large unit cells are necessary to accommodate lattice mismatch between Cu and C or the low concentration of impurity atoms. This makes it nontrivial to extract a meaningful band structure from density functional theory (DFT) calculations. We recently implemented an effective band structure (EBS) formalism that allows us to filter out relevant information on the electronic properties. The resulting EBS are directly compared to experimental results on CVD grown graphene functionalised with N and O in ultra-high vacuum, where we resolved the band structure from angle-resolved photoemission spectroscopy (ARPES) measurements. Combined, the computational and experimental results have important implications for the controlled modification of electronic properties in graphene.