Colloquium: Brian LeRoy

    Thursday, April 10, 2014 - 3:30pm - 5:00pm
    Meinel 307

    "Imaging Electronic Properties of Two-Dimensional Materials"


    Two-dimensional materials such as graphene and transition metal dichalcogenides are being extensively studied for potential electronic and optical applications. Recently it has become possible to create heterostructures of these materials in order to create designer bandstructures. Spatially resolved information is crucial to understand the properties of these heterostructures. Using a combination of scanning probe microscopy and optical spectroscopy, we have probed the local electronic properties of graphene heterostructures. These systems consist of a monolayer of graphene in contact with other materials ranging from insulators to two-dimensional semiconductors such as MoS2 and topological insulators. By using boron nitride, a wide band gap insulator, as a substrate, we observe an improvement in the electronic properties of graphene as well as a moire pattern due to the misalignment of the graphene and boron nitride lattices. We find that the periodic potential due to the boron nitride substrate creates new Dirac points in graphene, leading to changes in its electronic and optical properties. In bilayer graphene heterostructures, we observe that the optical properties of the material can be tuned with the rotation angle between the two lattices. Lastly, we have demonstrated how the stacking configuration of graphene structures can be modified with an electric field inducing a metal to semiconductor transition.

    Speaker Bio(s): 

    Brian LeRoy received his Ph.D. in physics in 2003 from Harvard University. He is an associate professor of physics at the University of Arizona. His research uses a combination of scanning probe microscopy, optical spectroscopy and electrical transport measurements to study low-dimensional systems. He has made important contributions to the study of two-dimensional electron gas systems in AlGaAs/GaAs, carbon nanotubes and graphene.