Transport measurements in graphene p-n-p transistors

Graphene is a monolayer of carbon atoms packed into a dense honeycomb crystal structure that can be viewed as an individual atomic plane extracted from graphite, as unrolled single-wall carbon nanotubes or as a giant flat fullerene molecule. Carbon atoms on 2D honeycomb lattice in graphene give rise to a linear band structure close to the Fermi energy. Graphene exhibits electronic properties that are distinctive for a 2D gas of particles described by the Dirac equation rather than the Schrodinger equation. Due to distinct 2D gas in graphene, on application of magnetic field perpendicular to its plane, the energy spectrum splits into non-equidistant Landau levels. When the Fermi level lies between the two Landau levels, longitudinal resistance vanishes and transverse resistance gets quantized. Such transport is well understood in terms of the edge channels propagating along the edges of the sample. 

In this talk, I will describe the tuning of local carrier density and its type by placing a local top gate which enables to study the scattering and mixing of electron and hole edge channels selectively. I will also focus on the difficulties associated with the direct atomic layer deposition of top gate dielectric which diminishes the electronic properties of graphene and our attempts to improve it.