▎ 摘　　要

Electric transport of double gated bilayer graphene devices is studied as a function of charge density and bandgap. A top-gated electrode can be used to control locally the Fermi level to create a pn junction between the double-gated and single-gated region. These bilayer graphene pn diodes are characterized by non-linear currents and directional current rectification, and we show that the rectified direction of the source-drain voltage can be controlled by using gate voltages. A systematic study of the pn junction characteristics allows to extract a gate-dependent bandgap value which ranges from 0 to 130meV. (C) 2012 American Institute of Physics. [doi:10.1063/1.3676441]