▎ 摘　　要

We theoretically demonstrate that the energy gaps of graphene quantum dots (GQDs) can be easily tuned by applying opposite electrostatic potentials to the two equally divided parts of them. This control of energy gaps by such an external electrostatic potential can be realized in various sizes or shapes of GQDs. We propose that the physical origin of the gap tunability is the delicate coupling between the two parts of GQDs with opposite electrostatic gate potentials. Our findings are quite useful for the application of GQDs to the electronic devices and photovoltaic devices. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704918]