  Thermoelectric power of a material, typically governed by its band structure
and carrier density, can be varied by chemical doping that is often restricted
by solubility of the dopant. Materials showing large thermoelectric power are
useful for many industrial applications, such as the heat-to-electricity
conversion and the thermoelectric cooling device. Here we show a full electric
field tuning of thermoelectric power in a dual-gated bilayer graphene device
resulting from the opening of a band-gap by applying a perpendicular electric
field on bilayer graphene. We uncover a large enhancement in thermoelectric
power at low temperature, which may open up a new possibility in low
temperature thermoelectric application using graphene-based device.
