Biased bilayer graphene: semiconductor with a gap tunable by electric   field effect
  We demonstrate that the electronic gap of a graphene bilayer can be controlled externally by applying a gate bias. From the magneto-transport data (Shubnikov-de Haas measurements of the cyclotron mass), and using a tight binding model, we extract the value of the gap as a function of the electronic density. We show that the gap can be changed from zero to mid-infrared energies to a value as large as 0.3 eV by using fields of < 1 V/nm, below the electric breakdown of SiO2. The opening of a gap is clearly seen in the quantum Hall regime. 
Eduardo V. Castro, K. S. Novoselov, S. V. Morozov, N. M. R. Peres,   J.M.B. Lopes dos Santos, Johan Nilsson, F. Guinea, A. K...