AbstractAlthough there are already many efforts to investigate the electronic structures of twisted bilayer graphene, a definitive conclusion has not yet been reached. In particular, it is still a controversial issue whether a tunable electrical (or transport) bandgap exists in twisted bilayer graphene film until now. Herein, for the first time, it has been demonstrated that a tunable electrical bandgap can be opened in the twisted bilayer graphene by the combination effect of twist and vertical electrical fields. In addition, we have also developed a facile chemical vapor deposition method to synthesize large-area twisted bilayer graphene by introducing decaborane as the cocatalyst for decomposing methane molecules. The growth mechanism is demonstrated to be a defined-seeding and self-limiting process. This work is expected to be beneficial to the fundamental understanding of both the growth mechanism for bilayer graphene on Cu foil and more significantly, the electronic structures of twisted bilayer graphene.