Graphene Bandgaps (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption One of the most unusual features of single-layer graphene (top) is that its conical conduction and valence bands meet at a point -- it has no bandgap. Symmetrical bilayer graphene (middle) also lacks a bandgap. Electrical fields (arrows) introduce asymmetry into the bilayer structure (bottom), yielding a bandgap (Δ) that can be selectively tuned. Credit Lawrence Berkeley National Laboratory Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.