Graphene Makes Transistors Tunable

The existence of an energy gap between the conduction and valence electron bands of a semiconductor is what makes it possible for the material to act as a semiconductor. In both single-layer and double-layer graphene [left and middle], the valence and conduction bands are in effect conical and meet at a point, with no band gap. The introduction of an electric field perpendicular to the layers [right] creates an asymmetry, which generates a band gap. Though small, the gap is tunable, creating possibilities for new devices.

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