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How does graphene’s minimum conductivity differ from the behavior of ordinary semiconductors?
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graphene
Atomic force microscopy image of water structures that were trapped beneath a sheet of graphene one atom thick.
The primary difference between graphene and ordinary semiconductors lies in their behavior at low doping levels. In conventional semiconductors, there are specific energy levels where electrons and holes lack allowed quantum states; consequently, for certain gate voltages or types of chemical doping, the material acts as an insulator.1
In contrast, graphene does not possess an insulator state. Its conductivity remains finite regardless of the level of doping, including at zero doping. This existence of a "minimal conductivity" in the undoped state is a striking distinction from the behavior of traditional semiconductors, which can be tuned to a non-conductive state.1