Two-dimensional electron and hole gases at the surface of graphite

We report two-dimensional (2D) electron and hole gases induced at the surface of graphite by the electric field effect. The 2D gases reside within a few near-surface atomic layers and exhibit mobilities up to 15 000 and 600. 2em{0ex}0000. 3em{0ex}cm^2∕V0. 2em{0ex}s at room and liquid-helium temperatures, respectively. The mobilities imply ballistic transport on scale. Pronounced Shubnikov--de Haas oscillations reveal the existence of two types of charge carries in both electron and hole gases.