Credit: © 2008 APS

Monoatomic layers of carbon known as graphene are being studied for possible applications in nanoscale electronic circuits. The initial goal is the fabrication of field-effect transistors — devices in which the current through a semiconducting material is controlled by the application of an external field. However, it is difficult to significantly change the resistance of graphene with an electric field because it is a semimetal rather than a semiconductor. The ideal solution would be to change graphene into a semiconductor.

Now, Xiaosong Wu and colleagues1 at the Georgia Institute of Technology have fabricated an all graphene device by placing graphene oxide — a semiconductor — between two electrodes of epitaxial graphene. A Schottky barrier of about 0.7 eV was created at the graphene/graphene oxide junction owing to the band gap in graphene oxide.

Changing epitaxial graphene into graphene oxide would be an important boost to device applications. Notably, the group found that annealing graphene oxide at 180 °C for 16 hours changed the Schottky barrier from 0.7 to 0.5 eV. Therefore, annealing could be used to produce a required band gap. Furthermore, electron irradiation of graphene oxide reduced the Schottky barrier to less than 0.5 eV, thus opening up the possibility of localized control of the band gap.