One-step and controllable bipolar doping of reduced graphene oxide using TMAH as reducing agent and doping source for field effect transistors

Simultaneous reduction and doping of the graphene oxide (GO) is an important issue for low temperature processed flexible electronic devices. A low temperature method for reduction and ambipolar doping has been developed which yield the doped reduced GO with wide range of work function with a mass production using tetra-methyl ammonium hydroxide (TMAH). The doping type of obtained reduced GO is tuned with TMAH concentration. XPS analysis revealed that the graphitic N is converted to oxidized N with increase of TMAH concentration. The work function is tuned via wide range variation in the carrier concentration in neutral (rGO-A, 4.46 eV), n-type (rGO-B, 3.90 eV) and p-type (rGO-C, 5.29 eV) regimes. The obtained Dirac voltages of field effect devices are -1 V, -31 V and +35 V with active layer of rGO-A, rGO-B and rGO-C, respectively. The n-type doping is due to incorporation of graphitic N, whereas, oxidized N acts as electron withdrawing group which causes p-type doping.