Improving Ion/Ioff In Bilayer Graphene Transistors by Molecular Functionalization

We propose a bilayer graphene (BLG) device concept that allows to overcome the problem of zero bandgap in pristine BLG by all-organic asymmetrical functionalization. The BLG is sandwiched between a top p-dopant layer (F4TCNQ) and a bottom n-dopant layer (APTES), establishing a transverse electric field needed for bandgap opening. We demonstrate the occurrence of n- and p-type doping by studying the separate effects of the interaction of single-layer graphene (SLG) with the two molecular species. We confirm the occurrence of doping by electrical measurements performed on functionalized SLG samples integrated in a back-gated SLG-FET structure. We measure excess charge concentrations of n=-1.3x10^13 cm-2 and n=+1.2x10^13 cm-2 for respectively n- and p-type doping. The results of DFT calculations further corroborate our experimental results and confirm that the BLG device structure proposed could pave the way for the use of graphene in microelectronics.