Chemically Modulated Band Gap in Bilayer Graphene Memory Transistors with High On/Off Ratio.

We report a chemically conjugated bilayer graphene field effect transistor demonstrating a high on/off ratio without significant degradation of the on-current and mobility. This was realized by introducing environmentally stable benzyl viologen as an electron-donating group and atmospheric dopants as an electron-withdrawing group, which were used as dopants for the bottom and top of the bilayer graphene, respectively. A high mobility of ∼3100 cm(2) V(-1) s(-1) with a high on/off ratio of 76.1 was obtained at room temperature without significant degradation of the on-current. This is attributed to low charge scattering due to physisorbed dopants without provoking sp(3) structural disorders. By utilizing our band-gap-opened bilayer graphene, excellent nonvolatile memory switching behavior was demonstrated with a clear program/erase state by applying pulse gate bias. The initial program/erase current ratio of ∼34.5 was still retained at higher than 10 even after 10(4) s.