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Opening of a tunable bandgap in graphene via oxygen plasma treatment: An building block for graphene-based electronics

A. Nourbakhsh, M. Cantoro, A. Klekachev, S. De Gendt, B. Sels

Keywords: graphene, oxygen plasma, Schottky diode


The results of experiments devoted to the modification of the pristine electronic properties of single-layer graphene by means of an oxygen plasma will be illustrated. Electrical characterization and photoluminescence measurements are carried out to investigate the opening of a bandgap in plasma-treated graphene; such a bandgap can be tuned by changing the plasma parameters. Modified graphene exhibits a ~2 eV optical bandgap and p-type semiconducting behavior; back-gated FETs with modified graphene as active channel possess Ion/Ioff up to 104. The experimental results are explained in terms of a functionalization of the pristine sp2 graphene lattice with chemisorbed epoxy groups. The effects of epoxidation on graphene optoelectronic properties are further investigated by ab initio calculations carried out in a DFT framework. They confirm that progressively larger bandgaps are introduced in graphene upon functionalization with increasing amount of oxygen. Furthermore, we demonstrate the potential of metal-contacted plasma-treated graphene rectifying junctions to fabricate Schottky diodes with turn-on voltages below 0.5 V. The use of low- (Al, Yb) and high- (Pd, Pt) work function metals, directly in contact with modified graphene, allows for the modulation of the Schottky barrier height. Our results suggest that an oxygen plasma treatment represents a valid approach to control graphene chemistry toward tunable-bandgap graphene-based electronics.
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