Fabrication of 2D heterojunction in graphene

Irradiation with very-low energy nitrogen ions is used to locally induce substitutional doping in graphene. Irradiated and non-irradiated areas are separated by a sharp boundary, stable up to 750 °C. Our experiments pave the way to the lithographic control of the electronic properties of graphene and provide a proof-of-principle for the fabrication of graphene-based heterojunctions.
A. Sala, Small 11(44), 5927–5931 (2015).

The exploitation of graphene in the next generation electronics depends on the capability of preserving and tailoring its electronic and transport properties. Substitutional implantation of exo-species into the C lattice mesh, B or N in particular, is an appealing functionalization method, as it is capable to alter the charge carrier density and even to open a bandgap. Since most devices require the fabrication of a heterojunction between a semiconducting active material and a metallic electrode, the development of lithographic tecniques for doping graphene is highly desirable. Here we report a proof-of-principle experiment demonstrating that low-energy N2+ ion irradiation through an aperture mask can be used to achieve local control on the doping in graphene and to create a 2-dimensional heterojunction between n-doped and neutral single-layer graphene on Ir(111). LEEM, XPEEM-XPS and microprobe-ARPES measurements, conducted at the Nanospectroscopy beamline at Elettra

showed that the doping pattern is resistant to annealing in UHV up to 800 °C and that the doping level can be varied as function of the increasing irradiation dose without considerable damage for the C mesh. Our results pave the way to a miniaturization of graphene heterojunctions: doping lithography at the nanometer scale would allow the creation of 2D nanocircuits, with promising performances in terms of density, efficiency and thermal dissipation.

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Fabrication of a 2D heterojunction in graphene via low energy N2+ irradiation;
A. Sala, G. Zamborlini, T.O. Menteş, A. Locatelli;
Small 11(44), 5927–5931 (2015); [Publication Date (Web): October 6, 2015];
doi: 10.1002/smll.201501473;
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