Reversible Tuning of the Electronic Properties of Graphene via Controlled Exposure to Electron Beam Irradiation and Anne
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Reversible Tuning of the Electronic Properties of Graphene via Controlled Exposure to Electron Beam Irradiation and Annealing Desalegne Teweldebrhan1, 2, Guanxiong Liu1, and Alexander A. Balandin1, 2 1 Nano-Device Laboratory, Bourne College of Engineering, University of California – Riverside, Riverside, CA 92521 U.S.A. 2 Material Science and Engineering Program, University of California – Riverside, Riverside, CA 92521 U.S.A. ABSTRACT Graphene reveals many extraordinary properties including extremely high room temperature carrier mobility and intrinsic thermal conductivity. Understanding how to controllably modify graphene’s properties is essential for its proposed applications. Here we report on a method for tuning the electrical properties of graphene via electron beam irradiation. It was observed that single-layer graphene is highly susceptible to the low-energy electron beams. We demonstrated that by controlling the irradiation dose one can change, by desired amount, the carrier mobility, shift the charge neutrality point, increase the resistance at the minimum conduction point, induce the “transport gap” and achieve current saturation in graphene. The change in graphene properties is due to defect formation on the graphene surface and in the graphene lattice. The changes are reversible by annealing until some critical irradiation dose is reached. INTRODUCTION Graphene is a single planer sheet of sp2-bound carbon atoms with many extraordinary properties. Such unique properties include an extremely high room temperature (RT) carrier mobility of up to ~15,000 cm2/Vs [1-2] and an extremely high intrinsic thermal conductivity exceeding ~3000 W/mK near RT for large flakes [3-4]. Recent experiments with modification of graphene surface via hydrogenation [5-6], ions irradiation [7], fluorination [8], and adsorption of individual gas molecules (NO2, NH3, etc.) [7] have shown that graphene’s properties can be altered and tuned for specific applications. However, little is known about the effect of the electron beam irradiation on graphene or graphene-based devices. Recently, it was also shown that graphene exposure to the electron beams (e-beams) results in modification of its surface [9-11]. It was demonstrated that electron irradiation leads to the appearance of the disorder D peak at ~1350 cm-1 in the Raman spectra of irradiated graphene [9]. Here we describe how the electrical properties of the single layer graphene (SLG) depend on the irradiation dose, and correlate the current – voltage characteristics with the evolution of Raman spectrum of irradiated graphene. EXPERIMENTAL DETAILS Graphene back-gate FET devices were fabricated with the electron beam lithography (EBL).
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Degenerately p+ doped silicon substrate was used to back-gate and tune the Fermi level in graphene. The graphene flakes were prepared by the standard micro-mechanical exfoliation from the high quality graphite. The flakes were transferred to the silicon substrate with 300-nm-thick layer of silicon oxide. Raman spectroscopy was used to verify
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