We present electronic transport measurements on etched graphene nanoribbons on silicon dioxide before and after a short hydrofluoric acid (HF) treatment. We report on changes in the transport properties, in particular, in terms of a decreasing transport gap and a reduced doping level after HF dipping. Interestingly, the effective energy gap is nearly unaffected by the HF treatment. Additional measurements on a graphene nanoribbon with lateral graphene gates support strong indications that the HF significantly modifies the edges of the investigated nanoribbons leading to a significantly reduced disorder potential in these graphene nanostructures.

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Here, we follow Molitor et al9 For extracting the transport gap, the data are smoothed with a running average over 0.5 V in Vbg and the regions with a linear increase in conductance next to the transport gap are fitted with a linear slope. From the intersection of these two (right and left) lines with G = 0, we obtain Vr and Vl and extract the size of the transport gap ΔVbg=(VrVl) and the position of the charge neutrality point Vcn=(Vr+Vl)/2. For the effective energy gap, the size of the largest Coulomb diamond like feature in a plot of dI/dV as a function of bias and back gate voltage is estimated.
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This also confirms that our GNRs are not suspended; when fully suspending individual nanoribbons we found αa0.05.

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The estimated values are C0/Cbg=24 and γ=8.5×104V2(Csg(1)/Cbg=1.15).

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