Electron Transport in Disordered Graphene Nanoribbons

Abstract

We report an electron transport study of lithographically fabricated graphene nanoribbons (GNRs) of various widths and lengths. At the charge neutrality point, a length-independent transport gap forms whose size is inversely proportional to the GNR width. In this gap, electrons are localized, and charge transport exhibits a transition between thermally activated behavior at higher temperatures and variable range hopping at lower temperatures. By varying the geometric capacitance, we find that charging effects constitute a significant portion of the activation energy.

Observation of the intrinsic bandgap behaviour in as-grown epitaxial twisted graphene

“…4a present the I-V curves of graphene directly grown by GF and C 60 on SiC, respectively, and show linear characteristics typical of zero bandgap graphene. However, twisted graphene (C 60 /GF) shows strong nonlinear I-V characteristics, which are commonly observed in graphene nanoribbons with a bandgap 23,24 . Han et al 23 determined the transport gap from the width of the DV ¼ 0 region of their plot of dI/dV versus V. Similarly, we estimated the bandgap from where the differential conductance (dI/dV)E0 as shown in Fig.…”

“…However, twisted graphene (C 60 /GF) shows strong nonlinear I-V characteristics, which are commonly observed in graphene nanoribbons with a bandgap 23,24 . Han et al 23 determined the transport gap from the width of the DV ¼ 0 region of their plot of dI/dV versus V. Similarly, we estimated the bandgap from where the differential conductance (dI/dV)E0 as shown in Fig. 4b, which results in a gap of B0.5 V. The I-V measurements at the different sample locations showed similar nonlinear I-V characteristics but with a gap in range from 0.2 to 0.5 V. It is well known that dI/dV versus V measurements can be affected by a variety of factors such as contact resistance, gating capacitance and so on, which can result in an overestimated bandgap size.…”

Nanotomy-based production of transferable and dispersible graphene nanostructures of controlled shape and size

“…The bandgap, determined by the edges of the steep logarithmic increase of current, scaled inversely with the GNR width: ~0 meV for w~50 nm, ~10 meV for w~25 nm and ~35 meV for w~15 nm (Fig. 5a-c) 45,47 . Further, Figure 5h shows that the minimum conductivity is centred at zero gate voltage (w~25 nm GNR film); thus, validating the bandgap measurement at 0 V gate potential.…”

“…channel-length dependence of the nonlinear bandgap 47 is expected to be inconsequential. We attribute the barriers to quantum confinement in the constituent GNRs.…”

“…As the transport in a film with a randomly overlaying GNRs is similar to that through a heavily distorted GNR, we calculated the average width of a distorted GNR, which would have a transition temperature (T*) of 12.5 meV (the T* we measured for 15 nm GNR). This was achieved via the correlation developed by Han et 47 . Consistently, the width from this correlation is 15.9 nm, similar to the width of the GNRs used in the film (15 nm).…”