Coulomb blockade and hopping conduction in graphene quantum dots array

Abstract

We show that the low temperature electron transport properties of chemically functionalized graphene can be explained as sequential tunneling of charges through a two dimensional array of graphene quantum dots (GQD). Below 15 K, a total suppression of current due to Coulomb blockade through GQD array was observed. Temperature dependent current-gate voltage characteristics show Coulomb oscillationswith energy scales of 6.2-10 meV corresponding to GQD sizes of 5-8 nm while resistance data exhibit an Efros-Shklovskii variable range hopping arising from structural and size induced disorder.

Broadband high photoresponse from pure monolayer graphene photodetector

“…4c). Obvious oscillations appear in the transfer curves at low temperatures and these oscillation peaks are gradually broadened with the temperature and disappear when the temperature is higher than 150 K. These observations are clear evidence of the Coulomb blockade effect 41,42 . To calculate the charge energy of the GQDs, we measured differential conductance (dI/dV) as functions of V G and V D , as shown in Fig.…”

“…It is observed that the I-V characteristics of the processed graphene is linear at 294 K for V D changes from À 1 V to 1 V, while it become remarkably nonlinear and highly symmetric, and the conductance reduces at low biases, at 12 K. These phenomena indicate the Coulomb blockade effect exists as carriers transport in the processed graphene sample. It is noted that the Schottky barrier formed between the contact and the graphene layer could also generate a decreased conductance at a lower bias, but this effect is excluded because it would also introduce a nonlinear effect at room temperature and an asymmetric behaviour at low temperatures 41 , which are not observed in our measurements. This means the observed phenomena comes from the graphene FET channel.…”

Metal nanoparticle field-effect transistor

“…2). The peaks of the Coulomb oscillations are non-periodic, in accordance with the sequential tunneling of the electrons through multiple particles and pathways [51]. In relative terms, the Coulomb oscillations can be seen most clearly just above the threshold voltage, since at these conditions the electrical field is sufficient to overcome the Coulomb blockade through the whole film for the first time and the charge transport most probably takes place along a single path or a small number of branches.…”

Efros-Shklovskii variable-range hopping in reduced graphene oxide sheets of varying carbonsp2fraction

“…In determining ξ, we used an effective dielectric constant of ε = 3.5 for RGO sheet. 32,57,58 Figure 5(b) shows a plot of ξ vs its corresponding carbon sp 2 fraction of the sheets. This demonstrates that with increasing sp 2 fraction, the localization length increases.…”

“…However, a clear understanding of the electronic transport properties of the RGO sheets is lacking as different study reports different conduction mechanisms such as Mott variable range hopping (VRH) and Efros-Shklovskii (ES-) VRH. 1,10,[29][30][31][32] Understanding of the electron transport properties of RGO is of great significance to realize the overreaching goals of functionalized graphene and its composites. The difference between the Mott and ES-VRH is in the details of their localization parameters, density of states (DOS) and interactions that manifest in the temperature dependence of resistance (R).…”