Soumya Dutta

In this work, we performed gated Kelvin Probe Force Microscopy on reduced graphene oxide thin-film transistors with time transient. This enabled us to probe the electronic density of states around the charge neutrality point in reduced graphene oxide thin film. The charge neutrality point is of significance to know the nature of the intrinsic doping of the thin film and the switching of the majority carriers in the transistor devices. We measured the transfer characteristics of the reduced graphene oxide transistor devices to estimate the intrinsic charge neutrality point. The results were in good agreement with the time-resolved gated surface potential measurements obtained using Kelvin probe force microscopy. We propose that gated time-resolved measurement of these semi-metals can be an effective tool to study the nature of electronic states.

We report a method to pattern graphene on silicon dioxide by a physical process utilizing its inter-facial properties with metal, silicon dioxide and polymer photoresist. The process utilizes the difference in adhesion energies of various interfaces between these materials with graphene. The mechanical forces involved in this process are strong enough to pattern multiple layers of graphene at once. As the sacrificial patterning layer is in flush contact with graphene, the process does not suffer from residual layers at the undesired sites, as in polymer-based stamp transfer techniques. We have calculated the adhesion energies of these interfaces using density functional theory (DFT), theoretical estimation and experimental methods using Atomic Force Microscopy (AFM). These observations are in good agreement with each other and defend the feasibility of the proposed graphene patterning method.