Carrier Transport in Lateral Graphene/Fluorinated-Graphene/Graphene TunnelJunction Formed with Area-Selective Fluorination

Abstract

Fluorination of graphene has been studied for patterning a graphene film without etching process by making graphene insulating in area-selective manners. Fluorinated-graphene (FG) is a promising 2-dimensional insulator because it has wide band gap and is stable at room temperature. Accordingly, the research activities for using FG as a tunnel insulator or dielectric material have been conducted in various ways. In this experiment, we fabricated a graphene/fluorinated-graphene/graphene (G/FG/G) tunnel junction along the lateral direction parallel to the substrate surface. The fabricated G/FG/G tunnel junction shows nonlinear current-voltage (I-V) characteristics similar to conventional vertical tunnel junctions. In case of small (sub-micron scale) junction widths, asymmetric I-V characteristics are observed due to the different local doping of graphene on both sides of tunnel barrier. As the junction width increases, the I-V curve becomes more symmetric since the graphene doping concentration on both sides of tunnel barrier becomes similar on average. From this tendency, the I-V characteristics of lateral G/FG/G tunnel junction can be concluded to be quite sensitive to the local doping of graphene. Differently from other vertical tunnel junctions, the lateral G/FG/G tunnel junction requires 1-dimensional model to explain its tunneling phenomenon. We constructed the 1-dimensional tunneling model and calculated the tunnel current density to compare with the 2-dimensional tunneling model for conventional vertical tunnel junctions. Our 1-dimensional tunneling model can be applied to lateral tunnel junctions made of recent 2-dimensional materials and give more accurate explanation about its physical mechanism as well.