Nanoscale fabrication of a three-dimensional stack of graphene layers using a focused ion beam

A top-down nanoscale stack fabrication approach involving the high-precision carving of a stack of graphene layers from a thin graphite flake via focused-ion-beam (FIB) three-dimensional (3D) etching is presented. Using this technology, etching was performed in the c-axis with the height of a few tens of nanometres. By reducing the stack height to 50 nm, a 3D stack of graphene layers coupled in a stacked manner was fabricated. The transport characteristics of the stack in the c-axis were studied and compared with the transport characteristics of the stack with a larger in-plane area and stack height value. The observed conductivity of the nanostack with a 50 nm height was one order smaller than the conductivity of the stack with a larger in-plane area and stack height value. Nonlinear current-voltage (I-V) characteristics were observed in all the studied temperatures, but the stack with a larger in-plane area and stack height value showed nonlinear characteristics only at lower temperatures. The observation of these temperature-dependent I-V characteristics was discussed in detail, and the tunneling characteristics were investigated using the Fowler-Nordheim tunneling model, which showed the best fit to the experiment data in this study.