Probing transconductance spatial variations in graphene nanoribbon field-effect transistors using scanning gate microscopy

We have used scanning gate microscopy to probe local transconductance in graphene nanoribbon (GNR) field-effect transistors (FETs) fabricated from chemical vapor deposition-grown graphene. Particularly, nanometer-scale (<= 100 nm, resolution limited) areas characterized by significant transconductance spatial variations were observed along the FET channel. These were attributed to the impurities at or close to the edges of the GNRs. Our results further show that a single such impurity site in a long-channel (similar to 2 mu m) GNR FET can essentially control the global device characteristics. This finding demonstrates the importance of controlling the spatial inhomogeneity of electronic properties in graphene and related nanostructures in order to realize their envisioned applications in new electronics. (C) 2012 American Institute of Physics. [doi:10.1063/1.3678034]