Quantum Dot Formation in Controllably Doped Graphene Nanoribbon.

We introduce the controllable doping from hydrogen silsesquioxane (HSQ) to graphene by changing its electron-beam exposure dose. Using HSQ as the dopant, a fine-resolution electron-beam resist allows us to selectively dope graphene with an extremely high spatial resolution of a few nanometers. Therefore, we can design and demonstrate the single quantum dot (QD)-like transport in the graphene nanoribbon (GNR) with the opening of the energy gap. Moreover, we suggest a rough geometric design rule in which a relatively short and wide GNR is required for observing the single QD-like transport. We envisage that this method can be utilized for other materials and for other applications, such as p-n junctions and tunnel field-effect transistors.