Pinpoint operando analysis of the electronic states of a graphene transistor using photoelectron nanospectroscopy

Graphene is a promising material for next-generation devices owing to its excellent electronic properties. Graphene devices do not, however, exhibit the high performance that is expected considering graphene's intrinsic electronic properties. Operando, i.e., gate-controlled, photoelectron nanospectroscopy is needed to observe electronic states in device operation conditions. We have achieved, for the first time, pinpoint operando core-level photoelectron nanospectroscopy of a channel of a graphene transistor. The direct relationship between the graphene's binding energy and the Fermi level is reproduced by a simulation assuming linear band dispersion. This operando nanospectroscopy will bridge the gap between electronic properties and device performance.