Accessing the spectral function of in operando devices by angle-resolved photoemission spectroscopy

Progress in performing angle-resolved photoemission spectroscopy (ARPES) with high spatial resolution on the order of 1 mu m or less (nanoARPES) has opened the possibility to map the spectral function of solids on this tiny scale and thereby obtain detailed information on the materials' local electronic band structure and many-body interactions. Recently, nanoARPES has been used to study simple electronic devices, based on two-dimensional materials, with the possibility of tuning the carrier type and density by field effect-gating, as well as passing a current through the device. It was demonstrated that nanoARPES can detect possible changes in the materials' electronic structure in these situations and that it can map the local doping, conductance, and mobility. This article reviews these first in operando ARPES results on devices and discusses the resulting new insights as well as the perspectives for future developments of the technique.