“…In this respect, X-ray photoelectron spectroscopy (XPS) has provided important contributions to semiconductor research, monitoring changes in the chemical state, band bending, and photoemission-induced surface charging [12,18,19,21]. Synchrotron light XPS has become a true microscopy technique, used recently for characterization of nanotubes, nanobelts, and NWs [22][23][24]. This study of undoped GaAs NWs prior to, and after, exposure to oxygen ambient demonstrates that by means of scanning photoelectron microscopy (SPEM) [25] it is possible to examine the interplay between NW diameter and conductance, combining full control of the surface chemical state with contactless monitoring of the changes in the conductivity along the axis of the NWs.…”