Abstract
We demonstrate in a photoemission electron microscopy (PEEM) study of Pt/YSZ in vacuum that an open circuit (OC) potential can develop which we attribute to an inner photoelectric effect caused by the irradiation with UV light. The appearance of an OC potential is linked to the existence of a high voltage (HV) of at least 5kV between sample and PEEM instrument. The OC potential grows with increasing HV reaching about −200mV at a HV of 12kV. The effect represents a potential artefact in PEEM studies of solid ionic conductors with sufficiently small band gap (<6eV for photons from D2 discharge lamp).
•A highlight of this paper is the finding of an artefact in PEEM studies of the Pt/YSZ interface caused by the presence of a strong electric field in connection with irradiation by UV photons.•The inner photoelectric effect causes a chemical modification of the YSZ catalyst as evidenced by the appearance of an open circuit potential.•The photo-induced OC potential rises with increasing high voltage from a value close to zero at 6kV to −500mV at 14kV.