Examples of thermally induced charge compensation in photoelectron spectroscopy of insulators

The electrical charging of insulating samples is a common problem in photoelectron spectroscopy. Although heating has been suggested as a way to minimize surface charging, systematic studies of this are scarce. We have found that during 8 keV photoelectron spectroscopy using a synchrotron, the extent of charging of three highly insulating materials could be significantly reduced with increasing temperature. The charging of glass and LiNbO3 samples could be almost completely compensated at a moderate temperature of ∼400 °C. Based on the temperature dependence of charging-induced binding energy shift, the activation energies of the charge compensation were evaluated to be about 0.73, 0.65, and 0.21 eV for a glass slide, cover glass, and LiNbO3, respectively. Furthermore, charge compensation was achieved by surface conduction rather than bulk conduction.