Highly efficient electron stimulated desorption of O+ from gadolinia-doped ceria surfaces.

Highly efficient electron stimulated desorption of O+ from gadolinia-doped ceria (GDC) surfaces annealed at 850 K in ultrahigh vacuum is observed and investigated. O+ desorption has a major threshold of approximately 40 eV and an intrinsic kinetic energy of approximately 5.6 eV. Since the threshold energy is close to Ce 5s and Gd 5s core levels, Auger decay of core holes is likely associated with O+ desorption from sites related to oxygen vacancies. The interactions of water and molecular oxygen with GDC surfaces result in a decrease in O+ desorption, suggesting that water and oxygen molecules adsorb mainly to oxygen vacancies. The dependence of O+ kinetic energies on the incident electron energy and temperature reveals surface charging as a result of electron trapping, hole trapping, and electron-hole recombination. The activation energy for surface charge dissipation is found to be 0.43 eV, close to the activation energy for ionic conduction (0.47 to 0.6 eV) in the same material.