Charging effects on electron-stimulated desorption of cations from gadolinia-doped ceria surfaces

Electron beam-induced charging and -stimulated desorption have been used to probe the electronic properties of gadolinia-doped ceria (GDC) surfaces. The main cationic desorption products resulting from electron bombardment are H+, H3O+ and O+. The dependence of the H+ and H3O+ ion kinetic energies and yields on the surface potentials have been systematically investigated. Positive potentials increase the cation kinetic energies linearly while negative potentials reduce the cation yields dramatically. The charging of GDC by electron beam bombardment is dependent on the incident electron energy: negative at lower energy and positive at higher energy. Irradiation with 400 eV electrons can produce a positive surface potential of several volts while irradiation of the sample with 75 eV electrons can produce a negative sample potential of at least -6 V. The positive charge caused by high-energy electron irradiation can be neutralized by the negative charge generated by low-energy electrons and vice versa. The probable hole traps are sites close to Gd3+, and the abundant presence of defects at oxygen vacancy-rich grain boundaries can serve as very effective electron traps