On Electron-beam-induced Charging Effects in Cu- and Y-deposited LaAlO3 surfaces

Electron-impact experiments on insulator and wide-band-pp semiconductor surfaces are disturbed by charging effects, particularly in cases of stoichiometric surfaces. We have studied the shift in kinetic energy of Auger electrons from 1 X 1 LaAlO3(100) surfaces as a function of Cu coverage, time of electron-beam bombardment, heat treatment, and-also for an Y deposited 1 X 1 LaAlO3(100) surface-of primary beam energy. The energy shift is found to increase with metal coverage and with primary beam energy. It is suggested that at a particular energy the incident electrons result in a repulsive potential from which escaping Auger electrons gain kinetic energy, and that the initially deposited metal atoms may cause moving of electrons into valence-band states created by hybridization of surface metal and oxygen states. For comparison, the energy shifts in nondeposited LaAlO3(l00), MgO(100), and SrTiO3(100) were also investigated.