The diffusion of Ti in MgO(100) was studied in MgO that had been pre-bombarded with inert ions (Ne+, Ar+, Kr+) in the keV energy range using various ion doses, energies, momenta, and penetration ranges. Diffusion was induced by annealing (1000C, 360s) following the pre-bombardment and Ti evaporation. This type of radiation-enhanced diffusion was termed non steady-state radiation-enhanced diffusion. The diffusion penetration profiles were analyzed by using secondary ion mass spectrometry depth profiling techniques and ion trajectory simulations. The observed diffusion behaviors were treated by using a previously developed model for non steady-state radiation-enhanced diffusion. A figure of merit, Σ, was introduced in order to assess the density of extended vacancy defects which were responsible for non steady-state radiation-enhanced diffusion and to compare non steady-state radiation-enhanced diffusion effects for various ion bombardment parameters. The observed trends in Σ were in agreement with experimentally observed radiation-enhanced diffusion effects, and provided a quantitative measure of their magnitudes. The results showed that the non steady-state radiation-enhanced diffusion effects and vacancy densities responsible for non steady-state radiation-enhanced diffusion were related to the degree of vacancy production in the simulations. It was found that non steady-state radiation-enhanced diffusion of Ti in MgO, and the density of extended vacancy defects responsible for non steady-state radiation-enhanced diffusion, reached a saturation level after a dose of about 1016/cm2 for 7keV Ar+ pre-bombardment. A threshold value of the vacancy production for the formation of extended vacancy defects for non steady-state radiation-enhanced diffusion at this dose was in the range of 94 to 111 vacancies/ion.

Ti Diffusion in Ion Prebombarded MgO(100) - Effects of the Irradiation Spectrum. M.Lu, C.Lupu, S.M.Lee, J.W.Rabalais: Journal of Vacuum Science & Technology A, 2002, 20[1], 180-8