An unusual diffusion enhancement of Ti in Ar+ pre-bombarded MgO(100) was observed during post-bombardment annealing at 1100C. Ti diffusion in the post-annealed sample was enhanced with respect to the sample without post-annealing. Thermal dissociation of small cationic vacancy clusters was known to be responsible for this type of radiation-enhanced diffusion, or non steady-state radiation-enhanced diffusion. It was inferred from previous work that the small vacancy clusters were mainly divacancies. The unusual diffusion enhancement was attributed to thermal dissociation of large vacancy clusters during post-annealing, leading to a divacancy creation mechanism. A model was proposed which qualitatively explains the observed diffusion enhancement.

Unusual Diffusion Enhancement of Ti in Ion Prebombarded MgO(100) during Post-Bombardment Annealing. M.Lu, C.Lupu, J.W.Rabalais: Journal of Vacuum Science & Technology A, 2003, 21[2], 359-62