The radiation-enhanced diffusion and ion-beam mixing of 18O, Ca and Zn buried tracer layers, in samples which had been grown by means of molecular beam epitaxy, were measured after bombardment with 2MeV Kr+ and 1MeV Ne+, He+ and H+ at temperatures ranging from 30 to 1500C. The ion-beam mixing parameter varied between 0.00001 and 0.00005nm5/eV for the various tracers, at 30C, and increased slowly with increasing temperature. These results were consistent with ballistic mixing. In the highest temperature range which was investigated (1350 to 1500C), the radiation-enhanced diffusion coefficient for 18O was proportional to the square root of the irradiation flux, and indicated an apparent activation enthalpy of 1.2eV. These dependences upon flux and temperature were indicative of recombination-limited kinetics, in which the measured activation enthalpy represented half of the migration enthalpy of anion vacancies. An activation enthalpy of 4.1eV was deduced for temperatures ranging from 1150 to 1350C. This unusually high value was attributed to the dissociation energy of small vacancy clusters. It was noted that measurements on the cation sub-lattice were limited to temperatures below 900C, due to an excessive thermal diffusivity that was associated with extrinsic vacancies which were linked to trivalent impurity-charge compensation.

Radiation Enhanced Diffusion in MgO. A.I.Van Sambeek, R.S.Averback, C.P.Flynn, M.H.Yang, W.Jäger: Journal of Applied Physics, 1998, 83[12], 7576-84