Radiation-Enhanced Diffusion and Defect Production During Ion Irradiation of MgO and Al(2)O(3)

120 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1997.Radiation enhanced diffusion of O$\sp{18}$, Ca and Zn buried tracer layers in MBE grown MgO was measured following irradiation with either 2.0 MeV Kr or 1.0 MeV Ne, He or H from 30 to 1500$\sp\circ$C. This represents the first reported RED measurements on an oxide system. Ion beam mixing at 30$\sp\circ$C on both sublattices was approximately 1.0 to 5.0 A$\sp5$/ev indicating the temperature independent mixing (ballistic mixing) is produced only by direct recoil and cascade events and that thermal spikes are not significant. D$\sb{\rm red}$ was proportional to the square root of the irradiation flux with an activation enthalpy of 1.2 eV for diffusion on the anion sublattice from 1350 to 1500$\sp\circ$C. The flux dependence is characteristic of kinetics in the recombination limited regime; accordingly, the measured activation enthalpy of 1.2 eV is identified as one-half the migration enthalpy of the anion vacancy. This assignment agrees with the predicted anion vacancy migration enthalpy of 2.1 to 2.4 eV. Between 1150$\sp\circ$C and 1350$\sp\circ$C an apparent activation enthalpy of 4.1 eV was measured. This enthalpy was attributed to vacancy clustering reactions. Measurements on the cation sublattice were conducted at temperatures below 900$\sp\circ$C. At higher temperatures excessive thermal diffusion from extrinsic vacancies stemming from trivalent impurities prevented measurements of RED.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD