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 Title: Radiation-Enhanced Diffusion and Defect Production During Ion Irradiation of MgO and Al(2)O(3) Author(s): Van Sambeek, Andrew I. Doctoral Committee Chair(s): Averback, R.S. Department / Program: Materials Science and Engineering Discipline: Materials Science and Engineering Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Physics, Radiation Abstract: 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. Issue Date: 1997 Type: Text Language: English Description: 120 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1997. URI: http://hdl.handle.net/2142/82882 Other Identifier(s): (MiAaPQ)AAI9737278 Date Available in IDEALS: 2015-09-25 Date Deposited: 1997
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