Insulator-conductor transition in 12CaO.7Al2O3 films: On the stability of the crystal lattice under Ar+ bombardment

Recent experimental studies suggest that thin films of a nano-porous complex oxide 12CaO.7Al2O3 (C12A7) are unusually stable under bombardment with energetic Ar+ ions [M. Miyakawa et al., J. Appl. Phys. 97 (2005) 023510.]. We employ classical Molecular Dynamics to study the processes induced by knock-on collisions of Ar+ with the C12A7 lattice. Our results suggest that such collisions predominantly affect the anion sublattice and form Frenkel defect pairs. We find that most of these Frenkel pairs are unstable and readily recombine with the extra-framework O2- ions present in the lattice at stoichiometric concentrations of ∼ 1.2 x 1021 cm-3. This process is further facilitated by fast diffusion of the extra-framework O2- ions. These results provide a useful insight in the design of new radiation-resistant materials