An experimental and theoretical evaluation of surface states in MgO and other alkaline earth oxides

Abstract

Excitons II and III can only be tentatively assigned, but they are attributed to surface ions in fourfold and threefold coordination, respectively, the ions being at steps, edges or kink sites rather than on low-index faces, and thereby having a similar character to bulk excitons bound at internal lattice imperfections. The increased covalency shown by ions in low coordination prevents the application of the Levine–Mark theory.