Surface modification of MgAl2O4 and oxides with heavy ions of fission fragments energy

In this paper we report on results of surface modification in several candidate materials for inert matrix fuel hosts (MgAl2O4, MgO and Al2O3) induced by (0.5–5) MeV/amu Kr, Xe and Bi ion bombardment in the fluence range of 2 × 1010–1012 ions/cm2. The size and shape of nanoscale hillock-like defects, each of which was created by the impact of a single ion, have been studied by using atomic force microscopy (AFM) technique. It was found that mean hillock height on sapphire and spinel surfaces depends linearly on the incident electronic stopping power. The hillocks are highest in MgAl2O4, having a lower threshold for the lattice disorder in the bulk material via relaxation of electronic excitations. As a possible reason for the hillocks formation, the plastic deformation due to the defects created by the Coulomb explosion mechanism in the target subsurface layer is suggested.