Temperature dependence of lattice disorder in Ar-irradiated (1 0 0), (1 1 0) and (1 1 1) MgO single crystals

To better appreciate dynamic annealing processes in ion irradiated MgO single crystals of three low-index crystallographic orientations, lattice damage variation with irradiation temperature was investigated. Irradiations were performed with 100 keV Ar ions to a fluence of 1 x 1015 Ar/cm2 in a temperature interval from -150 to 1100 oC. Rutherford backscattering spectroscopy combined with ion channeling was used to analyze lattice damage. Damage recovery with increasing irradiation temperature proceeded via two characteristic stages separated by 200 oC. Strong radiation damage anisotropy was observed at temperatures below 200 oC, with (1 1 0) MgO being the most radiation damage tolerant. Above 200 oC damage recovery was isotropic and almost complete recovery was reached at 1100 oC. We attributed this orientation dependence to a variation of dynamic annealing mechanisms with irradiation temperature.