Size-dependent radiation tolerance in ion irradiated TiN/AlN nanolayer films

Interface effects on ion-irradiation tolerance properties are investigated in nanolayered TiN/AlN films with individual layer thickness varied from 5nm to 50nm, prepared by pulsed laser deposition. Evolution of the microstructure and hardness of the multilayer films are examined on the specimens before and after He ion-implantation to a fluence of 4×1020m−2 at 50keV. The suppression of amorphization in AlN layers and the reduction of radiation-induced softening are observed in all nanolayer films. A clear size-dependent radiation tolerance characteristic is observed in the nanolayer films, i.e., the samples with the optimum layer thickness from 10nm to 20nm show the best ion irradiation tolerance properties, and a critical layer thickness of more than 5nm is necessary to prevent severe intermixing. This study suggests that both the interface characteristics and the critical length scale (layer thickness) contribute to the reduction of the radiation-induced damages in nitride-based ceramic materials.