Damage depth profile in α-Al2O3 induced by swift heavy ions

Abstract

Structural modifications of aluminium oxide induced by swift heavy ion irradiation are investigated. (0 0 0 1)-Al2O3 single crystals have been irradiated at room temperature along the c-direction by 92 MeV 129Xe23+ with fluences up to 1.2 × 1015 ions/cm2. High resolution and in-plane X-Ray diffraction is mainly used to characterize samples with various sensitivities to the surface and to the irradiated depth. As function of fluence the mechanisms of structural modifications are investigated. Different evolutions of the c-parameter (parallel to ion beam) and the a-parameter (perpendicular to ion beam), affected by irradiation in the MeV range, are observed. 2D maps around (0 0 0 6)-reflection indicate a clear broadening on 2θ axis with the formation of new contributions which are due to tensile strain induced by irradiation. In the damage profile, by combining with RBS/C and TEM results, we suggest that the c-parameter is larger near the surface and decreases gradually with depth. In addition, the damage profile evidences an increase of damaged depth as function of the fluence which occurs before saturation linked to the formation at the surface of an amorphous layer.