Reaction in Al2O3 surface layers upon ion implantation

Abstract

The mechanical properties of Al2O3 have been improved by implantation of C and N ions at doses of 1 × 1015 to 1 × 1018 ion cm−2. The hardness, fracture and scratch toughness of the implanted layers were examined. The increase in hardness was ca. 92% at 1 × 1017 N ions cm−2, but only 6% at 1 × 1017 C ions cm−2. The maximum fracture toughness was 95% greater than that of the unimplanted substrate at a fluence of 3 × 1017 N ions cm−2, and ca. 25% greater for 5 × 1017 C ions cm−2. The mechanisms of hardening and toughening by C and N ion implantation were investigated by XPS, electrical resistance and Raman spectroscopy measurements. The surface electric resistivity decreased to ca. 107 Ω cm for N+ or C+ ion implantation. Nitrogen implantation produced Al, AlN or AlON while carbon implantation led to a carbon film, Al, Al4C3 or Al4O4C on Al2O3. The hardening and toughening on Al2O3 surface layers was attributed to chemical reactions, with the amount of modification depending on the C and N ion implantation dose.