Reaction in Al2O3 surface layers upon ion implantation

The mechanical properties of Al2O3 have been improved by implantation of C and N ions at doses of 1 x 10(15) to 1 x 10(18) ion cm(-2). The hardness, f racture and scratch toughness of the implanted layers were examined. The in crease in hardness was ca. 92% at 1 x 10(17) N ions cm(-2), but only 6% at 1 x 10(17) C ions cm(-2). The maximum fracture toughness was 95% greater th an that of the unimplanted substrate at a fluence of 3 x 10(17) N ions cm(- 2), and ca. 25% greater for 5 x 10(17) C ions cm(-2). The mechanisms of har dening and toughening by C and N ion implantation were investigated by XPS, electrical resistance and Raman spectroscopy measurements. The surface ele ctric resistivity decreased to ca. 10(7) Omega cm for N+ or C+ ion implanta tion. Nitrogen implantation produced Al, AlN or AlON while carbon implantat ion led to a carbon film, Al, Al4C3 or Al4O4C on Al2O3. The hardening and t oughening on Al2O3 surface layers was attributed to chemical reactions, wit h the amount of modification depending on the C and N ion implantation dose .