THE LUMINESCENCE OF SAPPHIRE SUBJECTED TO THE IRRADIATION OF ENERGETIC HYDROGEN AND HELIUM-IONS

The luminescence of alpha-Al2O3 during He+ and H+ irradiation was meas ured in the 190-820 nm wavelength range. The luminescence evolution wi th the ion fluence exhibits two behaviours : (i) at low fluence, the a mount of F+ centres increases; (ii) at high fluences, these defects ar e completely (F centres) or partially (F+ centres) annihilated. This p henomenon results from two concomittant mechanisms : a conversion betw een F and F+ defects and a destruction of both luminescent species res ulting from the radiation-induced damage. By using a simple model we h ave determined the cross sections associated with creation (sigma(c)) and annihilation (sigma(a)) of the F+ centres. The irradiated samples were also investigated by cathodoluminescence and Auger electron spect roscopy. A higher concentration of structural defects and F+ centres i s evidenced at the sample area previously irradiated by ions, leading to an unsteady regime of the surface potential under electron excitati on.