Luminescence of sapphire and ruby induced by He and Ar ion irradiation

The luminescence spectra of sapphire(alpha-Al2O3) and ruby (alpha-Al2O3:Cr, Cr2O3 content 0.02%) induced by 200 keV He+ and Ar+ ion irradiation were measured at room temperature in the wavelength range of 250 to 450 nm, as a function of irradiation dose. The analysis of the measured spectra gave the existence of three main luminescence features in this wavelength region, namely F-center, F+-center and a band observed around 315 nm. alpha-Al2O3 under He+ irradiation showed the growth and decay of F-center and F+-center with increase of irradiation dose. F-center appeared earlier than F+-center and reached its maximum intensity around 1x10(14) He+/cm(2) while F+-center reached its maximum around 1x10(15) He+/cm(2). It suggests that F-center is easier to be produced by ion irradiation than F+-center, and a concentration quenching on F-center luminescence occurred above 1x10(14) He+/cm(2). Furthermore, the F-center luminescence was strongly suppressed by the existence of impurity Cr. On the other hand, the luminescence band around 315 nm appeared in the early stage of irradiation and showed only its decay part. The dose dependent behavior was similar to that of Cr3+ emission (R-line) in ruby in both He+ and Ar+ irradiation.