Optical properties tailoring by high fluence implantation of Ag ions on sapphire

Optical and structural properties of single crystalline α-Al2O3 were changed by the implantation of high fluences of Ag ions. Colourless transparent (101¯0) sapphire samples were implanted at room temperature with 160 keV silver ions and fluences up to 1 × 1017 Ag cm−2. Surface amorphization is observed at the fluence of 6 × 1016 Ag cm−2. Except for the lower fluences (below 6 × 1016 Ag cm−2) the optical absorption spectra reveal the presence of a band peaking in the region 450-500 nm, depending on the retained fluence. This band has been attributed to the presence of silver colloids, being thus 1 × 1016 Ag cm−2 below the threshold for colloid formation during the implantation. Annealing in oxidizing atmosphere promotes the recrystallization along with segregation of Ag followed by loss through evaporation. Recrystallization is retarded for annealing in reducing atmosphere and the Ag profile displays now a double peak structure after evaporation. Playing with the implantation fluence, temperature and annealing atmosphere controllable shifts of the position and intensity of the optical bands in the visible were achieved.