The defect structure of sapphire produced by implantation of Zr and Zr plus O: threshold fluence for amorphization and optical properties

Zirconium implantation-induced amorphization has been investigated with Rutherford back scattering spectrometry along a channeling direction (RBS-C) using 2 MeV He+. Ion implantation was carried out at the energy of 175 keV, with fluences of 2×1015 to 2×1016 Zr+/cm2 at room temperatures. The critical amorphization fluence at room temperature was determined as ∼1.5×1016 Zr+/cm2 corresponding to ∼ 40 dpa; ∼2.7% peak Zr-concentration) which is a lower damage energy than that reported for implantation with ions of similar mass and energy. The effect of post implantation of oxygen into a pre-implanted sample (with zirconium) was investigated. The RBS results show that oxygen implantation in a crystalline sample increases the damage only slightly and slightly broadens the Zr profile. For the fluences above thresh-old for amorphization, post implantation by oxygen has very little effect on the residual damage or on the Zr distribution. The presence of both F and F+ centers were indicated by optical absorption (OA) measurements. The OA spectra show the concentration of F and F+ centers increases with increasing fluence with some changes resulting from oxygen implantation of a pre-zirconium-implanted sapphire. This alters the relative concentrations of F and F+ centers. The F-type center concentrations for the samples were calculated using Smakula's equation. Photoluminescence (PL) at an excitation of 255 nm confirms the presence of both F and F+ centers with emission peaks at about 420 and 325 nm respectively. The PL spectra suggest that oxygen implantation decrease the concentration of the both species, consistent with the OA results (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)