Optical and structural behaviour of Cu-implanted sapphire

Synthetic m- and c-cut sapphire single crystals were implanted at room temperature with 100 keV copper ions with fluences up to 1.6 × 1017 cm− 2. The samples were annealed at 800, 900 and 1000 °C in oxidizing or reducing atmosphere. Surface damage is observed after implantation of low fluences, the amorphous phase occurring after implantation of 8.6 × 1016 cm− 2, as seen by Rutherford backscattering spectrometry under channelling conditions (RBS-C). After implantation of high fluences the presence of nanoprecipitates is inferred from both optical absorption and X-ray diffraction (XRD) studies. Thermal treatments in air anneal most of the implantation-related defects and promote the redistribution of the copper ions, in mixed spinel and oxide phases, epitaxially aligned with the matrix. On the contrary, similar heat treatments in vacuum lead to the development of copper nanoprecipitates up to 900 °C and enhanced out diffusion at 1000 °C (total Cu content drops by 90%), while the matrix remains with a thin highly damaged surface layer which pins the remaining copper.