Effect of crystal orientation on defect production and optical activation of Er-implanted sapphire

Defect production and optical activity of Er-implanted α-Al2O3 were studied as a function of implanted dose and crystal orientation. Erbium fluences in the range of 8x1013-4x1015 Er+/cm2 were implanted into single crystalline samples with either the m-axis or c-axis normal to the surface. The energy of the Er ions was 200 keV. We found that the number of displaced O atoms was about two times higher on samples with the c-axis normal to the surface compared to the m-samples. The annealing stages of the damage follow a similar behaviour for the m-axis and c-axis samples and the complete recovery occurs for temperatures above 1200 deg. C. The reconstruction of the lattice is accompanied by a reduction in the intensity of the photoluminescence signal above 825 deg. C. Since the amount of Er and its lattice site is maintained, it is concluded that the change on its surroundings was responsible for the decrease of optical activity