DISPLACEMENT DAMAGE EFFICIENCY IN SAPPHIRE

The efficiency of point defect production in sapphire by a variety of ion beams has been estimated by monitoring the oxygen vacancy colour centre concentration. Results are presented for H, D, He, B, N, Ne, Ar and Kr bombardment at both room temperature and 77 K. Experimentally determined values of the mean number of oxygen vacancies produced per incident ion are compared with theoretical values. The latter have been computed by solving the Lindhard integral equations to determine the partitioning of damage between the oxygen and aluminium sublattices. The stopping powers and cross sections of Ziegler, Biersack and Littmark have been used in these calculations and give significantly improved estimates of the damage energy. A significant Z1 variation in the damage efficiency is noted for low mass ions. The variation of damage efficiency with incident ion mass is discussed in terms of the primary knock-on spectrum.