Slow positron beam studies were made of Al-implanted samples of Hg0.78Cd0.22Te. Single crystals were implanted with 320keV Al ions to a fluence of up to 3 x 1012/cm2 at room temperature and to a fluence of 1014/cm2 at 100 and 300K. The effect of the native oxide layer upon the positron spectrum was considered, and it was shown that the oxide/crystal interface acted as a strong positron trap. By using both the core and valence annihilation components, it was possible to separate oxide-related positron effects at the surface from damage in the crystal itself. It was found that implantation introduced small vacancy clusters. On the basis of the relative Doppler parameters of the defects which were created, it was deduced that they were probably di-vacancies. The di-vacancy profile extended from the surface to a depth that was comparable to the mean Al implantation depth. At room temperature, di-vacancy creation reached saturation at a fluence of 3 x 1012/cm2; with an estimated di-vacancy concentration of 4 x 1016/cm3. After implantation at 100K, and annealing at 360K, the number of created di-vacancies exceeded 1018/cm3.

L.Liszkay, C.Corbel, L.Baroux, P.Hautojärvi, A.Declemy, P.O.Renault: Journal of Physics - Condensed Matter, 1995, 7[45], 8529-38