MERCURY IMPLANTED INTO ALUMINUM - ENHANCEMENT OF THE SUBSTITUTIONAL FRACTION BY PREIMPLANTATION OF KRYPTION

The substitutional fraction, f(s), of Hg implanted into Al single crys tals at 293 K and 77 K increases with increasing Hg concentration in t he region between about 0.1 at.% and 1 at.% from 0.05 to 0.3 at 293 K and from 0.55 to 0.80 at 77 K. In this concentration region the ratio of the critical angle for Hg to that of Al (PSI Hg1/2/PSI Al1/2) is sm aller than 1, indicating Hg-vacancy complex formation. Implantation of 1.6 x 10(16) Kr+/cm2 at 293 K and 77 K, followed by an implantation o f about 0.15 at.% Hg leads to an increase of PSI Hg1/2/PSI Al1/2 and t o a large increase of f(s) from 0.05 to 0.6 and from 0.55 to 0.82, res pectively. This large enhancement of the maximum f(s)-values are attri buted to the high vacancy trapping efficiency of the Kr atoms and of v acancy clusters, which reduces the density of mobile vacancies and thu s the probability of Hg-vacancy complex formation.