Metal impurity release from structural defects in polycrystalline material was studied after heat treatment, and a correlation was also established between impurity distributions and structural defects. Impurities were mapped using synchrotron-based X-ray fluorescence in the as-grown state, after rapid thermal annealing and after Al gettering. The object of the present work was to determine whether impurity release from structural defects limited the gettering of metal impurities. The results revealed that Ni and Cu impurities were found mainly at dislocations in as-grown crystals, and that the release of these impurities from defects occurred rapidly; with no apparent barrier to dissolution. Gettering treatments dissolved metal impurity precipitates which were 2 to 5nm in radius.

S.A.McHugo: Applied Physics Letters, 1997, 71[14], 1984-6