Diffusion behaviour of gold and mercury implanted into magnesium

The annealing behaviour of magnesium foils of high purity (99.99 %), implanted with 300-keV Au+ and Hg+ ions at 25 Centigrade with various doses ranging from 5 x 1014 to 5 x 1016 at./cm2, was investigated. The samples were analysed by the Rutherford backscattering spectrometry technique using a 2-MeV 4 He+ beam as a function of the annealing temperature. For the lowest-dose implant (1 x 1015 Au+/cm2) agglomeration of Au at the surface and out-diffusion is clearly observed. For high-dose implants the Au peak area decreases; However, it retains its shape with increasing annealing temperature. The decrease of the Au peak area occurs in two temperature stages indicating two different trapping centers. As the second stage at higher temperature increases in content relative to the first stage, it is speculated that the first stage is due to single Au atoms while the second one is due to Au precipitates. This study reveals that Hg atom diffusion is dependent on both the annealing temperature and the implanted dose. The Hg peak area decreases with increasing annealing temperature and reveals a shallow diffusion tail at a deeper depth. This indicates that Hg is released from a trap and is then subjected to a fast diffusion process. While for the low-dose implant (5 x 1014 Hg+/cm2) the release occurs at a nearly uniform rate, the high-dose sample (5 x 1016 Hg+/cm2) exhibits two release stages in the temperature regions between 150 Centigrade 250 Centigrade and between 300 Centigrade and 375 Centigrade. The second stage may be due to the dissolution of Hg precipitates. (Author)