Characterization of lead, mercury and gold implanted into magnesium

Abstract

Rutherford Backscattering Spectrometry (RBS) has been employed to analyze the depth distribution of 300 keV Pb+, Hg+ and Au+ ions implanted into magnesium thin foils at room temperature to fluences in the range from 1 × 1015 to 5 × 1016 ions/cm2. Changes in the distribution profile of each of the implanted ions due to isochronal annealing sequences, in the range from 150°C to 430°C, have been investigated. This study reveals that Pb and Hg atomic diffusion are dependent on both the annealing temperature and the implanted dose. The Pb and Hg peak areas decrease with increasing annealing temperature and reveal a shallow diffusion tail at a deeper depth. This indicates that Pb and Hg atoms are released from a trap and are then subjected to a fast diffusion process. The high dose sample (5 × 1016Hg+/cm2) exhibits two release stages in the temperature regions between 150°C and 250°C and between 300°C and 375°C. The second stage may be due to the dissolution of Hg precipitates. In contrast, the high dose Pb implanted sample does not show any other release stage. For the lowest dose implant, 1 × 1015 Au+/cm2, agglomeration of Au at the surface and outdiffusion is clearly observed. For high dose implants the Au peak area decreases, however 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 proportion relative to the first stage, it is speculated that the first stage is due to single Au atoms while the second is due to Au precipitates.