Rutherford back-scattering spectrometry and cross-sectional transmission electron microscopy were used to study the implantation of MeV Au+ ions. The measured range and straggle values for the implanted samples were found to be consistently larger than the values which were predicted by simulations. The magnitude of the discrepancies was such that the differences could not be attributed to implantation effects alone. The experimental results showed that a single Gaussian Au profile was obtained in the case of low-current low-energy implants. Low-power implants produced a single damage band which consisted of simple point defects. High-current high-energy implants led to the creation of more complex defect structures, such as dislocation networks. These arose as a result of dynamic beam recrystallization. Multiple layers of precipitation were observed, in material which had been implanted with MeV Au+ ions, when dynamic recrystallization occurred. Precipitation occurred because the local Au concentration exceeded the solid solubility during beam-induced recrystallization. Various mechanisms operated so as to cause an anomalous Au migration which resulted in the formation of multiple precipitate layers. One mechanism caused the implanted Au to segregate into a densely defected region. When the concentration exceeded the local solid solubility, Au precipitated out of the matrix. Another mechanism involved Au migration along the dislocations in a network. Here, the diffusing Au reached a dislocation node where it exceeded the local threshold for precipitation and therefore precipitated out. The occurrence of enhanced Au diffusion depended upon the degree of dynamic recrystallization which occurred during implantation.

T.L.Alford, N.D.Theodore: Journal of Applied Physics, 1994, 76[11], 7265-71