TRANSIENT RELEASE OF DEUTERIUM FROM BERYLLIUM AFTER PLASMA ION-IMPLANTATION

Transient release immediately following implantation has been observed when large 5.1 cm diameter Be disks were implanted with deuterium ions at a flux of 7.4 x 10(16) D/cm2 s. A series of experiments have been performed at temperatures ranging from 333 to 800 K. The release characteristics vary depending on whether the beryllium surface is clean or is covered with a thick oxide layer. When the surface is clean, the integrated release (D/cm2) increases monotonically with temperature and then levels off at 700 K. This behavior cannot be described with a diffusion-limited release but is consistent with a recombination-limited release model. Furthermore, the release rate exhibits approximately a t-1 time dependence, in good agreement with the results calculated using the model. The recombination coefficient has to be sufficiently small such that the ratio of the diffusivity to the recombination coefficient D/K(r) greater-than-or-equal-to 10(14) cm-2 at 600 K and must rise sharply with temperature. When the surface of the beryllium samples has a thick oxide layer present the release rate significantly changes and follows a t-0.3 dependence.