Formation of subsurface aluminum layers in beryllium by ion implantation and post-implant annealing.

摘要

Subsurface layers of aluminum were formed in both monocrystalline and polycrystalline beryllium by implanting high doses of 200 keV Al(sup +) ions into beryllium and subsequently annealing the implanted material. Contrary to conventional wisdom on ion implantation, such layers demonstrate that ion implantation can in fact, be used, to form an essentially pure layer of an implanted species in a target material. In single crystal targets implanted at approximately 50(degree)C, aluminum layer formation was critically dependent on the implanted dose. Cross-sectional transmission electron microscopy showed the aluminium layers were monocrystalline and had abrupt interfaces with the beryllium bulk and overlayer. Scanning electron microscopy revealed defects in the layers consisting of beryllium columns extending through the aluminum from the beryllium overlayer to the bulk. Study of implanted polycrystalline material showed that layer formation occurred for all grain orientations present, but that the defect density was grain dependent. An explanation of layer formation is developed based on the observed lamellar precipitate morphology in the as-implanted state and on predicted coarsening behavior of this morphology during annealing. 41 refs., 54 figs., 2 tabs.