In-Situ TEM Studies of Ion-Irradiated Materials

There are a number of vital areas of technology where the understanding of processes that occur when solids are irradiated with energetic particles is of great importance. In particular, components of both nuclear fission and fusion nuclear reactors may suffer numerous undesirable phenomena such as creep, embrittlement, swelling and blistering as a result of the injection of gas (from direct implantation or transmutation reactions) and high levels of radiation damage. Another example is the fabrication of microelectronic devices, where ions of dopant elements are intentionally introduced into semiconductors but where unwanted radiation damage is also inevitably introduced. Much processing must subsequently be carried out to remove this damage which generally has detrimental effects on electronic parameters. Although this field of study is a mature one with a large scientific literature, there are nonetheless areas that are distinctly lacking in the fundamental understanding that is needed underpin the important technological issues. In-situ TEM studies of ion-irradiated materials can give remarkable insights into fundamental aspects of radiation damage, in that dynamic processes are observed and recorded as they occur. The in-situ facility also offers the possibility of real-time observations of processes occurring during ion-irradiation at temperatures from cryogenic up to approximately 1000 degrees Celsius. Such studies are of particular importance in providing experimental data to inform modelling studies (such as molecular dynamics and kinetic Monte-Carlo simulations) and thus enable a detailed atomistic understanding of the radiation damage processes. This project is concerned with the building of a low-cost facility that will allow the study, in-situ in a transmission electron microscope (TEM), of processes occurring in materials under ion-irradiation and where ion irradiation can be used as a (much speeded up) simulation of processes occurring under neutron irradiation. It is anticipated that a total of eighteen months of the three-year project will be concerned with building the facility. Its capability will then be demonstrated by carrying out investigations in the following areas: the effects of helium incorporation and displacement damage in steels in connection with helium embrittlement in nuclear reactor materials; the effects of helium incorporation and displacement damage on tungsten in connection with helium embrittlement in potential fusion reactor materials; and ion-implantation-induced effects in elemental semiconductors (Si and Ge).