Measurements and modelling of solid phase lithium sputtering

Abstract

The absolute sputtering yields of D+, He+ and Li+ on deuterium saturated solid lithium have been measured and modelled at 45° incidence in the energy range 100-1000 eV. The Ion-surface InterAction Experiment (IIAX) was used to measure the absolute sputtering yield of lithium in the solid phase from bombardment with a Colutron ion source. The lithium sample was treated with a deuterium plasma from a hollow cathode source. Measurements also include bombardment of non-deuterium-saturated lithium surfaces. The results lead to the conclusion that the chemical state of the deuterium treated lithium surface plays a major role in the decrease of the lithium sputtering yield. Specifically, preferential sputtering of implanted deuterium atoms over lithium atoms in deuterium treated samples results in a decrease of at least 60% of the lithium sputtering yield, in the case of He+ bombardment. These results also demonstrate that lithium self-sputtering is well below unity and that the fraction of sputtered species in an ionic state ranges from 55 to 65% for incident particle energies between 100 and 1000 eV. Furthermore, correlation of Monte Carlo VFTRIM-3D simulations and IIAX experimental data demonstrate that the surface composition has a one to one ratio between deuterium and lithium components.