On the emission of MoCs+ molecular ions from Cs+ irradiated molybdenum surface

The present paper deals with the emission of atomic and molecular ions from elemental molybdenum surface under Cs+ bombardment to explore the MCs+ formation mechanism with changing Cs surface coverage. Integrated count of MoCs+ shows a monotonic increase with increasing primary ion energy (1–5 keV). Change in MoCs+ intensity is attributed to the variation of surface work function ϕ and cesium surface concentration cCs due to varying impact energies. Variation of cCs has been obtained from the expression, cCs ∝ 1/(1 + Y) where Y is the elemental sputtering yield estimated from TRIM calculations. Systematic study of the energy distributions of all species emerging from Mo target has been done to measure the changes in surface work function. Changing slopes of the leading parts of Cs+ energy distributions suggest a substantial depletion in surface work function ϕ with decreasing primary ion energies. Δϕ shows a linear dependence on cCs. The maximum reduction in surface work function Δϕmax = 0.69 eV corresponds to the highest value of cCs = 0.5. A phenomenological model, based on the linear dependence of ϕ on cCs, has been employed to explain the MoCs+ data.