The Energy Dependence of the Ionisation Coefficient in SIMS

Abstract

If the process of secondary ion formation is viewed as one in which the secondary ion is formed amongst the sputtered flux from the surface and then survives the outgoing trajectory to be analysed, we can write the yield in the energy range E to E + dE, and angle range θ to θ + dθ as

$${{\rm{Y}}^ + }\left( {{\rm{E,}}\theta } \right){\rm{dEd}}\theta = {\rm{N}}\left( {{\rm{E,}}\theta } \right){{\rm{R}}^ + }\left( {{\rm{E,}}\theta } \right){\rm{P}}\left( {{\rm{E,}}\theta } \right){\rm{dEd}}\theta$$

((1))

• where ⇅(E,θ) is the sputtered atom flux

• R⁺(E,θ) is the probability of ionisation in the ejection process

• P(E,θ) is the probability of surviving the outgoing trajectory in an ionised state.