Cluster ion sputtering: molecular ion yield relationships for different cluster primary ions in static SIMS of organic materials

Abstract An analysis is made of the molecular secondary ion yield (MSIY) variation with primary ion source mass and number, n , of constituent particles. The theory is based on the linear cascade model, extended into the nonlinear regime for higher deposition energy densities using Sigmund and Claussen's thermal spike model. The analysis is generalised to remove sample specificity and is evaluated for light, organic materials. It provides the MSIY dependence for this material as a function of the primary ion particle parameters. This is applied to the data of Kersting et al . and of Kollmer for the (M − H) − de‐protonated secondary ion yields, Y (M − H) − , from Irganox 1010 for Ga + , Cs + , SF 5 + , Au + , Au 2 + , Au 3 + and C 60 + primary ions. The previously postulated dependence of Y (M − H) − on the sputtering yield squared is validated. This formulation permits the prediction of Y (M − H) − for new primary ions such as Bi n + and C 70 + . It is shown that further MSIY gains of possibly up to an order of magnitude are attainable. For analysis, raising the MSIY is extremely helpful but it is the efficiency (the ratio of the MSIY to the disappearance cross‐section) that is critical. The distinction between the damage and disappearance cross‐sections is clarified and a description involving both terms and correlating with data for all ions is given. It is shown that the efficiency increases with Y (M − H) − , initially linearly and finally with a square root dependence. The chemical nature of the primary ion species is shown to be relatively unimportant in these processes. © Crown copyright 2007. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.

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