Development of a column delivering a collimated stream of Cs 0 for SIMS purposes

Abstract

In order to optimize SIMS analyses using the presence of reactive Cs for the purpose of enhancing negative secondary ion emission or working in the MCs x + mode, we have developed a column that delivers a collimated and adjustable stream of neutral Cs atoms to be deposited on the surface of the sample while this one is being analyzed. Using this new column, it was possible to introduce an analysis technique consisting of a X y+ ion bombardment (where X stands for any element excepting Cs) accompanied by a simultaneous deposition of Cs 0 at the surface of the sample. This experimental technique permits a successful decoupling of the sputtering and Cs introduction processes by avoiding the constraints imposed by an energetic Cs + ion bombardment. As a consequence, it becomes possible to optimize simultaneously the sensitivity of the analysis, by carefully adjusting the Cs concentration to its optimum value, and the depth resolution of the analysis, by choosing adequate primary bombardment conditions. In this paper, we will describe the new Cs 0 column, which is based on an evaporation of pure metallic Cs, and outline its performances in terms of deposition rates, stability, beam dimensions and purity of the Cs deposit.