Quantitative ToF-SIMS depth profiling of a multi-phased III-V semiconductor matrix via the analysis of secondary cluster ions.

An approach for quantification of time-of-flight (ToF)-SIMS depth profiling data is demonstrated using an independently characterised multilayer, an AlGaAs/GaAs stack from certified reference material BAM-L200. The sample was studied with a Bi cluster ion source as the analysis projectile and a Cs+ sputter beam. Under these conditions, the negative secondary ion yield is significantly enhanced, especially for cluster ions comprising all possible elemental combinations. Each cluster ion carries a number of sputtered neutrals so if all cluster ions containing an element could be collected and identified, a large population of secondary neutrals will be included in the analysis, improving the analytical signal and approaching a 'matrix-effect-free' measurement. By measuring the intensities of a range of secondary cluster ions of AliGajAsk− where i, j, k are integers such 0, 1, 2, and so on, the atomic counts for each major element were accumulated based on the elemental contents of those cluster ions. The summed atomic counts were then normalised without using the more common approach of applying relative sensitivity factors. The resulting elemental depth profiles show an excellent match to the structure and stoichiometry of the sample. The quantitative relationship of various elements and the interface appearance derived by this cluster ion approach are strongly competitive to the results available from XPS. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]