The Qtac can be equipped with a high current ion optical column fitted with an electron impact gas ion source operable with rare gases or oxygen. This ion gun is used for ultra-low energy sputtering in combination with LEIS analysis. In this dual beam depth profiling mode high resolution chemical depth profiles are obtained.
In contrast to SIMS, there is no need to use reactive sputter species, which lead to changes in sputter rate and ionisation yield close to the surface. The Qtac100 provides easy quantification even in the first few nanometres of the profile.
The example shows a LEIS sputter profile through a CrNi multilayer system. The LEIS analysis was done with a 5 keV Ne analysis beam. For sputtering, a 500 eV Ar beam was used. The plot on the right shows the liniarity of the correspondeing sensitivity factors over the full concentration range very nicely.