On the dynamic range in depth profiling with electron-gas SNMS

Despite of the high depth resolution around 1 nm achieved with the direct bombardment mode DBM of electron-gas SNMS, its dynamic range is mostly limited to 3 orders of magnitude. Detailed depth profile studies reveal that crater edge and memory effects contribute with 80% and 20%, respectively, to the limitations of the dynamic range in DBM-SNMS. An experimental remedy has been found by the installation of an additional aperture in the postionization chamber which allows a ''geometrical blanking''. Ey such means the dynamic range is improved by one order of magnitude. Further experiments have shown that the so-called Mesa technique as a specific method for the sample preparation leads to a somewhat smaller improvement.