MAXIMUM-ENTROPY QUANTIFICATION OF SIMS DEPTH PROFILES - BEHAVIOR AS A FUNCTION OF PRIMARY ION ENERGY

Previous publications have proposed the use of reconstruction as a method of quantification of SIMS depth profiles, taking the convolution integral as an approximate model for the measurement process in the dilute limit. We present here a demonstration of the maximum entropy (MaxEnt) reconstruction method for SIMS depth profile quantification at a number of primary ion energies. Neither implanted standard nor crater depth measurement are required by the technique, although both are used here as comparisons. The erosion rate calculated directly from the delta layer is found to be equivalent to that from crater depth measurement to within experimental accuracy. It is demonstrated that the MaxEnt reconstruction method can quantify a delta layer in ideal circumstances, removing all energy-dependent effects. For another sample (a set of three alleged delta layers) the MaxEnt reconstruction method is found to yield improvements in depth resolution at all energies, removing the energy dependence of the rise and decay slopes and almost halving the measured feature widths (full width at half-maximum). This improvement in accuracy in quantification has enabled us to analyse more critically the sample, demonstrating that the layers had finite widths, a fact that was not evident from conventional quantification methods.