The figure shows the ion implantation distribution of C in an Al0.8Ga0.2As / GaAs structure: 1) using only GaAs standard sample (solid line), 2) using GaAs standard sample with the PCOR-SIMS correction to account for the composition of the Al0.8Ga0.2As layer (broken line). In the case of 1), it can be seen that the C profile in the AlGaAs is displayed too low in the AlGaAs layer due to the effect of the matrix having Al in it. (See step at the Al0.8Ga0.2As/GaAs interface.) In case 2), the PCOR-SIMS correction has produced a smooth profile across the interface which is what is expected. In the case of multi-layer films of different materials, the concentration is usually determined from one standard sample, so the concentration is incorrect for materials (compositions) different from the standard sample. When viewing the data, it is important to note which standard sample material was used for quantification.
However, even if the material is different from the standard sample, if a comparison between unknown samples of the same material is desired, the accuracy of the relative comparisons will still be accurate because the quantification standard is the same. The absolute concentrations may be in error, but the relative concentrations between samples will still be correct, providing that the matrix composition between the samples is the same. In practical analysis, it is difficult to quantify all the layers accurately of a multi-layered film of dissimilar materials, so the relative comparison between samples is overwhelmingly often based on one standard sample.