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Samples with compositional gradients or layered structure can be studied
by varying the sampling depth but the spectra obtained cannot currently be
converted into compositional profiles without additional information.
A microlapping method can be employed to produce profiles when such
information is not available or when the depth of interest exceeds the decay
distances of the beam and/or thermal waves.
In these cases the microlapping device15, shown in
Figure 17,
allows planar samples to be analyzed with a spatial resolution of several
micrometers. Compositional profiles
are measured by initially measuring the spectrum at a shallow sampling depth and
then removing a few micrometers using the microlapping device. This sequence is repeated until the sample’s composition
versus depth has been determined to the desired depth.
Figure 17. MTEC
MicroLap equipment for removal of several micrometer increments of material from
layered or gradient materials allowing chemical species profiles to be
determined to arbitrary depths.