The technique of imaging time-of-flight secondary ion mass
spectrometry (TOF-SIMS) and dual beam depth profiling has been
used to study the composition of the surface of tabular silver
halide microcrystals. Analysis of individual microcrystals with
a size well below 1 μm from a given emulsion is possible.
The method is successfully applied for the characterization
of silver halide microcrystals with subpercent global iodide
concentrations confined in surface layers with a thickness below
5 nm. The developed TOF-SIMS analytical procedure is explicitly
demonstrated for the molecular imaging of adsorbed thiocyanate
layers (SCN) at crystal surfaces of individual crystals and
for the differentiation of iodide conversion layers synthesized
with KI and with AgI micrates (nanocrystals with a size between
10 and 50 nm). It can be concluded that TOF-SIMS as a
microanalytical, surface-sensitive technique has some unique
properties over other analytical techniques for the study of
complex structured surface layers of silver halide microcrystals.
This offers valuable information to support the synthesis of
future photographic emulsions.