The analysis of the TEM images of indium tin oxide (ITO)
clusters in ink solutions deposited from ink dispersions reveals that their
geometry arises from a diffusion limited cluster aggregation (DLCA) process. We
model films of ITO clusters as built through deposition of DLCA clusters made
of primary spherical nanoparticles of 13 nm in diameter. The deposition is then
followed by a further compactification process that imitates sintering. We
determine the conductivity of the sintered films by mapping the problem to that
of the resistor network in which the contact regions between the touching
spheres provide the dominant electric resistance. For a given volume fraction,
conductivity of the sintered films is shown to be larger than that for the
randomly packed spheres. However, the larger a typical radius of gyration of
the clusters the smaller the enhancement. We also provide numerical tests for
the routines used in the interpretation of the TEM images.
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