  Monolayers of colloidally synthesized cobalt-platinum nanoparticles of
different diameters characterized by TEM (transmission electron microscopy)
were deposited on structured silicon oxide substrates and characterized by SEM
(scanning electron microscopy), GISAXS (grazing incidence x-ray scattering),
and electric transport measurements. The highly ordered nanoparticle films show
a thermally activated electron hopping between spatially adjacent particles at
room temperature and Coulomb blockade at low temperatures. We present a novel
approach to experimentally determine the particles charging energies giving
values of 6.7-25.4 meV dependent on the particles size and independent of the
interparticle distance. These observations are supported by FEM (finite element
method) calculations showing the self-capacitance to be the determining value
which only depends on the permittivity constant of the surrounding space and
the particles radius.
