Poly(sulfonic acid)s and poly(ethylene oxide) unexpectedly form novel hydrogen-bonded interpolymer complexes in aqueous solution and on surfaces by layer-by-layer deposition.
The electron-tunneling (ET) current
through a barrier of thickness h is generally analyzed
with the Simmons model, j ∼ exp(−βh), where
β is the tunneling decay coefficient. We show that fluctuations
in barrier thickness produce apparent β values systematically
smaller than the real ones, which may lead to incorrectly postulating
long-range electron tunneling. We reached this conclusion by performing
the first tunneling studies through polyelectrolyte-multilayer films
of different average thicknesses using impedance spectroscopy and
EGaIn/Ga2O3 top contacts. We explained these
measurements with a model that considers ET through a film with a
Gaussian distribution of thicknesses, as observed by atomic force
microscopy. It is shown that even relatively small thickness fluctuations
can introduce a systematic error in the determination of β and
that when the average film thickness and its standard deviation become
commensurable, it is impossible to determine β.
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