Study of electron tunnelling through thin polymer films using a mercury probe technique

A non-destructive technique employing a mercury probe as a counter electrode was successfully developed in order to study the mechanism of charge transport through thin polymer films on silicon and aluminum substrates. The polyelectrolyte self-assembly technique was employed to form the organic films. Both DC and AC current-voltage characteristics were measured at room temperature. An exponential dependence of the tunnelling current on the film thickness was found, and a tunnelling coefficient of 3.3×10^-9 m^-1 was calculated. The observed voltage dependence was interpreted in terms of the model of a trapezoidal-triangular barrier. The peak in current-voltage characteristics of polymer films on aluminum substrates may be attributed to resonance tunnelling via surface states on the alumina/polymer film interface.