Current-dependent anisotropic conductivity of locally assembled silver nanoparticles in hybrid polymer films

The electrical behaviour of hybrid poly(ethylene terephthalate) films containing localised, percolating networks of silver nanoparticles separated by pure polymer is studied. The films resemble an array of parallel wires in the submicron range and, thus, exhibit anisotropic conductivity. In the high-conductivity direction at low amplitudes, the films show Ohmic behaviour, while at moderate voltage, non-linearity and a decreasing resistance is observed. The samples were found to heat up during the measurements and the deviation from Ohm’s law coincides with the Tg of the polymer. Microstructural analysis of the samples revealed an irreversible agglomeration of the particles at moderate voltages leading to the formation of filaments with higher metallic character than the random particle network.

Solvent crazed poly(ethylene terephthalate) films containing silver nanoparticles in the crazes show at low amplitudes Ohmic behaviour along the crazes and high resistances perpendicular to it. Gradual deviations from Ohmic behaviour occur when exceeding ±1 V due to an irreversible microstructural change in the particle network. Thermal annealing while applying voltage can be used to tune the material properties.Figure optionsDownload high-quality image (122 K)Download as PowerPoint slideResearch highlights
► Polymer films containing localised, percolating networks of metallic nanoparticles show anisotropic electrical conductivity.
► The resistance in the high-conductivity direction is approx. 2 × 1010 times less than perpendicular to it.
► At low amplitudes, the samples show Ohmic behaviour in the high-conductivity direction.
► At moderate voltages, non-linearity was observed due to an irreversible agglomeration of the particles to filaments.
► The agglomeration is accompanied by an irreversible reduction of the resistance and an increase of the temperature coefficient of resistance; i.e. the properties of the particle network approach that of bulk silver.