| This dissertation describes the electrical percolation and resistive switching behaviors of silver nanowire-polystyrene composites, which represent the first measurements of electrical percolation and resistive switching in bulk polymer composites containing finite-L/D cylinders. The measured percolation thresholds (&phisc) are more closely described by our simulations of networks of finite-L/D cylinders than by existing analytical models, which assume infinite L/D. Samples with compositions close to ilk also exhibit resistive switching at room temperature. We attribute this behavior to the field-induced formation of metallic filaments that bridge conductive nanowire clusters within the composites under sufficient applied fields. The reversibility of the switching depends on the sample composition, and reversible switching over 10 cycles was only observed for samples with volume fractions between 1-2 times &phis c. A single composition showed reversible switching at room temperature over more than 40,000 cycles. Resistive switching was measured between 300-10 K for two composites, and the switching voltages for both samples increased with decreasing temperature. Above 200 K, the switching for both samples was reversible, while below 200 K the metallic "on" state was irreversible. The reduced-temperature data are consistent with our interpretation that the switching is caused by the formation of metallic filaments under sufficient applied fields. |
