Programmable memory devices using gold nanoparticles capped with alkanethiols of different carbon chain lengths

Electrical bistability is demonstrated in a polymer memory device using polystyrene containing an organic conjugated compound (8-hydroxyquinoline) and gold nanoparticles (Au NPs) capped with different alkanethiols of carbon chain lengths as the active layer between two metal electrodes. Au NPs capped with three different alkanethiols [1-octanethiol (C8), 1-dodecanethiol (C12), and 1-octadecanethiol (C18)] are investigated for the correlation with the memory performance. Above a threshold voltage, the as-fabricated device can transit from low conductivity state to high conductivity state. By applying a certain positive voltage, the high conductivity state can return to the low conductivity state. The switch-on voltages of thiol-derivatized Au NPs based organic memory devices are almost the same. Current fluctuations appeared in the static current-voltage characteristic of Au NPs capped with a 1-octadecanethiol (C18) based memory device. This feature is related to quantized charging and discharging of Au NPs because of the Coulomb repulsion between electrons confined in nanocrystals.