Convertible Insulator-Conductor Transition in Silver Nanowire Networks: Engineering the Nanowire Junctions

Achieving a switchable conductance in metallic nanowire networks is of great importance for applications in wearable electronics, selectors, information storage, and neuromorphic computing. However, to realize the electricfield-induced switchable conductance, an insulating characteristic in a conductive network should be enabled first to allow a desirable switch window, and in turn, metal/oxide core-shell nanowires and nanowire-polymer composites have been proposed. Here, a novel strategy to tune the electrical conductance of Ag nanowire networks through engineering the interface of nanowire junctions is developed, without introducing an additional insulating layer. The initial device with a percolating network structure shows high resistivity due to the loose wire-to-wire contact, but it can be reversibly switched to a lower resistance state under an electric field. The observed switchable behavior is attributed to the Ag migration between the wire junctions. The device is also turned into a good conductor by formation of an intimate contact between nanowires. With further increasing the heating temperature, the junction resistance dominated network is then determined by individual Ag nanowires as a result of nanowire fragmentation, and a different threshold switching behavior is demonstrated. Furthermore, the overall conductance of the network is closely related with the nanowire density, and the electrical properties of the devices reveal a similar trend to those of the junction-modified samples.