Wafer-Scale Fabrication of Single Polypyrrole Nanoribbon-Based Ammonia Sensor

Ultra-long (>1 cm) polypyrrole (PPy) nanoribbons were batch-synthesized to predetermined locations on 4 inch Si wafers and flexible polyimide film with controlled thicknesses and widths via modified Lithographically Patterned Nanowire Electrodeposition (LPNE), which combines top-down "photolithography" and bottom-up "electrodeposition". The excessive lengths and lithographic approach enable subsequent patterning of electrodes for direct device fabrication. Electrical transport properties were investigated by temperature-dependent measurements, and back-gated FET measurements were performed to study the properties with respect to the conductivity of PPy nanoribbons. To demonstrate the utility of this approach these nanoribbon devices were interrogated as gas sensors in a conductometric fashion. They displayed excellent sensitivity toward ammonia vapor with a detection limit in the sub ppm. The sensitivity toward ammonia vapor was tuned by the conductivity of the PPy nanoribbons via chemical de/doping.