A chemically-responsive nanojunction within a silver nanowire.

The formation of a nanometer-scale chemically responsive junction (CRJ) within a silver nanowire is described. A silver nanowire was first prepared on glass using the lithographically patterned nanowire electrodeposition method. A 1–5 nm gap was formed in this wire by electromigration. Finally, this gap was reconnected by applying a voltage ramp to the nanowire resulting in the formation of a resistive, ohmic CRJ. Exposure of this CRJ-containing nanowire to ammonia (NH3) induced a rapid (<30 s) and reversible resistance change that was as large as ΔR/R0 = (+)138% in 7% NH3 and observable down to 500 ppm NH3. Exposure to water vapor produced a weaker resistance increase of ΔR/R0,H2O = (+)10–15% (for 2.3% water) while nitrogen dioxide (NO2) exposure induced a stronger concentration-normalized resistance decrease of ΔR/R0,NO2 = (−)10–15% (for 500 ppm NO2). The proposed mechanism of the resistance response for a CRJ, supported by temperature-dependent measurements of the conductivity for CRJs and density func...