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 Delta R/R-0 = (+)138% in 7% NH3 and observable down to 500 ppm NH3. Exposure to water vapor produced a weaker resistance increase of Delta R/R-0,R-H2O = (+)10-15% (for 2.3% water) while nitrogen dioxide (NO2) exposure induced a stronger concentration-normalized resistance decrease of Delta R/R-0,R-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 functional theory calculations, is that semiconducting p-type AgxO is formed within the CRJ and the binding of molecules to this AgxO modulates its electrical resistance.