A novel miniature gas ionization sensor based on freestanding gold nanowires


Freestanding gold nanowires (AuNW) were incorporated to fabricate a miniaturized gas ionization sensor. The device exhibited improved ensitivity in sub-Torr pressure (P) regime compared to similar devices reported earlier, since the room temperature breakdown voltage (Vb) as further reduced in low gas pressures or concentrations (N). Also excellent selectivity was achieved for pressures up to 10 Torr, while Vb emained almost unaffected by pressure. In the Vb–P characteristic below 1 Torr, Vb was less when the AuNWs was configured as cathode, and it tarted to decline until a Paschen-like (Vb)min was observed at very low pressures (0.3 <P< 0.5 Torr). The reduction of breakdown voltage in this ase, was attributed to the creation of an abnormally large amount of secondary electrons at the nanowire tips due to the increase in Townsend’s econdary ionization factor (ω/α) at very high reduced fields (E/N). The pre-breakdown I–V characteristic of the device, obtained at extreme low ressures showed polarity dependency. The field enhancement factor (β) of the AuNW array was estimated by operating the device in the ohmic ischarge region. The average aspect-ratio of the nanowires, which was extracted from the I–V characteristic, showed good agreement with SEM bservations. 2007 Elsevier B.V. All rights reserved.


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