Principles and mechanisms of gas sensing by GaN nanowires functionalized with gold nanoparticles

Electrical properties of a chemical sensor constructed from mats of GaN nanowires decorated with gold nanoparticles as a function of exposure to Ar, N2, and methane are presented. The Au nanoparticle decorated nanowires exhibited chemically selective electrical responses. The sensor exhibits a nominal response to Ar and slightly greater response for N2. Upon exposure to methane the conductivity is suppressed by 50% relative to vacuum. The effect is fully reversible and is independent of exposure history. We offer a model by which the change in the current is caused by a change in the depletion depth of the nanowires, the change in the depletion depth being due to an adsorbate induced change in the potential on the gold nanoparticles on the surface of the nanowires.