Gas Sensing With Mats of Gold-Nanoparticle Decorated GaN Nanowires

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> We report on the use of mats of gold nanoparticle decorated GaN nanowires as gas sensors. The sensing was by the repeated and reversible measurement of changes in the current-voltage characteristics of the mat of nanowires. The nanowires had diameters of about 200 nm and were many microns long. The mat was grown on a 1-cm diameter sapphire disk and was about 10 <formula formulatype="inline"> <tex>$\mu\hbox{m}$</tex></formula> thick. The selectivity mechanism is attributed to the details of the surface morphology of the gold nanoparticles decorating the surface of the nanowires. The changes in the currents are attributed to a depletion mechanism in the nanowires due to the formation of a Schottky barrier due to the presence of the gold on the inherently n-type GaN. We were able to detect CO, <formula formulatype="inline"><tex>$\hbox{CH}_{4}$</tex> </formula>, <formula formulatype="inline"><tex>$\hbox{CO}_{2}$</tex></formula>, <formula formulatype="inline"><tex>$\hbox{H}_{2}$</tex></formula>, and observed possible evidence of creation of the by-products of the water-gas shift reaction. </para>