Hydrogen sensing with Pt-functionalized GaN nanowires

Pt-coatings sputtered on to multiple GaN nanowires is shown to enhance their sensitivity for hydrogen at the hundreds of ppm level at 25 °C. GaN nanowires without a metal coating showed no detectable change in current when exposed to hydrogen under the same conditions. Pt-coated multiple GaN nanowires gave non-linear relative responses of ∼1.7% at 200 ppm up to ∼1.9% at 2000 ppm H2 in N2 after a 10-min exposure. More than 80% of the initial GaN conductance was recovered within 2 min after removal of hydrogen from the measurement medium. At higher temperatures, larger resistance changes and faster response and recovery were obtained. The adsorption activation energy of the sensor was 7.3 kcal mol−1 at 2000 ppm H2 in N2. Pt-coated GaN nanowire sensors resulted in much lower relative response than Pd-coated sensors.