Room temperature hydrogen detection using Pd-coated GaN nanowires

Multiple GaN nanowires produced by thermal chemical vapor deposition were employed as gas sensors for detection of hydrogen at concentrations from 200 - 1500 ppm in N-2 at 300 K. Palladium coating of the wires improved the sensitivity by a factor of up to 11 at low ppm concentrations relative to uncoated controls. The GaN nanowires showed relative responses of similar to 7.4% at 200 ppm and similar to 9.1% at 1500 ppm H-2 in N-2 after a 10 min exposure. Upon removal of hydrogen from the measurement ambient, similar to 90% of the initial GaN conductance was recovered within 2 min. Temperature dependent measurements showed a larger relative response and shorter response time at elevated temperature. The adsorption activation energy of the sensor was 2.2 kcal mol(-1) at 3000 pm H-2 in N-2. These sensors exhibit low power consumption (0.6 mW) at 300 K. (C) 2008 American Institute of Physics.