Detection of hydrogen with SnO2-coated ZnO nanorods

SnO2-coated ZnO nanorods on c-plane sapphire substrates were synthesized by pulsed laser deposition. The thickness of the polycrystalline SnO2 was 10 nm, as determined by high-resolution transmission electron microscopy, while the diameter of the ZnO nanorods was 30 nm. The sensitivity of the SnO2/ZnO structures to hydrogen was tested by depositing Ti/Au Ohmic contacts on a random array of the nanorods and measuring the current at fixed voltage. There was no response to 500 ppm H2 in N2 at room temperature, but we obtained a sensitivity of 70% at 400 8C. The SnO2/ZnO structures exhibit drift in their recovery characteristics and for sequential detection of hydrogen, as generally reported for SnO2 thin film sensors.