Hydrogen and ozone gas sensing using multiple ZnO nanorods

ZnO nanorods grown by site-selective molecular beam epitaxy show current-voltage characteristics that are sensitive to the presence of hydrogen or ozone in the measurement ambient for temperatures as low as ∼ 112°C for H₂ or room temperature for O₃. The sensitivity to hydrogen increases sharply with temperature and multiple nanorods contacted at both ends by ohmic electrodes show currents of ∼ 10^-8 A at 200°C and a differential current change of ∼ 18% when changing from a pure N₂ ambient to 10% H₂ in N₂. The nanorods are able to detect small concentrations (3%) of O₃ in O₂, with changes in current of ∼ 10^-7 A at 25°C. The sensitivity was 21% for O₃ at room temperature. The nanorods also show a strong response to above-band-gap illumination with ultraviolet light.