Glancing angle deposited WO3 nanostructures for enhanced sensitivity and selectivity to NO2 in gas mixture

We report the facile synthesis and the chemoresistive performances of villi-like WO3 nanostructures (VLWNs) which were fabricated by RF sputter with glancing angle deposition (GAD) mode. A fast deposition of GAD effectively forms self-assembled anisotropic nanostructures with high porosity and surface-to-volume ratio. The sensing tests were examined for NO2 detection in dry air and a mixture of reducing gases. As a result, these sensors at 200 °C exhibit an highly selective and sensitive NO2 detection down to 800 parts per trillion (ppt) level, and could also respond well to NO2 in the concentration range of 0.2-1 parts per million (ppm) without the interference of gas mixture. These results show that the enhanced sensing properties to NO2 are attributed to the highly efficient surface modulation by double potential barriers at nano-necks of WO3 nanostructures.