Research On H₂S Gas Sensing Properties Of WO₃Quasi-one-dimensional Nanostructures

Tungsten trioxide (WO3) gas sensors, having a simple structure, short response time, long life, and wide operating temperature range, have been found widespread commercial applications for monitoring toxic or flammable gases. However, detection of such gases with high sensitivity at room temperature still remains a challenge. In this paper, we try to characterize the adsorption process of H2S molecules on the surface of WO3nanowires for the purpose of understanding the mechanism of gas sensing at room temperature by characterizing electrical transport properties.Controllable preparation of quasi-one-dimensional WO3nanostructures has been achieved through simple hydrothermal method, and mono-dispersed WO3nanowres have been synthesized in large scale. Resistive sensors based on individual WO3nanowires with the structure of metal/WO3nanowire/metal have been fabricated with deep ultraviolet lithography. Electrical transport properties of these devices have been characterized at room temperature in air and hydrogen sulfide gas. Experimental results indicate that H2S adsorption will decrease the resistance of the devices, and even induce the electrical hysteresis phenomenon. Furthermore, the ohmic (Schottky) contacts between WO3nanowire and metal electrodes can be converted to Schottky (ohmic) contacts in H2S atmosphere. We suppose that H2S adsorption can desorb previously adsorbed O2and H2O molecules, which will release or trap electrons and then resulting in decrease or increase of the barrier height between the W03nanowire and metal electrodes. H2S molecules can also decompose into hydrogen ions and sulfur atoms on the surface of WO3nanowire, which will result in formation of hydrogen tungsten bronze and increase in the conductance of the device.Through further research, we hope to fabricate a prototype of gas sensor based on WO3nanowire with high sensitivity to toxic or flammable gases at room temperature.