Humidity-sensing performance of layer-by-layer self-assembled tungsten disulfide/tin dioxide nanocomposite

In this article, we demonstrate a humidity sensor based on WS2/SnO2 nanocomposite via layer-by-layer (LbL) self-assembly technique on a FR4 (Flame Resistant 4) epoxy substrate with interdigital electrodes (IDEs). The component, morphology, and chemical state of WS2/SnO2 film was fully examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The humidity sensing characteristics of WS2/SnO2 film sensor were investigated at room temperature. The WS2/SnO2 film sensor exhibited supreme sensing properties, including unprecedented response/sensitivity, rapid response rate, and good repeatability. The WS2/SnO2 film sensor illustrated 36 and 89 times higher responses than that of pure WS2 and SnO2 devices, respectively. To our knowledge, the sensor exhibited the unparalleled response and sensitivity among the existing humidity sensors ever reported. Moreover, the presented sensor demonstrated good performance in monitoring human respiration. We investigated the electrical characteristics of the WS2/SnO2 film by impedance spectroscopy and Bode plots. The equivalent circuit model was established, and the humidity sensitive mechanism of WS2/SnO2 nanocomposite film was systematically investigated. The present work demonstrates that LbL self-assembled WS2/SnO2 nanocomposite is an excellent material candidate for the fabrication of ultrahigh-performance humidity sensor.