Exfoliated MoS2 based Humidity Sensing

Abstract

In our paper, few layered MoS2 nanoflakes were exfoliated from the bulk powder in mixed solvent using a simple sonication assisted liquid exfoliation technique at room temperature. The successful exfoliation of the nanoflakes was characterized using various characterization tools like Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), and Atomic Force Microscopy (AFM). The humidity sensor was fabricated by drop-casting MoS2 nanoflakes on Pt-based Interdigitated Electrodes (IDEs). The sensing was carried out in an in-house gas test setup interfaced with a Semiconductor Parameter Analyzer (SPA) to record the measurements. The response of the sensor was studied by passing different levels of humidity through the gas chamber. The response was found to increase with increase in humidity level and was better than few recently reported results. The maximum response was found to be ~16 times at 75% RH. Since water is an electron donor and MoS2 is inherently n-type semiconductor, the conductivity of the MoS2 sensing layer increased in presence of humidity. The large surface to volume ratio and presence of inherent defects facilitated the adsorption and desorption of a large number of H2O molecules. The response time and recovery time of the sensor was 65 seconds and 72 seconds respectively. Thus we conclude that our MoS2 based humidity sensor with a maximum response of 16 times (75% RH) can act as a low power, highly sensitive and fast humidity sensor in various applications like indoor air quality monitoring, agriculture, semiconductor industry etc.