WS2/GO Nanohybrids for Enhanced Relative Humidity Sensing at Room Temperature

This paper reports humidity sensing performance of WS2/GO hybrid nanostructures. WS2, being a layered material, can be exfoliated into ultrathin nanosheets. These nanosheets when combined with other materials with lamellar structures easily form hybrid structures even when processed in liquid. Hybrid structures with materials like graphene oxide (GO) have several advantages for humidity sensing like increase in defect sites and oxygen rich groups, which ultimately enhance the performance of humidity sensor. Interdigitated electrodes (made of aluminum), fabricated using photolithography technique on Si/SiO2 substrate, was used as sensor device platform. The WS2/GO (in the wt% ratio of 1: 3) sensing layer showed excellent optimal response when exposed to different humidity levels. The response achieved was 65.8 times at 40% relative humidity (RH) and 590 times at 80% RH. The response time and recovery time was also found to be good, e.g., only 25 and 29 s, respectively, at 60% RH. The device showed repeatable results when exposed to the same RH%. The stability of device was tested for over a month and the response at each RH% have found to be the same with its day-zero performance. A fast response combined with excellent repeatability due to low hysteresis loss and high stability (in the ambient) of the device makes it an excellent sensing material. Overall, the performance of WS2/GO nanohybrid-based humidity sensors seems to be comparable to other established sensing nanomaterials used in solid state humidity sensors.