Characterisation of chemically exfoliated molybdenum disulfide with ultrasonication

Abstract

Molybdenum Disulfide (MoS2) a class of Transition Metal Dichalcogenide (TMD), has garnered renewed interest from researchers after the discovery of graphene. Two-dimensional MoS2 is expected to possess unique properties and have great potential in many areas of study including optoelectronics, photocatalytic applications – due to its direct band gap when monolayers are isolated.

There is a need for a scalable and efficient method to isolate nanosheets, however there are various methods which have drawbacks and limitations during the exfoliation process. In this study, a simple chemical exfoliation technique with ultrasonication was employed to exfoliate MoS2 nanosheets. Looking at the ultrasound equipment used, we found that probe ultrasonication had produced a higher concentration of nanosheets in a shorter period of time compared to bath ultrasonication with the same power.

The nanosheets obtained were then characterized using UV-Vis spectrometer, Scanning Electron Microscope (SEM), Raman Spectroscope, indicating no evidence of structural change that might occur during ultrasonication. Furthermore, the nanosheets were deposited on devices and experimented on their photocurrent and photoresponse. It is revealed that in one of the setups under white light illumination, a photoresponse was detected increase in current flow in the ON state and returned to normal in OFF state. Our device showed rapid response in rise and decay times and repeatability.