MoS2 cleaning by acetone and UV-ozone: Geological and synthetic material

The effects of poly(methyl methacrylate) PMMA removal procedures on the surface chemistry of both geological and synthetic MoS2 are investigated. X-ray photoelectron spectroscopy (XPS) is employed following acetone dissolution, thermal annealing, and ultraviolet-ozone (UV-O-3) treatment of PMMA-coated MoS2 samples. Specifically, we focus on the efficacy of polymer residue removal procedures and oxidation resistance of the different samples. Acetone dissolution followed by ultra-high vacuum (UHV) annealing was highly effective in removing carbon residues from one type of geological sample however not for a synthetic sample produced by sulfurization. Similarly, different types of samples require varying lengths of UV-O-3 exposure time for proper removal of residues, and some exhibit oxidation as a result. UV-O-3 exposure followed by a UHV anneal resulted in successful removal of carbon residues from MoS2 produced by sulfurization while a substantial carbon signal remained on a chemical vapor deposited MoS2 sample subjected to the same process. Differences in the effects of removal procedures are attributed to differences in surface morphology and material quality. For device fabrication applications, this work highlights the importance of developing PMMA removal processes specific to the MoS2 used with full consideration for the processing required to obtain the MoS2.