Recently I have switched to using the Exfoliation method of MoS2 and WS2 using PDMS as follows. I peel off the MoS2 and WS2 from the original sample, then apply it to PDMS and press it down, then peel it off quickly, then MoS2 or WS2 appears on PDMS, I continue to transfer from PDMS to Si/SiO2 270mm. This method can be used, however the monolayer after transferring to Si/SiO2 from PDMS often has stains on the entire surface. I wonder if anyone has encountered the same case as me, if so please help me solve it. Thank you.