Hello,
I am trying to exfoliate monolayer flakes of InSe and ReS2 for my device. Using scotch tape directly on the Si chips hasn't been very helpful, as it leaves a lot of debris and compacted flakes on the chip, making it very difficult to search for monolayer flakes under the microscope. Therefore, I have been using PDMS as an intermediate by transferring the flakes from the scotch tape onto the PDMS and then onto the Si chip. This method produces less debris and fewer compacted flakes. However, I still haven't been able to identify any monolayer flakes; most of the flakes I find are a few layers thick (3-6 layers). Does anyone have a more efficient method for easily exfoliating monolayer flakes of these 2D materials?
The optical contrast in optical microscopy of a monolayer InSe flake on a PDMS substrate is strangely low compared to that of a few-layer (2+) InSe flakes. The contrast is a little better when the magnification is low, but it was a very subtle improvement. I haven't tried yet, but coating a PDMS block with a PPC(polypropylene carbonate) film may enhance the contrast. (I read a paper discussing a similar effect on a graphene...)
The contrast is much better when the flake is once transferred to the SiO2 substrate.
I can't give very helpful tips because I'm struggling with exfoliating a few-layer InSe on SiO2 substrate, but I wish you luck.
Kikyung Jung Thank you for the response. I am able to get few layers of both InSe and ReS2 but not monolayers yet. I will try to coat the PDMS with PPC to see if there will be any improvements.
Do you do your exfoliation in a glovebox or just in open environment
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