I'm working on the exfoliation of monolayer WTe2 on SiO2 substrate in order to create a heterostructure for transport measurements, and I'm having trouble getting thin layers. I tried various methods in the answers under the question "How to mechanically exfoliate tmds on SiO2", but it didn't work out. What I usually do is to put a piece of crystal on a tape and fold the tape many times so that the crystals are all over the tape. Then I press the tape gently on to a wafer that is either untreated, acetone + IPA cleaned, or O2 plasma cleaned. After that I heat the tape and the wafer to a 80 degrees hot for a few minutes. Finally I detach the tape from the wafer as slowly and as smooth as possible. All the processes above are done in a glove box. What I get on the wafer are just thick and small flakes (yellow) accompanied by smaller blue fragments.
Can anyone share a precise exfoliation process suitable for WTe2? Many thanks in advance.
how thick is your sample?
I got 10nm thickness with almost the same process.
But after the first tape process done I put another tape on the face of the first tape .
and exfoliate that one. Now you will have more thin layer of WTe2 on the tape.
Now, use this tape to transfer on substrate.
I guess you will have at least 20nm thick sample. you can do more dilution by using 3rd or 4th tape and have more thin sample.
S. S. Mahtab Thanks for the answer. In this case I think I should try to do every step more carefully and make sure the surrounding is clean. Do you mind sharing the condition of the glove box in your group including the oxygen and humidity? Thanks!
Weifeng Zhi It was not inside the glove box. But we always have a dehumidifier on in our lab.
But I think Nitrogen ambient glove box will help more.
Exfoliating monolayer WTe2 can be challenging, as the material is known to be mechanically stable and difficult to exfoliate. Some tips that may help to improve the exfoliation process include:
It may also be helpful to seek advice from experts in the field or to consult the literature for more specific guidance on exfoliating WTe2.
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