NanoWiki

The Standard Way of exfoliating flakes is based on the seminal work on by Novoselov and Geim et al. (https://www.science.org/doi/10.1126/science.1102896). Many crystals can be exfoliated, but of course layered materials with only a weak van der Waals bonding between layers (aka van der Waals materials) are easiest. This manual assumes starting with a bulk crystal and working in the cleanroom.
You will need to bring following items:

• Bulk crystal of choice
• Scotch tape (Scotch brand is best, I prefer Magic or Crystal type, depending on the material)
• Tweezers
• Microscope glass slides
• Substrates of choice (typically Si/SiO<sub>x<\sub>)

The basic procedure is as follows:

1. Turn on a hotplate and set the temperature to 100 degrees Celsius. It will heat up while you're doing the rest of the steps.
2. Lay a long piece of Scotch tape face up (so sticky side up) along the table. It's a good idea to leave a bit hanging off the edge, for ease of picking it up later.
3. Make sure to affix the long tape to the table with some shorter pieces of tape (sticky side down) at the far end (away from the edge).
4. Now carefully place your bulk crystal on the long piece of tape, near the top side (away from the edge of the table). Gingerly press down to adhere.
5. Gently fold the tape over on itself, trapping the flake on both sides with tape. The crease of the fold should be very close the the crystal, as to leave enough room to repeat this procedure. Keep holding the rest of the tape. Press down slightly on the crystal to ensure good adhesion.
6. Quickly, but not too forcefully, pull the folded tape open, holding the fixed side with your other hand. This quick motion will cleave the crystal cleanly. Too much force might rip the tape and you will have to start over. You should be left with most of the bulk crystal left on the top, and a thin layer of crystal on the other side of the fold.
7. Now the procedure will depend on your needs and what material you are exfoliating. You always want to repeat this folding and pulling step a few times, so make sure you are working with the inner layer of the crystal.