Twisted-bilayer graphene devices fabricated with polymer-free graphene

The Mott-like insulator state and superconductivity realized by stacking two graphene sheets that are twisted near 1.1°, the “magic angle [1,2],” has stimulated a new wave of interest in this newfound material in the two-dimensional material family. We will present our recent work in fabricating twisted bilayer graphene heterostructures. Instead of using graphene exfoliated by tape, we obtain the graphene sheets by scratching thin graphite flake deposited on wafer with a razor blade. Combining with the pick-up technique[3], the graphene is free from any tape or polymer residue. Atomic force microscope images and transport measurements results indicate a high quality in the devices we made. Low temperature magnetoconductance measurements are also performed and the latest results will be discussed. [1] Y. Cao et al, Nature 556, 80-84(2018). [2] Y. Cao et al, Nature 556, 43-50 (2018). [3] L. Wang et al., Science 342, 614-617 (2013).