Raman Spectroscopy of Folded Tetralayer Graphenes Prepared by Atomic Force Microscope

In this work, we report that when a modulated force is applied to the edge of a bilayer graphene with an atomic force microscope (AFM), two kinds of folded tetralayer graphenes can be obtained: one has one rupture and the other has two ruptures. The twist angle between two bilayer graphenes is found to be in the range of 1.8°∼27.7°. Systematic Raman studies show that the position, width, and intensity of 2D and G peaks of the folded tetralayer graphene depend sensitively on these angles. Meanwhile, the intensity enhancement of G mode of twisted tetralayer graphenes has been observed at twist angles of 11.5° and 13.2°. At these two twist angles, the 2D peak of twisted tetralayer graphenes can be fitted by three Lorentzian peaks at laser energy of 2.33 and 2.41 eV. Using an AFM probe to fabricate twisted graphene has the advantages of high yield, controllable positions, and no introduction of chemical pollutants, which has many potentials in future electronics.