Fig. 2: Hetero-site nucleation and the growth process of tBLGs visualized by isotopic labeling in conjunction with micro-Raman spectroscopy.
From: Hetero-site nucleation for growing twisted bilayer graphene with a wide range of twist angles

a, b Feedstock feeding process for growth of isotope-labeled tBLG using the hetero-site nucleation strategy, where gas-flow perturbation is introduced at 5 min (a) and 10 min (b), respectively. c, d Resulting OM images of transferred tBLGs. The dashed lines guide the eye to the nucleation sites of the first and second graphene layers, represented by the intersections of blue and red lines, respectively. e, f Raman 2D13-intensity maps (integrated from 2560 to 2620 cm−1) of areas corresponding to (c) and (d), respectively. g Schematics of the isotopic distribution and corresponding growth processes of the tBLGs corresponding to (e, top) and (f, bottom), respectively. The blue and red rings represent the first and the second graphene layers, respectively. The time axis shows the nucleation times of the second layers, which can be controlled by the introduction of gas-flow perturbation.