Oxygen-Assisted CVD Growth of High-Quality Twisted Bilayer Graphene

Twisted bilayer graphene (tBLG) garners significant interest due to its unconventional superconductivity and correlated insulator behavior. However, challenges persist in preparing high-quality tBLG with clean interfaces and a broad range of twist angles. Herein, a chemical vapor deposition (CVD) method is presented that utilizes an oxygen-assisted strategy to grow high-quality tBLG with twist angles ranging from 0° to 30°. The continuous and stable oxygen supply not only facilitates rapid graphene growth, but also overcomes the self-limiting growth of monolayer graphene on liquid Cu. Consequently, the growth rate of tBLG reaches a record of 450 µm h^-1, with 86.9% of the tBLG grown with the assistance of the oxide substrate. The proportion of tBLG with small twist angles (0° < 𝜃 ≤ 3°) improves to ≈9.15%, one of the highest percentages for CVD-grown tBLG within this range. Density functional theory calculations explain in detail the assisted effect of oxygen on the rapid growth and twist angle distribution of tBLG. Furthermore, the presence of a clear moiré superlattice, ultrahigh Hall mobility of 20 616 cm² V^-1 s^-1, weak localization effect, and Shubnikov-de Haas oscillations corroborate the high-quality of tBLG. The research offers a new and feasible way of growing tBLG.