Raman Evidence of Moiré Diamondene Formation by High-Pressure

Moiré diamondene, a two-dimensional diamond-like material with partial interlayer covalent bonding, is predicted to host strongly correlated quantum effects but has not yet been experimentally synthesized. It exhibits a hybrid sp²-sp³ bonding character, comprising sp²-hybridized graphene domains and sp³-hybridized nano-diamond domains. We predict that moiré diamondene can be formed by applying a pressure of approximately 2 GPa to twisted bilayer graphene (TBG) on a diamond surface by first-principles calculations. Under a pressure of 2 GPa, the experimental Raman G band of TBG on the diamond anvil culet splits into two distinct peaks, denoted as the N1 and N2 bands. Supported by comparative experiments and theoretical modeling, we attribute the N1 band to the interlayer bonded regions and the N2 band to the unbonded graphene segments. Therefore, the G band splitting serves as direct spectroscopic evidence for the formation of moiré diamondene. We demonstrate that the synthesis relies on the simultaneous presence of high pressure, an interlayer twist angle, and a chemically active diamond (100) surface, which paves the way for synthesizing moiré diamondene.