Raman evidence for pressure-induced formation of diamondene

Abstract

Despite the advanced stage of diamond thin-film technology, with applications ranging from superconductivity to biosensing, the realization of a stable and atomically thick two-dimensional diamond material, named here as diamondene, is still forthcoming. Adding to the outstanding properties of its bulk and thin-film counterparts, diamondene is predicted to be a ferromagnetic semiconductor with spin polarized bands. Here, we provide spectroscopic evidence for the formation of diamondene by performing Raman spectroscopy of double-layer graphene under high pressure. The results are explained in terms of a breakdown in the Kohn anomaly associated with the finite size of the remaining graphene sites surrounded by the diamondene matrix. Ab initio calculations and molecular dynamics simulations are employed to clarify the mechanism of diamondene formation, which requires two or more layers of graphene subjected to high pressures in the presence of specific chemical groups such as hydroxyl groups or hydrogens.

Large bandgap of pressurized trilayer graphene

“…The experimental results suggest that a broad pressure range is needed to make the semimetallic trilayer transform to the semiconducting state completely, i.e., the ratio of semimetallic/ semiconducting states is pressure dependent. Such a mixed phase is also observed in compressed substrate-supported two-layer graphene (33,34). During decompression, the semiconducting phase remains unchanged down to a few GPa, but almost returns to its original state when quenched to ambient pressure, as shown in Fig.…”

“…Recently, a diamond-like carbon film was observed in twolayer graphene followed by sp 2 -sp 3 rehybridization through nanoindentationand compression methods (33,34). Previous experimental and theoretical results also demonstrated that graphite transformed into an sp 3 -bonded carbon phase (48)(49)(50)(51)(52)(53)(54)(55)(56) under cold compression, although the structure of the high-pressure phase is still controversial.…”

“…We pursued an alternate approach of tuning the interlayer hybridization of few-layer graphene with pressure to modulate the electronic structure. The graphene sample on a different substrate has quite different pressure response (33)(34)(35)(36). Furthermore, the behavior of graphene on a substrate at high pressure differs drastically from that of freestanding graphene (37), indicating that substrates obscure the intrinsic properties of graphene significantly.…”

Layer dependence of graphene-diamene phase transition in epitaxial and exfoliated few-layer graphene using machine learning

“…Recent research efforts have focused on the pressure induced formation of new phases in 2D materials. In particular, the formation of an ultrastiff phase, diamene, was found while locally pressurizing epitaxial graphene films [10,11]; other reports have shown the pressure induced formation of an insulating phase from exfoliated graphene flakes in a humid environment [12,13], and more recently the formation of bonitrol from hexagonal boron nitride was demonstrated [14].…”

Low temperature, pressureless sp2 to sp3 transformation of ultrathin, crystalline carbon films

“…Beyond graphene, a new nanocrystalline carbon material consisting of few atomic layers (FL) of diamond or lonsdaleite, also called diamane by Chernozatonskii et al who first predicted it [1], holds great technological promise and is attracting increasing interest [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. In such a material, sp 3 -bonded carbon atoms are arranged in a hexagonal lattice.…”