Diamond-like C2H nanolayer, diamane: Simulation of the structure and properties

Abstract

We consider a new C 2 H nanostructure based on bilayer graphene transformed under the covalent bond of hydrogen atoms adsorbed on its external surface, as well as compounds of carbon atoms located opposite each other in neighboring layers. They constitute a "film" of the 111 diamond with a thickness of less than 1 nm, which is called diamane. The energy characteristics and electron spectra of diamane, graphene, and diamond are calculated using the density functional theory and are compared with each other. The effective Young's moduli and destruction thresholds of diamane and graphene membranes are determined by the molecular dynamics method. It is shown that C 2 H diamane is more stable than CH graphane, its dielectric "gap" is narrower than the band gap of bulk diamond (by 0.8 eV) and graphane (by 0.3 eV), and is harder and more brittle than the latter.

Opening and tuning of band gap by the formation of diamond superlattices in twisted bilayer graphene

“…When interlayer C-C bonds are created between adjacent graphene planes within AB-and AA-aligned pairs of atoms, two-dimensional (2D) nanostructures are formed resembling the atomic structures of bulk cubic and hexagonal diamond, respectively. [23][24][25][26][27]29 In TBG, where the two graphene layers are rotated with respect to each other by twist angles θ between 0° and 60°, the honeycomb lattices of each layer generate a superlattice of domains that are characterized by a specific type of local alignment; these superlattices have the same symmetry with but a larger periodicity than the original honeycomb lattice and are called Moiré patterns. [43][44][45][46] For twist angles over the range from 0° to ~16° (or, equivalently, from ~44° to 60°), these local domains consist of AAand AB-stacked atoms.…”

“…[23][24][25][26][27] In these 2D diamond configurations, the structure is formed exclusively by sp 3 -hybridized C-C bonds, which are responsible for the insulating nature of these nanomaterials as they are for that of bulk cubic diamond.…”

“…[20][21][22] In multilayer graphene, another way of introducing sp 3 bonding and altering the electronic band structure is the formation of interlayer bonds, namely, covalent C-C bonds between atoms of adjacent graphene layers. 16 Several theoretical studies have demonstrated that hydrogenation and formation of such interlayer bonds usually opens a band gap in the electronic band structure; [23][24][25][26][27] again, however, depending on the spatial arrangement of these interlayer bonds, certain features of the electronic band structure of the pristine, non-bonded configuration are preserved. 16 In a recent study, 16 we showed that creation of interlayer C-C bonds in TBG with the individual graphene planes rotated with respect to each other by angles around 30° leads to the formation of superlattices of caged structures (fullerenes) that have the same periodicity with that of the Moiré pattern characteristic of the TBG; depending on the size of these local fullerene structures, the Dirac cones are either preserved or lost opening a narrow gap in the band structure.…”

“…Previous studies reported structures formed by interlayer bonding in AA-and ABstacked graphene bilayers, [23][24][25][26][27] as well as in MWCNTs of mixed chirality. 29 In those studies, hydrogen atoms at a surface coverage of 50% were used to passivate dangling bonds at the outer surfaces, being distributed on the surface in a checkerboard pattern; it was shown that the presence of these chemisorbed H atoms stabilized the interlayerbonded structures.…”

“…29 In those studies, hydrogen atoms at a surface coverage of 50% were used to passivate dangling bonds at the outer surfaces, being distributed on the surface in a checkerboard pattern; it was shown that the presence of these chemisorbed H atoms stabilized the interlayerbonded structures. The resulting configurations are characterized by a local crystalline structure that resembles that of diamond; some authors have called them "diamane" or "diamond-like C 2 H nanolayer", 24,27 while others have used the terms "hydrogenated bilayer graphene", 25 "hydrogenated few layer graphene", 26 or bilayer graphane. 23 In the study of Ref.…”