Influence of Size Effect on the Electronic and Elastic Properties of Diamond Films with Nanometer Thickness

Abstract

1The atomic structure and physical properties of few-layered 111 oriented diamond nanocrystals (diamanes), covered by hydrogen atoms from both sides are studied using electronic band structure calculations. It was shown that energy stability linear increases upon increasing of the thickness of proposed structures. All 2D carbon films display direct dielectric band gaps with nonlinear quantum confinement response upon the thickness. Elastic properties of diamanes reveal complex dependence upon increasing of the number of 111 layers. All theoretical results were compared with available experimental data.

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.…”