Conformations, electronic, and mechanical properties of monolayer diamene*

Experiments show that diamond-like (diamene) films can be obtained from multilayer graphene, either by compression or surface passivation. Based on DFT calculations, we predict that diamene assumes various conformations, requiring either one or both surfaces being passivated. Conformations with surfaces fully passivated exhibit insulating properties, whereas diamene films presenting a clean surface show variable electronic properties, from insulating to semiconducting and metallic. Interestingly, regardless being monolayers or having a clean surface, all conformers of diamene exhibit elastic moduli comparable to those of the corresponding sp³ bulk phase, retaining Young's moduli along their transverse direction that are between 50% and 80% of bulk phases. Moreover we suggest that diamene film can be obtained from multilayer graphene by means of compression and/or wear without the need of chemical passivants, and the energies and pressures involved in the transformation depend critically on the structure and chemistry of the interface with the substrate.