The Role of Structural Defects in the Growth of Two-Dimensional Diamond from Graphene

The presented work is devoted to the study of the formation of the thinnest diamond film (diamane). We investigate the initial stages of diamond nucleation in imperfect bilayer graphene exposed by the deposition of H atoms (chemically induced phase transition). We show that defects serve as nucleation centers, their hydrogenation is energy favorable and depends on the defect type. Hydrogenation of vacancies facilitates the binding of graphene layers, but the impact wanes already at the second coordination sphere. Defects influence of 5|7 is lower but promotes diamondization. The grain boundary role is similar but can lead to the final formation of a diamond film consisting of chemically connected grains with different surfaces. Interestingly, even hexagonal and cubic two-dimensional diamonds can coexist together in the same film, which suggests the possibility of obtaining a new two-dimensional polycrystal unexplored before.

Automated summary

This study focuses on the formation of the thinnest diamond film. By depositing hydrogen atoms on imperfect bilayer graphene, the initial stages of diamond nucleation are investigated. It is found that defects can serve as nucleation centers and their hydrogenation promotes the binding of graphene layers. Different defect types and grain boundaries play different roles in the diamondization process. Interestingly, two-dimensional hexagonal and cubic diamonds can coexist in the same film, suggesting the possibility of obtaining a new unexplored two-dimensional polycrystal structure.