Nanoengineering Defect Structures on Graphene

We present a new way of nanoengineering graphene by using defect domains. These regions have ring structures that depart from the usual honeycomb lattice, though each carbon atom still has three nearest neighbors. A set of stable domain structures is identified by using density functional theory, including blisters, ridges, ribbons, and metacrystals. All such structures are made solely out of carbon; the smallest encompasses just 16 atoms. Blisters, ridges, and metacrystals rise up out of the sheet, while ribbons remain flat. In the vicinity of vacancies, the reaction barriers to formation are sufficiently low that such defects could be synthesized through the thermally activated restructuring of coalesced adatoms.

Figure 1

Defect domains in graphene. (a) Top and (b) side view of a single defect blister of 24 carbon atoms with a height of 1.9 Å. (c) A Stone-Wales defect used to synthesize defect domains. (d) A defect-domain ribbon embedded in graphene. (e)–(f) Haeckelite, a carbon allotrope used to synthesize defect domains. In yellow (light gray) is shown a graphene overlay for visualization.

Figure 2

Mechanical response (pure dilation) of graphene, haeckelite, and a metacrystal of haeckelite-based defect-domain blisters. The points represent actual DFT data; the curves are a guide to the eye.

Figure 3

(a)–(b) A single inverse Stone-Wales defect. (c)–(f) Multiple defects can be aligned to form ridged contours which can be straight, curved, or even closed.

Figure 4

(a)–(b) Reaction path for a single adatom moving to the periphery of a divacancy. (c) Experimentally observed adatom positions [14]. (d)–(e) Creation of an inverse Stone-Wales defect on the periphery of a divacancy by one adatom hopping within the vicinity of another. (f) Final structure with blister shown in dark gray and divacancy identified within a dashed ellipse. Energies in both (a) and (f) are relative to the lowest point plotted.

Figure 5

(a) Top and (b) side view of a metacrystal formed from haeckelite-based defect-domain blisters. (c) A metacrystal defect: A less closely packed metacrystal contains an “atom” of negative polarity, a blister pushed down rather than up.