title: Implantation and atomic-scale investigation of self-interstitials in graphene.
abstract: Crystallographic defects play a key role in determining the properties of crystalline materials. The new class of two-dimensional materials, foremost graphene, have enabled atomically resolved studies of defects, such as vacancies,1-4 grain boundaries,(5-7) dislocations,(8,9) and foreign atom substitutions.(10-14) However, atomic resolution imaging of implanted self-interstitials has so far been reported neither in any three-dimensional nor in any two-dimensional material. Here, we deposit extra carbon into single-layer graphene at soft landing energies of ∼ 1 eV using a standard carbon coater. We identify all the self-interstitial dimer structures theoretically predicted earlier,(15-17) employing 80 kV aberration-corrected high-resolution transmission electron microscopy. We demonstrate accumulation of the interstitials into larger aggregates and dislocation dipoles, which we predict to have strong local curvature by atomistic modeling, and to be energetically favorable configurations as compared to isolated interstitial dimers. Our results contribute to the basic knowledge on crystallographic defects and lay out a pathway into engineering the properties of graphene by pushing the crystal into a state of metastable supersaturation.
authors.affiliation: Central Facility for Electron Microscopy, Group of Electron Microscopy of Materials Science, Ulm University , 89081 Ulm, Germany.
authors.forename: Ossi
authors.initials: O
authors.lastname: Lehtinen
authors.forename: Nilesh
authors.initials: N
authors.lastname: Vats
authors.forename: Gerardo
authors.initials: G
authors.lastname: Algara-Siller
authors.forename: Pia
authors.initials: P
authors.lastname: Knyrim
authors.forename: Ute
authors.initials: U
authors.lastname: Kaiser
keywords: HRTEM; MD; defects; graphene; implantation; self-interstitials