The investigation of cobalt intercalation underneath epitaxial graphene on 6H-SiC(0 0 0 1)

Abstract

The intercalation behaviour of cobalt underneath both epitaxial graphene monolayer and bilayer on 6H-SiC(0001) have been investigated by scanning tunneling microscopy (STM) and density functional theory (DFT). Upon deposition, cobalt atoms prefer to agglomerate into clusters on the epitaxial graphene. After annealing the sample to 850 °C, the intercalation of the adsorbed cobalt atoms into both monolayer and bilayer epitaxial graphene on SiC takes place, as observed by the atomically resolved STM images. Further studies based on DFT modeling and simulated STM images show that, resulting from the interplay between the intercalated cobalt atoms and the carbon layers sandwiching it, the most energetically favourable intercalation sites of cobalt atoms underneath monolayer and bilayer graphene differ. Furthermore, the results show energy barriers of 0.60 eV and 0.41 eV for cobalt penetration through mono-vacancy defects at monolayer and bilayer graphene.

Epitaxial graphene/silicon carbide intercalation: a minireview on graphene modulation and unique 2D materials

“…Epitaxial graphene can readily accommodate intercalation. 14,15,18,19,39,40 However, intercalation through pristine, multilayer EG is limited by defects native to the grown graphene layers. Thus, the low defect density afforded by high-temperature EG synthesis techniques can limit the lateral scale of intercalation.…”

“…19,27,34,40 Following this step, EG/SiC substrates are annealed at temperatures typically ≥600°C under ultra-high vacuum (UHV), to induce intercalation. 19,27,32,34,40 This synthesis approach is well suited to investigation of intercalated structures, due to the relative ease of characterizing samples in situ through LEED, ARPES, XPS, or a combination of all three techniques. Investigation of intercalated materials through scanning tunneling microscopy and spectroscopy is also common, and can reveal ordered intercalant structures underneath the graphene layers.…”

“…Investigation of intercalated materials through scanning tunneling microscopy and spectroscopy is also common, and can reveal ordered intercalant structures underneath the graphene layers. 16,28,[41][42][43][44] Elemental intercalation may also be achieved using gas-phase precursors such as H2, O2, air, and NH3. 9,17,31,32,36 In a similar fashion to metals deposited on EG, gas phase atomic species are hypothesized to adsorb onto the graphene surface and diffuse through graphene layers.…”

Thermally Activated Processes for Ferromagnet Intercalation in Graphene-Heavy Metal Interfaces

“…The energy required to activate each of these mechanisms is experimentally delivered by thermal annealing, and depends on the specific substrate onto which the Gr is grown and on the atomic species to be intercalated. DFT calculations indicate that the presence of a substrate lowers the energy barrier for the intercalation compared to free standing Gr, and that adatoms on top of Gr further reduce such barrier [22] [26].…”

Intercalated rare-earth metals under graphene on SiC

“…Metal intercalation under graphene on various substrates is by now common practice [1,2,3,4,5,6,7,8,9,10,11]. Indeed, it has been demonstrated that rare earth metals (RE = Nd, Sm, Dy, Er and Yb, and Eu, for example) deposited on graphene grown on SiC or Ir substrate can intercalate under the graphene lattice by annealing pre-deposited metals at elevated temperatures [1,4,9,12].…”