Direct Experimental Evidence of Metal-Mediated Etching of Suspended Graphene

Atomic resolution high angle annular dark field imaging of suspended, single-layer graphene, onto which the metals Cr, Ti, Pd, Ni, Al and Au atoms had been deposited was carried out in an aberration corrected scanning transmission electron microscope. In combination with electron energy loss spectroscopy, employed to identify individual impurity atoms, it was shown that nano-scale holes were etched into graphene, initiated at sites where single atoms of all the metal species except for gold come into close contact with the graphene. The e-beam scanning process is instrumental in promoting metal atoms from clusters formed during the original metal deposition process onto the clean graphene surface, where they initiate the hole-forming process. Our observations are discussed in the light of calculations in the literature, predicting a much lowered vacancy formation in graphene when metal ad-atoms are present. The requirement and importance of oxygen atoms in this process, although not predicted by such previous calculations, is also discussed, following our observations of hole formation in pristine graphene in the presence of Si-impurity atoms, supported by new calculations which predict a dramatic decrease of the vacancy formation energy, when SiOx molecules are present.Comment: final version accepted in ACS Nano + supplementary info. 22+6 pages, 4+5 figure

Effects of pore modification on the templating of guest molecules in a 2D honeycomb network

This work was supported by the UK Engineering Physical Sciences Research Council (EPRSC) and the EU.1,7-Diadamantanethioperylene-3,4:9,10-tetracarboxylic diimide, (Ad-S)(2)-PTCDI, adsorbed on Au (111) from solution was investigated by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). (Ad-S)(2)-PTCDI forms a well-ordered monolayer whose structure is described by a (2 root 63 x root 19) R19.1 degrees chiral unit cell containing four molecules. Codeposition of (Ad-S)(2)-PTCDI with 1,3,5-triazine-2,4,6-triamine (melamine) yields a honeycomb network whose (7 root 3 x 7 root 3)R30 degrees unit cell is identical to the unsubstituted PTCDI/melamine analogue. The effect of the adamantyl thioether moieties on the adsorption of guest molecules is investigated using adamantane thiol and C-60. While the thioether units do not affect the packing of adamantane thiol molecules a pronounced influence is seen in the case of fullerene. Pore modification involving different combinations of enantiomers of (Ad-S)(2)-PTCDI give rise to distinctly different arrangements of C-60 molecules. The diversity of patterns is further increased by the presence of unsubstituted PTCDI molecules.PostprintPeer reviewe