Native defects in ultra-high vacuum grown graphene islands on Cu(1 1 1)

Abstract

We present a scanning tunneling microscopy (STM) study of native defects in graphene islands grown by ultra-high vacuum (UHV) decomposition of ethylene on Cu(111). We characterize these defects through a survey of their apparent heights, atomic-resolution imaging, and detailed tunneling spectroscopy. Bright defects that occur only in graphene regions are identified as C site point defects in the graphene lattice and are most likely single C vacancies. Dark defect types are observed in both graphene and Cu regions, and are likely point defects in the Cu surface. We also present data showing the importance of bias and tip termination to the appearance of the defects in STM images and the ability to achieve atomic resolution.Finally, we present tunneling spectroscopy measurements probing the influence of point defects on the local electronic landscape of graphene islands.

Crystalline hydrogenation of graphene by scanning tunneling microscope tip-induced field dissociation of H2

“…[41] Turning now to the interaction of H/H 2 with graphene, Figures 2-5 discuss a sequence of experiments on a ~ 3000 nm 2 graphene island, subject to three of the field dissociation cycles illustrated above. As a baseline for comparison, an STM image of the pristine graphene island is shown in Fig 2a . Graphene islands are readily distinguished from the Cu(111) surface by the greatly reduced density of point defects, [35] , [36] and this is confirmed by atomically resolved images, which show contrast at the honeycomb centers spaced by the expected 2.46 Å (c.f. Supporting Information Fig.…”

“…STM images of graphene at low voltage are dominated by standing wave patterns associated with the scattering of the underlying Cu (111) surface state electrons, which produces a ring in the corresponding FFT [35]. Spherical scattering was used to assign faint depressions appearing on the graphene islands to defects remaining in the underlying Cu [36]. Surface state scattering is not as clear for the larger depressions which we The new defects are stable under typical imaging conditions and did not exhibit any motion in the several days we studied this region.…”

“…Graphene islands were grown on Cu(111) by thermal decomposition of ethylene in ultrahigh vacuum (UHV) at a base pressure of ~10 -10 mbar. [35][36][37] This method produces pristine graphene and interfaces which can be studied by STM without any exposure to air. [35,36] A clean Cu(111) surface was first prepared by cycles of Ar + sputtering and annealing at 600 °C, repeated until surface contamination was minimized in Auger electron spectra.…”

“…[35][36][37] This method produces pristine graphene and interfaces which can be studied by STM without any exposure to air. [35,36] A clean Cu(111) surface was first prepared by cycles of Ar + sputtering and annealing at 600 °C, repeated until surface contamination was minimized in Auger electron spectra. Graphene was grown by introducing 2x10 -5 mbar of ethylene gas into the UHV chamber while cycling the sample temperature 2-4 times from room temperature to ~950 °C, resulting in an average coverage < 0.25 monolayers.…”

“…In our experience, atomic resolution imaging of graphene/Cu(111) under typical tunneling conditions likely results from molecule-terminated tips, and we distinguish these from metal atom-terminated tips by imaging and spectroscopy on the Cu surface. [35,36] Image analysis was performed with the WSxM software [38].…”