Modification of electronic surface states by graphene islands on Cu(111)

Abstract

We present a study of graphene/substrate interactions on UHV-grown graphene islands with minimal surface contamination using \emph{in situ} low-temperature scanning tunneling microscopy (STM). We compare the physical and electronic structure of the sample surface with atomic spatial resolution on graphene islands versus regions of bare Cu(111) substrate. We find that the Rydberg-like series of image potential states is shifted toward lower energy over the graphene islands relative to Cu(111), indicating a decrease in the local work function, and the resonances have a much smaller linewidth, indicating reduced coupling to the bulk. In addition, we show the dispersion of the occupied Cu(111) Shockley surface state is influenced by the graphene layer, and both the band edge and effective mass are shifted relative to bare Cu(111).Comment: 12 pages, 3 figure

Comparative study of the interfaces of graphene and hexagonal boron nitride with silver

“…However, for an insulator a slight increase in the effective mass of the surface band was observed [23]. On the other hand, in the case of graphene on Au(111) [26] it remains unchanged or even decreases for a graphene layer grown on a copper crystal [24], which effect was attributed to an increased surface corrugation.…”

“…Relevant and quantitative information can * manuela.garnica@tum.de be extracted from the study of the evolution and modification of these states by the adsorption of gases [14][15][16], molecules [17][18][19][20][21][22], ionic films [23], and 2D honeycomb layers [24][25][26]. On the other hand, scanning tunneling spectroscopy (STS) has been exploited to investigate the unoccupied states of ultrathin layers on metals, in particular, the image potential states [24,[27][28][29]. They are bound to a solid by the response of the substrate to the presence of the electron and kept outside the surface by the reflective properties of the substrate.…”

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

“…We also notice that many 7 of these types of defects appear to be swept to the edges of graphene islands during growth (see Ref. 43 and Fig. 1a, b, and c).…”

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

“…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.…”