Interaction between graphene and copper substrate: The role of lattice orientation

Abstract

We present a comprehensive study of graphene grown by chemical vapor deposition on copper single crystals with exposed (100), (110) and (111) faces. Direct examination of the as-grown graphene by Raman spectroscopy using a range of visible excitation energies and microRaman mapping shows distinct strain and doping levels for individual Cu surfaces. Comparison of results from Raman mapping with X-ray diffraction techniques and Atomic Force Microscopy shows it is neither the crystal quality nor the surface topography responsible for the specific strain and doping values, but it is the Cu lattice orientation itself. We also report an exceptionally narrow Raman 2D band width caused by the interaction between graphene and metallic substrate. The appearance of this extremely narrow 2D band with full-width-at-half maximum (FWHM) as low as 16 cm -1 is correlated with flat and undoped regions on the Cu(100) and (110) surfaces.The generally compressed (~ 0.3% of strain) and n-doped (Fermi level shift of ~250 meV) graphene on Cu (111) shows the 2D band FWHM minimum of ~20 cm -1 . In contrast, graphene grown on Cu foil under the same conditions reflects the heterogeneity of the polycrystalline surface and its 2D band is accordingly broader with FWHM > 24 cm -1 .

In Situ Raman Spectroscopy of Solution-Gated Graphene on Copper

“…We can estimate a concentration of about 8 × 10 12 cm −2 , based on the assumption of a linear change in concentration of 1.35 × 10 12 cm −2 per 1 cm −1 G band blueshift [6,12]. This value is in good agreement with the range of concentrations observed in literature [11]. The changes induced by our gate lead to a further blueshift of about 5 cm −1 , which corresponds to an additional change in concertation of about 7 × 10 12 cm −2 .…”

“…Thus, our measurements point towards n-type doping of graphene on copper immersed in solution. Literature data for graphene on copper not immersed in solution also report n-type doping [11]. With this information at hand, we can take the literature values for the G and 2D Raman shifts of unstrained, undoped graphene E G = 1580 cm −1 , E 2D0 = 2644 cm −1 [11][12][13] for a 633nm laser excitation and estimate both strain and carrier concentration.…”

“…The resulting strain should lead to a blueshift of the G band of about 12 cm −1 [11,12]. We hence expect a strained but undoped graphene to have a G band Raman shift of 1592 cm −1 .…”

Single-Layer Graphene Synthesis on a Al2O3(0001)/Cu(111) Template Using Chemical Vapor Deposition

“…48 In addition, graphene doping by the Cu substrate is strongly influenced over time as a result of copper template oxidation after growth. 49 This is shown by Raman analysis during a controlled Cu oxidation experiment (see Fig.…”

Comparative Morphological Analysis of Graphene on Copper Substrate obtained by CVD from a Liquid Precursor

“…Single Cu crystals, with grain having different crystallographic orientations, will cause uniform or biaxial strain (compression up to 0.3%) of the continuous graphene film [59]. Therefore, graphene obtained on a single Cu crystal will obviously be more uniform and less defected as compared to frequently used polycrystalline substrate.…”