Imaging local electronic corrugations and doped regions in graphene

Schultz, Brian J.; Patridge, Christopher J.; Lee, Vincent; Jaye, Cherno; Lysaght, Patrick; Smith, Christian W.; Barnett, Joel; Fischer, Daniel A.; Prendergast, David; Banerjee, Sarbajit

doi:10.1038/ncomms1376

Cited by 114 publications

(151 citation statements)

References 44 publications

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“…hybridization state of carbon atoms in the near-surface region of carbon-based materials, such as diamond [45][46][47][48][49] , amorphous carbon 14,29,[50][51][52] , graphene 53,54 , and polymers [55][56][57] . The dependence of the intensity of the detected spectral features on the orientation of the final state orbital with respect to the electric field vector of the incident photon beam 58 also allows the surface molecular orientation of nanomaterials [59][60][61] and adsorbates 62 to be investigated.…”

Section: Introductionmentioning

confidence: 99%

Quantitative Evaluation of the Carbon Hybridization State by Near Edge X-ray Absorption Fine Structure Spectroscopy

2016

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The characterization of the local bonding configuration of carbon in carbon-based materials is of paramount importance since the properties of such materials strongly depend on the distribution of carbon hybridization states, the local ordering, and the degree of hydrogenation. Carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectroscopy is one of the most powerful techniques for gaining insights into the bonding configuration of near-surface carbon atoms. The common methodology for quantitatively evaluating the carbon hybridization state using C1s NEXAFS measurements, which is based on the analysis of the sample of interest and of a highly ordered pyrolytic graphite (HOPG) reference sample, was reviewed and critically assessed, noting that inconsistencies are found in the literature in applying this method. A theoretical rationale for the specific experimental conditions to be used for the acquisition of HOPG reference spectra is presented together with the potential sources of uncertainty and errors in the correctly computed fraction of sp 2 -bonded carbon. This provides a specific method for analyzing the distribution of carbon hybridization state using NEXAFS spectroscopy. As an illustrative example, a hydrogenated amorphous carbon film was analyzed using this method, and showed good agreement with X-ray photoelectron spectroscopy (which is surface sensitive).Furthermore, the results were consistent with analysis from Raman spectroscopy (which is not surface sensitive), indicating the absence of a structurally different near-surface region in this particular thin film material. The present work can assist surface scientists in the analysis of NEXAFS spectra for the accurate characterization of the structure of carbon-based materials.3

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Section: Introductionmentioning

confidence: 99%

Quantitative Evaluation of the Carbon Hybridization State by Near Edge X-ray Absorption Fine Structure Spectroscopy

2016

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“…Experimentally, Ref. [43] and [47] have found that the more edge C atoms are probed in XAS, the higher the intensity of the pre-edge peak. Moreover, Other kinds of structure modulations like charged-specie adsorption may also create such a pre-edge peak [43,48,49].…”

Section: Edge Effectsmentioning

confidence: 99%

“…The reduced dimensionality and the presence of the edge atoms can strongly modify the electronic and transport properties of graphene. The local electronic structure at the edge of a graphene has been measured by X-ray absorption microscopy [43] and EELS [44,45]. Here we study XANES of a zigzag-type edge terminated by hydrogen, and focus on several particular kinds of carbon atoms which are colored pink and labelled by numbers as shown in Fig.…”

Section: Edge Effectsmentioning

confidence: 99%

X-ray absorption spectra of graphene and graphene oxide by full-potential multiple scattering calculations with self-consistent charge density

Krüger

Natoli

et al. 2015

Phys. Rev. B

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X-ray absorption near edge structure (XANES) of graphene, graphene oxide and diamond are studied by the recently developed real-space full potential multiple scattering (FPMS) theory with space-filling cells. It is shown how accurate potentials for FPMS can be generated from self-consistent charge densities obtained with other schemes, especially the projector augmented wave method. Compared to standard multiple scattering calculations in the muffin-tin approximation, FPMS gives much better agreement with experiment. The effects of various structural modifications on the graphene spectra are well reproduced. (1) Stacking of graphene layers increases the peak intensity in the higher energy region. (2) The spectrum of the C atom located at the edge of graphene sheet shows a prominent pre-edge structure. (3) Adsorption of oxygen gives rise to the so-called interlayer-state peak. Moreover, O K-edge spectra of graphene oxide are calculated for three types of bonding, C-OH, C-O-C and C-O, and the proportions of these bondings at 800 • C are deduced by fitting them to the experimental spectrum.

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“…For carbon K-edge NEXAFS spectroscopy, in particular, the resolvable energy difference between the resonant X-ray excitations of a core-level (1s) electron to unoccupied molecular orbitals (either π* or σ*) allows the identification of the bonding configuration and hybridization state of carbon atoms in the near-surface region for many materials, including diamond 6,13,21,22,24,25,[33][34][35][36][37][38] , diamond-like carbon [39][40][41][42][43][44][45][46] , graphene 26,47,48 , and polymers [27][28][29][30][31][32] , as well as the determination of the surface molecular orientation of nanomaterials 18,19,49,50 and adsorbates [14][15][16] .…”

Section: Introductionmentioning

confidence: 99%

Accounting for Nanometer-Thick Adventitious Carbon Contamination in X-ray Absorption Spectra of Carbon-Based Materials

et al. 2014

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Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is a powerful technique for characterizing the composition and bonding state of nanoscale materials and the top few nanometers of bulk and thin film specimens. When coupled with imaging methods like photoemission electron microscopy, it enables chemical imaging of materials with nanometerscale lateral spatial resolution. However, analysis of NEXAFS spectra is often performed under the assumption of structural and compositional homogeneity within the nanometer-scale depth probed by this technique. This assumption can introduce large errors when analyzing the vast majority of solid surfaces due to the presence of complex surface and near-surface structures such as oxides and contamination layers. An analytical methodology is presented for removing the contribution of these nanoscale overlayers from NEXAFS spectra of two-layered systems to provide a corrected photo-absorption spectrum of the substrate. This method relies on the subtraction of the NEXAFS spectrum of the overlayer adsorbed on a reference surface from the spectrum of the two-layer system under investigation, where the thickness of the overlayer is independently determined by X-ray photoelectron spectroscopy (XPS). This approach is applied to NEXAFS data acquired for one of the most challenging cases: air-exposed hard carbon-based materials with adventitious carbon contamination from ambient exposure. The contribution of the adventitious carbon was removed from the as-acquired spectra of ultrananocrystalline diamond (UNCD) and hydrogenated amorphous carbon (a-C:H) to determine the intrinsic photoabsorption NEXAFS spectra of these materials. The method alters the calculated fraction of sp 2 -hybridized carbon from 5 to 20%, and reveals that the adventitious contamination can be

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Imaging local electronic corrugations and doped regions in graphene

Cited by 114 publications

References 44 publications

Quantitative Evaluation of the Carbon Hybridization State by Near Edge X-ray Absorption Fine Structure Spectroscopy

Quantitative Evaluation of the Carbon Hybridization State by Near Edge X-ray Absorption Fine Structure Spectroscopy

X-ray absorption spectra of graphene and graphene oxide by full-potential multiple scattering calculations with self-consistent charge density

Accounting for Nanometer-Thick Adventitious Carbon Contamination in X-ray Absorption Spectra of Carbon-Based Materials

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