Determination of bonding in amorphous carbons by electron energy loss spectroscopy, Raman scattering and X-ray reflectivity

Ferrari, Andrea C.; Kleinsorge, B.; Adamopoulos, George; Robertson, John; Milne, W. I.; Stolojan, Vlad; Brown, L. M.; Libassi, A.; Tanner, B. K.

doi:10.1016/s0022-3093(00)00035-1

Cited by 85 publications

(41 citation statements)

References 10 publications

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“…These typical peaks of amorphous carbon films lie at around 1560 and 1360 cm -1 respectively for visible (VIS) excitation, and correspond to in-plane stretching and sixfold ring breathing vibrations of sp 2 sites [33]. In addition, the T peak at around 1060 cm -1 , associated with C-C sp 3 vibrations [34,35], can be hardly observed with UV excitation for a-C:Cu(28) (Fig. 4a).…”

Section: Resultsmentioning

confidence: 96%

Effect of the metal concentration on the structural, mechanical and tribological properties of self-organized a-C:Cu hard nanocomposite coatings

Pardo

Buijnsters

Endrino

et al. 2013

Applied Surface Science

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174 GPa for the film with a Cu content of 28 at.%. In parallel, a 50% drop in the nanohardness from about 28 GPa towards 14 GPa is observed for these coatings. An increase in the Cu content also produces an increment of the coefficient of friction in reciprocating sliding tests performed against a corundum ball counterbody. As compared to the metal free film, a nearly four times higher coefficient of friction value is detected in the case of a Cu content of 28 at.%. Nevertheless, the carbon-copper composite coatings produced a clear surface protection of the substrate evidenced by a reduced wear loss for Cu contents below 5 at.%.

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Section: Resultsmentioning

confidence: 96%

Effect of the metal concentration on the structural, mechanical and tribological properties of self-organized a-C:Cu hard nanocomposite coatings

Pardo

Buijnsters

Endrino

et al. 2013

Applied Surface Science

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“…Raman spectra (data not shown) in the range of 1100 to 2000 cm − 1 displayed two main bands D and G [47] ascribed to carbon species. According to previous works [57][58][59], the D-band is associated to non-deactivating carbon (amorphous carbon) and the G-band is related to deactivating carbon (graphitic carbon). The carbon deposition on used Ni-Cu samples was determined by TPO as shown in Table 2.…”

Section: Used Samplesmentioning

confidence: 95%

Influence of copper on nickel-based catalysts in the conversion of glycerol

Miranda

Chimentão

Szanyi

et al. 2015

Applied Catalysis B: Environmental

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The catalytic transformation of glycerol to value-added compounds was investigated over bimetallic Ni-Cu/y-Al2 O3 catalysts with Ni/Cu atomic ratios of 8/1, 4/1, 2/1, 1/1, 1/2, 1/4, and 1/8. XPS analysis revealed that the surface composition of the catalyst exhibited progressive enrichment of Cu as its content in the catalyst increased. H2 -chemisorption indicated that the total number of exposed Ni atoms decreased as the Cu content increased. As a result, deep hydrogenolysis to produce CH4 was inhibited by the addition of Cu to the Ni catalyst, yielding higher selectivity toward the dehydration products of glycerol such as hydroxyacetone.FTIR spectra of adsorbed CO reveal that Cu asserts both geometric and electronic effects on the adsorption properties of Ni. The geometrical effect is visualized by the progressive disappearance of the bridge-bound adsorbed CO on metallic Ni by the incorporation of Cu. This suggests that the deep hydrogenolysis of glycerol to CH4 formation requires an ensemble of adjacent active Ni atoms. The electronic effect of Cu on Ni is indicated by the red shift of the IR peak of adsorbed CO as the Cu content increases. The electronic interaction between Cu and Ni species was also substantiated by XANES results. HTREM revealed metal particles very well distributed on the support with particle size of 1.5 to 5 nm. The Ni-Cu samples were not a total intermetallic alloys..

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“…Even though EELS allows the fraction of carbon atoms in sp 2 -and sp 3 -hybridization state to be quantified through the analysis of the low loss region (from 0 to 40 eV) or the high loss region at the C1s 11,15,[36][37][38] , it requires the film to be removed from the substrate or for a cross-section to be produced. Additionally, the acquisition of the C1s is usually carried out with limited energy resolution of approximately 0.5 eV 11,44 .…”

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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Determination of bonding in amorphous carbons by electron energy loss spectroscopy, Raman scattering and X-ray reflectivity

Cited by 85 publications

References 10 publications

Effect of the metal concentration on the structural, mechanical and tribological properties of self-organized a-C:Cu hard nanocomposite coatings

Effect of the metal concentration on the structural, mechanical and tribological properties of self-organized a-C:Cu hard nanocomposite coatings

Influence of copper on nickel-based catalysts in the conversion of glycerol

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

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