Structure of amorphous carbon from near-edge and extended x-ray absorption spectroscopy

Dı́az, J.; Monteiro, O.R.; Hussain, Zahid

doi:10.1103/physrevb.76.094201

Cited by 38 publications

(41 citation statements)

References 46 publications

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“…The pronounced dip in intensity 302.5 eV is caused by a bandgap in the unoccupied density of states (and is therefore a good indication of insulating or semiconducting character) 38 whilst a subsequent peak at 327 eV is caused by multiple scattering events and is a good indication of crystallographic order. 39 Similar to previous studies, 40 area 1 exhibits an additional weak "pre-edge" peak at 285.5 eV that is attributed to excitation to a p* state and is therefore indicative of the formation of unsaturated, sp 2 bonded carbon. The spectrum from area 1, however, retains the other distinctive The high-angle dark field image collected within the region labelled "spectrum image" and (e) the spatial distribution of the pre-edge (sp 2 bonding) feature indicated in the core-loss spectra within the spectrum image region.…”

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confidence: 65%

High resolution structural characterisation of laser-induced defect clusters inside diamond

Salter

Booth

Courvoisier

et al. 2017

Applied Physics Letters

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Laser writing with ultrashort pulses provides a potential route for the manufacture of three-dimensional wires, waveguides, and defects within diamond. We present a transmission electron microscopy study of the intrinsic structure of the laser modifications and reveal a complex distribution of defects. Electron energy loss spectroscopy indicates that the majority of the irradiated region remains as sp3 bonded diamond. Electrically conductive paths are attributed to the formation of multiple nano-scale, sp2-bonded graphitic wires and a network of strain-relieving micro-cracks.

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confidence: 65%

High resolution structural characterisation of laser-induced defect clusters inside diamond

Salter

Booth

Courvoisier

et al. 2017

Applied Physics Letters

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“…5e) of the unprocessed soot of the EURO 3 passenger car shows also a high absorption of the aromatic carbon at 285.2, as well as at 292 and 305 eV. Again, this points to a high graphitic content in these particles (Diaz et al, 2007). Similar to the EURO 2 transporter emissions, the absorption intensity of the carboxyl-C is low and no phenol-C nor quinone-C absorption is observed.…”

Section: Stxm-nexafs Characterizationmentioning

confidence: 48%

“…aged wood combustion particle. A broad absorption feature at 305 eV indicates a high π-bond conjugation (Diaz et al, 2007). Due to the inhomogeneous composition of soot small shifts in the maxima of the transition energies of the single particles are expected.…”

Section: Particle Morphology and Size Distributionmentioning

confidence: 99%

Aging induced changes on NEXAFS fingerprints in individual combustion particles

et al. 2011

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Abstract. Soot particles can significantly influence the Earth's climate by absorbing and scattering solar radiation as well as by acting as cloud condensation nuclei. However, despite their environmental (as well as economic and political) importance, the way these properties are affected by atmospheric processing of the combustion exhaust gases is still a subject of discussion. In this work, individual soot particles emitted from two different vehicles, a EURO 2 transporter, a EURO 3 passenger car, and a wood stove were investigated on a single-particle basis. The emitted exhaust, including the particulate and the gas phase, was processed in a smog chamber with artificial solar radiation. Single particle specimens of both unprocessed and aged soot were characterized using near edge X-ray absorption fine structure spectroscopy (NEXAFS) and scanning electron microscopy. Comparison of NEXAFS spectra from the unprocessed particles and those resulting from exhaust photooxidation in the chamber revealed changes in the carbon functional group content. For the wood stove emissions, these changes were minor, related to the relatively mild oxidation conditions. For the EURO 2 transporter emissions, the most apparent change was that of carboxylic carbon from oxidized organic compounds condensing on the primary soot particles. For the EURO 3 car emissions oxidation of primary soot particles upon photochemical aging has likely contributed as well. Overall, Correspondence to: M. Ammann (markus.ammann@psi.ch) the changes in the NEXAFS fingerprints were in qualitative agreement with data from an aerosol mass spectrometer. Furthermore, by taking full advantage of our in situ microreactor concept, we show that the soot particles from all three combustion sources changed their ability to take up water under humid conditions upon photochemical aging of the exhaust. Due to the selectivity and sensitivity of the NEXAFS technique for the water mass, also small amounts of water taken up into the internal voids of agglomerated particles could be detected. Because such small amounts of water uptake do not lead to measurable changes in particle diameter, it may remain beyond the limits of volume growth measurements, especially for larger agglomerated particles.

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“…In the following we will distinguish the sp 2 phase in aromatic clusters (probed only by Raman) and graphene-like clusters (probed by Raman and XRD). It has to be kept in mind that even if the structure of amorphous carbon has been studied for decades, no final model has been developed and the discussion is still lively 18,38,[44][45][46][47] . Most likely the majority of the sp 2 phase in sputter-deposited a-C is located in distorted aromatic ringsystems, but also chain-like structures and non-aromatic ring systems can occur.…”

Section: Discussionmentioning

confidence: 99%

Influence of doping (Ti, V, Zr, W) and annealing on the sp2 carbon structure of amorphous carbon films

Adelhelm

Balden

Rinke

et al. 2009

Journal of Applied Physics

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The influence of the transition metal (Ti, V, Zr, W) doping on the carbon matrix nanostructuring during the thin film growth and subsequent annealing is investigated. Pure and metal-doped amorphous carbon films (a-C, a-C:Me) were deposited at room temperature by non-reactive magnetron sputtering. The carbon structure of as-deposited and post-annealed (up to 1300 K) samples was analyzed by X-ray diffraction (XRD) and Raman spectroscopy.The existence of graphene-like regions in a-C is concluded from a (10) diffraction peak. A comparison of the XRD and Raman results suggests that XRD probes only the small amount of 2-3 nm large graphene-like regions, whereas the majority of the sp 2 phase is present in smaller distorted aromatic clusters which are probed only by Raman spectroscopy. Annealing leads to an increase of the graphene size and the aromatic cluster size. During the carbon film growth the addition of metals enhances ordering of sp 2 carbon in sixfold aromatic clusters compared to a-C, Ti and Zr showing the strongest effect, W the lowest. This order qualitatively corresponds with the catalytic activity of the respective carbides found during graphitization of carbide-doped graphites published in the literature. With annealing, carbide crystallite formation and growth occurs in a-C:Me films, which destroys the initial carbon structure, reduces the size of the initially formed aromatic clusters and the differences in carbon structure introduced by different dopants. For high annealing temperatures the carbon structure of a-C:Me films is similar to that of a-C, and is determined only by the annealing temperature.2

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Structure of amorphous carbon from near-edge and extended x-ray absorption spectroscopy

Cited by 38 publications

References 46 publications

High resolution structural characterisation of laser-induced defect clusters inside diamond

High resolution structural characterisation of laser-induced defect clusters inside diamond

Aging induced changes on NEXAFS fingerprints in individual combustion particles

Influence of doping (Ti, V, Zr, W) and annealing on the sp2 carbon structure of amorphous carbon films

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