Correlation between bonding structure and microstructure in fullerenelike carbon nitride thin films

• The bonding structure of highly ordered fullerenelike (FL) carbon nitride (CNx) thin films has been assessed by x-ray absorption near-edge spectroscopy (XANES). Samples with different degrees of FL character have been analyzed to discern spectral signatures related to the FL microstructure. The XANES spectra of FL-CNx films resemble that of graphitic CN x, evidencing the sp2 hybridization of both C and N atoms. The FL structure is achieved with the promotion of N in threefold positions over pyridinelike and cyanidelike bonding environments. In addition, the relative p* / σ* XANES intensity ratio at the C(1s) edge is independent of the FL character, while it decreases ∼40% at the N(1s) edge with the formation of FL arrangements. This result indicates that there is no appreciable introduction of C-sp3 hybrids with the development of FL structures and, additionally, that a different spatial localization of π electrons at C and N sites takes place in curved graphitic structures. The latter has implications for the elastic properties of graphene sheets and could, as such, explain the outstanding elastic properties of FL-CNx.

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