Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 57: Frontiers of Electronic-Structure Theory: Focus on the Interface Challenge VI (joint session O/CPP/DS/TT)

O 57.10: Vortrag

Mittwoch, 3. April 2019, 17:15–17:30, H9

Origin of carbon 1s binding energy shifts in amorphous carbon materials — •Michael Walter^1,4,5, Filippo Mangolini², Robert W. Carpick³, and Michael Moseler^4,5 — ¹FIT, University of Freiburg, Germany — ²University of Texas at Austin, USA — ³University of Pennsylvania, USA — ⁴Fraunhofer IWM, Freiburg, Germany — ⁵Physikalisches Institut, Universität Freiburg, Germany

The quantitative evaluation of the carbon hybridization state by X-ray photoelectron spectroscopy (XPS) has been a surface-analysis problem for the last three decades due to the challenges associated with the unambiguous identification of the characteristic binding energy values of sp²- and sp³-bonded carbon. Here, we compute the binding energy values for model structures of various carbon allotropes, including graphite, diamond, doped-diamond, and amorphous carbon (a-C), using density functional theory (DFT). The large band-gap of diamond allows defects to pin the Fermi level, which results in large variations of the C(1s) core electron energies for sp³-bonded carbon, in agreement with the large spread of experimental C(1s) binding energy values for sp³ carbon. In case of hydrogen-free a-C, the C(1s) core electron binding energy for sp³ carbon atoms is approximately 1 eV higher than the binding energy for sp²-hybridized carbon. However, the introduction of hydrogen hinders the unambiguous quantification of the carbon hybridization state on the basis of C(1s) XPS alone. This work can assist surface scientists in the use of XPS for the accurate characterization of carbon-based materials.