Probing symmetry-breaking defects in polished graphitizable <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>s</mml:mi><mml:msup><mml:mi>p</mml:mi><mml:mn>2</mml:mn></mml:msup></mml:mrow></mml:math> carbons using angle-resolved polarized Raman scattering
Y. Hbiriq, M.R. Ammar, Cristiano Fantini, Louis Hennet, Mustapha Zaghrioui
Abstract
Raman scattering is commonly used to quantify defects in $s{p}^{2}$ carbons, mostly based on the values of the double-resonant D-band intensity. It is well known that this peculiar band undergoes changes when the $s{p}^{2}$ carbon is polished. However, the physical process behind this phenomenon is unclear so far. In this paper, we provide a deep understanding of the fundamental optical properties of the polishing-induced defects by combining angle-resolved polarized Raman scattering and theoretical calculations. We address the question regarding the types of these additional defects that participate in the intervalley double-resonance Raman process and contribute to the spatially inhomogeneous increase of the relative D-band intensity. The study was performed on anthracene-based coke pyrolyzed at $2000\phantom{\rule{0.16em}{0ex}}{}^{\ensuremath{\circ}}\mathrm{C}$ and uses highly oriented pyrolytic graphite with known crystallographic orientations as a model material. The results shed light on the types of defects as well as the D-band peculiar behavior as a function of the spatial orientation of graphene layers dictated by polishing with respect to the fixed direction of the incident and scattered light. Moreover, the insignificant change in ${I}_{2\mathrm{D}}/{I}_{\mathrm{G}}$, the width and the position of the G band after polishing, and the insensitivity of less ordered carbons to this process are also discussed.