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Spot Profile Analysis Low Energy Electron Diffraction of Plasma-Enhanced Chemical Vapor Deposition Grown Epitaxial Few-Layer Graphene on Sapphire

Niels Ganser, Marko A. Kriegel, Umut Kaya, Jixi Zhang, Rodney D. L. Smith, Marika Schleberger, Wolfgang Mertin, Gerd Bacher, Michael Horn-von Hoegen

cond-mat.mtrl-sciarXiv:2607.14922

Abstract

We demonstrate the use of high-resolution spot-profile analysis low-energy electron diffraction to determine the mean grain size of plasma-enhanced chemical vapor deposition grown few-layer graphene on sapphire (Al2O3). The diffraction patterns exhibit broadened graphene spots, pronounced diffuse scattering, and azimuthally extended features, indicating finite crystallite size and rotational disorder. By analyzing the finite-size broadening of the specular (00) spot with an Airy-type diffraction profile, we determine a mean grain diameter of 3.7\,nm for the as-grown graphene layer. Post-growth annealing under ultrahigh-vacuum conditions increases the mean grain size to about 5.7\,nm and 6.8\,nm, respectively. These results establish SPA-LEED as a sensitive reciprocal-space method for quantifying the structural coherence of directly grown graphene on insulating substrates.

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