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

作者：Niels Ganser, Marko A. Kriegel, Umut Kaya, Jixi Zhang, Rodney D. L. Smith, Marika Schleberger, W. Mertin, Gerd Bacher, Michael Horn-von Hoegen · 发表于：arXiv (Cornell University) · 年份：2026 · 研究领域：Graphene research and applications、Advanced Electron Microscopy Techniques and Applications、Optical Coatings and Gratings

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 (Al$_2$O$_3$). 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.