Analysis of the Angle-Resolved X-ray Photoelectron Emission Spectra of Highly Oriented Pyrolytic Graphite

The interest in van der Waals materials is associated with their unique physical and chemical properties and prospects for technological applications. In this work, the object of study is highly oriented pyrolytic graphite as a model of such materials. The results of measurements by angle-resolved X-ray photoelectron spectroscopy are presented. The experiments are performed at detection angles of 0°, 60°, 80°, and 85° from the normal to the sample surface, which makes it possible to localize the signal produced by the upper layer of highly oriented pyrolytic graphite as much as possible. A method for reconstructing the differential cross section of inelastic electron energy losses from experimental X-ray photoelectron spectra is presented. Using this method, the differential cross section of inelastic electron scattering in highly oriented pyrolytic graphite is reconstructed at each detection angle. The obtained cross sections are compared with the cross sections reconstructed for graphene with a varying number of layers. The determining influence of collective plasmon electron energy losses on the formation of the energy loss spectrum in heterogeneous van der Waals materials is indicated.