Acoustoemission of Graphite and Graphene

Abstract

In this paper, we propose a model of the acoustic emission mechanism of natural graphite and graphene. The thickness of the surface layer R(I) of graphite varies from 0.9 nm in the parallel to 2.46 nm in the perpendicular plane and contains three graphene monolayers. Corrugations on the surface of free graphene arise due to high internal stresses, leading to significant deformation energy. An estimate of the deformation energy associated with the reconstruction of the surface of graphite and graphene is proposed. We imagine a graphite nanolayer as a potential well with infinitely high walls, then the energy levels of the nanolayer are determined by one fundamental parameter - the lattice constant of the crystal. The lattice constant a changes in the R(I) layer due to size effects. As soon as the parameter a stops changing, the spectrum of quantum states passes into a continuous spectrum, where the classical Drude– Lorentz laws are fulfilled for graphite. Since the surface layer of graphite is a two-dimensional quantum medium, three quantum planes of graphite with a1, a2 and a3 should be considered. The article considers one-, two- and three-layer graphene. The Fermi surface of graphene degenerates into the Dirac point, and the Fermi energy is zero. For two-layer graphene, the Fermi energy is EF = 0.9 eV, and for three-layer graphene - EF = 1.2 eV. Namely, all three quantum levels participate in the acoustic emission of graphite and graphene. In the article, it can be considered proven that in natural graphite (as well as in all solids), acoustic emission occurs due to the reconstruction of its surface, leading to the emergence of a surface layer R(I) and deformation energy Ed. The article proposes a thermoacoustics model that contains only experimentally determined parameters, and their accuracy is quite acceptable.