Electronic Structure of Tin Dioxide Thin Films

The electronic structure of tin dioxide (001) nanofilms in a wide range of thicknesses has been modeled by the method of linearized coupled plane waves in the framework of the density functional theory in the generalized gradient approximation. The spectra of the total and local partial densities of electronic states characterizing the electronic structure of atoms spread out in various layers of the films under consideration are calculated. It is shown that the influence of the surface leads to the appearance of energy features of the density of states localized in the bang gap. A model describing the layered transformation of the electronic structure during the transition from the surface to the volume of the crystal SnO₂ is proposed. A film (001) with a thickness of 8 elementary cells for SnO₂ is considered as a model object. It is found that the surface electronic states arising in the band gap in SnO₂(001) films are spatially strongly localized – their density drops to almost zero by the third atomic layer from the surface. The applicability of the combined use of the layered superlattice method and the core hole method for modeling X-ray absorption spectra in nanofilms is considered. It is established that when calculating the XANES spectra for atoms in the surface layer of SnO₂ nanofilms, the influence exerted by the surface is significantly greater than the influence exerted by the core hole. Therefore, when calculating the XANES spectra for atoms in the surface layer of nanofilms, the core hole can be neglected in the first approximation.