Browsing by Subject "Impurity"

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Open Access
Electronic structure of β-Si3N4 crystals with substitutional icosagen group impurities
(National Institute of Optoelectronics, 2017) Kutlu, E.; Narin, P.; Atmaca, G.; Sarıkavak-Lişesivdin, B.; Lişesivdin, S. B.; Özbay, Ekmel
The β-Si3N4 crystals are widely used in industrial and electronics areas. Therefore, β-Si3N4 has drawn the attention of researchers for many years. In this study, effects of icosagen group impurity atoms in the IIIA group on the electronic properties of the β-Si3N4 crystal were analyzed by using the density functional theory. As a result of these analyses, it was determined that the electronic properties of the crystal change significantly. Basic electronic characteristics for pure β-Si3N4 crystal and icosagen group impurity β-Si3N4 crystals, such as band structures, densities of states, binding energies, and formation energies were investigated. We identified that the band gap of the β-Si3N4 crystal was affected significantly by the impurity, and this change was varying linearly in line with the formation energy for the impurity cases. As a result of calculations, the Al-impurity was found to be the lowest-energy impurity state.
Open Access
Magnetic polaritons, magnetostatic waves and effective-medium approximation for antiferromagnetic superlattice with impurity in parallel magnetic field
(Springer, 2012) Tagiyeva, Rehile T.; Tanatar, Bilal
We derive the general effective-medium expression for the surface-guided magnetic polaritons and magnetostatic waves, which propagate in the antiferromagnetic superlattice with antiferromagnetic impurity film, and investigate the influence of the external magnetic field on the energy of localized magnetic polaritons. Similarly as in the free-standing antiferromagnetic film, the spectrum of magnetic polaritons in the presence of an external magnetic field is reciprocal in the sense that the frequency is independent of the direction of propagation. In the system under consideration one finds both the surface polaritons which are strongly localized in the antiferromagnetic film which acts as a waveguide, and waves which are weakly localized within film. The first waves are the pure surface modes or guided modes where excitations have a standing-wavelike character. This important feature of the localized magnetic polaritons enables us to use these antiferromagnetic systems in the technologies for devices (for example, in resonators) that work at wavelengths in the infrared region. Second waves have the very small value of the decay parameter and appear in the regions where the surface mode penetrates into the bulk band, i.e. the magnetic polaritons are weakly localized in the impurity film region. Now we obtain themixed type mode having both bulk and surface characteristics. Also, the general way in which the dispersion curves vary with the volume fraction of the superlattice components and with impurity film is illustrated in this study.