Quantum Chemical Study of Point Defects in Tin Dioxide
First-principles calculations based on the density functional theory (DFT) within the generalized gradient approximation (GGA), and the introduction of intra-atomic interaction term for strongly correlated \(d\) -electrons (DFT+\(U)\) , have been utilized
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Abstract First-principles calculations based on the density functional theory (DFT) within the generalized gradient approximation (GGA), and the introduction of intraatomic interaction term for strongly correlated d-electrons (DFT+U ), have been utilized to study defective SnO2 crystals. Introduction of some impurities, such as fluorine, gallium, aluminium and chromium affect the structural, electronic properties and magnetic properties of tin dioxide. F-doping produces alterations in the structure, with Sn atoms moving away from the impurity and O atoms moving closer to it; and, the system presents n-type electrical conductivity. Ga impurity incorporation distorts its surrounding, with the atoms moving closer to the impurity whereas the electrical properties of crystal remain unchanged. Results for Al impurity doping are almost the same as those for the Ga-doping. Cr presence produces the atoms in the neighbourhood of the point defect to move towards it, the band gap width has been slightly reduced and we observe the occurrence of a local magnetic moment.
R. Rivera (B) · A. Stashans The Grupo de Fisicoquímica de Materiales, Universidad Técnica Particular de Loja, Loja, Ecuador e-mail: [email protected] A. Stashans e-mail: [email protected] F. Marcillo · A. Chamba The Grupo de Fisicoquímica de Materiales, and Escuela de Ingeniería Química, Universidad Técnica Particular de Loja, Loja, Ecuador e-mail: [email protected] A. Chamba e-mail: [email protected] P. Puchaicela The Grupo de Fisicoquímica de Materiales, and Departamento de Geología, Minas e Ingeniería Civil, Universidad Técnica Particular de Loja, Loja, Ecuador e-mail: [email protected] G.-C. Yang et al. (eds.), Transactions on Engineering Technologies, Lecture Notes in Electrical Engineering 275, DOI: 10.1007/978-94-007-7684-5_2, © Springer Science+Business Media Dordrecht 2014
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Keywords DFT+U · Electrical conductivity doping · Microstructure · SnO2 .
R. Rivera et al.
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Electronic properties
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Impurity
1 Introduction Tin dioxide (SnO2 ) is a semiconductor oxide that crystallizes with the rutile structure. It can be described through a tetragonal crystalline lattice that belongs to the space 14 (P4 /mnm), in which tin atoms are in the centre of an almost regular group D4h 2 oxygen octahedron [1, 2]. The primitive unit cell of this material is composed by two formula units (6 atoms), and the lattice parameters are a = 4.74 Å and c = 3.188 Å [1]. The stoichiometric form of SnO2 acts as an insulator, but it usually shows a no stoichiometric form, which contains a high presence of oxygen deficiencies (tin interstitials and oxygen vacancies). These defects are responsible of its behaviour as an n-type semiconductor with a direct band-gap width of 3.6 eV [2]. The formation energy of these intrinsic point defects is reduced [3], being the reason of their high presence in this crystal. Tin dioxide belongs to a certain type of materials that present high electrical conductivity and also a high optical transparency in the visible rang
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