Electronic Origin of Defect States in Fe-Doped LiNbO3 Ferroelectrics

We investigate the role of Fe in the electronic structure of ferroelectric LiNbO3 by density-functional theory calculations. We show that Fe2+ on the Li site (Fe2+Li) features a displacement opposite to the direction of spontaneous polarization and acts as a trigger for the bulk photovoltaic (PV) ef...

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Bibliographic Details
Published inAdvances in condensed matter physics Vol. 2016; no. 2016; pp. 1 - 10
Main Authors Noguchi, Yuji, Miyayama, Masaru, Inoue, Ryotaro
Format Journal Article
LanguageEnglish
Published Cairo, Egypt Hindawi Publishing Corporation 01.01.2016
Hindawi Limited
Wiley
Subjects
Defects
Electronics
Ferroelectric materials
Ferroelectrics
Lithium
Optics
Orbitals
Photovoltaic cells
Reduction
Solar cells
Studies
Values
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Summary:We investigate the role of Fe in the electronic structure of ferroelectric LiNbO3 by density-functional theory calculations. We show that Fe2+ on the Li site (Fe2+Li) features a displacement opposite to the direction of spontaneous polarization and acts as a trigger for the bulk photovoltaic (PV) effect. In contrast to Fe3+ on the Li site that forms the defect states (1e, a, and 2e) below the conduction band minimum, the reduction from Fe3+ to Fe2+ accompanied by a lattice relaxation markedly lowers only the a state (dz2) owing to a strong orbital hybridization with Nb-4d. The a state of Fe2+Li provides the highest electron-occupied defect state in the middle of the band gap. A reduction treatment of Fe-LN is expected to increase the concentration of Fe2+ and therefore to enhance the PV effect under visible light illumination.
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ISSN:1687-8108
1687-8124
DOI:10.1155/2016/2943173