Optical spectroscopy and band gap analysis of hybrid improper ferroelectric Ca3Ti2O7

We bring together optical absorption spectroscopy, photoconductivity, and first principles calculations to reveal the electronic structure of the room temperature ferroelectric Ca3Ti2O7. The 3.94 eV direct gap in Ca3Ti2O7 is charge transfer in nature and noticeably higher than that in CaTiO3 (3.4 eV...

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Bibliographic Details
Published in:Applied physics letters 2016-06, Vol.108 (26)
Main Authors: Cherian, Judy G., Birol, Turan, Harms, Nathan C., Gao, Bin, Cheong, Sang-Wook, Vanderbilt, David, Musfeldt, Janice L.
Format: Article
Language:English
Subjects:
Applied physics
Calcium titanate
Charge transfer
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
Electronic structure
Ferroelectric materials
Ferroelectricity
First principles
Photoconductivity
Spectrum analysis
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Summary:We bring together optical absorption spectroscopy, photoconductivity, and first principles calculations to reveal the electronic structure of the room temperature ferroelectric Ca3Ti2O7. The 3.94 eV direct gap in Ca3Ti2O7 is charge transfer in nature and noticeably higher than that in CaTiO3 (3.4 eV), a finding that we attribute to dimensional confinement in the n = 2 member of the Ruddlesden-Popper series. While Sr substitution introduces disorder and broadens the gap edge slightly, oxygen deficiency reduces the gap to 3.7 eV and gives rise to a broad tail that persists to much lower energies.
ISSN:0003-6951
1077-3118
DOI:10.1063/1.4954404