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Title: Optical spectroscopy and band gap analysis of hybrid improper ferroelectric Ca 3Ti 2O 7

Here, we bring together optical absorption spectroscopy, photoconductivity, and first principles calculations to reveal the electronic structure of the room temperature ferroelectric Ca 3Ti 2O 7. The 3.94 eV direct gap in Ca 3Ti 2O 7 is charge transfer in nature and noticeably higher than that in CaTiO 3 (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.
Authors:
 [1] ; ORCiD logo [2] ;  [1] ;  [2] ;  [2] ; ORCiD logo [2] ;  [1]
  1. Univ. of Tennessee, Knoxville, TN (United States)
  2. The State Univ. of New Jersey, Piscataway, NJ (United States)
Publication Date:
Grant/Contract Number:
FG02-01ER45885
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 108; Journal Issue: 26; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Univ. of Tennessee, Knoxville, TN (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
OSTI Identifier:
1467576
Alternate Identifier(s):
OSTI ID: 1259373