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Title: Role of oxygen vacancies on light emission mechanisms in SrTiO 3 induced by high-energy particles

Light emission under MeV hydrogen and oxygen ions in stoichiometric SrTiO 3 are identified at temperatures of 100 K, 170 K and room-temperature. MeV ions predominately deposit their energies to electrons in SrTiO 3 with energy densities orders of magnitude higher than from UV or x-ray sources but comparable to femtosecond lasers. The ionoluminescence (IL) spectra can be resolved into three main Gaussian bands at 2.0 eV, 2.5 eV and 2.8 eV, whose relative contributions strongly depend on irradiation temperature, electronic energy loss and irradiation fluence. Two main bands, observed at 2.5 eV and 2.8 eV, are intrinsic and associated with electron–hole recombination in the perfect SrTiO 3 lattice. The 2.8 eV band is attributed to recombination of free (conduction) electrons with an in-gap level, possibly related to self-trapped holes. Self-trapped excitons (STEs) are considered suitable candidates for the 2.5 eV emission band, which implies a large energy relaxation in comparison to the intrinsic edge transition. The dynamics of electronic excitation, governs a rapid initial rise of the intensity; whereas, accumulated irradiation damage (competing non-radiative recombination channels) accounts for a subsequent intensity decrease. The previously invoked role of isolated oxygen vacancies for the blue luminescence (2.8 eV) does not appearmore » consistent with the data. An increasing well-resolved band at 2.0 eV dominates at 170 K and below. It has been only previously observed in heavily strained and amorphous SrTiO 3, and is, here, attributed to transitions from d(t 2g) conduction band levels to d(e g) levels below the gap. In accordance with ab initio theoretical calculations they are associated to trapped electron states in relaxed Ti 3+ centers at an oxygen vacancy within distorted TiO 6 octahedra. The mechanism of defect evolution monitored during real-time IL experiments is presented. In conclusion, the light emission data confirm that IL is a useful tool to investigate lattice disorder in irradiated SrTiO 3.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4]
  1. Univ. of Tennessee, Knoxville, TN (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States); Missouri Univ. of Science and Technology, Rolla, MO (United States)
  3. Centro de Microanalisis de Materiales, Madrid (Spain)
  4. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Journal of Physics. D, Applied Physics
Additional Journal Information:
Journal Volume: 50; Journal Issue: 15; Journal ID: ISSN 0022-3727
Publisher:
IOP Publishing
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; Luminescence; SrTiO3; Ion irradiation; Oxygen vacancies
OSTI Identifier:
1348342

Crespillo, M. L., Graham, J. T., Agulló-López, F., Zhang, Y., and Weber, W. J.. Role of oxygen vacancies on light emission mechanisms in SrTiO3 induced by high-energy particles. United States: N. p., Web. doi:10.1088/1361-6463/aa627f.
Crespillo, M. L., Graham, J. T., Agulló-López, F., Zhang, Y., & Weber, W. J.. Role of oxygen vacancies on light emission mechanisms in SrTiO3 induced by high-energy particles. United States. doi:10.1088/1361-6463/aa627f.
Crespillo, M. L., Graham, J. T., Agulló-López, F., Zhang, Y., and Weber, W. J.. 2017. "Role of oxygen vacancies on light emission mechanisms in SrTiO3 induced by high-energy particles". United States. doi:10.1088/1361-6463/aa627f. https://www.osti.gov/servlets/purl/1348342.
@article{osti_1348342,
title = {Role of oxygen vacancies on light emission mechanisms in SrTiO3 induced by high-energy particles},
author = {Crespillo, M. L. and Graham, J. T. and Agulló-López, F. and Zhang, Y. and Weber, W. J.},
abstractNote = {Light emission under MeV hydrogen and oxygen ions in stoichiometric SrTiO3 are identified at temperatures of 100 K, 170 K and room-temperature. MeV ions predominately deposit their energies to electrons in SrTiO3 with energy densities orders of magnitude higher than from UV or x-ray sources but comparable to femtosecond lasers. The ionoluminescence (IL) spectra can be resolved into three main Gaussian bands at 2.0 eV, 2.5 eV and 2.8 eV, whose relative contributions strongly depend on irradiation temperature, electronic energy loss and irradiation fluence. Two main bands, observed at 2.5 eV and 2.8 eV, are intrinsic and associated with electron–hole recombination in the perfect SrTiO3 lattice. The 2.8 eV band is attributed to recombination of free (conduction) electrons with an in-gap level, possibly related to self-trapped holes. Self-trapped excitons (STEs) are considered suitable candidates for the 2.5 eV emission band, which implies a large energy relaxation in comparison to the intrinsic edge transition. The dynamics of electronic excitation, governs a rapid initial rise of the intensity; whereas, accumulated irradiation damage (competing non-radiative recombination channels) accounts for a subsequent intensity decrease. The previously invoked role of isolated oxygen vacancies for the blue luminescence (2.8 eV) does not appear consistent with the data. An increasing well-resolved band at 2.0 eV dominates at 170 K and below. It has been only previously observed in heavily strained and amorphous SrTiO3, and is, here, attributed to transitions from d(t 2g) conduction band levels to d(e g) levels below the gap. In accordance with ab initio theoretical calculations they are associated to trapped electron states in relaxed Ti3+ centers at an oxygen vacancy within distorted TiO6 octahedra. The mechanism of defect evolution monitored during real-time IL experiments is presented. In conclusion, the light emission data confirm that IL is a useful tool to investigate lattice disorder in irradiated SrTiO3.},
doi = {10.1088/1361-6463/aa627f},
journal = {Journal of Physics. D, Applied Physics},
number = 15,
volume = 50,
place = {United States},
year = {2017},
month = {2}
}