skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Evidence of Eu{sup 2+} 4f electrons in the valence band spectra of EuTiO{sub 3} and EuZrO{sub 3}

Abstract

We report on optical band gap and valence electronic structure of two Eu{sup 2+}-based perovskites, EuTiO{sub 3} and EuZrO{sub 3} as revealed by diffuse optical scattering, electron energy loss spectroscopy, and valence-band x-ray photoelectron spectroscopy. The data show good agreement with the first-principles studies in which the top of the valence band structure is formed by the narrow Eu 4f{sup 7} electron band. The O 2p band shows the features similar to those of the Ba(Sr)TiO{sub 3} perovskites except that it is shifted to higher binding energies. Appearance of the Eu{sup 2+} 4f{sup 7} band is a reason for narrowing of the optical band gap in the title compounds as compared to their Sr-based analogues.

Authors:
 [1];  [2];  [3]; ;  [4];  [5];  [6]
  1. National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)
  2. Materials Research Laboratory, University of Nova Gorica, Vipavska 13, 5000 Nova Gorica (Slovenia)
  3. International Center for Young Scientists (ICYS), MANA, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)
  4. Department of Materials Science and Engineering, McMaster University, Hamilton, Ontario L8S 4L7 (Canada)
  5. International Center for Materials Nanoarchitectonics, MANA, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)
  6. National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan)
Publication Date:
OSTI Identifier:
22089496
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 112; Journal Issue: 8; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; BINDING ENERGY; ELECTRONIC STRUCTURE; ENERGY-LOSS SPECTROSCOPY; EUROPIUM COMPOUNDS; LIGHT SCATTERING; PEROVSKITES; SPECTRA; TITANATES; TITANIUM OXIDES; X-RAY PHOTOELECTRON SPECTROSCOPY; ZIRCONATES

Citation Formats

Kolodiazhnyi, T., Valant, M., Williams, J. R., Bugnet, M., Botton, G. A., Ohashi, N., and Sakka, Y.. Evidence of Eu{sup 2+} 4f electrons in the valence band spectra of EuTiO{sub 3} and EuZrO{sub 3}. United States: N. p., 2012. Web. doi:10.1063/1.4761933.
Kolodiazhnyi, T., Valant, M., Williams, J. R., Bugnet, M., Botton, G. A., Ohashi, N., & Sakka, Y.. Evidence of Eu{sup 2+} 4f electrons in the valence band spectra of EuTiO{sub 3} and EuZrO{sub 3}. United States. doi:10.1063/1.4761933.
Kolodiazhnyi, T., Valant, M., Williams, J. R., Bugnet, M., Botton, G. A., Ohashi, N., and Sakka, Y.. 2012. "Evidence of Eu{sup 2+} 4f electrons in the valence band spectra of EuTiO{sub 3} and EuZrO{sub 3}". United States. doi:10.1063/1.4761933.
@article{osti_22089496,
title = {Evidence of Eu{sup 2+} 4f electrons in the valence band spectra of EuTiO{sub 3} and EuZrO{sub 3}},
author = {Kolodiazhnyi, T. and Valant, M. and Williams, J. R. and Bugnet, M. and Botton, G. A. and Ohashi, N. and Sakka, Y.},
abstractNote = {We report on optical band gap and valence electronic structure of two Eu{sup 2+}-based perovskites, EuTiO{sub 3} and EuZrO{sub 3} as revealed by diffuse optical scattering, electron energy loss spectroscopy, and valence-band x-ray photoelectron spectroscopy. The data show good agreement with the first-principles studies in which the top of the valence band structure is formed by the narrow Eu 4f{sup 7} electron band. The O 2p band shows the features similar to those of the Ba(Sr)TiO{sub 3} perovskites except that it is shifted to higher binding energies. Appearance of the Eu{sup 2+} 4f{sup 7} band is a reason for narrowing of the optical band gap in the title compounds as compared to their Sr-based analogues.},
doi = {10.1063/1.4761933},
journal = {Journal of Applied Physics},
number = 8,
volume = 112,
place = {United States},
year = 2012,
month =
}
  • The chemical composition and band alignment at the heterointerface between atomic layer deposition-grown zinc oxide (ZnO) and hydrogenated amorphous silicon (a-Si:H) is investigated using monochromatized X-ray photoelectron spectroscopy. A new approach for obtaining the valence band offset ΔE{sub V} is developed, which consists in fitting the valence band (VB) spectrum obtained for a-Si:H with a thin ZnO overlayer as the sum of experimentally obtained VB spectra of a bulk a-Si:H film and a thick ZnO film. This approach allows obtaining ΔE{sub V} = 2.71 ± 0.15 eV with a minimum of assumptions, and also yields information on the change in band bending of both substratemore » and ZnO film. The band offset results are compared to values obtained using the usual approach of comparing valence band edge-to-core level energy differences, ΔE{sub B,CL} − ΔE{sub B,VB}. Furthermore, a theoretical value for the VB offset is calculated from the concept of charge neutrality level line-up, using literature data for the charge neutrality levels and the experimentally determined ZnO/a-Si:H interface dipole. The thus obtained value of ΔE{sub V}{sup CNL} = 2.65 ± 0.3 eV agrees well with the experimental ΔE{sub V}.« less
  • Phase-pure, stoichiometric, unstrained, epitaxial (001)-oriented EuTiO{sub 3} thin films have been grown on (001) SrTiO{sub 3} substrates by reactive molecular-beam epitaxy. Magnetization measurements show antiferromagnetic behavior with T{sub N}=5.5 K, similar to bulk EuTiO{sub 3}. Spectroscopic ellipsometry measurements reveal that EuTiO{sub 3} films have a direct optical band gap of 0.93{+-}0.07 eV.
  • A quantitative scale of ionicity based on x-ray photoemission studies of the valence-band density of states of many A/sup N/B/sup 8-N/ and A/sup N/B/sup 10-N/ crystals is discussed. The scale is empirical. It involves allocating the energy splitting of the two most tightly bound valence-band peaks between covalent and ionic contributions. Several ternary alloys and chalcopyrite-type crystals were also included in this study. The scale was found to be superior to the molecular orbital approach of Coulson and the thermochemical scale of Pauling because of the symmetrical treatment of covalent and ionic contributions. It appears to have wider applicability thanmore » the Phillips-Van Vechten scale. The strengths and weaknesses of the proposed scale are discussed. 44 references, 5 figures, 3 tables.« less
  • Acetylene adsorbs dissociatively on the ZnO(0001) surface, as on other metal oxides, to form acetylide intermediates, CCH. Propyne also dissociates via surface acid-base reactions; however, potential adsorbates include methylacetylide (CH{sub 3}CC) and propargyl (CH{sub 2}CCH) species. Ultraviolet photoelectron spectra (UPS) of the adsorbed intermediates formed from propyne and allene on the ZnO(0001) surface demonstrate that both react to form propargyl intermediates. UPS also provide useful fingerprints of {sigma}-bonded acetylides on both metal and metal oxide surfaces.