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Title: Investigation of surface defect states in CeO{sub 2-y} nanocrystals by Scanning−tunneling microscopy/spectroscopy and ellipsometry

Synthesis process strongly influences the nanocrystalline CeO{sub 2-y} defective structure. The presence of surface defects, in the form of oxygen vacancies in different charge states (F centers), can change the electronic properties of ceria nanocrystals. Nanocrystalline CeO{sub 2-y} samples were synthesized using three different methods (precipitation, self-propagating room temperature, and hydrothermal synthesis). Raman spectroscopy was used to identify the presence of oxygen vacancies which presumably were formed at the nanoparticle surface. The defect concentration depended on the crystallite size of differently prepared CeO{sub 2-y} samples. Scanning tunneling microscopy/spectroscopy and ellipsometry were employed to investigate the electronic band structure of defective CeO{sub 2-y} nanocrystals. Scanning tunneling spectroscopy measurements demonstrated that inside the band gap of CeO{sub 2-y} nanocrystals, besides the filled 4 f states, appeared additional states which were related to occupied and empty F center defect states. From the ellipsometric measurements, using the critical points model, the energy positions of different F centers states and the values of the reduced band gap energies were determined. The analysis of obtained data pointed out that depending on the synthesis method, different types of F centers (F{sup +} and F{sup 0}) can be formed in the CeO{sub 2-y} nanocrystals. The formation of differentmore » F center defect states inside the ceria gap have a strong impact on the electrical, optical, and magnetic properties of ceria nanocrystals.« less
Authors:
; ; ; ;  [1] ;  [2] ;  [3]
  1. Institute of Physics, Pregrevica 118, University of Belgrade, 11 000 Belgrade (Serbia)
  2. Institute for Nuclear sciences “Vinča,” Materials Science Laboratory, University of Belgrade, 11 000 Belgrade (Serbia)
  3. Institute for Multidisciplinary Research, Kneza Viseslava 1a, University of Belgrade, 11 000 Belgrade (Serbia)
Publication Date:
OSTI Identifier:
22402820
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 23; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CERIUM OXIDES; CHARGE STATES; ELLIPSOMETRY; F CENTERS; F STATES; HYDROTHERMAL SYNTHESIS; MAGNETIC PROPERTIES; NANOSTRUCTURES; OXYGEN; RAMAN SPECTROSCOPY; SCANNING TUNNELING MICROSCOPY; SURFACES; TEMPERATURE RANGE 0273-0400 K; TUNNEL EFFECT