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Title: Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide

First-principles density-functional theory (DFT) calculations are used to study the atomistic structure, structural energetics, and electron density near the O monovacancy (VOn; n=0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta2O5) and also at vacuum and metallic Ta interfaces. We calculate multivariate vacancy formation energies to evaluate stability as a function of oxidation state, distance from interface plane, and Fermi energy. VOn of all oxidation states preferentially segregate at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta2O5, VO0 are characterized by structural contraction and electron density localization, while VO2+ promote structural expansion and are depleted of electron density. In contrast, interfacial VO0 and VO2+ show nearly indistinguishable ionic and electronic signatures indicative of a reduced VO center. Interfacial VO2+ extract electron density from metallic Ta indicating VO2+ is spontaneously reduced at the expense of the metal. This oxidation/reduction behavior suggests careful selection and processing of both oxide layer and metal electrodes for engineering memristor device operation.
Authors:
 [1] ;  [1]
  1. Sandia National Laboratories (SNL), Albuquerque, NM (United States)
Publication Date:
OSTI Identifier:
1184499
Report Number(s):
SAND--2014-18988J
Journal ID: ISSN 0021-8979; JAPIAU; 540613
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 117; Journal Issue: 8; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Research Org:
Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS