• transition metal oxides;
  • density function theory;
  • electronic structures;
  • resistive memories;
  • defects;
  • Ta2O5;
  • polymorphs


Thumbnail image of graphical abstract

The structures and electronic properties of Ta2O5 polymorphs were calculated using density-functional theory employing the generalized gradient approximation with on-site Coulomb corrections. Using this approach, a pseudo-hexagonal structure was found to be a stable polymorph of Ta2O5 over δ- and β-Ta2O5 and metastable relative to other recently proposed structures. Its diffraction spectrum and bandgap energy are in good agreement with experimental data. Therefore, the pseudo-hexagonal structure might form in polycrystalline films and affect the switching process of resistive memory devices. Moreover, a neutral oxygen vacancy is found to induce an occupied defect state at 2.5 eV above the top of the valence band, in agreement with X-ray photoelectron spectroscopy results. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)