Deep electron and hole polarons and bipolarons in amorphous oxide

Moloud Kaviani, Jack Strand, Valery V. Afanas'Ev, Alexander L. Shluger

    Research output: Contribution to journalArticle

    28 Citations (Scopus)

    Abstract

    Amorphous (a)-HfO2 is a prototype high dielectric constant insulator with wide technological applications. Using ab initio calculations we show that excess electrons and holes can trap in a-HfO2 in energetically much deeper polaron states than in the crystalline monoclinic phase. The electrons and holes localize at precursor sites, such as elongated Hf-O bonds or undercoordinated Hf and O atoms, and the polaronic relaxation is amplified by the local disorder of amorphous network. Single electron polarons produce states in the gap at ∼2 eV below the bottom of the conduction band with average trapping energies of 1.0 eV. Two electrons can form even deeper bipolaron states on the same site. Holes are typically localized on undercoordinated O ions with average trapping energies of 1.4 eV. These results advance our general understanding of charge trapping in amorphous oxides by demonstrating that deep polaron states are inherent and do not require any bond rupture to form precursor sites.

    Original languageEnglish
    Article number020103
    JournalPhysical Review B
    Volume94
    Issue number2
    DOIs
    Publication statusPublished - 2016 Jul 21

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics

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  • Cite this

    Kaviani, M., Strand, J., Afanas'Ev, V. V., & Shluger, A. L. (2016). Deep electron and hole polarons and bipolarons in amorphous oxide. Physical Review B, 94(2), [020103]. https://doi.org/10.1103/PhysRevB.94.020103