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Issue 40, 2018
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Nonstoichiometry, structure, and properties of Ba1−xTiOy thin films

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Abstract

The effects of growth conditions on the chemistry, structure, electrical leakage, dielectric response, and ferroelectric behavior of Ba1−xTiOy thin films are explored. Although single-phase, coherently-strained films are produced in all cases, small variations in the laser fluence during pulsed-laser deposition growth result in films with chemistries ranging from BaTiO3 to Ba0.93TiO2.87. As the laser fluence increases, the films become more barium deficient and the out-of-plane lattice parameter expands (as much as 5.4% beyond the expected value for Ba0.93TiO2.87 films). Stoichiometric BaTiO3 films are found to be three orders of magnitude more conducting than Ba0.93TiO2.87 films and the barium-deficient films exhibit smaller low-field permittivity, lower loss tangents, and higher dielectric maximum temperatures. Although large polarization is observed in all cases, large built-in potentials (shifted loops) and hysteresis-loop pinching are present in barium-deficient films – suggesting the presence of defect dipoles. The effects of these defect dipoles on ferroelectric hysteresis are studied using first-order reversal curves. Temperature-dependent current–voltage and deep-level transient spectroscopy studies reveal at least two defect states, which grow in concentration with increasing deficiency of both barium and oxygen, at ∼0.4 eV and ∼1.2 eV above the valence band edge, which are attributed to Image ID:c8tc02725k-t1.gif defect–dipole complexes and Image ID:c8tc02725k-t2.gif defect states, respectively. The defect states can also be removed via ex post facto processing. Such work to understand and control defects in this important material could provide a pathway to enable better control over its properties and highlight new avenues to manipulate functions in these complex materials.

Graphical abstract: Nonstoichiometry, structure, and properties of Ba1−xTiOy thin films

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Publication details

The article was received on 04 Jun 2018, accepted on 07 Sep 2018 and first published on 10 Sep 2018


Article type: Paper
DOI: 10.1039/C8TC02725K
Citation: J. Mater. Chem. C, 2018,6, 10751-10759
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    Nonstoichiometry, structure, and properties of Ba1−xTiOy thin films

    A. Dasgupta, S. Saremi, X. Ruijuan, L. R. Dedon, S. Pandya, A. R. Damodaran and L. W. Martin, J. Mater. Chem. C, 2018, 6, 10751
    DOI: 10.1039/C8TC02725K

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