A computational search for wurtzite-structured ferroelectrics with low coercive voltages

Hiroki Moriwake, Rie Yokoi, Ayako Taguchi, Takafumi Ogawa, Craig A.J. Fisher, Akihide Kuwabara, Yukio Sato, Takao Shimizu, Yosuke Hamasaki, Hiroshi Takashima, Mitsuru Itoh

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    1 Citation (Scopus)

    Abstract

    Ferroelectricity has recently been observed in wurtzite-structured Sc-doped AlN thin films, five years after our initial prediction of ferroelectricity in wurtzite compounds based on first-principles calculations. The thin films exhibited a much higher coercive voltage (3 MV/cm) than that of conventional perovskite-structured ferroelectric material PbTiO3, however, making it difficult to switch the films' polarity and limiting their practical application. To identify tetrahedral ferroelectric materials with low coercive voltages, we have carried out a wider exploration of candidate binary compounds, from halides to chalcogenides to pnictogenides, using first-principles methods. The overall trend is for polarization switching barriers to decrease with decreasing anion-To-cation radius ratio, with the lowest barriers found in monovalent compounds such as the copper and silver halides; e.g., CuCl is calculated to have a switching barrier of 0.17 eV/f.u. and that of AgI is 0.22 eV/f.u., values similar in magnitude to that of PbTiO3 (0.20 eV/f.u.). Applying an epitaxial tensile strain to the basal plane is also effective for lowering the potential barrier further, with barriers in both AgI and CuCl decreasing to 0.04 eV/f.u. when a 5% in-plane expansion is applied. The results suggest that tetrahedral ferroelectrics with moderate coercive voltages (below 100 kV/cm) should be achievable.

    Original languageEnglish
    Article number121102
    JournalAPL Materials
    Volume8
    Issue number12
    DOIs
    Publication statusPublished - Dec 1 2020

    All Science Journal Classification (ASJC) codes

    • Materials Science(all)
    • Engineering(all)

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