Prediction of Intrinsic Ferroelectricity and Large Piezoelectricity in Monolayer Arsenic Chalcogenides.
basic_science · Level V
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- Record sourced from PubMed, PMID 33135906.
- Also identified by DOI 10.1021/acs.nanolett.0c03511.
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Abstract
Two-dimensional materials that exhibit spontaneous electric polarization are of notable interest for functional materials. However, despite the prediction of many two-dimensional polar materials, the number of experimentally confirmed two-dimensional ferroelectrics is far less than bulk ferroelectrics. We provide strong evidence that the <i>Pmn</i>2<sub>1</sub> phase of arsenic chalcogenides As<sub>2</sub>X<sub>3</sub> (X = S, Se, and Te), which include the recently isolated monolayer orpiment, are intrinsic ferroelectrics and demonstrate strong in-plane piezoelectricity. We found the calculated energy barriers for collectively reversing the electric polarization or moving a 180° domain wall are reasonable compared to previously reported ferroelectrics. We propose a high-symmetry structure (with <i>Pmmn</i> space group) that transforms into the ferroelectric <i>Pmn</i>2<sub>1</sub> phase by a soft B<sub>2u</sub> phonon mode. By studying other soft modes of the high-symmetry <i>Pmmn</i> structure, we identify several undiscovered metastable polymorphs, including a polar phase (with a <i>P</i>2<sub>1</sub> space group) with sizable piezoelectricity.