Highly Polarizable Semiconductors and Universal Origin of Ferroelectricity in Materials with a Litharge-Type Structural Unit

Ziye Zhu; Jiaming Hu; Yubo Yuan; Hua Wang; Xiao Lin; Wenbin Li

doi:10.1021/acs.nanolett.5c00569

paper

Highly Polarizable Semiconductors and Universal Origin of Ferroelectricity in Materials with a Litharge-Type Structural Unit

arXiv:2412.11577 · doi:10.1021/acs.nanolett.5c00569

Abstract

We discover that a large family of [Pb $_{2}$ F $_{2}$ ]- and [Bi $_{2}$ O $_{2}$ ]-based mixed-anion materials with a litharge-type structural unit are highly polarizable layered semiconductors on the edge of ferroelectricity. First-principles calculations demonstrate that in this family of materials, compounds as diverse as PbFBr, BiOCl, BiCuOSe, Bi $_{2}$ OS $_{2}$ , and Bi $_{5}$ O $_{4}$ S $_{3}$ Cl exhibit static dielectric constants an order of magnitude higher than typical semiconductors. Additionally, they undergo a ferroelectric transition when subjected to a few percent of tensile strain. The ferroelectric transitions of these materials are found to have a universal origin in the strong cross-bandgap hybridization of the cation $p$ orbitals, enabled by the cation 6s $^{2}$ lone-pair electrons and the litharge-type structure of the [Pb $_{2}$ F $_{2}$ ] and [Bi $_{2}$ O $_{2}$ ] layers, as demonstrated by the strain-induced ferroelectric transition in the archetypal litharge $I^\pm$ -PbO. These results establish materials with a litharge-type structural unit as a large and versatile family of highly polarizable layered semiconductors in proximity to ferroelectricity, offering vast opportunities for multifunctional materials design.

7 pages, 3 figures