Issue 19, 2023

Structural, optical and transport properties of layered europium disulfide synthesized under high pressure

Abstract

Materials readily forming stacks down to monolayer thickness and simultaneously possessing a finite bandgap are highly attractive from both fundamental and applied points of view. In this work, high-quality single-crystal samples of a novel layered compound, europium disulfide (EuS2), were synthesized under high-temperature–high-pressure conditions and characterized by complementary methods. According to single-crystal X-ray diffraction, the compound crystallizes in a monoclinic structure (space group P21/a). Flakes down to 1–2 nm thick can be obtained by mechanical exfoliation; the angular dependence of the polarized Raman intensity allows determination of the flakes' orientation. Infrared spectra demonstrate a rich structure in a broad energy range, possibly arising from excitonic effects and interatomic transitions in Eu ions. Measurements of the Seebeck coefficient and ab initio modeling show that the material is a p-type semiconductor with a 0.9 eV indirect bandgap. At low temperatures, electrical conductivity follows Mott's law, implying the presence of defects, possibly related to the disordering of covalent S–S bonds.

Graphical abstract: Structural, optical and transport properties of layered europium disulfide synthesized under high pressure

Supplementary files

Article information

Article type
Paper
Submitted
09 Dec 2022
Accepted
06 Apr 2023
First published
12 Apr 2023

CrystEngComm, 2023,25, 2966-2978

Structural, optical and transport properties of layered europium disulfide synthesized under high pressure

E. A. Ekimov, S. N. Nikolaev, A. G. Ivanova, V. A. Sidorov, A. A. Shiryaev, I. I. Usmanov, A. L. Vasiliev, V. V. Artemov, M. V. Kondrin, M. A. Chernopitsskiy and V. S. Krivobok, CrystEngComm, 2023, 25, 2966 DOI: 10.1039/D2CE01647H

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