A metallic CrS$_2$ phase bridging the gap between two- and three-dimensional dichalcogenides

TL;DR

This paper reports the synthesis and structural analysis of a novel CrS₂ phase with a ladder-like structure bridging 2D and 3D dichalcogenides, exhibiting metallic behavior and potential ionic conduction channels.

Contribution

The study introduces a new CrS₂ phase with a unique ladder-type structure confirmed by electron diffraction and DFT calculations, expanding the understanding of dichalcogenide structures.

Findings

Confirmed CrS₂ composition and ladder-like structure via electron diffraction.

DFT calculations indicate strong covalent Cr-S bonds and metallic behavior.

Electrical measurements show resistivity of 2-20 mΩ·cm at 4 K.

Abstract

We report on the high-pressure synthesis of a CrS$_2$ phase in the form of single-crystalline nanorods. A structural refinement of Precession Electron Diffraction Tomography data confirms the nominal CrS$_2$ composition and unveils a ladder-type structure formed by portions of 1T-type CrS$_2$ layers characteristic of two-dimensional (2D) dichalcogenides connected by chains of edge-sharing CrS$_6$ octahedra characteristic of 3D dichalcogenides with marcasite structure. Ab initio density functional theory calculations of the relaxed structure confirm the stability of this structure and indicate a strong overlap of the 3d states of Cr with the 3p states of S, thus suggesting strong covalent Cr-S bonds and metallic behavior. Electrical resistivity, $\varrho$, measurements on single nanorods confirm this behavior and yield $\varrho \sim 2-20$ m$\Omega$ cm at 4 K. The proposed ladder-like structure of CrS$_2$ forms open channels along the chain direction, which may be suitable for ionic conduction.