Two-Dimensional Noble-Metal Chalcogenides and Phosphochalcogenides

Abstract

Noble-metal chalcogenides, dichalcogenides, and phosphochalcogenides are an emerging class of two-dimensional materials. Quantum confinement (number of layers) and defect engineering enables their properties to be tuned over a broad range, including metal-to-semiconductor transitions, magnetic ordering, and topological surface states. They possess various polytypes, often of similar formation energy, which can be accessed by selective synthesis approaches. They excel in mechanical, optical, and chemical sensing applications, and feature long-term air and moisture stability. In this Minireview, we summarize the recent progress in the field of noble-metal chalcogenides and phosphochalcogenides and highlight the structural complexity and its impact on applications.

Keywords: Raman spectroscopy; density functional calculations; noble-metal dichalcogenides; sensors; two-dimensional materials.

Figure 1

Overview of the main structural prototypes of the NM(D/P)Cs. Commonly used abbreviations, the space group (SG), and the SG number (#) are given in parentheses. Structures are shown along the directions indicated in brackets. Possible means to achieve phase transitions are shown with arrows.

Figure 2

Structural relationships between the PdS₂ and PdPS structures. The CdI₂ prototype can be transformed via the pyrite‐type to the PdS₂‐type structure, and the pyrite structure is the parent for the PdPS structure. Note that the PdPS structure consists of six atomic layers, two of them are connected by phosphorus bonds. Layers that are antisymmetric with respect to each other are indicated with an asterisk (*).

Figure 3

A) Relationship of the 1t prototype to the marcasite prototype, B) relationship of the marcasite prototype to the pyrite structure, and C) relationship of the verbeekite and 1T structures.

Figure 4

Calculated Raman spectra and band structures for monolayer (ML), bilayer (BL), and bulk polymorphs of some exemplary layered NM(D/P)Cs.