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.

Layer-dependent band engineering of Pd dichalcogenides: a first-principles study

“…Bulk PdS 2 and PdSe 2 exhibit an orthorhombic pyrite phase with an elongated c-axis (figure 1(c)) resulting to a square-planar coordination. Moreover, both have a slightly larger b-axis than a-axis (table 1) leading to a nondegenerate Pd d-orbitals [60]. Hence, PdS 2 and PdSe 2 exhibit similar band characteristics.…”

“…The reason behind the preference of PdTe 2 stable bulk structure to 1T originates from the interplay between oxidation state and charge distribution, which are the key factors to understand the stability of these polymorphs [58]. To demonstrate these phenomena, it is useful to note that Pt-based TMDs have a quadrivalent oxidation state due to the inclusion of f-orbitals, thus exhibiting 1T phase [59,60]. PdX 2 , on the other hand, have a lower divalent oxidation state, which can be achieved by formation of (X 2 ) 2− dimers due to the pairing the chalcogen atoms.…”

“…PdX 2 , on the other hand, have a lower divalent oxidation state, which can be achieved by formation of (X 2 ) 2− dimers due to the pairing the chalcogen atoms. This low oxidation state results to stable pyrite-and marcasite-type structures [60]. Kempt et al [60] have shown that the 1T phase of PdS 2 and PdSe 2 results to a higher oxidation state as compared to the pyrite phase which have a lower oxidation state, thus preferring the pyrite structure.…”

“…This low oxidation state results to stable pyrite-and marcasite-type structures [60]. Kempt et al [60] have shown that the 1T phase of PdS 2 and PdSe 2 results to a higher oxidation state as compared to the pyrite phase which have a lower oxidation state, thus preferring the pyrite structure. Interestingly, they found that the 1T and pyrite phase of PdTe 2 demonstrated no difference in their oxidation states.…”

Electronic and structural characterisation of polycrystalline platinum disulfide thin films

“…14 Due to this versatility, TMDs are poised to play important roles in the elds of electronics, 15 optoelectronics, 16 electrochemical sensors 17 and catalysis, 18 to name but a few. One of the less-explored branches of TMD materials is noble-transition-metal dichalcogenides (NTMDs), 19 , (MX 2 : M ¼ Pt and Pd, and X ¼ S, Se and Te) which are predicted to exhibit different structural and electronic properties in comparison with well-studied MoS 2 . 20,21 One member of the NTMD group is platinum disulde (PtS 2 ), of which ultrathin lms have recently been synthesised.…”