Recent Progress on 2D Noble‐Transition‐Metal Dichalcogenides

Abstract

Emerging classes of 2D noble-transition-metal dichalcogenides (NTMDs) stand out for their unique structure and novel physical properties in recent years. With the nearly full occupation of the d orbitals, 2D NTMDs are expected to be more attractive due to the unique interlayer vibrational behaviors and largely tunable electronic structures compared to most transition metal dichalcogenide semiconductors. The novel properties of 2D NTMDs have stimulated various applications in electronics, optoelectronics, catalysis, and sensors. Here, the latest development of 2D NTMDs are reviewed from the perspective of structure characterization, preparation, and application. Based on the recent research, the conclusions and outlook for these rising 2D NTMDs are presented.Very recently, group-10 noble TMDs (NTMDs) have been reintroduced as new 2D materials, displaying many fascinating properties including widely tunable bandgap, moderate carrier mobility, anisotropy, and ultrahigh air stability. [34][35][36][37] Unlike most common TMDs with less d-electrons, the d orbitals of NTMDs are nearly fully occupied, and the corresponding p z orbital of interlayer chalcogen atoms are highly hybridized, leading to strong layer-dependent properties and interlayer interactions. [36,38] For example, it has been predicted that PtS 2 holds a layerdependent bandgap from 0.25 to 1.6 eV, [36] bridging the gap between graphene and most TMDs that with large gap. Besides, the calculated mobility based on PtS 2 , PtSe 2 , and PdSe 2 field effect transistors (FETs) is as high as ≈200 cm 2 V −1 s −1 , [36,37,39] larger than most other TMDs. Moreover, NTMDs possess high air stability, and the performance of the PtSe 2 FET remains nearly unchanged after 5 months air exposure. [37] Specially, PdS 2 and PdSe 2 hold novel puckered pentagonal structure and thus exhibit very interesting anisotropic properties, [39,40] which may bring even more physics and applications. Additionally, PtTe 2 and PdTe 2 are type-II Dirac fermions, making them great platform for investigating novel transport related to topological phase transition and chiral anomaly. [41,42] Nowadays, the 2D NTMDs is becoming increasingly fascinating in the 2D materials research.In this review, we highlight a comprehensive report of the recent research progress in 2D NTMDs such as PtS 2 , PtSe 2 , PdS 2 , PdSe 2 , PtTe 2 , and PdTe 2 . In order to understand the internal relation between structural characteristics and physical properties, this review begins with a brief summary of the structure of 2D NTMDs and their transitions. Then, some recent progress on their preparation methods, including mechanical exfoliation of the bulk materials, chemical vapor deposition (CVD), molecular beam epitaxy (MBE), is reviewed along with the performance of the resulting 2D NTMDs as high-performance candidate for field effect transistors, photodetectors, catalysis, and sensors. Finally, this review is concluded with the existing challenges and a future perspective for these rising 2D NTMDs. Structure of 2D NTM...

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