Metallic transition metal dichalcogenides (TMDs) have exhibited various exotic physical properties and hold the promise of novel optoelectronic and topological devices applications. However, the synthesis of metallic TMDs is based on gas-phase methods and requires high-temperature condition. As an alternative to the gas-phase synthetic approach, lower temperature eutectic liquid-phase synthesis presents a very promising approach with the potential for larger-scale and controllable growth of high-quality thin metallic TMD single crystals. Here, the first realization of low-temperature eutectic liquid-phase synthesis of type-II Dirac semimetal PtTe 2 single crystals with thickness ranging from 2 to 200 nm is presented. The electrical measurement of synthesized PtTe 2 reveals a record-high conductivity of as high as 3.3 × 10 6 S m −1 at room temperature. Besides, the weak antilocalization behavior is identified experimentally in the type-II Dirac semimetal PtTe 2 for the first time. Furthermore, a simple and general strategy is developed to obtain atomically thin PtTe 2 crystal by thinning as-synthesized bulk samples, which can still retain highly crystalline and exhibits excellent electrical conductivity. The results of controllable and scalable low-temperature eutectic liquid-phase synthesis and layer-by-layer thinning of high-quality thin PtTe 2 single crystals offer a simple and general approach for obtaining different thickness metallic TMDs with high meltingpoint transition metal.

Recent studies have found that some transition metal dichalcogenides (TMDs) with their own defects are difficult to store in the air for a long time. Worse stability of TMDs under extreme conditions has also been reported. Therefore, monitoring the oxidation and degradation processes of TMDs can directly guide the stability prediction of TMD-based devices and monitor TMDs quality. Herein, with the case of molybdenum disulfide, UV–ozone defect engineering is used to simulate the oxidation and degradation of TMDs under severe conditions. Surface-enhanced Raman scattering based on a chemical mechanism was first introduced to the dynamic monitoring of defect evolution in the oxidation and degradation of TMDs, and succeeds in tracking the TMDs oxidation state by the quantitative method. It is expected that this technology can be extended to the quantification and tracking of oxidation and degradation of other 2D materials.

Multiaxial molecular ferroelectrics (MFe) attain great attention due to their number of equivalent ferroelectric axes, an essential characteristic for many applications of these polar polycrystalline materials. Here we report a systematic approach to reveal the temperature‐dependent Raman spectroscopic investigation of the vibrational properties of a [Hdabco]ReO4 (dabco = 1,4‐diazabicyclo[2.2.2]octane), a multiaxial MFe thin film. The Raman spectra allowed to obtain information relative to the change in molecular symmetry governed by the order–disorder phase transition. This phase transition is manifested by the temperature‐dependent peak shift, full width half maximum and intensity of distinct vibrational modes. The experimental observation reveals that ferroelectric phase transition is mainly driven by the reorientation motion of the ReO4− anions and monopronated dabco cations. Hence, we demonstrated that the Raman spectroscopy is a very useful tool to characterize the newly emerged MFe system.