Stabilization of the Nano-Sized 1T Phase through Rhenium Doping in the Metal-Organic CVD MoS2 Films

Coexisting Phases in Transition Metal Dichalcogenides: Overview, Synthesis, Applications, and Prospects

Over the past decade, significant advancements have been made in phase engineering of two-dimensional transition metal dichalcogenides (TMDCs), thereby allowing controlled synthesis of various phases of TMDCs and facile conversion between them. Recently, there has been emerging interest in TMDC coexisting phases, which contain multiple phases within one nanostructured TMDC. By taking advantage of the merits from the component phases, the coexisting phases offer enhanced performance in many aspects compared with single-phase TMDCs. Herein, this review article thoroughly expounds the latest progress and ongoing efforts on the syntheses, properties, and applications of TMDC coexisting phases. The introduction section overviews the main phases of TMDCs (2H, 3R, 1T, 1T', 1Td), along with the advantages of phase coexistence. The subsequent section focuses on the synthesis methods for coexisting phases of TMDCs, with particular attention to local patterning and random formations. Furthermore, on the basis of the versatile properties of TMDC coexisting phases, their applications in magnetism, valleytronics, field-effect transistors, memristors, and catalysis are discussed. Lastly, a perspective is presented on the future development, challenges, and potential opportunities of TMDC coexisting phases. This review aims to provide insights into the phase engineering of 2D materials for both scientific and engineering communities and contribute to further advancements in this emerging field.

Metallic 1T phase molybdenum disulfide cocatalyst with abundant edge and substrate active sites for enhanced photocatalytic hydrogen production activity of zinc indium sulfide nanoflowers

The formation of composites by loading co-catalysts on semiconductor photocatalysts to improve hydrogen (H2) evolution performance is a feasible strategy. Metallic 1T phase molybdenum disulfide (MoS2) as cocatalysts were decorated on zinc indium sulfide (ZnIn2S4) nanoflowers by a grinding method to construct 1T-MoS2@ZnIn2S4 composites. The H2 production rate of 1T-MoS2@ZnIn2S4 composites with optimum 7 wt% 1T-MoS2 loading achieves 15.6 mmol g-1 h-1, 5.5 times higher than ZnIn2S4 nanoflowers. The apparent quantum efficiency (AQY) increases from 3.1 % (ZnIn2S4 nanoflowers) to 13.0 % (1T-MoS2@ZnIn2S4 composites) under the wavelength light irradiation at λ = 370 nm. The loading of metallic 1T-MoS2 with abundant edge and substrate active sites on ZnIn2S4 can enhance visible light absorption, promote the transfer of electrons, and inhibit carrier recombination, thereby improving photocatalytic performance. This work offers inspiration for the design of composite photocatalysts with efficient photocatalytic capabilities.

Temperature-Dependent Structural and Electrical Properties of Metal-Organic CVD MoS2 Films

Metal-Organic CVD method (MOCVD) allows for deposition of ultrathin 2D transition metal dichalcogenides (TMD) films of electronic quality onto wafer-scale substrates. In this work, the effect of temperature on structure, chemical states, and electronic qualities of the MOCVD MoS2 films were investigated. The results demonstrate that the temperature increase in the range of 650 °C to 950 °C results in non-monotonic average crystallite size variation. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and Raman spectroscopy investigation has established the film crystal structure improvement with temperature increase in this range. At the same time, X-Ray photoelectron spectroscopy (XPS) method allowed to reveal non-stoichiometric phase fraction increase, corresponding to increased sulfur vacancies (VS) concentration from approximately 0.9 at.% to 3.6 at.%. Established dependency between the crystallite domains size and VS concentration suggests that these vacancies are form predominantly at the grain boundaries. The results suggest that an increased Vs concentration and enhanced charge carriers scattering at the grains' boundaries should be the primary reasons of films' resistivity increase from 4 kΩ·cm to 39 kΩ·cm.