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

Abstract

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′, 1T d ), 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.

A Mini Review: Phase Regulation for Molybdenum Dichalcogenide Nanomaterials

“…For TMDCs, there exist several phase structures, basically including 1H/2H (1H for monolayer and 2H for multilayer) and 1T, where H and T represent hexagonal and trigonal, and the numbers indicate the number of layers in the unit cell, respectively [ 7 ]. More specifically, the 1H phase corresponds to a trigonal prismatic coordination of the M atoms, with two layers of X atoms vertically aligned, leading to an ABA stacking, while the 1T phase corresponds to an octahedral coordination of the M atoms, with one of the X layers shifted compared to the other leading to an ABC stacking [ 16 , 17 ]. Some TMDCs have a special twisted octahedral structure, which is named the 1T′ phase.…”