2D WS₂: From Vapor Phase Synthesis to Device Applications

Abstract

The discovery of graphene has triggered the research on 2D layer structured materials. Among many 2D materials, semiconducting transition metal dichalcogenides (TMDs) are widely considered to be the most promising ones due to their excellent electrical and optoelectronic characteristics. Tungsten disulfide (WS2) is a kind of such TMDs with fascinating properties, such as the high carrier mobility, appropriate band gap, strong light–matter interaction with the large light absorption coefficient, very large exciton binding energy, large spin splitting, and polarized light emission. All these interesting properties can make the 2D WS2 being highly favorable for applications in memristors, light‐emitting devices, optical modulators, and many others. Here, the comprehensive review on the properties, vapor phase synthesis, electronic and optoelectronic applications of 2D WS2 is presented. This review does not only serve as a design guideline to elevate the material quality of 2D WS2 films via enhanced synthesis approaches, but also provides valuable insights to various strategies to improve their device performances. With the fast development of wafer‐scale synthesis methods and novel device structures, 2D WS2 can undoubtedly be a rising star for the next‐generation devices in the near future.

Synthesis of WS2 by Chemical Vapor Deposition: Role of the Alumina Crucible

“…The contribution of trions decreases gradually, reaching a minimum that corresponds to the maximum of PL emission. The increase in S vacancies (n-type doping) could explain the redshift of neutral exciton energy [37,38]. Thus, the redshift in the central peak position corresponds to the increase in contribution due to the trions (see Table 1).…”

Low-defect-density WS2 by hydroxide vapor phase deposition

“…Among the typical TMD monolayers, WS 2 exhibits high mobilities and saturation velocities for both electrons and holes based on the full-band Monte Carlo analysis of the Boltzmann transport equation 10 , 11 . Conventional CVD methods can provide scalable WS 2 monolayers through the direct sulfidation of either tungsten trioxide (WO 3 ) or other oxygen-containing precursors 12 – 14 . Although single crystal WS 2 flakes can be achieved, abundant defects are still present 15 , 16 , which in turn leads to insufficient performance for advanced electronic devices.…”

A study on the effect of phase conversion of tungsten nanostructures on their electrochemical energy storage performance

“…Tungsten disulfide (WS 2 ) is another trending material among transition-metal dichalcogenides (TMD), which is considered a next generation 2D TMD for energy storage applications. [24][25][26][27][28] WS 2 possesses many optoelectronic properties similar to tungsten oxides. According to the theoretical models, in comparison with other TMDs, WS 2 exhibits the highest mobility because of its reduced effective mass.…”