Vapor–Liquid–Solid Growth of Site-Controlled Monolayer MoS₂ Films Via Pressure-Induc ed Supercritical Phase Nucleation

Abstract

In this study, a novel pressure-induced supercritical phase nucleation method is proposed to synthesize monolayer MoS2 films, which is promoter free and can avoid contamination of films derived from these heterogeneous promoters in most of the existing techniques. The low-crystallinity and size-controlled MoO2(acac)2 particles are recrystallized on the substrate via the pressure-sensitive solvent capacity of supercritical CO2 and these particles are used as growth sites. The size of single-crystal MoS2 on the substrate is found to be dependent on the wetting area of the pyrolyzed precursor droplets (MoO2) on the surface, and the formation of continuous films with high coverage is mainly controlled by the coalescence of MoO2 droplets. It is enhanced by the increase of the nucleation site density, which can be adjusted by the supersaturation of the supercritical fluid solution. Our findings pave a new way for the controllable growth of MoS2 and other two-dimensional materials and provide sufficient and valuable evidence for vapor–liquid–solid growth.

The effect of sulfuration reaction rates with sulphur concentration gradient dependence on the growth pattern and morphological evolution of MoS2 in laminar flow

“…2(b) and (c)), indicating a likely association with the melting point. In conjunction with prior research, it indicates that from the temperature where the second heat absorption occurs up to 820 °C (growth temperature), MoO 2 gradually transitions into a molten state, 22 as expressed by chemical eqn (2). In summary, it is concluded that the melting point of MoO 2 (acac) 2 increases with higher crystallinity, and there exists a positive correlation between crystallinity and σ.…”

“…Furthermore, according to crystal growth kinetics, the step advancement rate decreases with the increase in step height. 22 Hence, from our experimental results, it is observed that the lateral size of multilayers is smaller than that of single layers. Considering the crystal size and quality, σ is selected as 19, with 1 g sulfur powder as a controlled variable for subsequent investigation.…”

“…The details of the process and devices could be found in our previous work. 22 The process of predeposition of precursors is as follows: MoO 2 (acac) 2 was first dissolved in scCO 2 , and then the temperature and pressure in the autoclave were adjusted to the predetermined values (T = 50 °C, p = 20 MPa). After the temperature was increased to 50 °C, magnetic stirring was turned on and maintained at 400 rpm for 24 hours to ensure that the precursors dissolved completely.…”

“…Further details regarding the influence of σ on the precursor particle growth can be found in our previous research. 22 Moreover, the particles with low crystallinity lead to a lower melting temperature. In particular, precursors with different phases lead to essentially distinct subsequent sulfuration growth mechanisms.…”

Morphological evolution of MoxW1−xS2/MoS2 heterostructures modulated with a growth dynamic process by one-step chemical vapor deposition

“…51 At a certain temperature and the same hydrophilicity, the maximum area of the molten particles migrating on the surface is limited. 52 At a low Mo : W ratio, the droplet size is large and the MoS 2 is encapsulated in the droplet. The presence of dangling bonds at the edges of MoS 2 serves as a nucleation site and ultimately forms a lateral heterostructure.…”