Reaction mechanism transformation of LPCVD-grown MoS2 from isolated triangular grains to continuous films

CVD Synthesis of Intermediate State-Free, Large-Area and Continuous MoS2 via Single-Step Vapor-Phase Sulfurization of MoO2 Precursor

“…This results in a prominent gradient-like concentration distribution of the MoS2 nucleation sites at the substrate surface, which then serves as the blueprint for the final growth pattern (see schematic shown in Figure 1c). Numerical simulations performed by R. A. Vila et al [53] using finite element modelling revealed a decreasing concentration gradient on the surface of the substrate as the distance from the Mo-source increases, and that the concentration gradient pattern is characterized as distinct parabolic growth zones commonly found in experiments [24,29,36,45,49]. Moreover, the presence of such a concentration gradient means that the local Mo:S ratio varies along the length of the growth substrate, increasing the probability of morphology evolutions [53], oxysulfide formations [33,36,48,[50][51][52] and MoS2 domain-shape changes [24].…”

“…While we believe that the results presented in this work are a significant step forward, we have not yet demonstrated wafer-scale growth and/or wafer-scale uniformity of continuous monolayer MoS2. In a recent work employing MoO3 precursors [49], two kinds of growth regimes were identified: a diffusion regime and a surface-reaction regime, which corresponded to whether a large or small amount of MoO3 precursor was used for the growth, respectively. While in the diffusion regime, a gradient-like growth pattern, similar to those found in this work, was observed, in the surface reaction regime, the growth of continuous films with more than 90% wafer coverage was reported.…”

“…CVD-grown MoS2 has been synthesized via the sulfurization of Mo containing precursors, such as Mo [16], MoO2 [17][18][19][20] and MoO3 , among which the use of MoO3 powder as the precursor has remained the most popular method owing to the possibility of obtaining large area single crystal and also continuous films [41][42][43][44][45][46][47][48][49].In fact, in very recent work, Q. Wang et al [46] have employed a customized multisource CVD system to successfully demonstrate the wafer-scale growth of MoS2 using MoO3 as the precursor material. While these accomplishments are noteworthy, the poisonous nature (strong irritant and carcinogen according to GHS classification) and low evaporation temperature (350 °C) of MoO3 powder means that harmful exposure to this material is more likely, posing a serious health hazard situation.…”

Controllable Selenization Transformation from MoO2 to MoSe2 by Gas Pressure‐Mediated Chemical Vapor Deposition

“…The gas pressure‐mediated synthesis of MoSe 2 was carried out in a three‐temperature‐zone VPCVD. [ 26 ] As shown in Figure a, a quartz boat containing 30 mg MoO 3 (Sigma‐Aldrich, 99.99%) was placed in the central heating zone, and a corundum crucible containing 1 g Se powder (Sigma‐Aldrich, 99.95%) was placed upstream 20 cm away from MoO 3 powder. The 300 nm SiO 2 /Si substrate was faced down toward the MoO 3 powder.…”

Strategies for Controlled Growth of Transition Metal Dichalcogenides by Chemical Vapor Deposition for Integrated Electronics

“…As shown in Figure g,h, S and MoO 3 sources were loaded in several inner-miniature quartz tubes to achieve the precise kinetic control for the growth of single-crystalline MoS 2 . To control the nucleation density by adjusting the precursor concentration, a partial pressure programming LPCVD system was reported . The concentration and distribution were controlled by changing the amount of solid MoO 3 and the height between substrate and precursor.…”