A Novel Carbon-Assisted Chemical Vapor Deposition Growth of Large-Area Uniform Monolayer MoS2 and WS2

Abstract

Monolayer MoS2 can be used for various applications such as flexible optoelectronics and electronics due to its exceptional optical and electronic properties. For these applications, large-area synthesis of high-quality monolayer MoS2 is highly desirable. However, the conventional chemical vapor deposition (CVD) method using MoO3 and S powder has shown limitations in synthesizing high-quality monolayer MoS2 over a large area on a substrate. In this study, we present a novel carbon cloth-assisted CVD method for large-area uniform synthesis of high-quality monolayer MoS2. While the conventional CVD method produces thick MoS2 films in the center of the substrate and forms MoS2 monolayers at the edge of the thick MoS2 films, our carbon cloth-assisted CVD method uniformly grows high-quality monolayer MoS2 in the center of the substrate. The as-synthesized monolayer MoS2 was characterized in detail by Raman/photoluminescence spectroscopy, atomic force microscopy, and transmission electron microscopy. We reveal the growth process of monolayer MoS2 initiated from MoS2 seeds by synthesizing monolayer MoS2 with varying reaction times. In addition, we show that the CVD method employing carbon powder also produces uniform monolayer MoS2 without forming thick MoS2 films in the center of the substrate. This confirms that the large-area growth of monolayer MoS2 using the carbon cloth-assisted CVD method is mainly due to reducing properties of the carbon material, rather than the effect of covering the carbon cloth. Furthermore, we demonstrate that our carbon cloth-assisted CVD method is generally applicable to large-area uniform synthesis of other monolayer transition metal dichalcogenides, including monolayer WS2.

Progress and development on the synthesis and application of two-dimensional molybdenum disulphide

“…71,82,83 The synthesis of 2D MoS 2 by CVD approaches involve decomposition and annealing of precursors like (NH 4 ) 2 MoS 4 , ammonium heptamolybdate (AHM), thiourea, sulphur powder and MoO 3 at high temperature, the precursors consists of both metal (Mo) and chalcogen (S) elements. 27,71,[84][85][86][87][88][89] The decomposition of precursors takes place under reductive and inert environment, to eliminate oxidation and enhance the conversion of precursor into MoS 2. 83,90 To undergo reaction between the precursor (Mo and S) and to synthesize MoS 2 , the precursor should be heated to sufficient and optimal conditions (often very high temperatures > 700 °C).…”

“…Due to their remarkable chemical and optical properties, 2D MoS 2 materials are the most studied materials amongst other TMD materials. [26][27][28] 2D MoS 2 has garnered a lot of research interest recently and this is evidenced in the exponentially increasing publication numbers. [29][30][31] Figure 1 shows the number of publication of 2D MoS 2 materials indicating the rising trend of interest in 2D MoS 2 .…”

Nucleation and growth studies of large-area deposited WS2 on flexible substrates

“…During the WS 2 film growth the substrate has a significant impact concerning the film quality and topography. Most of the studies have been performed on amorphous SiO 2 [21,22], sapphire model substrates [23][24][25][26][27] and graphene/HOPG [28,29]. Recently, on W-Au alloy substrate Wang et al demonstrated a strategy for preferentially forming antisite defects during WS 2 growth [30].…”