EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Two-dimensional Transition Metal Dichalcogenides (2D-TMDs) have been in the spotlight for the last two decades due to their potential impact in future electronics, thermal and chemical applications. By tuning their composition, number of layers and strain we can control mechanical strength, bandgap, charges mobility, and thermal conductivity. Among them, 2D-MoS2 is of particular interest for post-Si (flexible) electronics, bio- and gas- sensing and catalysis. Chemical Vapor Deposition (CVD) is currently used to produce high-quality MoS2 with controlled defects, crystallinity, and morphology. However, these characteristics are strongly influenced by specific features of the substrate, like the presence of surface defects or sample roughness. Monolayers of MoS2 have been mainly grown in atomically flat substrates, like SiO2, sapphire, copper or HOPG. The smooth surfaces and low density of defects of these substrates typically result in high to complete monolayer growths with relatively large domain sizes. Alternatively, an initiator like PTAS can be deposited on the surface before synthesis to favour nucleation and to achieve high coverage. However, little is known on the growth of MoS2 on highly defective as well as rough substrates. These substrates are specifically relevant for applications requiring high surface areas, like catalysis.
In this contribution we investigate the interplay between substrate roughness on the morphology of CVD-grown MoS2. For this purpose, we have compared the physico-chemical properties of MoS2 grown on atomically flat SiO2/Si reference substrate with those obtained in pyrolytic graphite with surface roughness varying between few micrometres to nanometres. Additionally, we determine the effect of PTAS on these set of samples by performing synthesis on uncoated, partially-, and totally- PTAS coated samples.
The outcome of this work sheds light on how the substrate density of defects and roughness and the presence of PTAS correlate with the MoS2 morphology.