Can Metals Other than Au be Used for Large Area Exfoliation of MoS2 Monolayers?

Au-mediated exfoliation of 2D transition-metal dichalcogenides (TMDs) has received significant attention due to its ability to produce large-area monolayer (ML) flakes. This process has been attributed to strong TMD/Au binding energy (BE) as well as the uniform strain between the TMDs and Au. However, large-area exfoliation of TMDs with other metals that have even stronger theoretical BE than Au/TMD is not successful, leading to question whether the BE plays any role in the exfoliation process. Here, successful demonstration of large-area ML MoS2 using Cu, Ni, and Ag with various predicted strain, including Pd with almost no strain, but stronger BE than Au/MoS2 is demonstrated. Optical micrographs show MoS2 flakes with 100s of mu m in size with a yield of several tens to hundreds of ML flakes per exfoliation. Photoluminescence and Raman spectroscopy confirm the ML nature of the flakes, while electrical transport measurements show mobilities of approximate to 6 cm(2) V-1 s(-1) with a current on-off ratio approximate to 10(8) consistent with high-quality ML MoS2. Given that MoS2 can be exfoliated with metals that have strong BE irrespective of their strain values suggests that BE is the primary mechanism in successful exfoliation of large-area ML MoS2.

Automated summary

Successful exfoliation of large-area monolayer (ML) MoS2 has been demonstrated using metals with strong binding energy (BE), indicating that BE is the primary mechanism for successful exfoliation.