Speaker
Description
Atomically thin materials - or two-dimensional (2D) materials – confine electrons at the ultimate thickness, giving rise to electrical and optical properties that can enable new quantum devices. Developing these devices requires large-area and high-quality monolayers. A limitation thus far has been that samples made by mechanical exfoliation techniques, thinning down crystals made of weakly bonded layers, are restricted in size to only a few microns. Bottom-up growth methods yielding large area monolayers, such as chemical vapour deposition (CVD), however, have lower sample quality. Therefore, it is desirable to develop methods that result in large area monolayers, while preserving the high quality of the crystal.
In this presentation, an exfoliating method based on 150nm Au film successfully used to disassemble bulk van der Waals crystals is presented. Specifically, this presentation demonstrates micron-size crystals of transition metal dichalcogenides such as MoS2, WSe2, and WS2 deposited on the surface of Si/SiO2 wavers. This presentation discusses how different parameters of the process influence the flatness and size of the exfoliated films and how this process can be implemented to create millimeter-size monolayers. To determine the quality of the atomically thin layers obtained with this method, optical and electrical characterization were performed and compared to the results obtained with measurements of mechanically exfoliated flakes and CVD grown films. This method opens the possibilities of producing high-quality macroscopic monolayers that can be used for high quality devices.
Acknowledgment: This work was performed with support from funding from the National Sciences and Engineering Research Council (NSERC) Discovery Grant (No. RGPIN-2016-06717)
