Reflected light reveals the layer count in three 2D semiconductors
Optical measurements calibrated against atomic force microscopy offered a quick way to identify monolayer and few-layer flakes on a specified substrate.
Jia-Peng Wu, Le Wang and Liyuan Zhang compared the reflected light from MoS₂, MoSe₂ and WSe₂ flakes on silicon substrates with a 275 nm oxide layer. The spectra shifted with the number of layers.
The researchers checked the flake thicknesses by atomic force microscopy and used a thin-film optical model to interpret the spectra. Once calibrated for that substrate, reflection measurements could screen new flakes without a separate thickness scan for each one.