Study of Structural and Optoelectronic Properties of Thin Films Made of a Few Layered WS(2) Flakes

We report a surfactant-free exfoliation method of WS(2) flakes combined with a vacuum filtration method to fabricate thin (<50 nm) WS(2) films, that can be transferred on any arbitrary substrate. Films are composed of thin (<4 nm) single flakes, forming a large size uniform film, verified by AFM and SEM. Using statistical phonons investigation, we demonstrate structural quality and uniformity of the film sample and we provide first-order temperature coefficient χ, which shows linear dependence over 300–450 K temperature range. Electrical measurements show film sheet resistance R(S) = 48 MΩ/□ and also reveal two energy band gaps related to the intrinsic architecture of the thin film. Finally, we show that optical transmission/absorption is rich above the bandgap exhibiting several excitonic resonances, and nearly feature-less below the bandgap.