The isolation of few-layered transition metal dichalcogenides has mainly been performed by mechanical and chemical exfoliation with very low yields. In this account, a controlled thermal reduction-sulfurization method is used to synthesize large-area (~1 cm(2)) WS2 sheets with thicknesses ranging from monolayers to a few layers. During synthesis, WOx thin films are first deposited on Si/SiO2 substrates, which are then sulfurized (under vacuum) at high temperatures (750-950 °C). An efficient route to transfer the synthesized WS2 films onto different substrates such as quartz and transmission electron microscopy (TEM) grids has been satisfactorily developed using concentrated HF. Samples with different thicknesses have been analyzed by Raman spectroscopy and TEM, and their photoluminescence properties have been evaluated. We demonstrated the presence of single-, bi-, and few-layered WS2 on as-grown samples. It is well known that the electronic structure of these materials is very sensitive to the number of layers, ranging from indirect band gap semiconductor in the bulk phase to direct band gap semiconductor in monolayers. This method has also proved successful in the synthesis of heterogeneous systems of MoS2 and WS2 layers, thus shedding light on the controlled production of heterolayered devices from transition metal chalcogenides.

Few‐layered films of WS2, synthesized by chemical vapor deposition on quartz, are successfully used as light sensors. The film samples are structurally characterized by Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and high‐resolution transmission electron microscopy. The produced samples consist of few layered sheets possessing up to 10 layers. UV–visible absorbance spectra reveals absorption peaks at energies of 1.95 and 2.33 eV, consistent with the A and B excitons characteristic of WS2. Current–voltage (I–V) and photoresponse measurements carried out at room temperature are performed by connecting the WS2 layered material with Au/Ti contacts. The photocurrent measurements are carried out using five different laser lines ranging between 457 and 647 nm. The results indicate that the electrical response strongly depends on the photon energy from the excitation lasers. In addition, it is found that the photocurrent varies non‐linearly with the incident power, and the generated photocurrent in the WS2 samples varies as a squared root of the incident power. The excellent response of few‐layered WS2 to detect different photon wavelengths, over a wide range of intensities, makes it a strong candidate for constructing novel optoelectronic devices.

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