Mechanical Exfoliation and Characterization of Single‐ and Few‐Layer Nanosheets of WSe 2 , TaS 2 , and TaSe 2

Single‐ and few‐layer transition‐metal dichalcogenide nanosheets, such as WSe 2 , TaS 2 , and TaSe 2 , are prepared by mechanical exfoliation. A Raman microscope is employed to characterize the single‐layer (1L) to quinary‐layer (5L) WSe 2 nanosheets and WSe 2 single crystals with a laser excitation power ranging from 20 μW to 5.1 mW. Typical first‐order together with some second‐order and combinational Raman modes are observed. A new peak at around 308 cm −1 is observed in WSe 2 except for the 1L WSe 2 , which might arise from interlayer interactions. Red shifting of the A 1 g mode and the Raman peak around 308 cm −1 is observed from 1L to 5L WSe 2 . Interestingly, hexagonal‐ and monoclinic‐structured WO 3 thin films are obtained during the local oxidation of thinner (1L–3L) and thicker (4L and 5L) WSe 2 nanosheets, while laser‐burned holes are found during the local oxidation of the WSe 2 single crystal. In addition, the characterization of TaS 2 and TaSe 2 thin layers is also conducted.