title: Mechanical exfoliation and characterization of single- and few-layer nanosheets of WSe₂ , TaS₂ , and TaSe₂.
abstract: Single- and few-layer transition-metal dichalcogenide nanosheets, such as WSe₂ , TaS₂, and TaSe₂, are prepared by mechanical exfoliation. A Raman microscope is employed to characterize the single-layer (1L) to quinary-layer (5L) WSe₂ nanosheets and WSe₂ 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 WSe₂ except for the 1L WSe₂, which might arise from interlayer interactions. Red shifting of the A(1g) mode and the Raman peak around 308 cm⁻¹ is observed from 1L to 5L WSe₂. Interestingly, hexagonal- and monoclinic-structured WO₃ thin films are obtained during the local oxidation of thinner (1L-3L) and thicker (4L and 5L) WSe₂ nanosheets, while laser-burned holes are found during the local oxidation of the WSe₂ single crystal. In addition, the characterization of TaS₂ and TaSe₂ thin layers is also conducted.
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
authors.forename: Hai
authors.initials: H
authors.lastname: Li
authors.forename: Gang
authors.initials: G
authors.lastname: Lu
authors.forename: Yanlong
authors.initials: Y
authors.lastname: Wang
authors.forename: Zongyou
authors.initials: Z
authors.lastname: Yin
authors.forename: Chunxiao
authors.initials: C
authors.lastname: Cong
authors.forename: Qiyuan
authors.initials: Q
authors.lastname: He
authors.forename: Lu
authors.initials: L
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Ding
authors.forename: Ting
authors.initials: T
authors.lastname: Yu
authors.forename: Hua
authors.initials: H
authors.lastname: Zhang