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Investigation of the structural, dielectric, and optical properties of MoSe2 nanosheets

In this research, solvothermal synthesized MoSe2 nanosheets were analyzed to determine their structure and optical properties. Measurements through atomic force microscopy, scanning electron microscopy, and transmission electron microscopy confirmed the formation of MoSe2 nanosheets. The energy-dispersive x-ray results revealed the presence of high-purity MoSe2 and an atomic percentage ratio of Mo:Se ∼ 1:1.93. Additionally, x-ray diffraction and Raman showed the crystal structure of MoSe2 and the existence of a two-dimensional (2D) layer, respectively. The linear optical properties of the MoSe2 nanosheets were analyzed by Fourier transform infrared (FTIR) spectroscopy and the Kramers–Kronig method. The FTIR research indicated the vibrational modes of several chemical groups, thus proving the presence of MoSe2 ions. For the varying concentrations of MoSe2 nanosheets in dimethylformamide, the third-order nonlinear optical properties of MoSe2 nanosheets were determined in detail using the Z-scan approach and a continuous-wave Nd:YAG laser. As the transmittance measurements in an open aperture Z-scan setup indicated, all the synthetized samples had saturable absorption. Similar investigations using a close-aperture Z-scan technique proved that all samples had nonlinear refractive indices in the range of 10−7 cm2/W with a positive sign and self-focusing behavior. Moreover, the third-order susceptibility and the figure of merit were found to be in the order of 10−5 esu and 10−4 esu cm, respectively. The findings of this study provide insight about modified 2D materials and expand the use of MoSe2 nanosheets in photonic devices.