| Popis: |
A detailed comparison of Raman (excitation of 488 and 632.8 nm) and IR spectra (ATR and diffuse scattering) was made for MoS 2 nanoparticles and microcrystallites. Under resonant excitation of 632.8 nm, a change in the ratio of the intensities of the ν 3 (A 1g ) and ν 1 (E 1g ) bands was detected by more than 102 times, as well as a consistent doubling of the size of the MoS 2 unit cell, which leads to the observation of sharp lines of acoustic vibrations TA, LA ZA, inactive vibrations, as well as the anomalous high oxidation rate of MoS 2 to MoO 3 . In the IR absorption spectra, for the first time, negative polarity bands for the overtones 3ν 2 and 3ν 3 were observed, and a significantly higher intensity of the bands in the diffuse scattering spectra of nanocrystallites was found in comparison with the spectra of MoS 2 microcrystallites. The observation of the glow of vibrational overtones proves the important role of nonlinear resonant wave processes (NRWP) for the vibrational modes of MoS 2 . The role of strong vibrational-electron interactions leading to the induction of new electronic states in the MoS 2 band gap, as well as the NRWP in vibrational spectroscopy of MX 2 dichalcogenides, is analyzed. |
