Anisotropic Angle Dependence of the Raman Response in a Layered Quasi-One-Dimensional NbS3 Crystal

Characterizing the lattice vibrational behavior using the Raman spectroscopic technique was one of the goals of research in two-dimensional (2D) material systems. Herein, using the parallel and vertical polarization Raman scattering method, we reported a significantly anisotropic Raman optical response of the (001) surface in a layered quasi-one-dimensional NbS₃ semiconductor crystal. The angular dependence of the Raman scattering intensity showed that major Raman peaks should be assigned to the A_g vibrational mode and the synthesized single crystal belonged to the triclinic phase, which was first revealed by the Raman spectroscopy method. In addition, the Raman spectroscopy results, which were obtained by density functional perturbation theory (DFPT) calculations, were qualitatively consistent with the experimental results. Moreover, the effect of lattice vibrational anharmonicity on the Raman peak position was studied by temperature-dependent Raman scattering spectra from 80 to 290 K; when the temperature was increased, we observed linearly softening phenomena for all of the Raman shifts, and the first-order temperature coefficients of the six Raman peaks were estimated by the Grüneisen model, which were more pronounced than those reported for other layered materials.