Raman tensor of layered MoS₂

Abstract

Raman tensors, one of the basic physical properties of M o S 2 , are rarely reported. Here, angle-resolved polarized Raman scatterings on basal and cross planes of layered M o S 2 were carried out using the geometry configuration of parallel polarization, and the Raman tensors of three optical vibration modes were systematically studied. As a polar vibration mode, the differential polarizability of the A 1 g mode corresponding to the Raman tensor along the c direction is larger than that along the a direction. In addition, it is also larger than that formed by E 2 g and E 1 g modes. All the experimental results above are beneficial to the understanding of inelastic light-scattering process of M o S 2 .

Laser tuning in AlN single crystals

“…The measurement geometry is shown in Fig. 1a [24][25][26][27][28][29][30][31][32][33][34], where a polarizer with fixed polarization direction was placed in the collecting optical path to ensure that the polarization direction of scattering light was strictly consistent with that of pump light. In order to avoid the influences of pump light absorption and resonance Raman scattering on the intensity of scattering light, 488-nm Ar+ gas laser was used as pump light and focused on the AlN surface through a 50× quartz lens [35][36][37][38][39].…”

Revealing the nanogeometry of WS2 nanoflowers by polarization-resolved Raman spectroscopy

“…Furthermore, given the chirality of the TMDs valleys and the resonant influence of the excitons on the Raman response, studying the interaction of TMDs phonons with circularly polarized light is important [30][31][32]. As the Raman effect depends on the polarizability of the material, the interaction of TMDs with polarized light is described by a Raman polarizability tensor [31,33,34]. It is important to note that these tensors are defined with respect to the atomic axes, e.g., typically assuming flat-layered TMDs with the excitation light perpendicular to it.…”

“…Thus, the polarization-resolved Raman response of for instance a vertical TMDs wall will be completely different than that of a flat layer, e.g. modes that are usually allowed/forbidden in cross-polarization will now be absent/observed [20,[33][34][35]. Therefore, polarizationresolved Raman studies will provide insight in the flowers' nanogeometry and orientation.…”

Raman tensor of layered black phosphorus

“…Angle-resolved polarized Raman (APR) spectroscopy, as an undamaged tool, is powerful to measure Raman tensor. It has been performed in our previous work which studied the Raman polarization characteristic of anisotropic crystal, such as MoS 2 , black arsenic and AlN [2,[15][16][17][18][19][20][21]. Recently, BP has attracted much attention in the aspects of optical and electrical anisotropy.…”