Angle-Resolved Polarized Magneto-Raman Scattering of Two-Dimensional Hybrid Hexylammonium Lead Iodide Perovskite

Conventional 3D hybrid halide perovskites are promising materials for future electronics and optoelectronics and applications in spin-electronic devices due to their unique properties, such as high coherent emission, high defect tolerances, strong spin-orbit coupling, and strong light-matter interactions. However, there is a challenge in the applicability of these conventional perovskites due to their poor environmental stability. Lowering the dimensionality of these materials has been the key to this problem, offering more stable performance and better moisture resistance. This is attributed to the hydrophobic organic spacers that passivate the inorganic layers in 2D hybrid organic-inorganic perovskites (2D HOIPs). 2D HOIPs are composed of inorganic layers made of metal halide octahedra separated by organic cations layers. This work presents angle-resolved polarized Raman spectroscopy measurements of 2D HOIP hexylammonium lead iodide [(HA)2PbI4], that includes phonon modes down to 20 cm^-1. Polarized Raman spectroscopy is a very effective method for assigning the phonon symmetry, which can be assigned using computational methods we describe. The polarized Raman scattering measurements were carried out in the backscattering geometry at low and room temperatures. We utilized two halfwave plates to control the incident polarization and the analyzer, such as the sample can be rotated under parallel and cross-polarization configurations. The experiments reveal the anisotropy of the Raman active modes. We also present magneto-Raman measurements at different temperatures, under parallel and cross polarization configurations.