In-Depth Analysis of 2D Materials Using Angle-Resolved Polarized Raman Spectroscopy

Raman spectroscopy is a non-destructive analytical technique used to characterize the composition, structure, and properties of various materials. By utilizing the polarization of incident and scattered light in angle-resolved polarized Raman spectroscopy (ARPRS), it is possible to analyze material properties as a function of crystallographic orientation. Recently, ARPRS has emerged as a versatile technique for the in-depth characterization of 2D materials, particularly those with low symmetry. Here, we will present examples from our ongoing research, demonstrating the use of ARPRS in addressing significant issues in several 2D material systems.<br/><br/>The first example highlights our recent ARPRS study of black arsenic-phosphorus (b-As_xP_1-x) alloys [1]. These 2D materials have an orthorhombic honeycomb puckered crystal structure similar to black phosphorus (BP) but exhibit enhanced properties and environmental stability. ARPRS measurements in this study enable the clear identification of all As-P vibrational modes, particularly the in-plane modes, which are challenging to resolve using regular Raman spectroscopy.<br/><br/>The second example demonstrates the use of ARPRS to analyze Fe₃GeTe₂, one of the most promising 2D magnetic materials. Fe₃GeTe₂ exhibits strong magnetic anisotropy, high-temperature ferromagnetic ordering even at monolayer thickness, and high environmental stability. ARPRS analysis provides compelling evidence for the unambiguous attribution of the <i>A¹_g </i>and <i>E²_2g</i> vibrational modes to specific peaks observed in the Raman spectrum of Fe₃GeTe₂, thereby resolving existing confusion in the literature.<br/><br/>Finally, the third example discusses our recent ARPRS study of CVD-grown Cr₂Se₃. The results suggest that under certain growth conditions, the computationally predicted triclinic phase can be formed.<br/><br/>These examples collectively demonstrate the capabilities of ARPRS in advancing our understanding of the properties and behaviors of 2D materials. By providing detailed insights into their structure, this technique will continue to play a significant role in the advanced characterization and fundamental research of these systems.<br/><br/>[1] Irziqat et al., “Angle-resolved polarized Raman study of layered b-As_xP_x-1 alloys: Identification of As-P vibrational modes”, <i>Journal of Alloys and Compounds</i>, 992, p.174609 (2024).