Excitation-Dependent Anisotropic Raman Response of Atomically Thin Pentagonal PdSe 2 .

The group-10 noble-metal dichalcogenides have recently emerged as a promising group of two-dimensional materials due to their unique crystal structures and fascinating physical properties. In this work, the resonance enhancement of the interlayer breathing mode (B1) and intralayer A _g ¹ and A _g ³ modes in atomically thin pentagonal PdSe ₂ were studied using angle-resolved polarized Raman spectroscopy with 13 excitation wavelengths. Under the excitation energies of 2.33, 2.38, and 2.41 eV, the Raman intensities of both the low-frequency breathing mode B1 and high-frequency mode A _g ¹ of all the thicknesses are the strongest when the incident polarization is parallel to the a axis of PdSe ₂ , serving as a fast identification of the crystal orientation of few-layer PdSe ₂ . We demonstrated that the intensities of B1, A _g ¹ , and A _g ³ modes are the strongest with the excitation energies between 2.18 and 2.38 eV when the incident polarization is parallel to PdSe ₂ a axis, which arises from the resonance enhancement caused by the absorption. Our investigation reveals the underlying interplay of the anisotropic electron-phonon and electron-photon interactions in the Raman scattering process of atomically thin PdSe ₂ . It paves the way for future applications on PdSe ₂ -based optoelectronics.
Competing Interests: The authors declare no competing financial interest.
(© 2022 The Authors. Published by American Chemical Society.)