Identification of phonon vibrational modes for the layered Ta2Se metal-rich chalcogenide

Layered metal-rich chalcogenides are a new class of two-dimensional (2D) materials consisting of densely packed metal layer units separated by van der Waals (vdW) gaps, yet their physical properties remain unexplored, particularly on phonon vibrational modes. Here, we report the phonon vibrational characteristics of 2D metal-rich Ta2Se chalcogenide through Raman spectroscopy and density functional perturbation theory (DFPT) calculations. Highly c-axis-oriented single crystalline Ta2Se flakes were grown using the arc-melting process. Temperature-dependent electrical resistivity and Hall-effect measurements on Ta2Se reveal a metallic electrical ground state with a high hole carrier concentration (~2 × 1021 cm−3). Raman spectroscopy identifies two distinct peaks at 184 cm−1 and 213 cm−1, which remain invariant in both thick (145 nm) and thin (11.68 nm) samples, indicating robust phonon vibrations down to 12 layers. Based on DFPT calculations and polarized Raman experiments, we confirm that both peaks correspond to A1g Raman-active modes oscillating along the c-axis.