Probing lattice vibration and surface electronic state in a layered (NH4)2V3O8 single crystal
Two-dimensional layered structure of a single crystal is regarded as an ideal feature for physical and chemical fundamental studies. Herein, we demonstrated a high-quality (NH4)2V3O8 single crystal with a layered tetragonal structure prepared via a hydrothermal method. The lattice vibrational behavior and surface electronic state of (NH4)2V3O8 layers were systematically investigated via polarized Raman scattering spectroscopy and ultraviolet photoelectron spectroscopy (UPS), respectively. It was found that all Raman peaks of (NH4)2V3O8 could be clearly identified as four active Raman modes through parallel and perpendicular polarization configurations in the backscattering geometry for (001) crystal surface. The UPS results indicated that the valence band maximum of (NH4)2V3O8 was mainly composed of localized vanadium 3d states, which was further confirmed by the density functional theory calculations.