β-As Monolayer: Vibrational Properties and Raman Spectra

Recently, semiconducting and other extraordinary properties of the monolayer of the V-group element have attracted a broad interest and attention. The success of experimentally growing antimonene and black phosphorus makes the arsenic monolayer a reasonable candidate for two-dimensional semiconductors. By using DFT calculation, we investigate the vibrational properties and Raman spectra of the buckled honeycomb monolayer of arsenic (β-As) for four commonly used laser lines. By calculating Raman tensor of each active modes of the β-As monolayer, we obtained polarization angle-dependent Raman intensities when the wave vector of incident light is parallel and perpendicular with the plane of the β-As monolayer. We found that the nonresonant Raman spectra have two peaks at 235 and 305 cm^-1 that correspond to the in-plane vibrating mode E_g and out-of-plane vibrating mode A_1g, which is similar to germanene, blue phosphorene, and β-Sb monolayer Raman spectra. There are two (four) minima and two (four) maxima when the polarization direction of scattered light is parallel (perpendicular) to that of the incident light and the wave vector of the incident light is parallel to the β-As monolayer. The Raman intensities of neither parallel polarization configuration nor perpendicular polarization configuration depend on the polarization direction when the wave vector of incident light is perpendicular to the β-As monolayer. The relation between shapes of the polar plots and relative values of Raman tensor elements is found. The Raman intensities decrease with increasing wavelength of incident laser lines in most cases. Our results will help experimentalists to identify the existence and the orientation of the β-As monolayer while they are growing the β-As monolayer.