Structural, electronic and optical properties of two-dimensional (M_2/3Y_1/3)₂CO₂ (M = Mo,W) iMXene

Two-dimensional (2D) transition metal carbides and nitrides, known as MXenes, are continuously growing in terms of both crystalline and composition varieties. They have received significant attention in science and technology. The new members of MXenes with in-plane ordered double transition metals have been named as iMXenes. In this study, we have investigated the electronic structures and optical properties of 2D (Mo_2/3Y_1/3)₂CO₂ and (W_2/3Y_1/3)₂CO₂ iMXene monolayers, using a set of density functional theory calculations. We found that the (Mo_2/3Y_1/3)₂CO₂ and (W_2/3Y_1/3)₂CO₂ 2CO2 are semiconductors with indirect bandgaps of 0.477 eV and 0.655 eV, respectively. To investigate the optical properties, we calculated the absorption spectrum and reflectivity percentage of these structures along x and z directions using the real and imaginary parts of the dielectric function. It is observed that the real and imaginary parts of their dielectric functions possess many peaks in the energy region of less than 3.1 eV. Interestingly, they show high absorption in the visible and UV regions, implying the potential applications of these semiconducting iMXenes in solar cells and optical nanodevices. (paper)