Ferroelectric properties inducted by transition metal intercalation

Transition-metal dichalcogenides (TMD) have been explored in the last decades due to its structural and electronic properties. In particular, selenide materials, such as MoSe₂ present higher stability and resistance to oxidation when compared to other TMDs, resulting in the application of this specific material in several nanodevices. Because of the semiconductor and non-magnetic characteristics of MoSe₂, several processes including adsorption, defects induction, and intercalation are being considered to engineer its electronic and structural properties. As a Van der Waals (vdW) material, the stacking of MoSe₂ layers, particularly the 2H, allows the intercalation of foreign atoms with different coordinations to each layer. This anisotropy in the number of bonds induces the polarization of the electronic cloud inside the vdW gap, enabling the emergence of ferroelectric properties. With this scenario, we have explored the metal intercalation in the bilayer MoSe₂ using computational simulations based on the Density Functional Theory (DFT). We investigated the effect of concentration and coordination number of transition metals intercalated in MoSe₂. In particular, we explored the ones found to be stable when forming tetrahedral complexes, such as Iron, Cobalt, Nickel, Copper, and Zinc. By repositioning the intercalated atoms, the inversion of the tetrahedral structure leads to the electric dipole flipping, opening a way for the application in two-dimensional devices.