Structural, electronic and optical properties of 2D nitride MXene nanolayers under tensile and compressive strain

Using density functional theory, this article calculated the optical and electrical properties of two-dimensional nitride MXene nanolayers. These structures contain M2NO2 MXenes (M = Zr, Ti, Hf and Sc). The effect of tensile and compressive strain on the physical properties of nanolayers was investigated. The electronic properties showed that Sc2NO2 nanolayers are semiconductors in the up and down spins with an energy gap of 2.59 eV and 1 eV, respectively, which can be used in spintronic industries. Also, Zr2NO2, Ti2NO2 and Hf2NO2 nanolayers are metals. The structural results show that all compounds are stable. In the spin-up state, the gap energy in Sc2NO2 nanolayers increases with increasing compressive strain. In the spin-down state, the opposite of this behavior occurs. Hf2NO2 nanolayers in 6 % tensile strain and Zr2NO2 nanolayers in 4 % tensile strain were very close to the edge of semi-metals. The results of DOS and PDOS confirmed the electronic band structure and d orbitals showed the greatest effect in the metallic and semi-metallic properties of the nanolayers. Optical properties showing the highest refractive index are related to Sc2NO2 nanolayers and the highest amount of absorption occurs in the ultraviolet region. Reducing and increasing the tensile and compressive strain has a great effect on the absorption and reflection of light. The results of this article showed that we can obtain different optical and electrical properties of nanolayers by strain engineering.