Tuning electronic structures and optical properties of Ti2CO2 MXenes by applying stress

Functionalized MXenes have attracted great interest due to their unique electrical, magnetic, optical, and electrochemical properties. In this paper, the effect of interlayer coupling on the electronic structures of Ti2CO2 MXenes is investigated by using density functional theory. Due to the interlayer coupling, the band structures of Ti2CO2 nanosheet are split, generating an indirect band gap of 0.869 eV, which is smaller than that of Ti2CO2 monolayer (1.044 eV). Biaxial strain can be used to achieve the transitions of direct-indirect-negative band gaps semiconductor. The interlayer interaction effectively inhibits the structural changes under stress, resulting that the band gap of nanosheet be adjusted in a large stress range. Furthermore, the change trend of imaginary part ε2 of the dielectric function indicates that stress has an obvious regulatory effect on the optical transition. The different responses of monolayer and nanosheet under stress provides more choice for the optical devices of Ti2CO2 MXenes.