Manipulating electronic properties of two-dimensional MXenes Cr₂TiC₂FCl by phonon vibration

Although the manipulation of physical properties is common in applications of two-dimension (2D) materials, it is rare to tailor electronic properties by phonon vibration. In this article, we tailor the electronic band structure of Cr₂TiC₂FCl monolayer from indirect semiconducting state to metallic state by phonon modes ( $A_1^2$ , $A_1^5$ , and $A_1^6$ mode) with the Raman and infrared active. The $A_1^4$ mode makes Cr₂TiC₂FCl monolayer become direct semiconductor with a little gap, which can elevate the optical absorption efficiency of Cr₂TiC₂FCl monolayer, especially in the visible region. Meanwhile, both the conduction band minimum (CBM) and valence band maximum (VBM) are contributed by the spin-down channel; so, the electron hopping between VBM and CBM also does not need the participation of spin flipping and chiral phonon in Cr₂TiC₂FCl monolayer under the $A_1^4$ mode. These results are significant for the application of 2D materials in the semiconductor laser, solar cell, and photodetector.