The structural, elastic, electronic, and optical properties of Janus Zr2COT (T = S, Se, and Te) MXenes

The structural, elastic, electronic, and optical properties of Janus Zr2COT (T = S, Se, and Te) MXenes have been investigated using the first-principles calculations. Their stability is confirmed by the elastic properties, phonon spectrum analysis, and molecular dynamics simulations. The elastic properties of the Zr2COT MXenes are isotropic. Moreover, the Young's modulus (Y) and Poisson's ratio (ν) decrease and increase with the element changing from S to Te, respectively. The electronic structures show that the Zr2COS is an indirect band gap semiconductor, whereas the Zr2COSe and Zr2COTe turn into metal. Furthermore, the semiconductor-metal and metal-semiconductor transitions for Zr2COS and Zr2COSe can be induced by strain engineering, respectively. The dielectric function, absorption coefficient, and refractive index of the Zr2COS can be modulated by applying tensile strain. Significantly, the Zr2COS shows high absorption in the visible and ultraviolet regions. The static dielectric constant ε1(0) and static refractive index n(0) decrease monotonously with the increase of the tensile strain. These results show the promising potential applications of Zr2COT MXenes in sensors and optoelectronic nanodevices.