Tunable structural and electronic properties of C4XY (X ≠ Y = H, Cl and F) monolayers by functionalization, electric field and strain engineering

Abstract

In this work, we systematically investigate the electronic and mechanical properties of diamane C₄X₂ (X = H, Cl and F) monolayers as well as the formation of Janus functionalized X/Y-diamane C₄ XY (X ≠ Y = H, Cl and F) monolayers by replacing one side of X atoms by other Y atoms. Our results showed that both the C₄X₂ and C₄ XY monolayers exhibit semiconducting characteristics with direct band gaps at the Γ point. The functionalized X/Y group leads to a decrease in the band gap of the C₄ XY monolayers in comparison with that of the C₄X₂ monolayers. Furthermore, the elastic constants, Young and shear moduli and phonon dispersion curves of the functionalized X/Y-diamane confirm that they are mechanically and dynamically stable at room temperature. The electronic properties of Janus C₄ FCl monolayers are known to be very sensitive to an external electric field and strain engineering. Both an external electric field and strain engineering not only give rise to a change in the band gap values but also lead to a transition from semiconductor to metal in the Janus C₄ FCl monolayer. Our findings will provide useful guidance for understanding and designing possible potential applications based on Janus functionalized X/Y-diamane C₄ XY materials.