Versatile tailoring of electronic conduction in 2D transition metal carbides via surface termination engineering: Nonequilibrium quantum mechanical study

Two-dimensional (2D) transition metal carbides (MXenes) are promising electron conducting materials. Noticeably, they intrinsically have surface functionality and the control of surface termination has proven robust and efficient for modulating MXenes’ mechanical and optical properties. However, its effects to MXenes’ electronic conduction have rarely been studied. Using nonequilibrium quantum mechanical simulations, here we showed that surface termination engineering can be powerful means of regulating the electric conductance of Ti₃C₂T_x MXenes. Two extreme fully oxygen-terminated (Ti₃C₂O₂) and bare (Ti₃C₂) surfaces were considered since oxygen is one of dominant surface terminations of MXenes. We revealed that Ti₃C₂ are superior electric conductors compared to Ti₃C₂O₂, showing five-times high performance in our system. We further explored this issue by gradually increasing the surface oxygen-terminated degree of the scattering region of Ti₃C₂. The conductance underwent an S-like variation, representing significant 7.5-times tunability showing minimum at the oxygen-termination portion of 50%. Ti₃C₂O₂ with various surface bareness also exhibited significant and dynamic conduction variation with minimum around 40%, but in a quantitatively different manner due to the use of oxygen-terminated electrodes.