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

Abstract

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 Ti3C2Tx 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.