Ti₂CO₂/Ti₂CF₂ van der Waals heterostructure with robust Schottky barriers under electric fields

Transition metal carbides, nitrides and carbonitrides (MXenes) are considered as multifunctional materials due to their various elemental composition possibilities, surface functional tunability, various magnetic orders, and large spin–orbit coupling. Herein, a novel Ti₂CO₂/Ti₂CF₂ heterostructure is designed and its electronic and interfacial properties are investigated based on first-principles calculations. Our results reveal that the band structures of Ti₂CO₂ and Ti₂CF₂ layers are well preserved in the heterostructure due to the van der Waals interaction between the two layers, and a n-type Schottky contact forms due to the band bending at the interface. The most striking and much novel property is that the Schottky barrier height is nearly independent of the intensity of external electric field which is kept along the direction perpendicular to the Ti₂CO₂ or Ti₂CF₂ plane. The result denotes that a Fermi level pinning behavior occurs upon varying the intensity of electric field, which can change the doping concentration of electrons in the Ti₂CO₂ layer. This robust Schottky barrier opens the possibility of MXenes device designs for nanoelectronics.