Modulating the Schottky barrier of MXenes/2D SiC contacts via functional groups and biaxial strain: a first-principles study

Abstract

Two-dimensional (2D) graphene-like SiC has attracted intense interest recently due to its unique electrical and physical properties. In implementing 2D semiconductors in device applications, one of the main challenges so far has been the formation of a high-quality Schottky barrier owing to the strong Fermi level pinning (FLP) at the interface of traditional metal–2D semiconductor contacts. In this paper, the 2D MXenes Ti₃C₂T₂ (T = F, O, OH) are proposed to serve as electrodes for 2D SiC. The structural and barrier properties of the Ti₃C₂T₂/SiC contacts were systematically investigated based on first-principles calculations combined with the GGA-PBE and HSE06 functionals. It is found that Ti₃C₂T₂ can be bonded with 2D SiC by van der Waals (vdW) interactions. Weak FLP is exhibited at Ti₃C₂T₂/SiC vdW contacts. The type of contact can be tuned by changing the functional T group of Ti₃C₂T₂. Ti₃C₂F₂/SiC and Ti₃C₂O₂/SiC contacts exhibit a p-type Schottky contact and p-type Ohmic contact, respectively, whereas an n-type Ohmic contact occurs in the Ti₃C₂(OH)₂/SiC contact. In addition, the calculated tunneling possibility (T_B) is ∼20% between Ti₃C₂T₂ and SiC, indicating weak bonding at the Ti₃C₂T₂/SiC vdW junctions. Furthermore, the Schottky barrier height and T_B of the Ti₃C₂(OH)₂/SiC contacts can be modulated via the biaxial strain. The controllable contact type and barrier in Ti₃C₂T₂/SiC contacts provide guidelines for developing high-performance 2D SiC optoelectronic and electronic devices.