Energy-level Alignments and Schottky Barrier Heights of Metal-2D Material Interfaces

As the technological applications of 2D material-based electronics continue to rise, an understanding of the physical underpinnings of the energy barriers between metal-2D material contacts becomes critically important. Experimentally, these interfaces are often found to be controlled by Fermi-level pinning, which prevents the tuning of Schottky barrier heights by the modification of the contact metal work function.
Theoretically, the high computational cost of these systems has largely restricted first principles studies to DFT-level calculations. The effects of dielectric screening, which are important even in atomically thin 2D materials¹, are therefore also ignored. Moreover, the small unit cells considered do not allow for the inclusion of defects, which can affect the energy-level alignment at the interface.
In this work we use the newly-developed XAF-GW approach² to study large supercells at the many-body GW level, thus including the full effects of dielectric screening. We examine the origin of the Schottky barrier heights of metal-2D material interfaces, including the effects of dielectric screening, structural reconstruction, and defects.

(1) Noori; Cheng; Xuan; Quek 2D Mater. 2019, 6 (3), 035036
(2) Xuan.; Chen.; Quek J. Chem. Theory Comput. 2019, 15 (6), 3824