Variation of defect states with the number of layers in 2D materials

The high sensitivity of two-dimensional (2D) materials to surroundings makes layer number an important consideration in designing devices for opto-electronic and quantum applications. However, the theoretical prediction on the variation process of defect level with increasing layer number is challenging due to the high computational cost. Here, we used a recently developed continuum model^[1] to explore the layer-dependent effects. The scheme removes the defect-free layers from the density-functional-theory (DFT) calculations and captures their effects on the defect by replacing the electrostatic effect of the defect-free layers with a continuum dielectric function. Application of this method to defects in multilayer hBN (from monolayer to five-layer and bulk) reveals that defect levels become shallower with increasing layer number due to the increased dielectric screening, and the reduction process of ionization energy is highly dependent on the level of theory (DFT or many-body perturbation theory) as a result of the presence of self-interaction error and the absence of non-local screening effect in DFT.

[1] D. Wang and R. Sundararaman, Phys. Rev. Mater. 3, 083803 (2019)