Effects of a single vacancy on electronic properties of a Ca2N electride bilayer

Abstract

We present the optimized geometric and electronic structures of a defective Ca2N bilayer with a monovacancy. Using first-principles calculations, we investigate effects of a vacancy on the electronic properties of interlayer anionic electrons (IAEs) and surface anionic electrons (SAEs) in defect-free and defected structures. The electron density is non-uniform in the interlayer region of the defective Ca2N bilayer. In the absence of Ca atoms, electrons at a specific position of the interlayer decrease by about 40% compared with a defect-free bilayer. Besides, we obtain simulated images for scanning tunneling microscopy (STM) to explain the SAE states of the 2D electride bilayer. The STM simulation can determine which atom is missing from the STM images. We hope that our study will enable one to understand how defects affect the properties of electrides.