Jinwoong Chae1,Gunn Kim1
Sejong University1
Electrons act as anions in the cavities of a positively charged framework in electrides, which are ionic crystals. Electrides have unique features such as low work functions and resistance anisotropy. Two-dimensional electron gas (2DEG) on the surface of dicalcium nitride (Ca<sub>2</sub>N), which is one of the two-dimensional (2D) electrides, attracts attention, even for the monolayer. However, because electrides are readily degraded by air and moisture due to their high reactivity, it is expected that their unstable surface's electrical properties of electrides will be easily altered. Here, we introduce the electronic properties of the bilayer Ca<sub>2</sub>N with point defects by using ab initio calculations based on density functional theory. The 2DEG on the surface is spin-polarized for the outermost Ca atom vacancy (V<sub>out-Ca</sub>), whereas the other models are not spin-polarized. The formation energy is 1.89 eV for V<sub>out-Ca</sub>, and the formation energy for the N atom vacancy (V<sub>N</sub>) is 2.78 eV, which is the highest case. We calculated that the work function for V<sub>out-Ca</sub> is 3.19 eV lower than pristine bilayer Ca<sub>2</sub>N (3.38 eV), whereas the other cases have larger work functions (3.46 and 3.45 eV) than pristine bilayer Ca<sub>2</sub>N. Finally, we consider the substitutional H or N impurity atom for V<sub>out-Ca</sub>. In these cases, we can confirm that the electrical characteristics of 2DEG on the surface have changed.