Oxidation, Stability, and Magnetic Ground States of Two-Dimensional Layered Electrides

Abstract

Two-dimensional electrides have emerged as a new class of layered materials, in which excess electrons exist in the interlayer spacing. These anionic electrons cause exotic electronic properties, such as low work function, high electronic mobility, and magnetic anisotropy. However, they render the surface of the electrides remarkably reactive; therefore, the surfaces are prone to oxidation. In this study, we investigated the oxidation mechanisms of two representative electrides, Ca2N and Y2C, using first-principles calculations. The adsorption of atomic and molecular oxygen on Ca2N and Y2C monolayers was observed to be highly exothermic (∼5 eV/atom). Upon adsorption, triplet O2 molecules spontaneously dissociated on both monolayers owing to an enormous charge transfer from the surfaces (∼1.4e/atom). The dissociated O atoms had no magnetic moments, while the electride surfaces exhibited a complex ferrimagnetic ground state caused by the charge transfer and structural deformation accompanying the O2 adsorption. Similar adsorption behaviors were observed even for increased electride thicknesses, implying that our findings are also applicable to the multilayers of the electrides. The present work shed more light on the oxidation mechanism of two-dimensional electrides and may serve as a valuable guide for the synthesis of stable layered electrides.