Two-dimensional electron gas on the Gd₂C electride surface: A first-principles study

Electrides are interesting ionic compounds in which electrons behave as anions in the interior of a positively charged framework. Gd2C is a type of stable layered electrides. Although previous research has focused on the bulk properties of Gd2C, few studies have focused on ultrathin layers or surfaces for two-dimensional (2D) characteristics. In this talk, we present our first-principles study of the electronic properties of few-layer Gd2C structures. We show that Gd2C has a work function of 3.35 eV. Because the interlayer region has changed to the surface by exfoliation, the properties of the electron gases once located in the interlayer in the past will also change. We found that the surface anionic electrons accounted for about 25% of the number of electrons in the interlayer region in the absence of an external electric field. When we applied an external electric field, the number of surface electrons increased, and the increase was proportional to the square of the field intensity. Since the electronic properties of 2D materials can be understood through scanning tunneling spectroscopy (STS), we also performed the STS simulations. At −0.9eV, the STS image was blurred because of surface anionic electrons. In contrast to the spin-up electron, an interlayer band of the spin-down electron crossed the Fermi level in the ultrathin Gd2C layers. Our findings open a possibility that the spin-polarized electronic gas in the few-layer electride could be used for spintronics.