Electric Field Effect on the Electronic Structure of Two-Dimensional Y2C Electride

Abstract: Electrides are ionic compounds, in which electrons confined in the interstitial spaces serve as anions, and are attractive owing to their exotic physical and chemical properties in terms of their low work function and efficient charge transfer characteristics. Depending on the topology of anionic electrons, the surface electronic structures of electrides can be significantly altered. In particular, the electronic structures of two-dimensional (2D) electride surfaces are of interest, because the localized anionic electrons at the interlayer space can be naturally exposed to cleaved surfaces. In this paper, we report the electronic structure of 2D Y2C electride surface, using scanning tunneling microscopy and first-principles calculations, revealing that anionic electrons at cleaved surface are absorbed into the surface and subsequently resurged onto the surface by an electric field. It is highlighted that the estranged anionic electrons caused by the electric field occupy the slightly shifted crystallographic site compared to the bulk Y2C electride. We also measured the work function of the Y2C single crystal and it showed slightly lower value than calculated value which appears to be due to the electric field from the STM junction.