Two-Dimensional Transition-Metal Electride Y2C

Abstract

Electrides are ionic crystals in which the anionic electrons are confined to interstitial subnanometer-sized spaces. At present, the reported electrides only consist of main-group elements. Here, we report a layered-structure transition-metal hypocarbide electride, Y2C, with quasi-two-dimensional (quasi-2D) anionic electrons confined in the interlayer space. Physical properties measurements reveal polycrystalline Y2C exhibits semimetallic behavior, and paramagnetism with an effective magnetic moment of ∼0.6 μB/Y, because of the existence of localized d-electrons. Photoelectron spectroscopy measurements illustrate the work function of polycrystalline Y2C is 2.9 eV, lower than Y metal, revealing the loosely bound nature of the anionic electrons. Density functional theory calculations indicate the density of states at the Fermi level originates from the states at interstitial sites and the Y 4d-orbitals, supporting the confinement of anionic electrons within the interlayer space. These results demonstrate that Y2C is a quasi-2D electride in term of [Y2C]1.8+·1.8e–, and the coexistence of the anionic electrons and the Y 4d-electrons leads to the semimetallic behavior.