Atomic adsorption on monolayer Cu2Se: a first-principles study.

Monolayer Cu2Se is a novel two-dimensional (2D) material, but its fundamental properties have not been adequately investigated. Hence, in this work, we investigate the adsorption behaviors of various elements on monolayer Cu2Se using first-principles density functional theory calculations. The considered elements include metals (Li, Na, Al, K, Ca, Fe, Co, Ni, Cu, Zn, Pd, Ag, Pt, and Au) and nonmetals (H, B, C, N, and O). The adsorption of all these atoms is exothermic with substantial binding energy. Although monolayer Cu2Se forms strong bonds with all the adsorbates, it still preserves its layered structure. This atomic adsorption substantially modifies the electronic properties of the 2D Cu2Se. In particular, N, Fe, Co, Ni, and Au adatoms give rise to mid-gap states within the bandgap of monolayer Cu2Se; furthermore, except for Au, the other adatoms exhibit magnetic moments. Naturally, this electronic structure modification also leads to changes in the work function of monolayer Cu2Se. The present work demonstrates that atomic adsorption can optimize the properties of monolayer Cu2Se.