Atomically thin transition metal layers: atomic layer stabilization at the oxide interface*

We have performed first-principles calculations to explore the possibility of synthesizing atomically thin transition metal (TM) layers. It is found that the formation energies of free-standing TM layers are significantly higher than similar sp-bonded monolayers such as silicene and borophene. It is shown that the TM layers can be stabilized by surface passivation with HS, C₆H₅S₂, or O, and that O passivation is most effective leading to thermodynamically stable TM monolayers for most of the TM elements. For the surface oxygen passivation case, the atomic and electronic structures of stabilized TM monolayers are investigated. It is suggested that the large-area synthesis of these 2D TM layers can be extended to general TM elements not having bulk layered structure by employing metal atomic layer deposition (ALD) methods. Our prediction based on the density functional theory calculations is supported by a recent experiment, where atomically thin W film was fabricated by ALD on the oxide substrate and shown gate-controllable electronic property. In relation to the experiment, we also investigate the interface effects on the electronic property of the stabilized W monolayers.