Ultrathick MA2N4(M'N) Intercalated Monolayers with Sublayer-Protected Fermi Surface Conduction States: Interconnect and Metal Contact Applications

Recent discovery of ultrathick MoSi₂N₄(MoN)_n monolayers open up an exciting platform to engineer two-dimensional (2D) material properties via intercalation architecture. In this study, a series of ultrathick MA₂N₄(M'N) monolayers (M, M' = Mo, W; A = Si, Ge) is computationally investigated under both homolayer and heterolayer intercalation architectures, in which the same and different species of transition metal nitride inner core sublayer are intercalated by outer passivating nitride sublayers, respectively. The MA₂N₄(M'N) are stable metallic monolayers with excellent mechanical strength. Intriguingly, the metallic states around Fermi level are localized within the inner core sublayer. Carrier conduction mediated by electronic states around the Fermi level is thus spatially insulated from the external environment by the native outer nitride sublayers, suggesting the potential of MA₂N₄(M'N) in back-end-of-line metal interconnect applications. N and Si (or Ge) vacancy defects at the outer sublayers create ‘punch through’ states around the Fermi level that bridges the carrier conduction in the inner core sublayer and the outer environment, forming an electrical contact akin to the ‘via' structures of metal interconnects. It is further shown that MoSi₂N₄(MoN) can serve as a quasi-Ohmic contact to 2D WSe₂. These findings reveal the potential of ultrathick MA₂N₄(MN) monolayers in interconnect and metal contact applications.