Suppression of conductivity deterioration of copper thin films by coating with atomic-layer materials

Abstract

Theoretical calculations are performed to explore the electronic structures and electron conducting properties of copper (Cu) thin films coated with graphene or h-boron-nitride (h-BN) layers. The Shockley surface states of Cu surfaces are preserved by the graphene and h-BN coatings which prevent the surface oxidation of Cu because of the weak interaction between the Cu surface and graphene or the h-BN layers. Furthermore, the Shockley surface states in Cu thin films possess quasi-two dimensional free-electron characteristics and exhibit a high conductivity of 1.62 × 107 (Ωm)−1 at room temperature. These hybrid structures may be suitable as interconnects in memory devices that can stably store data for long periods.

Effect of encapsulation on electronic transport properties of nanoscale Cu(111) films

“…Our calculated value for the effective mass matches well with the theoretical value, 0.38 m e , reported by Cuong et al . 29 and González-Herrero et al . 21 for Cu(111) surfaces.…”

“…The chemical bond between Cu and O is 1.85 Å and is in good agreement with the theoretical value reported by Cuong et al . 29 and experimental value of 1.85 Å 30,31 . The formation of Cu-O is in general energetically stable 30 .…”

“…The strong covalent bonding between carbon atoms in Gr offers a very high diffusion barrier against O penetration. A recent molecular dynamics simulations based study 29 reported 20 eV energy barrier for O diffusion through graphene. Such a high energy barrier indicates that the diffusion is unlikely to happen.…”

“…Using Boltztrap, our computed effective electronic conductivity ( σ / τ ) value 1.72 × 10 21 (Ω ms ) −1 for bulk Cu at room temperature matches well with the theoretical value reported by Cuong et al . 29 . This gives the resistivity of bulk Cu to be ρ = 2.15 × 10 −8 Ω m which agrees well with the experimental value of 1.72 × 10 −8 Ω m 41 .…”

A novel graphene barrier against moisture by multiple stacking large-grain graphene

“…Graphene, a two-dimensional carbon (C) layer, is a candidate for ultra-thin barrier layers because of its atomically thin crystal structure 2 . In addition to a potential diffusion barrier 3–6 , graphene has been reported as a candidate capping layer to enhance the electromigration (EM) reliability 7 , electrical conductivity, and thermal conductivity of Cu interconnects 8,9 .…”