Room-temperature epitaxy of Cu on Si(111) using partially ionized beam deposition

The epitaxial growth of Cu on Si(111) substrate at room temperature was achieved using the Partially Ionized Beam (PIB) deposition technique in a conventional (10⁻⁴ Pa) vacuum without prior in situ cleaning of the substrate or post-annealing of the film. The beam contained ≍2% of Cu self-ions, and a bias of 0 to 4.2 kV was applied to the substrate during deposition. X-ray diffraction studies showed the existence of a twin structure in the epitaxial Cu layer deposited at 1 kV. A mechanism of epitaxial growth of Cu(111) on Si(111) substrate via an η″—Cu₃Si intermediate phase is proposed. Based on the crystal structure of η″—Cu₃Si, it is demonstrated that the geometrical lattice matching concept provides a simple picture of lattice continuity at the interface in this epitaxial system.