Deposition of Mg on Si(111)7 × 7 produces an epitaxial magnesium silicide layer. Under identical annealing conditions, the thickness of this Mg${}_2$Si(111) layer increases with deposition amount, reaching a maximum of 4 monolayer (ML) and decreasing to ∼3 ML at higher Mg coverage. Excess Mg coalesces into atomically flat, crystalline Mg(0001) films. This surprising growth mode can be attributed to the accidental commensurability of the Mg(0001), Si(111), and Mg${}_2$Si(111) interlayer spacing and the concurrent minimization of in-plane Si mass transfer and domain-wall energies. The commensurability of the interlayer spacing defines a highly unique solid-phase epitaxial growth process capable of producing trilayer structures with atomically abrupt interfaces and atomically smooth surface morphologies.

• Received 1 March 2013

DOI:https://doi.org/10.1103/PhysRevB.88.045415