Stranski–Krastanov-like growth of an Ag film on a metallic glass

We have studied the morphology of a bulk-crystalline metal, Ag, deposited on a clean surface of a metallic glass, Zr–Ni–Cu–Al. At 190–300 K, the films exhibit Stranski–Krastanov-like growth, wherein three-dimensional clusters form atop an Ag wetting layer that is 4–5 monolayers thick. Above this coverage, cluster growth competes with growth of the flatter regions. The cluster density increases with decreasing temperature, indicating that the conditions of island nucleation are far-from-equilibrium. Within a simple model where clusters nucleate whenever two mobile Ag adatoms meet, the temperature-dependence of cluster density yields an (reasonable) upper limit for the value of the Ag diffusion barrier on top of the Ag wetting layer of 0.32 eV. Overall, this prototypical study suggests that it is possible to grow films of a bulk-crystalline metal that adopts the amorphous character of a glassy metal substrate, if film thickness is sufficiently low.