Roughening and faceting in a Pb thin film growing on the Pb(110) surface

Abstract

Using high-resolution low-energy electron diffraction, we have observed nonconventional dynamic scaling during the molecular-beam-epitaxy growth of Pb/Pb(110). The growth front becomes increasingly rough as more Pb atoms are deposited. At a low growth rate, the interface width w changes with deposition time t in a scaling form w∼${\mathit{t}}^{\mathrm{\beta }}$ with β=0.77±0.05. The other scaling hypothesis involving the lateral correlation length ξ∼${\mathit{t}}^{\mathrm{\beta }/\mathrm{\alpha }}$ is no longer valid and the local roughness increases dramatically. However, the short-range height-height correlation function H(r) still scales with r, the horizontal distance between two points in the surface, in the form of H(r,t)∼f(t)${\mathit{r}}^{2\mathrm{\alpha }}$ with α=1.33±0.05. At the later stage of growth, the rough surface eventually induces an anistropic {111} faceting. Faceting is found to occur earlier when the deposition rate is high.