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\ensuremath{\sim}${\mathit{t}}^{\mathrm{\ensuremath{\beta}}}$ with \ensuremath{\beta}=0.77\ifmmode\pm\else\textpm\fi{}0.05. The other scaling hypothesis involving the lateral correlation length \ensuremath{\xi}\ensuremath{\sim}${\mathit{t}}^{\mathrm{\ensuremath{\beta}}/\mathrm{\ensuremath{\alpha}}}$ is no longer valid and the local roughness increases dramatically.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)\ensuremath{\sim}f(t)${\mathit{r}}^{2\mathrm{\ensuremath{\alpha}}}$ with \ensuremath{\alpha}=1.33\ifmmode\pm\else\textpm\fi{}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.