ROUGHENING AND FACETING IN A PB THIN-FILM GROWING ON THE PB(110) SURFACE

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 approximately t(beta) with beta = 0.77 +/- 0.05. The other scaling hypothesis involving the lateral correlation length xi approximately t(beta/alpha) is no longer valid and the local roughness increases dramatically.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) approximately f(t)r2alpha with alpha = 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.