Surface growth and anomalous scaling of sputter-deposited Al films

Thin Al films are sputter deposited on Si(1 0 0) substrates and the surface growth is studied by atomic force microscopy. The scaling analysis reveals intrinsic anomalous scaling and multi-scaling in surface growth of the films. The anomalous scaling is characterized by the local roughness exponent and the local growth exponent, αloc=1.0±0.1 and βloc=0.35±0.02, respectively, the global ones, α=1.6 and β=0.56±0.03, and the coarsening exponent 1/z=0.36. The rms local slope scales with time as ρ∝t0.19±0.02. The anomalous scaling is related to the nonlocal shadowing effect during film growth. Together with the unstable growth and the global roughening, surface smoothing is also observed, which is ascribed to surface diffusion of the adatoms during film growth.