Super-roughening scaling behaviour of Si surface morphology at grazing incidence low energy ion beam sputtering

The morphological evolution on Si (1 0 0) surface for grazing incidence (75°) and low energy (500 eV) Ar+ sputtering is studied at various ion fluences. The ion induced surface topography was characterized by atomic force microscopy. Initially ion sputtering generates irregular dot-like structure on the surface. These dots begin to elongate along the ion beam direction with the increase of sputtering time and then transform to needle shaped structure at the late stage of sputtering. The morphological data are quantitatively analyzed within the framework of the dynamic scaling theory. Estimated scaling exponents do not follow the conventional Family-Vicsek relation rather exhibit typical anomalous scaling. A crossover in scaling behaviour of local surface width is observed at fluence 1.5 × 1018 cm−2, above which the eroded surface shows super-rough scaling behaviour along the axis of the conical structures with global exponents αs = α = 1.6 ± 0.1, β = 0.99 ± 0.03 and local exponents αlocal = 1 and βlocal = 0.63 ± 0.05. The importance of nonlocal ion reflection effects for the development of super-rough scaling is discussed.