The authors have conducted research regarding ripple formation on an atomically flat cleaved Si surface by low-energy Ar+ ion bombardment. The cleaved atomically flat and smooth plane of a Si wafer was obtained by cutting vertically against the orientation of a Si (100) wafer. Next, the cleaved surface was sputtered by a 1 keV Ar+ ion beam at ion-incidence angles of 0°, 60°, 70°, and 80°. The results confirm the successful ripple formation at ion-incidence angles of 60°–80° and that the wavelength of the ripples increases with the increase of the ion-incidence angle, as well as the inverse of ion doses. The direction of the ripple also changes from perpendicular to parallel to the projection of the ion-beam direction along the surface with the increasing ion-incidence angle. The authors have also observed the dose effects on surface roughness of cleaved Si surface at the ion-incidence angle of 60°, where the surface roughness increases with the increased ion dose. Finally, to understand the roughening mechanism, the authors studied the scaling behavior, measured the roughness exponent α, and compared the evolution of scaling regimes with Cuerno’s one-dimensional simulation results.

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We have investigated the changes of ripple morphology of an atomically°at cleaved Si surface due to Ar þ ion bombardment. The cleaved atomically°at and smooth plane of Si wafer was obtained by cutting vertically against the orientation°at of a Si (100) wafer. Then, the cleaved surface was bombarded by 1 keV Ar þ ion beam at ion incidence angle of 0 , 50 , 60 , 70 , and 80 . The ripples structure were depends on ion dose and angle formed on atomically°at surface at ion incidence angle of 50 , 60 , 70 , and 80 . Ripples were unclear and small at ion doses of 1:0 Â 10 18 ions=cm 2 but pronounced at ion dose of 8:0 Â 10 18 ions=cm 2 . The wave lengths of ripples were measured and the maximum wave length is 425 nm at ion incidence angle of 70 and ion dose of 8:0 Â 10 18 ions=cm 2 . Results show that the wave length of ripple depends on ion doses and angle of ion incidence. It was also observed that the wave vector of ripple changes with changing the angle of ion incidence. This research is concluded by discussing the wave vector changing mechanism with the help of BH model.

Etching of surfaces by ion beam sputtering is widely used to pattern surfaces. Recent studies using the high-spatial-resolution capability of the scanning tunneling microscope, atomic force microscope and SEM (Scanning Electron Microscopy) disclose in fact that ion bombardment creates repetitive structures at micro-nanometre scale, waves (ripples), checkerboards or pyramids. The phenomenon is related to the interaction between ion erosion and diffusion of adatoms (vacancies), which causes surface re-organization. In this paper we investigated the ripple pattern formation on Si substrates by low energy Ar+ ion bombardment and the dose effect on ripple size. We also briefly discussed the irradiation effects (at normal incidence) on ripple pattern for different irradiation time. Finally, based on Bradley and Harper (BH) theory we proposed a model to understand the mechanism of ripple pattern change due to Ar+ ion beam irradiation.