Atomic force microscopy study of 60-keV Ar-ion-induced ripple patterns on Si(100)

The evolution of a ripple pattern on Si(100) surfaces induced by 60 keV Ar+ beam incident at 60degrees with the surface normal has been studied as a function of bombardment time using ex situ atomic force microscopy (AFM) in ambient condition. The ripple wavelength (l) and roughness amplitude (W) increase with bombardment time following a scaling law lproportional tot(gamma) and Wproportional tot(beta), where gamma=0.64+/-0.08 to a crossover value 0.22+/-0.07 and beta=0.76+/-0.03 to a crossover at 0.27+/-0.11. The ripple orientation and average wavelength observed in the early stage patterned morphology can be described by a linear continuum model. However, the scaling exponents for the power law variation of roughness amplitude and wavelength with bombardment time are not consistent with predictions of the linear model or the Kuramoto-Sivashinsky-equation-based nonlinear model.