Study of 1.5Â keV Ar atoms beam induced ripple formation on Si surface by atomic force microscopy

The topography of Si(1 0 0) and Si(1 1 1) surfaces after irradiation with 1.5 keV Ar atoms beam incident at 45° with respect to the surface normal has been studied as a function of atom fluence using atomic force microscopy. The sputtered silicon (1 0 0) samples exhibit ripple pattern, with the average value of the ripple wavelength increasing from 15 nm to 19 nm as fluence increases from 1.7 × 1017 atoms/cm2 to 5.1 × 1017 atoms/cm2, though the height of ripples remains same i.e. 1.02 nm. On the other hand, in case of Si(1 1 1) samples, the average value of the ripple wavelength increases from 22 nm to 40 nm with fluence increasing from 1.7 × 1017 atoms/cm2 to 5.1 × 1017 atoms/cm2. A close view of the surface morphologies of Si(1 0 0) and Si(1 1 1) showed that the ripples on Si(1 1 1) surface are, more regular than Si(1 0 0). When the fluence is further increased, it is found that the wavelength of ripple tends to saturate and the height tends to decrease, as a result the surface becomes smooth at higher (∼6.8 × 1017 atoms/cm2) fluence.