Sputter-erosion dynamics of Ni(1 1 0) surface

We have studied the morphological evolution of Ni(1 1 0) surface induced by low-energy ion sputtering at room temperature with scanning tunneling microscopy. We found that there are two different time regimes in the sputtering processes. In the first regime, a ripple structure is formed with the wave vector along the direction [1 1̄ 0] due to the strong diffusion bias along the direction and the surface roughness increases fast with time. However, in the second regime, three-dimensional mounds are formed with absent anisotropy and the logarithmic surface roughness becomes saturated.