Surface evolution by solid-state diffusion

If the smoothing process occurs by solid-state diffusion of atoms along the surface, it can be shown [13] that the height will change in time according to 

the shortest wavelength surface roughness features decay most rapidly while the longer wavelength roughness features decay more slowly. This feature-dependent decay speed is analogous to other transient diffusion processes (recall, e.g., the discussion of transient diffusion in Chapter 4, where we saw that the sharpest features in a concentration profile decay most rapidly). 

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