The bunching of permeable steps, caused by the drift of adatoms, was studied. Unlike impermeable steps, bunching could occur with step-up drift. When the diffusion length was short, the terrace width between bunches increased as tβ (where β was about ½) via collisions and coalescence. Following power-law growth, the system reached a steady state in which an array of similar bunches coexisted with a few single steps on large terraces. When the diffusion length was long, β approached unity.

Growth of Permeable Step Bunches Formed by Drift of Adatoms. M.Sato, M.Uwaha, Y.Saito: Surface Science, 2001, 493[1-3], 480-6