Spontaneous pattern formation on ion bombarded Si(001)

Spectroscopic light scattering was used to monitor periodic ripple evolutio n on Si(001) in situ during Ar+ sputtering. Analysis indicates that under h igh flux the concentration of mobile species on the surface is temperature and ion flux independent. This is due to an effect of ion collision cascade s on the concentration of mobile species. We thereby measure the migration energy on the surface to be 1.2 +/- 0.1 eV. The technique is generalizable to any material, including high temperature and insulating materials for wh ich surface migration energies are notoriously difficult to measure.