Spontaneous nanoscale corrugation of ion-eroded SiO2: the role of ion-irradiation-enhanced viscous flow.

Grazing incidence x-ray scattering was used to determine the temperature and ion-energy dependence of nanoscale corrugations that form on an amorphous SiO2 surface eroded by Ar+ ions. The corrugation wavelength lambda* shows a nearly linear dependence on ion energy. Between room temperature and approximately 200 degrees C, lambda* depends weakly on temperature and above approximately 200 degrees C it shows an Arrhenius-like increase. Ion-assisted viscous relaxation in a thin surface layer is shown to be the dominant smoothing process during erosion; the rate of viscous smoothing scales as (lambda*)(-4).