Spontaneous Nanoscale Corrugation of Ion-ErodedSiO2: 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 ${\mathrm{SiO}}_2$ surface eroded by ${\mathrm{Ar}}^{+}$ ions. The corrugation wavelength ${\lambda }^{*}$ shows a nearly linear dependence on ion energy. Between room temperature and $\sim 200°\mathrm{C}$, ${\lambda }^{*}$ depends weakly on temperature and above $\sim 200°\mathrm{C}$ 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 $({\lambda }^{*}{)}^{-4\mathrm{}}$.