Nanorippling of GaAs (001) surface near the threshold energy of   sputtering at normal ion incidence
  Ripple formation driven by Ehrlich-Schwoebel barrier is evidenced for normal incidence 30 eV Ar+ bombardment of GaAs (001) surface at elevated target temperature. The pattern follows the symmetry of the bombarded crystal surface. The results can be described by a non-linear continuum equation based on biased diffusion of adspecies created by ion impact. 
Debasree Chowdhury, Debabrata Ghose*, Safiul Alam Mollick, Biswarup   Satpati and Satya Ranjan Bhattacharyya
cond-mat.mtrl-sci