The effects of surface ripples on sputtering erosion rates and secondary ion emission yields

The rate of erosion by non-normal incidence ion bombardment of a sinusoidally rippled surface is calculated analytically for an arbitrary dependence of the sputtering yield on the angle of ion incidence and spatial derivatives of the surface gradient as a function of the ratio of the ripple amplitude to wavelength. It is shown that, relative to the value for a flat surface, the erosion rate first increases and then decreases as this ratio increases, but before this decrease can occur, interpeak shadowing of the incident ion flux changes the ripple habit to sawtooth form and the erosion rate reaches a steady-state value. The influence of this variation on the sputtered atom yield and, therefore, on secondary ion yield is also evaluated and shown to compare favorably with experimental studies of the behavior of this parameter. (C) 1999 American Institute of Physics. [S0021-8979(99)05901- 0].