FLUX DENSITY EQUATIONS FOR TOPOGRAPHICAL EVOLUTION OF FEATURES ON ION BOMBARDED SURFACES.

A two dimensional model of an asperity protruding above a planar surface is used to derive an expression for the flux density at a profile of arbitrary shape originating from a linear emitter. Analytical solutions are found for asperities of linear and sinusoidal profile. The solutions have a general significance and will for example, describe the incidence onto a substrate of evaporated atoms or diffusely emitted light from a line source. In this work results are used to give qualitative predictions of the changes of shape to be expected due to redeposition of sputtered atoms onto features standing proud of a planar surface during bombardment by an ion beam. These predictions are compared with scanning microscope observations of the evolution of conical features on argon bombarded amorphous surfaces. It is found that several of the observed effects can be qualitatively explained by the model.