Surface ripple amplification and attenuation by sputtering with diametrically opposed ion fluxes

Monodirectional, obliquely incident, ion bombardment fluxes can generate travelling wave or ripple structures on surfaces as a result of competition between sputtering erosion effects and relaxation processes. It is shown that if two independent ion fluxes, incident in diametrically opposite directions, are employed then the resulting surface structure is a static wave with an amplitude which is time modulated and which, periodically, results in a flat surface. This behaviour may be useful in sputter depth profiling applications.