Influence of crystal orientation on pattern formation of focused-ion-beam milled Cu surfaces

The erosion profiles of Cu surfaces after focused ion beam sputtering have been investigated as a function of crystal orientation and ion beam incidence. We find that all patterns are aligned with crystallographic axes and have wavelengths of about 0.5 mu m. The patterns depend strongly on the crystal orientation, typically with similar patterns for neighboring orientations, but may also be influenced by the ion beam direction. For orientations close to {100}, we find however that surfaces stay smooth for all incidence angles. The results are discussed in the context of current continuum models and indicate that modifications to the models are required to account for the effect of crystal orientation.