Interplay of erosion and redeposition processes in seed cone formation

Cones developed on Cu surfaces bombarded with a focused Xe⁺ ion beam while simultaneously supplying Mo ‘‘seeds’’ by sputtering were observed by transmission electron microscopy. Cone morphology was found to depend heavily on the distance from the center of the ion beam, i.e., on the local ion‐flux density; the shape was cone‐like near the center, but less so farther from the center. In the central area, where the ion flux was largest, Mo layers were epitaxially grown on cone slopes, whereas the deposition of sputtered seed atoms on cone tops was enhanced in the peripheral area where the flux density was lowest. These findings indicate that the ion etching and the redeposition of sputtered seed atoms took place in a competitive manner, and the morphology and structure of the final cones were determined by the predominant process.