Nanopatterning by multiple-ion-beam sputtering

We conducted a systematic study on nanopatterning by multiple-ion-beam sputtering, focusing on the superposition of the simple patterns formed by individual ion beams. When Au(001) is simultaneously sputtered by two ion beams at grazing incidence, both nanodot and nanohole patterns are obtained. If a rippled surface is subsequently sputtered at normal incidence, a nanobead pattern is obtained. All of the obtained patterns consist of the nanopatterns formed by individual ion beams; however, the superposition of nanopatterns is not realized in its ideal form. We also discuss the microscopic mechanism of pattern formation by multiple-ion-beam sputtering, and consider the questions and possibilities remaining to be explored.