Large-area fabrication of periodic Fe nanorings with controllable aspect ratios in porous alumina templates

Highly uniform Fe nanoring arrays in porous anodic alumina templates are fabricated by physical vapour deposition and grazing ion milling techniques. The nanorings have aspect ratios ranging from 0.8 to 4, depending on the deposition conditions. The outer diameter of the individual nanorings, and the area density and distribution patterns are completely determined by the template used. Selected-area electron diffraction reveals that these nanorings have a polycrystalline microstructure. The nanoring fabrication method demonstrated here can be extended to other materials.