Ion-beam nano-patterning by using porous anodic alumina as a mask

Abstract

Anodized aluminium oxide (AAO) with self-organized and ordered nano-hole arrays may bea good candidate for an irradiation mask to modify the properties of a nano-scaleregion. In order to use AAO as a mask for ion beam patterning, the ion beamtransmittance of AAO should first be tested. In an AAO with a high aspect ratio (about100), anodized from Al bulk foil, the ion beam transmittance was extremely low.However, when AAO with low aspect ratio (about 5), fabricated with thin film Al onSiO2, was irradiated with 80 keV Co ions, the Co ion transmittance was enormouslyimproved. After selective etching of the unirradiated region, ion beam patterned 80 nmSiO2 dot arrays have been fabricated. This shows a potential of AAO with a low aspect ratio foran ion beam patterning nano-mask. In order to demonstrate the ion beam nano-patterning,magnetic nano-patterning was performed. A Co/Pt multilayer film with a perpendicularmagnetic anisotropy was ion irradiated through an AAO mask with a low aspect ratio,460 nm height and 50 nm diameter, and the magnetic properties were investigatedby MOKE. The formation of a magnetic nano-pattern was confirmed by MFM.