Perpendicular patterned media in an (Al0.9Ga0.1)2O3/GaAs substrate for magnetic storage

By using electron beam lithography, chemically assisted ion beam etching, and electroplating, we have fabricated high aspect ratio magnetic columns, 60–170 nm in diameter, embedded in an aluminum–gallium–oxide/gallium–arsenide ${\mathrm{[(Al}}_{\mathrm{0.9}}{\mathrm{Ga}}_{\mathrm{0.1}}{\mathrm{)}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{3}}\mathrm{/GaAs]}$ substrate. In our previous work, we demonstrated storage of data in individual columns spaced 2 μm apart. Here the electroplated Ni columns are in the form of tracks (0.5 and 0.25 μm in the down-track direction, and 1 μm in the cross-track direction), corresponding to areal densities of 1.3 and 2.6 Gbits/in.², respectively. In this report we describe in more detail the issues in the fabrication of patterned media samples, such as dry etching and oxidation of AlGaAs, and electrodeposition of Ni into GaAs substrate. Initial characterization of the resulting magnets using magnetic force microscopy are also presented.