V. Sundar, X.M. Yang, Y. Liu, Z. Dai, J. Zhu, B. Zhou, K. Lee, T. Chang, D. Laughlin, J-G Zhu
Carnegie Mellon University,
Keywords: templated growth, nanoimprint lithography, additive approach, bit patterned media
Summary:In this work, we present a novel additive approach for the fabrication of high-density nanostructures for applications in next-generation recording and memory technologies. By co-sputtering two immiscible materials, and by designing a template1,2 with a specific material and dome-shaped morphology, we illustrate that nanodots of one material embedded in a matrix of a different material can be fabricated. This concept exploits the difference in surface mobilities of the two immiscible species as they land on the template surface during sputtering. The species with the higher relative surface mobility predominantly grows within the trenches between the domes, while the species with the lower surface mobility grows on the tops of the domes. By pre-fabricating a template with a regular arrangement of domes, thus enabling the fabrication of a highly uniform two-phase microstructure. Aiming at next-generation bit patterned magnetic recording media, nanodots of a magnetic cobalt-platinum (CoPt) alloy in a matrix of amorphous non-magnetic silicon oxide has been fabricated at a dot density of 1 Terabit-per-square-inch. The isolation of the magnetic dots is illustrated through high-resolution transmission electron microscopy and its effect on the magnetic properties of the film are discussed. Figure 1 shows the plane-view transmission electron micrograph of the templated media, illustrating the regular arrangement of CoPt nanodots in a silicon oxide matrix. The growth of CoPt and the oxide is illustrated through a cross-section image in Figure 2, using energy dispersive x-ray spectroscopy-based elemental mapping and the accompanying high-angle annular dark field image. In the corresponding elemental maps, we see that the Co grows on top of the patterned ruthenium dome, while the silicon oxide (which is darker than the higher ‘z’ cobalt in the HAADF image) grows within the trench between adjacent domes. This technique can be further extended for the fabrication of a variety of nanostructures, such as nanowires, and for a variety of nanodots by choosing appropriate immiscible material combinations.