Nanoimprint Lithography and Self-Assembly of Functional Metallopolymers and Their Applications in Ultrahigh-Density Perpendicular Magnetic Recording Media

Modern technology depends on fast, reliable data processing and storage. Hard ferromagnetic (L1o-phase) FePt alloy nanoparticles (NPs) with extremely high magnetocrystalline anisotropy are considered to be one of the most promising candidates for the next generation of ultrahigh-density data storage systems. The question of how to generate ordered patterns of L1o-FePt NPs and how to transform the technology to the practical application is challenging. Among different types of patterning technology, traditional methods such as UV-photolithography only provide submicrometer resolution and electron-beam lithography is not suitable for the fabrication of ordered nanostructured arrays of magnetic NPs over large areas because of the high cost, complicated procedures and instruments, and the high demand of materials. Nanoimprint lithography (NIL) is a powerful and cost-effective technology for high- throughput patterning with high resolution. It can be used to imprint different kinds of polymers, allowing its wide application in information storage. Since NIL offers sub-5 nm patterning resolution over very large areas, it is indeed desirable for fabricating bit patterned media (BPM). Unlike traditional lithographic approaches, which achieve pattern definition through the use of photons or electrons, NIL relies on direct mechanical molding of the resist or functional materials and can therefore achieve resolution beyond the limitations set by light diffraction or beam scattering by the conventional techniques. Although nanoimprinting has been used with FePt continuous thin films recently, multiple processing steps are necessary for preparing the nanosized bits. It has been difficult to create BPM with FePt NPs by NIL because the mechanical rigidity of NPs does not allow them to transfer the negative pattern of the mask directly. In this proposal, a new series of soluble metallopolymers consisting of Fe and/or Pt atoms will be developed which combine the merits of both FePt NPs and NIL, thereby creating a ground-breaking method for the simple and rapid fabrication of BPM at very low cost using these metallopolymers as single-source precursors. This represents a novel study to adopt NIL to achieve the high-throughput nanopatterning of hard magnetic NPs. The work can be extended to other hard magnetic NPs such as CoPt, Co3Pt and SmCo5. Additionally, the use of low-cost, self-assembly approach involving functional bimetallic block-copolymers would also be adopted for the generation of nanopatterned magnetic metal alloy NPs with well-defined nanostructures. Such investigation provides a new avenue towards fabricating ultrahigh-density BPM for the next generation of magnetic recording technology and sparks new approach to data storage.