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Tailoring writability and obtaining better signal-to-noise ratio performance by tuning the magnetic and microstructural properties of FePt media is of great interest in the bid to achieve high areal densities for next generation hard disk drives (HDDs). Conventional ways to tune FePt media are primarily by either the insertion of additional layers, or by inclusion of segregants such as B, C, Ni, SiO2 etc. Here we describe an approach that involves modifying growth kinetics by N inclusion, via plasma treatment in FePt bilayers (consisting of a hard and a soft FePt layer). The soft FePt layer aids in obtaining easy writability, while nitrogen plasma treatment of the interface of the two FePt layers facilitates suitable tailoring of the microstructure. This approach contributed to lowering of grain dimension as well as reduction in domain sizes in the FePt bilayers, but with the unwanted side-effects of reduction in squareness and ordering. However, we further propose a method to alleviate these concerns by the deposition of the soft FePt layer in partial nitrogen atmosphere, that restored the squareness and ordering while retaining the smaller domains obtained by nitrogen plasma treatment. Thus, the proposed approach provides a potential direction towards meeting the mutually conflicting requirements of easy writability and better signal-to-noise ratio performance in FePt media. ASTAR (Agency for Sci., Tech. and Research, S’pore) Accepted version

To explore the full capabilities of proton beam writing (PBW) as a lithographic tool it is important to investigate potential new resist materials. In PBW the interactions of the protons with the resist are comparable to the electron interactions with the resist in electron beam writing. In both techniques the induced secondary electrons will modify the molecular structure of the resist, therefore electron beam resists are potential candidates for PBW. Here we discuss resist properties such as contrast and sensitivity of two new negative resists for PBW. The first resist is a spin-coatable TiO2 resist for which sub 10 nm resolution has been reported using electron beam writing. In PBW smooth side walls have been observed for this resist. Despite a relative low sensitivity of this resist for PBW (8000 nC/mm2) it has potential applications in the area of integrated optical components such as waveguides and gratings because of its high refractive index. WL-7154 is a UV-sensitive negative resist and shows high sensitivity for PBW (4 nC/mm2). This resist could function as a mold for Ni electroplating to fabricate Ni stamps for nanoimprint- and soft-lithography.