Direct-Write 3D Nanoprinting of High-Resolution Magnetic Force Microscopy Nanoprobes

Magnetic devices play an important role in modern electronic, sensing or data storage applications. Toexploit their full potential, high-resolution Magnetic Force Microscopy (MFM) is established asstandard characterization technology as part of the research and development loop. Due to theongoing trend towards smaller and smaller active feature sizes, the demands on high-resolution MFMtips are also increasing. Based on that motivation, we here aim on the fabrication of MFM nanoprobeswith functional apex radii in the sub-10 nm regime. Traditional products mostly base on additionalmagnetic coatings, which increases the apex radii and therefore limits the lateral resolution duringAtomic Force Microscopy (AFM) based MFM measurements. Another disadvantage of a magneticcoating is local delamination, which can occur due to the mechanical stress during scanning and leadto a change (or even complete loss) in magnetic sensitivity. Therefore, it was the goal to fabricate fullymagnetic nanoscale tips, that do not require additional coating. Focused Electron Beam InducedDeposition (FEBID) was used for additive, direct-write 3D-nanoprinting of such magnetic tips on prefinishedself-sensing AFM cantilevers.[1],[2] For that, a novel HCo3Fe(CO)12 precursor was used, which isone of the few precursors, providing metal contents above 90 at.% after initial FEBID fabrication.[3] Toexplore the possibilities, we comprehensively studied the parameter space and their implications onmorphology, structure and chemistry in detail by using SEM, EDX, and TEM and STEM EELS (Figure 1.a).Next, the tip geometry was further optimized by an advanced, dynamic pattering sequence to fulfil thehigh demands for AFM operation.[4] Additionally, the fabricated tips were subjected to different postprocessingprocedures such as post-irradiation with electrons, thermal treatments and purificationprotocols to explore and identify the most promising fabrication window. The basic performance ofsuch MFM tips is then demonstrated with special focus on lateral resolution, magnetic phase shift andsignal-to-noise ratio. Fully optimized FEBID-MFM tips were then tested on various magnetic samples(magnetic multilayer system (Figure 1.b-e), hard disc drives, magnetic recording tapes) andbenchmarked to commercially available MFM tips (Figure 1.b-c). Finally, the wear resistance of suchMFM nanoprobes was evaluated during a continuous operation scan over a period of 3.7 hours, whichrevealed the high durability of the presented concept (Figure 1.d-e). By that, we demonstrate thesuccessful 3D-nanoprinting of MFM tips on self-sensing cantilevers, which fulfils the high requirementswhen aiming on industrially relevant MFM tips using FEBID-based 3D nanoprinting.