Harald Plank

Coupling electronic spin degrees of freedom to the motion of micromechanical resonators could enable quantum-enhanced force sensing, the exploration of macroscopic non-Gaussian states, and information transduction for hybrid quantum systems. A promising route exploits Zeeman shifts of spin states induced by the displacement of resonators functionalized with magnetic nanostructures. However, established nanomagnet fabrication methods, such as thin-film patterning, are incompatible with the inherently fragile nature of microresonators. Here, we report the successful growth of soft-ferromagnetic Co3Fe pillars, with a 500 nm diameter and 2000 nm height, on 50 nm thick SiN trampoline membranes by focused electron beam induced deposition (FEBID). We show that this functionalization preserves mechanical quality factors up to 7 × 106, confirming that the FEBID process is noninvasive to the resonator. Using nitrogen-vacancy scanning magnetometry, we probe the magnetic properties of a pillar in external fields up to 15 mT and observe a clear opening of its hysteresis loop, indicative of ferromagnetic behavior with a small but finite coercivity. At an NV-Co3Fe pillar apex distance of ∼300 nm we directly measure magnetic field gradients of 3 × 104 T m–1.

Based on previously reported 3D nanoprinted probes for magnetic force microscopy (MFM) , a new class of dual‐functional atomic force microscopy ( AFM ) probes – termed MC‐Probes – is presented that integrates magnetic (M) and conductive (C) functionality in a single, monolithic structure. 3D nanoprinting via Focused Electron Beam Induced Deposition allows direct exploitation of the intrinsic magnetic and conductive properties of the employed Co ₃ Fe precursor. The coating‐free probes feature sub‐10 nm apex radii combined with a mechanically robust pillar geometry, designed to support both contact and tapping‐mode operation depending on the cantilever choice. Comprehensive characterization reveals electrical resistivity ≈ 2 × 10 ³ · µΩ · cm and full tip resistances of, ∼ 1 − 10 k Ω comparable to commercial conductive probes. Mechanical tests confirm apex durability under contact‐mode loads up to. 3 − 4 N · m ⁻¹ MC‐Probe functionality is demonstrated through conductive AFM (CAFM) and MFM measurements performed in the FUSIONScope™ on custom SiO ₂ /Au/Co ₃ Fe test structures. While the current cantilever availability required separate cantilevers optimized for contact and tapping operation, the results establish the foundation for future single‐cantilever dual‐mode integration. Beyond the present study, MC‐Probes open promising perspectives for streamlined correlative investigations across CAFM, MFM, Kelvin probe force microscopy, electrostatic force microscopy, scanning spreading resistance microscopy, and related advanced AFM modes.

The transition from planar to three-dimensional (3D) magnetic nanostructures represents a significant advancement in both fundamental research and practical applications, offering vast potential for next-generation technologies like ultrahigh-density storage, memory, logic, and neuromorphic computing. Despite being a relatively new field, the emergence of 3D nanomagnetism presents numerous opportunities for innovation, prompting the creation of a comprehensive roadmap by leading international researchers. This roadmap aims to facilitate collaboration and interdisciplinary dialogue to address challenges in materials science, physics, engineering, and computing. The roadmap comprises eighteen sections, roughly divided into three blocks. The first block explores the fundamentals of 3D nanomagnetism, focusing on recent trends in fabrication techniques and imaging methods crucial for understanding complex spin textures, curved surfaces, and small-scale interactions. Techniques such as two-photon lithography and focused electron beam-induced deposition enable the creation of intricate 3D architectures, while advanced imaging methods like electron holography and synchrotron x-ray tomography provide nanoscale spatial resolution for studying magnetization dynamics in three dimensions. Various 3D magnetic systems, including coupled multilayer systems, artificial spin-ice, magneto-plasmonic systems, topological spin textures, and molecular magnets are discussed. The second block introduces analytical and numerical methods for investigating 3D nanomagnetic structures and curvilinear systems, highlighting geometrically curved architectures, interconnected nanowire systems, and other complex geometries. Finite element methods are emphasized for capturing complex geometries, along with direct frequency domain solutions for addressing magnonic problems. The final block focuses on 3D magnonic crystals and networks, exploring their fundamental properties and potential applications in magnonic circuits, memory, and spintronics. Computational approaches using 3D nanomagnetic systems and complex topological textures in 3D spintronics are highlighted for their potential to enable faster and more energy-efficient computing.

Following Moore`s law, the performance of devices should double within a two‐year span, which can either be done by reducing the size of the individual components or adapting the working mechanism. In most cases the same mantra applies – pushing the size while keeping the quality. As manufacturing techniques are approaching the atomic scale, however, miniaturization reaches its intrinsic limit, shifting focus toward higher‐dimensional architectures realized by stacking planar layers or fabricating true, free‐standing nanostructures. A mask‐less, additive manufacturing technique with the capability to produce such 3D structures at the nanoscale is called Focused Electron Beam Induced Deposition (FEBID). Applying a focused electron beam in a conventional scanning electron microscope together with a gaseous metal‐precursor gives access to a vast library of complex, 3D nanostructures, which exhibit feature sizes down to the 10 nm‐range and can be printed in a single step on most substrates. This review aims at introducing the technique to a broader scientific community, breaking down the most important processing routes and highlighting disciplines explored so far ranging from nanooptics and nanomagnetism, over scanning probes and field emitters to sensing and particle trapping. Finally, a future roadmap of the technique is discussed, and prospective research focus identified.

Electron-assisted oxidation of Co–Si-based focused electron beam induced deposition (FEBID) materials is shown to form an oxide bilayer with a total thickness of less than 15 nm by phase separation.

Nanoelectromechanical systems (NEMS) have shown outstanding performance in the detection of small masses down to single proton sensitivity. To obtain a high enough throughput for application in practical mass spectrometry, NEMS resonators are arranged in two-dimensional (2D) arrays. However, all state-of-the-art electromechanical transduction methods rely on electrical lines placed close to the mechanical resonators, which drastically restricts the density of 2D resonator arrays. An exception is the transduction by surface acoustic waves (SAWs), which has so far only been shown for the transduction of single nanomechanical pillar resonators. Here, we demonstrate the transduction of pillar pairs by SAWs. The pillars have a diameter of 700 nm and show a mass responsivity of −588 ± 98 ng−1. The distances between the pillar pairs are 70 nm and 14.3 µm. SAW transduction enabled us to measure both pillars of each pair with electrical lines no closer than 300 µm, illustrating the potential of SAWs to transduce dense arrays of pillar resonators, a crucial step toward practical mass spectrometry with NEMS.

Electron-induced fragmentation of the HFeCo₃(CO)₁₂ precursor allows direct-write fabrication of 3D nanostructures with metallic contents of up to >95 at %. While microstructure and composition determine the physical and functional properties of focused electron beam-induced deposits, they also provide fundamental insights into the decomposition process of precursors, as elaborated in this study based on EDX and TEM. The results provide solid information suggesting that different dominant fragmentation channels are active in single-spot growth processes for pillar formation. The use of the single source precursor provides a unique insight into high- and low-energy fragmentation channels being active in the same deposit formation process.

Plasmonic nanoparticles reveal unique optical properties and are increasingly incorporated into commercial products and technologies, ranging from photovoltaics to biological and chemical sensors. Shifting and tuning their plasmonic response according to the targeted application strongly depends on the ability to control the geometry in every detail and has not been reliably demonstrated for complex 3D nano‐architectures yet. Following that motivation, it herein presents how Focused Electron Beam Induced Deposition (FEBID), a highly flexible additive 3D direct‐write technology with spatial nano‐scale precision, is used for the controlled and tunable fabrication of plasmonically active 3D nanostructures that exhibit highly concentrated, well defined and predictable local plasmonic resonances. As model systems, planar Au nanowires and 3D nano‐tips of various geometries are prepared via FEBID and plasmonically characterized via scanning transmission electron microscopy based electron energy loss spectroscopy (STEM‐EELS) mapping measurements. The findings are complemented with corresponding plasmon simulations, revealing very good agreement with experimental findings. This way, on‐demand spectral tuning of the plasmonic response becomes accessible via upfront modeling and design of suitable 3D nanostructures, to achieve customized plasmonic responses, therefore paving the way for yet unrealized plasmonic applications in 3D space.

Magnetism plays a pivotal role in many biological systems. However, the intensity of the magnetic forces exerted between magnetic bodies is usually low, which demands the development of ultra-sensitivity tools for proper sensing. In this framework, magnetic force microscopy (MFM) offers excellent lateral resolution and the possibility of conducting single-molecule studies like other single-probe microscopy (SPM) techniques. This comprehensive review attempts to describe the paramount importance of magnetic forces for biological applications by highlighting MFM’s main advantages but also intrinsic limitations. While the working principles are described in depth, the article also focuses on novel micro- and nanofabrication procedures for MFM tips, which enhance the magnetic response signal of tested biomaterials compared to commercial nanoprobes. This work also depicts some relevant examples where MFM can quantitatively assess the magnetic performance of nanomaterials involved in biological systems, including magnetotactic bacteria, cryptochrome flavoproteins, and magnetic nanoparticles that can interact with animal tissues. Additionally, the most promising perspectives in this field are highlighted to make the reader aware of upcoming challenges when aiming toward quantum technologies.

One of the challenges of nanoelectromechanical systems (NEMS) is the effective transduction of the tiny resonators. Vertical structures, such as nanomechanical pillar resonators, which are exploited in optomechanics, acoustic metamaterials, and nanomechanical sensing, are particularly challenging to transduce. Existing electromechanical transduction methods are ill-suited as they put constraints on the pillars' material and do not enable a transduction of freestanding pillars. Here, we present an electromechanical transduction method for single nanomechanical pillar resonators based on surface acoustic waves (SAWs). We demonstrate the transduction of freestanding nanomechanical platinum-carbon pillars in the first-order bending and compression mode. Since the principle of the transduction method is based on resonant scattering of a SAW by a nanomechanical resonator, our transduction method is independent of the pillar's material and not limited to pillar-shaped geometries. It represents a general method to transduce vertical mechanical resonators with nanoscale lateral dimensions.