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Two-dimensional semiconductors, such as molybdenum disulfide (MoS2), exhibit a variety of properties that could be useful in the development of novel electronic devices. However, nanopatterning metal electrodes on such atomic layers, which is typically achieved using electron beam lithography, is currently problematic, leading to non-ohmic contacts and high Schottky barriers. Here, we show that thermal scanning probe lithography can be used to pattern metal electrodes with high reproducibility, sub-10-nm resolution, and high throughput (105 μm2 h−1 per single probe). The approach, which offers simultaneous in situ imaging and patterning, does not require a vacuum, high energy, or charged beams, in contrast to electron beam lithography. Using this technique, we pattern metal electrodes in direct contact with monolayer MoS2 for top-gate and back-gate field-effect transistors. These devices exhibit vanishing Schottky barrier heights (around 0 meV), on/off ratios of 1010, no hysteresis, and subthreshold swings as low as 64 mV per decade without using negative capacitors or hetero-stacks.

This article in the press

  • “Breakthrough reported in fabricating nanochips”. Article on Phys.org.

  • “Groundbreaking method creates better and cheaper nanochips” featured on Cordis.

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Stabilizing and manipulating topological magnetic quasiparticles in thin films is of great interest for potential applications in data storage and information processing. Here, we present a strategy for stabilizing magnetic vortices and Bloch lines with controlled position, vorticity, and chirality in a continuous exchange bias system. By tailoring vectorially the unidirectional anisotropy of the system at the nanoscale, via thermally assisted magnetic scanning probe lithography, we show experimentally and via micromagnetic simulations the non-volatile creation of vortex-antivortex pairs. In addition, we demonstrate the deterministic stabilization of cross and circular Bloch lines within patterned Néel magnetic domain walls. This work enables the implementation of complex functionalities based on the control of tailored topological spin-textures in spintronic and magnonic nanodevices.

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Magnonics is gaining momentum as an emerging technology for information processing. The wave character and Joule heating-free propagation of spin-waves hold promises for highly efficient computing platforms, based on integrated magnonic circuits. The realization of such nanoscale circuitry is crucial, although extremely challenging due to the difficulty of tailoring the nanoscopic magnetic properties with conventional approaches. Here we experimentally realize a nanoscale reconfigurable spin-wave circuitry by using patterned spin-textures. By space and time-resolved scanning transmission X-ray microscopy imaging, we directly visualize the channeling and steering of propagating spin-waves in arbitrarily shaped nanomagnonic waveguides, with no need for external magnetic fields or currents. Furthermore, we demonstrate a prototypic circuit based on two converging nanowaveguides, allowing for the tunable spatial superposition and interference of confined spin-waves modes. This work paves the way to the use of engineered spin-textures as building blocks of spin-wave based computing devices.

This article in the press

  • “Nanoscale spin-wave circuits based on engineered reconfigurable spin-textures”
    Feature article on Phys.org.

  • “Con le onde di spin a un passo dai processori di domani” featured on Galileonet (Italian)

  • “Politecnico di Milano: I processori del futuro sempre più vicini” featured on Le Scienze (Italian)

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Magnonics is envisioned to enable highly efficient data transport and processing, by exploiting propagating perturbations in the spin-texture of magnetic materials. Despite the demonstrations of a plethora of proof-of-principle devices, the efficient excitation, transport and manipulation of spin-waves at the nanoscale is still an open challenge. Recently, we demonstrated that the spin-wave excitation and propagation can be controlled by nanopatterningreconfigurable spin-textures in a continuous exchange biased ferromagnetic film. Here, we show that by patterning 90° stripe-shaped magnetic domains, we spatially modulate the spin-wave excitation in a continuous film, and that by applying an external magnetic field we can reversibly “switch-off” the spin-wave excitation. This opens the way to the use of nanopatterned spin-textures, such as domains and domain walls, for exciting and manipulating magnons in reconfigurable nanocircuits.

TALKING ABOUT SWING PROJECT AT 2 SPIE CONFERENCES

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The search of novel tools controlling the physical and chemical properties of matter at the nanoscale is crucial for developing next-generation integrated systems, with applications ranging from computing to medicine. Here, we show that thermal scanning probe lithography (t-SPL) can be a flexible tool for manipulating with nanoscale precision the surface properties of a wide range of specifically designed systems. In particular, we show that via t-SPL, we pattern nanoscale chemical patterns on polymeric substrates, which are then used to specifically bind extracellular matrix (ECM) proteins to the polymer surface. We demonstrate that the concentration of immobilized proteins can be controlled by varying the tip temperature, so that nanoscale protein gradients can be created. On a different system, we show that, by performing t-SPL on a thin film magnetic multilayer, in an external magnetic field, we are able to write reversibly magnetic patterns with arbitrarily oriented magnetization and tunable magnetic anisotropy. This demonstrates that t-SPL represents a novel, straightforward and extremely versatile method for the nanoscale engineering of the physicalchemical properties in a wide variety of materials.

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Magnonics represents a promising alternative to conventional electronics for the development of energy efficient computing platforms. In this context, the nanoscale engineering of spin textures is highly appealing for the development and realization of new nanomagnonic device concepts. Here, we show that reconfigurable nanopatterned spin textures can be used to manipulate spin waves. Magnetic domains and domain walls are written by thermally assisted magnetic scanning probe lithography (tam-SPL) in exchange bias systems. In such structures, we demonstrate through microfocused Brillouin Light Scattering and time resolved scanning transmission X-ray microscopy measurements, the channeling and propagation of confined spin waves. This work opens the way to the use of engineered spin-textures as building blocks of magnonics computing devices.

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