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Magnetic patterning by electron beam assisted carbon lithography
The exploitation of the unique physical properties of thin films and heterostructures are opening intriguing opportunities for magnetic storage technology. These artificial materials will in fact enable novel architectures for a multitude of magnetic devices and sensors, promoting a significant improvement in storage density, functionality and efficiency. Their usage will also contribute to diminish the consumption of materials that are rare and difficult to extract, being often detrimental to the environment. With these objectives in mind, researchers are now looking with great attention at the combination of thin ferromagnetic layers with 2-dimensional crystals like graphene and transition metal dichalcogenides. Due to their layered structure, these systems exhibit very favorable magnetic properties, which can be tuned through thickness and interfacial interactions. For instance, graphene-cobalt stacks display an enhanced perpendicular magnetic anisotropy, a feature that is especially important for non-volatile memories.
The fabrication of layered materials, however, is still a very challenging process. Not only it requires atomic precision in the deposition of the various layers but also the ability to create nano or microstructures of arbitrary shape. Conventional lithography in conjunction with chemical etching permits nowadays to sculpture the matter with great accuracy, at lateral resolution close to the nanometer. Yet, this approach poses an important limitation, that is, the material can only be shaped by erosion. The ability to vary the chemical composition, by adding atoms for example, is instead very desirable for many applications. To date, this can be done by stimulating the fragmentation of suitable carrier molecules using photons or electrons. So far, various methods based on focused beam induced processing methods have been devised, which can be readily employed to deposit carbonaceous layers and metallic nanostructures. These methods, however, cannot be applied when ultra-clean, ultra-high vacuum (UHV) conditions are needed, as happens for the case of semiconductor industry.
>Read more on the Elettra website
Figure 1.  (left) Scheme of the protocol for printing chemo-magnetic patterns in ultrathin Co on Re(0001). (a) The film is exposed to CO at room temperature. The irradiation with a focused electron beam (yellow) stimulates the dissociation of the molecule, which results in the accumulation of atomic carbon on the surface. (b) Subsequently, the sample is annealed above 170 °C to desorb molecularly adsorbed CO from the non-irradiated surface regions. (c) LEEM image of an e-beam irradiated disk. Disk diameter: 1 μm; Co thickness: 4 atomic layers; irradiation energy: 50 eV; CO dose: 9.75 L; (d) Intensity profile across the orange line in the LEEM image in (c) and fit using a step function convoluted with a Gaussian of full width at half-maximum of 30 nm. The dashed blue lines indicate the 15–85% distance between minimum and maximum intensity. (e) XMCD-PEEM image of the same region at the Co L3 edge. (f) Intensity profiles across the blue and orange dashed lines in the XMCD-PEEM image in (e). The magnetic stripes indicate out-of-plane magnetic anisotropy. The stripe period is 120 nm. Adapted with permission from [1].
Copyright (2018) American Chemical Society.
Shedding new light on laser additive manufacturing
Additive manufacturing (AM, also known as 3D printing) allows us to create incredibly complex shapes, which would not be possible using traditional manufacturing techniques. However, objects created using AM have different properties from traditional manufacturing routes, which is sometimes a disadvantage.
Laser additive manufacturing (LAM) uses a laser to fuse together metallic, ceramic or other powders into complex 3D shapes, layer by layer. The cooling rates are extremely rapid, and since they are unlike conventional processes we don’t know the optimal conditions to obtain the best properties, delaying the uptake of LAM in the production of safety-critical engineering structures, such as turbine blades, energy storage and biomedical devices. We need a method to see inside the process of LAM to better understand and optimise the laser-matter interaction and powder consolidation mechanisms.
Based in the Research Complex at Harwell, a team of researchers have worked with scientists at I12, the Joint Engineering Environment Processing (JEEP) beamline and the Central Laser Facility to build a laser additive manufacturing machine which operates on a beamline, allowing you to see into the heart of the process, revealing the underlying physical phenomena during LAM.
>Read more on the Diamond Light Source website
Picture: The Additive Manufacturing Team from the Research Complex at Harwell on the Joint Engineering Environment Processing (JEEP, I12) beamline. The Laser Additive Manufacturing Process Replicator (or LAMPR) on the right is used to reveal the underlying physical phenomena during LAM.
W2 SLS Slider
The Swiss Light Source (SLS) at the Paul Scherrer Institut is a third-generation synchrotron light source. SLS provides photon beams of high brightness for research in physics, biology and chemistry.
