The polarization state of an ultrafast laser is dynamically controlled using two Spatial Light Modulators and additional waveplates. Consequently, four states of polarization, linear horizontal and vertical, radial and azimuthal, all with a ring intensity distribution, were dynamically switched at a frequency ν = 12.5 Hz while synchronized with a motion control system. This technique, demonstrated here for the first time, enables a remarkable level of real-time control of the properties of light waves and applied to real-time surface patterning, shows that highly controlled nanostructuring is possible. Laser ablation of Induced Periodic Surface Structures is used to directly verify the state of polarization at the focal plane.

Understanding nanoscale molecular order within organic electronic materials is a crucial factor in building better organic electronic devices. At present, techniques capable of imaging molecular order within a polymer are limited in resolution, accuracy, and accessibility. In this work, presented are secondary electron (SE) spectroscopy and secondary electron hyperspectral imaging, which make an exciting alternative approach to probing molecular ordering in poly(3‐hexylthiophene) (P3HT) with scanning electron microscope‐enabled resolution. It is demonstrated that the crystalline content of a P3HT film is reflected by its SE energy spectrum, both empirically and through correlation with nano‐Fourier‐transform infrared spectroscopy, an innovative technique for exploring nanoscale chemistry. The origin of SE spectral features is investigated using both experimental and modeling approaches, and it is found that the different electronic properties of amorphous and crystalline P3HT result in SE emission with different energy distributions. This effect is exploited by acquiring hyperspectral SE images of different P3HT films to explore localized molecular orientation. Machine learning techniques are used to accurately identify and map the crystalline content of the film, demonstrating the power of an exciting characterization technique.

The excellent mechanical properties of spider dragline silk are closely linked to its multiscale hierarchical structuring which develops as it is spun. If this is to be understood and mimicked, multiscale models must emerge which effectively bridge the length scales. This study aims to contribute to this goal by exposing structures within Nephila dragline silk using low-temperature plasma etching and advanced Low Voltage Scanning Electron Microscopy (LV-SEM). It is shown that Secondary Electron Hyperspectral Imaging (SEHI) is sensitive to compositional differences on both the micro and nano scale. On larger scales it can distinguish the lipids outermost layer from the protein core, while at smaller scales SEHI is effective in better resolving nanostructures present in the matrix. Key results suggest that the silks spun at lower reeling speeds tend to have a greater proportion of smaller nanostructures in closer proximity to one-another in the fiber, which we associate with the fiber's higher toughness but lower stiffness. The bimodal size distribution of ordered domains, their radial distribution, nanoscale spacings, and crucially their interactions may be key in bridging the length scale gaps which remain in current spider silk structure-property models. Ultimately this will allow successful biomimetic implementation of new models.

Carbon and carbon/metal systems with a multitude of functionalities are ubiquitous in new technologies but understanding on the nanoscale remains elusive due to their affinity for interaction with their environment and limitations in available characterization techniques. This paper introduces a spectroscopic technique and demonstrates its capacity to reveal chemical variations of carbon. The effectiveness of this approach is validated experimentally through spatially averaging spectroscopic techniques and using Monte Carlo modeling. Characteristic spectra shapes and peak positions for varying contributions of sp2‐like or sp3‐like bond types and amorphous hydrogenated carbon are reported under circumstances which might be observed on highly oriented pyrolytic graphite (HOPG) surfaces as a result of air or electron beam exposure. The spectral features identified above are then used to identify the different forms of carbon present within the metallic films deposited from reactive organometallic inks. While spectra for metals is obtained in dedicated surface science instrumentation, the complex relations between carbon and metal species is only revealed by secondary electron (SE) spectroscopy and SE hyperspectral imaging obtained in a state‐of‐the‐art scanning electron microscope (SEM). This work reveals the inhomogeneous incorporation of carbon on the nanoscale but also uncovers a link between local orientation of metallic components and carbon form.

characterization tool to reveal and visualize nanostructural variations across micron-scale spatial dimensions. We report that despite similarity in overall ordered fraction, there are distinct differences in the nanoscale order/ disorder maps of natural silk fibers from both Bombyx mori and Antheraea mylitta.The structural hierarchy of silkworm silks surrounds a sericin glue that binds two microscopic fibroin brins (≈15 µm), [3] which are comprised of ≈200 nm microfibers and nanofibrils [8] and, finally, nanoscale phases, which can be ordered or disordered, [4] as shown in the schematic diagram in Figure 1a.Using low-voltage standard SEM of a cryo-snapped and plasma-exposed silk fibers of B. mori silk and A. mylitta silk, it is possible to visualize bright nanostructures (Figure 1a) due to topographical contrast, but such contrast is problematic for accurate nanoscale dimension measurements due to a feature size-and shape-dependent edge effect. [9] Furthermore, the topography can be caused by different mechanisms, and it is therefore prone to artefacts introduced by sample preparation. Nevertheless, we observe that the average area fraction of these nanostructures is similar in both silks, however in A. mylitta silk, the round nanostructures seem smaller, denser, and interconnected.In order to determine the nature of these bright nanostructures and their dimensions, we applied SEHI. SEHI exploits the distinctiveness of secondary electron (SE) signals in carbonbased material [10] for hyperspectral imaging (HI) and has the advantage of being able to avoid the confounding influence of topology, which beleaguers standard SEM (see Section S6 in the Supporting Information). The concept of HI is well established in vibrational spectroscopies, [11a] where images are formed from several different energy regions, and based on distinctive peaks in the spectrum. This is demonstrated in the schematic in Figure 1d. Here we collect SE spectra from the high-density nanoscale regions, as established by comparison of backscattered electron density maps [12] (Section S1, Supporting Information), which we find correlate with the bright features in the standard SEM images in Figure 1a. This allows us to investigate which peaks in the SE spectra are related to high density (Section S3, Supporting Information), and thus to high order (Section S1, Supporting Information). We then apply the HI concept to quantitatively map the different phases in silks by imaging with an energy window of 3.9 ± 0.3 eV which was specifically selected to map high-order regions and is free from topographical artefacts Nanostructures underpin the excellent properties of silk. Although the bulk nanocomposition of silks is well studied, direct evidence of the spatial variation of nanocrystalline (ordered) and amorphous (disordered) structures remains elusive. Here, secondary electron hyperspectral imaging can be exploited for direct imaging of hierarchical structures in carbon-based materials, which cannot be revealed by any other standard characterizat...

Transmission electron microscopy with in situ ion irradiation has been used to examine the ionbeam-induced amorphisation of crystalline silicon under irradiation with light (He) and heavy (Xe) ions at room temperature. Analysis of the electron diffraction data reveal the heterogeneous amorphisation mechanism to be dominant in both cases. The differences in the amorphisation curves are discussed in terms of intra-cascade dynamic recovery, and the role of electronic and nuclear loss mechanisms.

Highly Oriented Pyrolitic Graphite presents a layered structure. In this work, we propose a theoretical and computational model for taking into account the anisotropic structure of graphite in the Monte Carlo simulations of charge transport. In particular, the dielectric characteristics, such as the inelastic mean free path and energy losses, are treated by linearly combining the contribution to these observables along the two main orthogonal directions identifying the crystalline structure (along the layer plane and perpendicular to it). Energy losses are evaluated from ab initio calculations of the dielectric function of the system along these two perpendicular directions. Monte Carlo simulated spectra, obtained with this approach, are compared with acquired experimental data of Reflection Electron Energy Loss and Secondary Electron spectra showing a good agreement. These findings validate the idea of the importance of considering properly-weighted inter-planar and intra-planar interactions in the simulation of electron transport in layered materials.

We investigated the effect of the feeding formulation (premixed powders of pure components versus solvent-blended mixture) of polystyrene–C60 composites on the dispersion and reagglomeration phenomena developing along the barrel of a twin-screw extruder. The dispersion of C60 in the PS matrix is studied over different length scales using a combination of optical microscopy, spin-echo small-angle neutron scattering (SESANS), small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS). When a solvent-blended mixture is used as the feeding formulation, the inlet material contains essentially molecularly dispersed C60 as revealed by the nanodomains with very small phase contrast. However, C60 reagglomeration occurs along the extruder, creating a morphology still containing only nanodomains but with much higher phase contrast. In the case of mixed powders, the material evolves from the initial macroscopic mixture of pure polystyrene and C60 into a composite simultaneously containing micro- and nanoaggregates of C60 as well as C60 molecularly dispersed in the matrix. Our results show that the two different initial feeding formulations with widely different initial morphologies converge along the extruder, through opposite morphological pathways, into a similar final nanomorphology which is dictated by the interplay between the thermodynamics of the system and the flow. Correlations between the morphological evolution along the extruder and the thermorheological properties of the composites are identified.