The LaserFIB: new application opportunities combining a high-performance FIB-SEM with femtosecond laser processing in an integrated second chamber.

The development of the femtosecond laser (fs laser) with its ability to provide extremely rapid athermal ablation of materials has initiated a renaissance in materials science. Sample milling rates for the fs laser are orders of magnitude greater than that of traditional focused ion beam (FIB) sources currently used. In combination with minimal surface post-processing requirements, this technology is proving to be a game changer for materials research. The development of a femtosecond laser attached to a focused ion beam scanning electron microscope (LaserFIB) enables numerous new capabilities, including access to deeply buried structures as well as the production of extremely large trenches, cross sections, pillars and TEM H-bars, all while preserving microstructure and avoiding or reducing FIB polishing. Several high impact applications are now possible due to this technology in the fields of crystallography, electronics, mechanical engineering, battery research and materials sample preparation. This review article summarizes the current opportunities for this new technology focusing on the materials science megatrends of engineering materials, energy materials and electronics.

Sculpturing wafer-scale nanofluidic devices for DNA single molecule analysis.

We present micro- and nanofluidic devices with 3D structures and nanochannels with multiple depths for the analysis of single molecules of DNA. Interfacing the nanochannels with graded and 3D inlets allows the improvement of the flow and controls not only the translocation speed of the DNA but also its conformation inside the nanochannels. The complex, multilevel, multiscale fluidic circuits are patterned in a simple, two-minute imprinting step. The stamp, the key of the technology, is directly milled by focused ion beam, which allows patterning nanochannels with different cross sections and depths, together with 3D transient inlets, all at once. Having such a variety of structures integrated in the same sample allows studying, optimizing and directly comparing their effect on the DNA flow. Here, DNA translocation is studied in long (160 µm) and short (5-40 µm) nanochannels. We study the homogeneity of the stretched molecules in long, meander nanochannels made with this technology. In addition, we analyze the effect of the different types of inlet structures interfacing short nanochannels. We observe pre-stretching and an optimal flow, and no hairpin formation, when the inlets have gradually decreasing widths and depths. In contrast, when the nanochannels are faced with an abrupt transition, we observe clogging and hairpin formation. In addition, 3D inlets strongly decrease the DNA molecules' speed before they enter the nanochannels, and help capturing more DNA molecules. The robustness and versatility of this technology and DNA testing results evidence the potential of imprinted devices in biomedical applications as low cost, disposable lab-on-a-chip devices.

Advancing FIB assisted 3D EBSD using a static sample setup.

A new setup for automatic 3D EBSD data collection in static mode has been developed using a conventional FIB-SEM system. This setup requires no stage or sample movements between the FIB milling and EBSD mapping. Its capabilities were tested experimentally on a coherent twin boundary of an INCONEL sample. Our result demonstrates that this static setup holds many advantages in terms of data throughput and quality as compared with other ones requiring stage/sample movements. The most important advantages are the better slice alignment and an improved orientation precision in 3D space, both being prerequisite for a reliable grain boundary characterization.

Nanofibers in a hyaluronan-based pericellular matrix.

The extracellular matrix of the brain is a highly organized hyaluronan-based supramolecular assembly that is involved in neuronal pathfinding, cell migration, synaptogenesis and neuronal plasticity. Here, we analyze the structure of the hyaluronan-rich pericellular matrix of an oligodendroglial precursor cell line using helium ion beam scanning microscopy at a subnanometer resolution. We find that thin nanofibers are the ultimate building elements of this oligodendroglial pericellular matrix. These structures may participate in the regulation of oligodendroglial maturation and motility.

Focused ion beam (FIB) combined with high resolution scanning electron microscopy: a promising tool for 3D analysis of chromosome architecture.

Focused ion beam (FIB) milling in combination with field emission scanning electron microscopy (FESEM) was applied to investigations of metaphase barley chromosomes, providing new insight into the chromatin packaging in the chromosome interior and 3D distribution of histone variants in the centromeric region. Whole mount chromosomes were sectioned with FIB with thicknesses in the range of 7-20nm, resulting in up to 2000 sections, which allow high resolution three-dimensional reconstruction. For the first time, it could be shown that the chromosome interior is characterized by a network of interconnected cavities, with openings to the chromosome surface. In combination with immunogold labeling, the centromere-correlated distribution of histone variants (phosphorylated histone H3, CENH3) could be investigated with FIB in three dimensions. Limitations of classical SEM analysis of whole mount chromosomes with back-scattered electrons requiring higher accelerating voltages, e.g. faint and blurred interior signals, could be overcome with FIB milling: from within the chromosome even very small labels in the range of 10nm could be precisely visualized. This allowed direct quantification of marker molecules in a three-dimensional context. Distribution of DNA in the chromosome interior could be directly analyzed after staining with a DNA-specific platinorganic compound Platinum Blue. Higher resolution visualization of DNA distribution could be performed by preparation of FIB lamellae with the in situ lift-out technique followed by investigation in dark field with a scanning transmission electron detector (STEM) at 30kV.

Focused ion beam preparation of atom probe specimens containing a single crystallographically well-defined grain boundary.

Needle-shaped atom probe specimens containing a single grain boundary were produced using the focused ion beam (FIB) of a two-beam FIB/SEM (scanning electron microscope) system. The presented specimen preparation approach allows the unprecedented study of a grain boundary which is well characterised in its crystallographic orientation by means of the field ion microscope (FIM) and the tomographic atom probe (TAP). The analysis of such specimens allows in particular the determination of solute excess atoms at this specific grain boundary and hence the investigation of the segregation behaviour. The crucial preparation steps are discussed in detail in the present study for the Sigma 19 a {331} 110 grain boundary of a 40 at.ppm-Bi doped Cu bi-crystal. Transmission electron microscope (TEM) images and TAP analyses of the atom probe tips demonstrate unambiguously the presence of the selectively prepared grain boundary in the apex region of some of the specimens.

Colloidal quantum dots in all-dielectric high-Q pillar microcavities.

We have fabricated all-dielectric high-Q optical pillar resonators with embedded colloidal CdSe/ZnS quantum dots or rods as light emitters by focused ion beam milling. Three-dimensional light confinement and distinct pillar microcavity modes are observed. Results from a waveguide model for the mode patterns and their spectral positions are in excellent agreement with the experimental data. Cavities with elliptical cross sections show higher quality factors in the short axis direction than do circular resonators of the same cross-sectional area.