Segregation of materials in double precursor electron-beam-induced-deposition: a route to functional magnetic nanostructures.

Here we report an observation of the phenomenon of spatial segregation of two materials in double precursor electron beam induced deposition. Segregation occurs under proper deposition conditions in a single spot illumination due to generic variation of electron current density within an electron beam. Combining precursors for magnetic (dicobaltoctacarbonyl) and non-magnetic (tetraethyl orthosilicate) properties we demonstrate a one-step fabrication process for magnetic tubules at the scale of 100 nm. Electron holography applied on the cross-section of thus prepared tubules reveals the concentration of the magnetic field in the cobalt rich shell, corroborating spatially distributed functionality. We elaborate the numerical model describing the observed phenomenon and defining the conditions for its practical achievement.

Comparison of different preparation methods of biological samples for FIB milling and SEM investigation.

When a new approach in microscopy is introduced, broad interest is attracted only when the sample preparation procedure is elaborated and the results compared with the outcome of the existing methods. In the work presented here we tested different preparation procedures for focused ion beam (FIB) milling and scanning electron microscopy (SEM) of biological samples. The digestive gland epithelium of a terrestrial crustacean was prepared in a parallel for FIB/SEM and transmission electron microscope (TEM). All samples were aldehyde-fixed but followed by different further preparation steps. The results demonstrate that the FIB/SEM samples prepared for conventional scanning electron microscopy (dried) is suited for characterization of those intracellular morphological features, which have membranous/lamellar appearance and structures with composition of different density as the rest of the cell. The FIB/SEM of dried samples did not allow unambiguous recognition of cellular organelles. However, cellular organelles can be recognized by FIB/SEM when samples are embedded in plastic as for TEM and imaged by backscattered electrons. The best results in terms of topographical contrast on FIB milled dried samples were obtained when samples were aldehyde-fixed and conductively stained with the OTOTO method (osmium tetroxide/thiocarbohydrazide/osmium tetroxide/thiocarbohydrazide/osmium tetroxide). In the work presented here we provide evidence that FIB/SEM enables both, detailed recognition of cell ultrastructure, when samples are plastic embedded as for TEM or investigation of sample surface morphology and subcellular composition, when samples are dried as for conventional SEM.

FIB/SEM characterization of carbon-based fibers.

The aim of this paper is to show how a focused ion beam combined with a scanning electron microscope (FIB/SEM machine) can be adopted to characterize composite fibers with different electrical behavior and to gain information about their production and modification. This comparative morphology investigation is carried out on polyacrylonitrile (PAN) carbon fibers and their chemical precursor (the oxidized PAN or oxypan) which has different electrical properties. Fibers are imaged by electron and ion beams and sectioned by the focused ion beam (FIB). A sample of oxypan fibers processed by a radio frequency (RF) plasma is also investigated and the role of the conductive carbon layer around their unmodified, insulating bulk is discussed. A suitable developed edge detection technique (EDT) on electron, ion images, and after the FIB sectioning, provides quantitative information about the thickness of the created layer.

Carbon fiber composite targets for nuclear fusion technology: a focused ion beam/scanning electron microscope investigation.

Carbon fiber composite (CFC) targets are investigated by a focused ion beam/scanning electron microscope (FIB/SEM) in a joint project aiming at the development of robust divertors in the International Thermonuclear Experimental Reactor (ITER). These mockups are exposed to a plasma that simulates the off-normal thermal loads foreseen for ITER and display a rich, puzzling impact scenario. Morphological elements are identified at the exposed surface and beneath it, and are examined in order to point out the relevant processes involved. Each technique adopted is discussed and evaluated.

Focused ion beam characterization of plasma-assisted deposition on polymer films at the nanoscale.

In this paper, a novel technique is presented for the characterization at the nanoscale of plasma-assisted deposit on polyethylene-terephthalate (PET) polymer films. In previous studies, some microcharacterization and morphology analyses of plasma-assisted deposition were performed by atomic force microscopy (AFM). In the work presented here, we analysed the thickness and homogeneity of plasma-assisted deposits by focused ion beam (FIB). This technique with 5-7 nm resolution requires no sample preparation and relies on a sequence of operations on a relatively fast time scale, so that it is easy to make thorough investigations of the sample. We performed electron and ion imaging of the surface of the material, and a subsequent ionic cutting allowed the study of the morphology of the same sample. We developed a novel approach to the edge detection techniques (EDT) in images for a fast evaluation and monitoring of the deposited layer.