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- ItemFeature Adaptive Sampling for Scanning Electron Microscopy([London] : Macmillan Publishers Limited, part of Springer Nature, 2016) Dahmen, Tim; Engstler, Michael; Pauly, Christoph; Trampert, Patrick; de Jonge, Niels; Mücklich, Frank; Slusallek, PhilippA new method for the image acquisition in scanning electron microscopy (SEM) was introduced. The method used adaptively increased pixel-dwell times to improve the signal-to-noise ratio (SNR) in areas of high detail. In areas of low detail, the electron dose was reduced on a per pixel basis and a-posteriori image processing techniques were applied to remove the resulting noise. The technique was realized by scanning the sample twice. The first, quick scan used small pixel-dwell times to generate a first, noisy image using a low electron dose. This image was analyzed automatically and a software algorithm generated a sparse pattern of regions of the image that require additional sampling. A second scan generated a sparse image of only these regions, but using a highly increased electron dose. By applying a selective low-pass filter and combining both datasets, a single image was generated. The resulting image exhibited a factor of ≈3 better SNR than an image acquired with uniform sampling on a Cartesian grid and the same total acquisition time. This result implies that the required electron dose (or acquisition time) for the adaptive scanning method is a factor of ten lower than for uniform scanning.
- ItemAuthor Correction: Salt concentration and charging velocity determine ion charge storage mechanism in nanoporous supercapacitors([London] : Nature Publishing Group UK, 2019) Prehal, C.; Koczwara, C.; Amenitsch, H.; Presser, V.; Paris, O.Correction to: Nature Communications; https://doi.org/10.1038/s41467-018-06612-4; published online 08 October 2018 The original version of this Article contained an error in the Acknowledgements, which was incorrectly omitted from the end of the following: ‘The research leading to these results has received funding from the European Community’s Horizon 2020 Framework Programme under grant agreement nº 730872.’ This has been corrected in both the PDF and HTML versions of the Article.
- ItemSpot profile analysis and lifetime mapping in ultrafast electron diffraction: Lattice excitation of self-organized Ge nanostructures on Si(001)(Melville, NY : AIP Publishing LLC, 2015) Frigge, T.; Hafke, B.; Tinnemann, V.; Witte, T.; Horn-von Hoegen, M.Ultrafast high energy electron diffraction in reflection geometry is employed to study the structural dynamics of self-organized Germanium hut-, dome-, and relaxed clusters on Si(001) upon femtosecond laser excitation. Utilizing the difference in size and strain state the response of hut- and dome clusters can be distinguished by a transient spot profile analysis. Surface diffraction from {105}-type facets provide exclusive information on hut clusters. A pixel-by-pixel analysis of the dynamics of the entire diffraction pattern gives time constants of 40, 160, and 390 ps, which are assigned to the cooling time constants for hut-, dome-, and relaxed clusters.
- ItemPlastic Deformation Modes of CuZr/Cu Multilayers([London] : Macmillan Publishers Limited, part of Springer Nature, 2016) Cui, Yan; Abad, Oscar Torrents; Wang, Fei; Huang, Ping; Lu, Tian-Jian; Xu, Ke-Wei; Wang, JianWe synthesized CuZr/Cu multilayers and performed nanoindentation testing to explore the dependence of plastic deformation modes on the thickness of CuZr layers. The Cu layers were 18 nm thick and the CuZr layers varied in thickness from 4 nm to 100 nm. We observed continuous plastic co-deformation in the 4 nm and 10 nm CuZr − 18 nm Cu multilayers and plastic-induced shear instability in thick CuZr layers (>20 nm). The plastic co-deformation is ascribed to the nucleation and interaction of shear transformation zones in CuZr layers at the adjacent interfaces, while the shear instability is associated with the nucleation and propagation of shear bands in CuZr layers. Shear bands are initialized in the CuZr layers due to the accumulated glide dislocations along CuZr-Cu interfaces and propagate into adjacent Cu layers via slips on {111} plane non-parallel to the interface. Due to crystallographic constraint of the Cu layers, shear bands are approximately parallel to {111} plane in the Cu layer.
- ItemLocal variations of HER2 dimerization in breast cancer cells discovered by correlative fluorescence and liquid electron microscopy(Washington, DC [u.a.] : Assoc., 2015) Peckys, Diana B.; Korf, Ulrike; de Jonge, NielsThe formation of HER2 homodimers plays an important role in breast cancer aggressiveness and progression; however, little is known about its localization. We have studied the intra- and intercellular variation of HER2 at the single-molecule level in intact SKBR3 breast cancer cells. Whole cells were visualized in hydrated state with correlative fluorescence microscopy and environmental scanning electron microscopy (ESEM). The locations of individual HER2 receptors were detected using an anti-HER2 affibody in combination with a quantum dot (QD), a fluorescent nanoparticle. Fluorescence microscopy revealed considerable differences of HER2 membrane expression between individual cells and between different membrane regions of the same cell (that is, membrane ruffles and flat areas). Subsequent ESEM of the corresponding cellular regions provided images of individually labeled HER2 receptors. The high spatial resolution of 3 nm and the close proximity between the QD and the receptor allowed quantifying the stoichiometry of HER2 complexes, distinguishing between monomers, dimers, and higher-order clusters. Downstream data analysis based on calculating the pair correlation function from receptor positions showed that cellular regions exhibiting membrane ruffles contained a substantial fraction of HER2 in homodimeric state. Larger-order clusters were also present. Membrane areas with homogeneous membrane topography, on the contrary, displayed HER2 in random distribution. Second, HER2 homodimers appeared to be absent from a small subpopulation of cells exhibiting a flat membrane topography, possibly resting cells. Local differences in homodimer presence may point toward functional differences with possible relevance for studying metastasis and drug response.