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Andreas Schmid, Andreas Scholl
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June 15, 2017: Ultramicroscopy
Jon Alkorta, Matthieu Marteleur, Pascal J Jacques
Conventional HR-EBSD is attracting much interest due to its ability of measuring relative crystal misorientations and microstresses with great accuracy. However, this technique needs the use of simulated patterns in order to get absolute values of crystal orientation and stresses and thus expand its use to intergranular analyses. Simulation-based approaches have shown many limitations due to the poor correlation with the real patterns specially when Bragg simulations are considered. This paper presents an improved algorithm based on gradient-based correlation techniques that makes simulation-based HR-EBSD possible...
June 14, 2017: Ultramicroscopy
Cezary Dziekoński, Wojciech Dera, Dariusz M Jarząbek
In this paper we present a simple and direct method for the lateral force calibration constant determination. Our procedure does not require any knowledge about material or geometrical parameters of an investigated cantilever. We apply a commercially available microforce sensor with advanced electronics for direct measurement of the friction force applied by the cantilever's tip to a flat surface of the microforce sensor measuring beam. Due to the third law of dynamics, the friction force of the equal value tilts the AFM cantilever...
June 14, 2017: Ultramicroscopy
Theodore Stenmark, R C Word, R Könenkamp
Using photoemission electron microscopy (PEEM) we present a comparative analysis of the wavelength dependence of propagating fields in a simple optical slab waveguide and a thin film photonic crystal W1-type waveguide. We utilize an interferometric imaging approach for light in the near-ultraviolet regime where a 2-photon process is required to produce photoelectron emission. The typical spatial resolution in these experiments is < 30nm. Electromagnetic theory and finite element simulations are shown to be in good agreement with the experimental observations...
June 13, 2017: Ultramicroscopy
Shu Jian Chen, Xupei Yao, Changxi Zheng, Wen Hui Duan
Non-equilibrium molecular dynamics was used to simulate the dynamics of atoms at the atom probe surface and five objective functions were used to quantify errors. The results suggested that before ionization, thermal vibration and collision caused the atoms to displace up to 1Å and 25Å respectively. The average atom displacements were found to vary between 0.2 and 0.5Å. About 9 to 17% of the atoms were affected by collision. Due to the effects of collision and ion-ion repulsion, the back-calculated positions were on average 0...
June 12, 2017: Ultramicroscopy
U Schürmann, C Chluba, N Wolff, D Smazna, R Lima de Miranda, P Junker, R Adelung, E Quandt, L Kienle
In situ measurements are a pivotal extension of conventional transmission electron microscopy (TEM). By means of the shape memory alloy NiTi thin film Functional Grids were produced for in situ straining as alternative or at least complement of expensive commercial holders. Due to the martensite-austenite transition temperature straining effects can be observed by use of customary heating holders in the range of 50 to 100°C. The grids can be produced in diversified designs to fit for different strain situations...
June 9, 2017: Ultramicroscopy
N Gauquelin, K H W van den Bos, A Béché, F F Krause, I Lobato, S Lazar, A Rosenauer, S Van Aert, J Verbeeck
Nowadays, aberration corrected transmission electron microscopy (TEM) is a popular method to characterise nanomaterials at the atomic scale. Here, atomically resolved images of nanomaterials are acquired, where the contrast depends on the illumination, imaging and detector conditions of the microscope. Visualization of light elements is possible when using low angle annular dark field (LAADF) STEM, annular bright field (ABF) STEM, integrated differential phase contrast (iDPC) STEM, negative spherical aberration imaging (NCSI) and imaging STEM (ISTEM)...
June 3, 2017: Ultramicroscopy
Giulio Pozzi, Peng-Han Lu, Amir H Tavabi, Martial Duchamp, Rafal E Dunin-Borkowski
It has recently been shown that an electron vortex beam can be generated by the magnetic field surrounding the tip of a dipole-like magnet. This approach can be described using the magnetic Aharonov-Bohm effect and is associated with the fact that the end of a long magnetic rod can be treated approximately as a magnetic monopole. However, it is difficult to vary the magnetisation of the rod in such a setup and the electron beam vorticity is fixed for a given tip shape. Here, we show how a similar behaviour, which has the advantage of easy tuneability, can be achieved by making use of the electrostatic Aharonov-Bohm effect associated with an electrostatic dipole line...
June 2, 2017: Ultramicroscopy
F F Krause, A Rosenauer, J Barthel, J Mayer, K Urban, R E Dunin-Borkowski, H G Brown, B D Forbes, L J Allen
This paper addresses a novel approach to atomic resolution elemental mapping, demonstrating a method that produces elemental maps with a similar resolution to the established method of electron energy-loss spectroscopy in scanning transmission electron microscopy. Dubbed energy-filtered imaging scanning transmission electron microscopy (EFISTEM) this mode of imaging is, by the quantum mechanical principle of reciprocity, equivalent to tilting the probe in energy-filtered transmission electron microscopy (EFTEM) through a cone and incoherently averaging the results...
June 2, 2017: Ultramicroscopy
Young-Hwa Oh, Sung-Il Kim, Miyoung Kim, Seung-Yong Lee, Young-Woon Kim
Ionic transport in the reverse direction of an electric field is caused by momentum transfer from free electrons to metal ions, i.e., electromigration (EM), which is a critical factor leading to copper (Cu) interconnect failure in integrated circuits under extreme operating conditions. We investigated Cu self-diffusion paths under electrical bias using in situ transmission electron microscopy (TEM). An electric current was applied to multigrain Cu lines in the TEM instrument for durations of up to the order of 10(4)s to trace EM-induced Cu movement around voids and hillocks...
May 23, 2017: Ultramicroscopy
Hu Luo, Shaohui Yin, Guanhua Zhang, Chunhui Liu, Qingchun Tang, Meijian Guo
Ion-beam-thinning is a well-established sample preparation technique for transmission electron microscopy (TEM), but tedious procedures and labor consuming pre-thinning could seriously reduce its efficiency. In this work, we present a simple pre-thinning technique by using magnetorheological (MR) polishing to replace manual lapping and dimpling, and demonstrate the successful preparation of electron-transparent single crystal silicon samples after MR polishing and single-sided ion milling. Dimples pre-thinned to less than 30 microns and with little mechanical surface damage were repeatedly produced under optimized MR polishing conditions...
May 20, 2017: Ultramicroscopy
Jakob Spiegelberg, Ján Rusz, Klaus Leifer, Thomas Thersleff
Quantitative analysis of noisy electron spectrum images requires a robust estimation of the underlying background signal. We demonstrate how modern data compression methods can be used as a tool for achieving an analysis result less affected by statistical errors or to speed up the background estimation. In particular, we demonstrate how a multilinear singular value decomposition (MLSVD) can be used to enhance elemental maps obtained from a complex sample measured with energy electron loss spectroscopy. Furthermore, the usage of vertex component analysis (VCA) for a basis vector centered estimation of the background is demonstrated...
May 20, 2017: Ultramicroscopy
Robert C Word, Rolf Könenkamp
Photonic and plasmonic fields at surfaces can have complicated spatial distributions, which are reflected in the corresponding photoelectron yields imaged in PEEM. These can include the intricate moiré patterns on the surfaces of photonic and plasmonic structures and bright fringe field patterns at their edges. Understanding field distributions requires an understanding of how the guided modes develop, propagate, and interfere with each other and with the incident far-field light. Recent efforts in PEEM include the use of normal incidence excitation in addition to or in lieu of oblique incidence to alter the yield distributions...
May 19, 2017: Ultramicroscopy
Jiří Škvarla, Juraj Škvarla
A procedure is introduced for measuring the radius of spherical colloid particles from the curvature of upper parts of their central cross-sectional profiles obtained by atomic force microscopy (AFM). To minimize the possible compression and displacement of the spheres, AFM is operated in a mode rendering a constant ultralow pN force on the tip. The procedure allows us to evaluate the mean radius of nearly monodisperse submicrometer spheres of silica in their natively hydrated state in aqueous electrolyte solutions, irrespective of whether they are coagulated or not...
May 16, 2017: Ultramicroscopy
Vahid R Adineh, Ross K W Marceau, Yu Chen, Kae J Si, Tony Velkov, Wenlong Cheng, Jian Li, Jing Fu
We present a novel approach for analysis of low-conductivity and insulating materials with conventional pulsed-voltage atom probe tomography (APT), by incorporating an ultrathin metallic coating on focused ion beam prepared needle-shaped specimens. Finite element electrostatic simulations of coated atom probe specimens were performed, which suggest remarkable improvement in uniform voltage distribution and subsequent field evaporation of the insulated samples with a metallic coating of approximately 10nm thickness...
May 13, 2017: Ultramicroscopy
Johannes Jobst, Jaap Kautz, Maria Mytiliniou, Rudolf M Tromp, Sense Jan van der Molen
In a lot of systems, charge transport is governed by local features rather than being a global property as suggested by extracting a single resistance value. Consequently, techniques that resolve local structure in the electronic potential are crucial for a detailed understanding of electronic transport in realistic devices. Recently, we have introduced a new potentiometry method based on low-energy electron microscopy (LEEM) that utilizes characteristic features in the reflectivity spectra of layered materials [1]...
May 13, 2017: Ultramicroscopy
A Quesada, R Gargallo-Caballero, Y Montaña, M Foerster, L Aballe, J F Fernández, J de la Figuera
High aspect-ratio Fe nanostrips are known to reversibly switch from a single-domain magnetic state to a multidomain diamond pattern as a function of temperature (T) and width. This magnetic bistability can be understood by the temperature-dependent balance between magnetocrystalline, shape and magnetoelastic anisotropies and has potential applications in magnetic logic devices. However, as Fe nanostructures easily oxidize, protecting the surface with capping layers may be required, which could largely affect the anisotropy balance...
May 13, 2017: Ultramicroscopy
A V Kondratov, O Y Rogov, R V Gainutdinov
A significant part of the optical metamaterial phenomena has the plasmonic nature and their investigation requires very accurate knowledge of the fabricated structures shape with a focus on the periodical features. We describe a consistent approach to the shape reconstruction of the plasmonic nanostructures. This includes vertical and tilted spike AFM probes fabrication, AFM imaging and specific post-processing. We studied a complex-shaped chiral metamaterial and conclude that the described post-processing routine extends possibilities of the existing deconvolution algorithms in the case of periodical structures with known rotational symmetry, by providing valuable information about periodical features...
May 11, 2017: Ultramicroscopy
B H Stenger, A L Dorsett, J H Miller, E M Russell, C A Gabris, S Chiang
The growth of low-dimensional nanostructures of Au on Ge(110) and their temperature-induced motion were observed with Low Energy Electron Microscopy (LEEM). Ge(110) was dosed with 0.5-4 ML of Au and heated to 850°C. Above 500°C, liquid AuGe eutectic alloy islands grew on the surface. Islands were 0.3-3.0µm in width, 1-10µm in length, and elongated in the [11¯0] direction. Above 600°C, islands began moving with speeds of 0.1-1.0µm/s, absorbing smaller stationary islands upon collision and increasing in size to more than 100µm in width...
May 10, 2017: Ultramicroscopy
Y R Niu, A A Zakharov, R Yakimova
The Sn intercalation into a buffer layer graphene grown on 4H-SiC(0001) substrate has been studied with spectroscopic photoemission and low energy electron microscope. Both SnSix and SnOx interfacial layers are found to form below the buffer layer, converting it into a quasi-free-standing monolayer graphene. Combining the various operation modes of the microscope allows a detailed insight into the formation processes of the interlayers and their thermal stability. In particular, at the interface we observed a reversible transition from silicide to oxide after exposure to ambient pressure and subsequent annealing...
May 10, 2017: Ultramicroscopy
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