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Yufan Luo, Sean B Andersson
Undersampling is an efficient way to increase the imaging rate of atomic force microscopy (AFM). One major challenge in this approach is retaining the quality of the final images while reducing the amount of measurements enough to have a significant improvement in the imaging time. Clearly, the decision of where to acquire data points plays an important role in producing accurate image reconstructions of the sample surface with the best allocation of measurements depending on the specific sample under study...
October 31, 2018: Ultramicroscopy
Simon Hettler, Jo Onoda, Robert Wolkow, Jason Pitters, Marek Malac
We studied the charging behavior of an amorphous carbon thin film kept at liquid-nitrogen temperature under focused electron-beam irradiation. Negative charging of the thin film is observed. The charging is attributed to a local change in the work function of the thin film induced by electron-stimulated desorption similar to the working principle of the hole free phase plate in its Volta potential implementation at elevated temperature. The negative bias of the irradiated film arises from the electron beam induced desorption of water molecules from the carbon film surface...
October 29, 2018: Ultramicroscopy
Mengkun Tian, Ondrej Dyck, Jingxuan Ge, Gerd Duscher
Thickness measurements of nanomaterials are usually performed using transmission electron microscopy (TEM) techniques such as convergent beam electron diffraction (CBED) patterns analysis and the log-ratio method based on electron energy-loss spectroscopy (EELS) spectrum. However, it is challenging to obtain both the thickness and elemental information, especially in non-crystalline materials or for very thin samples. In this work, we establish a series of procedures to calculate the areal density of the material by directly measuring the inelastic scattering probability in a thin sample...
October 26, 2018: Ultramicroscopy
Sriram Vijayan, Mark Aindow
Micro electro mechanical systems (MEMS) based TEM specimen heating holders exhibit excellent thermal stability and minimal specimen drift, which allows thermally-activated processes to be studied dynamically at high spatial resolution. The advantages of MEMS-based devices arise from the very small thermal masses of the sample studied, but this poses particular challenges for the precise measurement of specimen temperature. Previously, it has been proposed that the size-dependent sublimation behavior of Ag nanoparticles could be used to measure the specimen temperature by applying the Kelvin equation, but the effects of the capping ligands used in the nanoparticle synthesis and of electron beam heating have limited the application of such approaches...
October 26, 2018: Ultramicroscopy
K S Vikrant, G R Jayanth
Replacement of an atomic force microscope (AFM) probe is an unavoidable aspect of the instrument's use, since its tip gets blunted or contaminated with use. Here, we propose a technique to replace only the tip of the AFM probe. Significantly, the technique is compatible with all the conventional modalities and media in which AFM is operated. The proposed technique employs a paraffin wax micro-particle as an integrated adhesive microgripper. By suitably controlling the phase of this material, it is employed to pick up and detach tips, and to grip them firmly while interacting with samples...
October 19, 2018: Ultramicroscopy
Timothy J Pennycook, Gerardo T Martinez, Peter D Nellist, Jannik C Meyer
Radiation damage places a fundamental limitation on the ability of microscopy to resolve many types of materials at high resolution. Here we evaluate the dose efficiency of phase contrast imaging with electron ptychography. The method is found to be far more resilient to temporal incoherence than conventional and spherical aberration optimized phase contrast imaging, resulting in significantly greater clarity at a given dose. This robustness is explained by the presence of achromatic lines in the four dimensional ptychographic dataset...
October 18, 2018: Ultramicroscopy
Niels de Jonge
Several errors are present in the equations of the article Ultramicroscopy 187 (2018) 113-125. Yet, the calculations described in the paper and used for the figures were conducted using the correct equations, so that the results and the conclusions are based on correct calculations.
October 18, 2018: Ultramicroscopy
Yu Xia
Current issues associated with laser-assisted atom probe tomography of insulators are addressed by investigating laser-induced carrier dynamics and field evaporation kinetics. It is shown that for typical insulators with slow carrier recombination compared to the sub-picosecond laser pulse, hole accumulation at the surface plays a key role. By carrying out density functional theory calculations on a MgO cluster, it is found that the critical evaporation field strength decreases linearly as the surface hole density increases...
October 18, 2018: Ultramicroscopy
Elisah J VandenBussche, David J Flannigan
We identify and quantify several practical effects likely to be present in both static and ultrafast electron-scattering experiments that may interfere with the Debye-Waller (DW) effect. Using 120-nm thick, small-grained, polycrystalline aluminum foils as a test system, we illustrate the impact of specimen tilting, in-plane translation, and changes in z height on Debye-Scherrer-ring intensities. We find that tilting by less than one degree can result in statistically-significant changes in diffracted-beam intensities for large specimen regions containing > 105 nanocrystalline grains...
October 9, 2018: Ultramicroscopy
Tadas Paulauskas, Robert F Klie
High-energy electrons that are used as a probe of specimens in transmission electron microscopy exhibit a complex and rich behavior due to multiple scattering. Among other things, understanding the dynamical effects is needed for a quantitative analysis of atomic-resolution images and spectroscopic data. In this study, state-correlation functions are computed within the multislice approach that allow to elucidate behaviors of transversely bound states in crystals. These states play an important role as a large fraction of current density can be coupled into them via focused electron probes...
October 5, 2018: Ultramicroscopy
Z Lee, U Kaiser, H Rose
The annular differential phase contrast (ADPC) mode in a third-order spherical aberration-corrected scanning transmission electron microscope (STEM) has recently been realized at an operating voltage of 300 kV by inserting a physical Fresnel phase plate in front of the objective lens and by using a detector geometry which matches that of the Fresnel phase plate [1]. By image calculation we explore the feasibility of this mode for the voltage range of 20-80kV. Alternatively, we mimic the Fresnel phase plate material-free with the help of the adjustable aberrations of the corrector...
September 26, 2018: Ultramicroscopy
Angus J Wilkinson, David M Collins, Yevhen Zayachuk, Rajesh Korla, Arantxa Vilalta-Clemente
Multivariate statistical methods are widely used throughout the sciences, including microscopy, however, their utilisation for analysis of electron backscatter diffraction (EBSD) data has not been adequately explored. The basic aim of most EBSD analysis is to segment the spatial domain to reveal and quantify the microstructure, and links this to knowledge of the crystallography (e.g. crystal phase, orientation) within each segmented region. Two analysis strategies have been explored; principal component analysis (PCA) and k-means clustering...
September 21, 2018: Ultramicroscopy
Haojian Lu, Yongbing Wen, Hao Zhang, Hui Xie, Yajing Shen
Atomic Force Microscopy (AFM) has been intensively used for imaging, characterization and manipulation at the micro- and nanoscale. Taking into account that the material is usually anisotropic, it needs to be characterized in various regions and orientations. Although recent advances of AFM techniques have allowed for large area scan of the sample on a two-dimensional plane, mapping a three-dimensional (3D) sample at a full orientation of 360° remains challenge. This paper reports a multiparametric imaging atomic force microscope via robot technique for 360° mapping and 3D reconstruction of the sample's topography and nanomechanical properties...
September 21, 2018: Ultramicroscopy
Christoph Mahr, Knut Müller-Caspary, Robert Ritz, Martin Simson, Tim Grieb, Marco Schowalter, Florian F Krause, Anastasia Lackmann, Heike Soltau, Arne Wittstock, Andreas Rosenauer
Images acquired in transmission electron microscopes can be distorted for various reasons such as e.g. aberrations of the lenses of the imaging system or inaccuracies of the image recording system. This results in inaccuracies of measures obtained from the distorted images. Here we report on measurement and correction of elliptical distortions of diffraction patterns. The effect of this correction on the measurement of crystal lattice strain is investigated. We show that the effect of the distortions is smaller than the precision of the measurement in cases where the strain is obtained from shifts of diffracted discs with respect to their positions in images acquired in an unstrained reference area of the sample...
September 21, 2018: Ultramicroscopy
Yanyan Wang, Sen Wu, Linyan Xu, Yanan Zeng
Atomic Force Microscopy (AFM) plays a vital role in nanoscience and nanotechnology due to its nanoscale resolution. However, the realization of highly precise measurement for AFM is still a challenge. A main factor is the positioning accuracy of the piezoelectric scanner (PZT), affected significantly by the hysteresis of PZT. The paper reports a new dynamic polynomial fitting method modeling hysteresis to achieve the inverse model of the PZT. The inverse model is used as the feedforward input, combined with the fuzzy feedback controller proposed in our former paper, to correct the nonlinear errors induced by the hysteresis...
September 21, 2018: Ultramicroscopy
H Özgür Özer
We report simultaneous Force -static deflection of the cantilever-, Force Gradient and Scanning Tunneling topography images of Si(111)(7 × 7) surface using an off-resonance small amplitude non-contact atomic force microscopy technique with improved force sensitivity. The signal-to-noise ratio of the fiber interferometer used to detect the deflections of the cantilever was improved by applying an RF-modulation into the diode laser, which suppresses the noise in the laser. The measured sensitivity of ∼20 fm/√Hz allows us to obtain atom resolved images of the surface in static deflection of the cantilever, simultaneously with the other imaging channels...
September 21, 2018: Ultramicroscopy
Hyun Wook Shin, Yoonho Ahn, Jong Yeog Son
We investigate the ferroelectric properties and crystal structures of Bi3 TaTiO9 (BTTO) thin films deposited on single-crystal Nb-doped (100) SrTiO3 substrates via pulsed laser deposition. The BTTO films exhibited either a (001)-epitaxial crystalline structure or a mixed a- and c-oriented polycrystalline structure depending on the substrate temperature. The ferroelectric polarization and piezoelectric coefficient of the mixed a- and c-oriented film were larger than those of the (001)-epitaxial film because its polar axis was perpendicular to the c-axis...
September 21, 2018: Ultramicroscopy
Shahriar Dastjerdi, Mohammad Abbasi
In this paper, the effects of crack size and its location have been investigated on the free vibration of an atomic force microscopy (AFM) cantilever applying transfer matrix method. By modeling the crack as a torsional spring and considering the boundary conditions at the contact point with sample's surface, the AFM cantilever vibration behavior has been formulated. Afterwards, the characteristic equation has been derived applying the transfer matrix. At the end, the effects of crack size and its location have been investigated on the flexural resonant frequency and sensitivity of the AFM cantilever...
September 21, 2018: Ultramicroscopy
Weidong Zhao, Wei Cui, Shujun Xu, Yuanyuan Wang, Ke Zhang, Deyu Wang, Ling-Zhi Cheong, Flemming Besenbacher, Cai Shen
Charge transfer plays fundamental roles in information transmission in cells, especially in neurons. To date, direct observation of charge propagation in neurons at nanometer level has not been achieved yet. Herein, a combined charge injection and Electrostatic Force Microscopy (EFM) detection approach is applied to directly study charge propagation and distribution at nanometer resolution in spines and synapses of hippocampal neurons. Charge density, charge mobility and membrane potential in neural signal transmission process through the spines of axons and dendrites of hippocampal neurons were investigated quantitatively...
September 21, 2018: Ultramicroscopy
N Jiang
No abstract text is available yet for this article.
September 21, 2018: Ultramicroscopy
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