Scanning Electron Microscopy with Samples in an Electric Field

Frank, L.; Hovorka, Miloš; Mikmeková, Šárka; Mikmeková, Eliška; Müllerová, Ilona; Pokorná, Zuzana

doi:10.3390/ma5122731

Cited by 22 publications

(10 citation statements)

References 55 publications

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“…When tuning the landing energy of electrons to what is known as the second critical energy, we get nonconductive samples imaged free of charging artifacts [3]. The dynamical theory of electron diffraction indicates [4], and practice confirms [5], that in the 10 2 eV range the grain contrast of polycrystals substantially increases and even the distribution of residual strains inside grains becomes visible [6]. Below 50 eV, the absorption of hot electrons injected into samples is low enough to allow the electron reflectance in the (00) spot to respond to the local density of empty electron states available in the direction of motion, which provides an alternative method of determining the local crystallographic system and its orientation [7].…”

mentioning

confidence: 63%

Scanning Electron Microscopy With Slow Electrons

Frank¹,

Mikmeková²,

Pokorná³

et al. 2013

Microsc Microanal

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When focusing the primary electron beam in a scanning electron microscope (SEM) using a standard electromagnetic or electrostatic lens with the main aberration coefficients independent of the beam energy, we get a spot size proportional to (energy) -3/4 [1]. However, an immersion electrostatic lens has aberrations proportional to the lower of the electron energies existing on both its sides, so when retarding the primary beam with a bias applied directly to the sample via the cathode lens, we get a spot extending only as (energy) -1/4 at the lowest energies, with the overall spot size remaining within one order of magnitude throughout the full energy scale [1]. The above-sample field not only retards the primary electrons but also accelerates the signal electrons and collimates them towards the optical axis, thereby ensuring excellent collection efficiency for all energies. A below-sample detector enables performance of the transmission mode at any energy [2].Scanning low energy electron microscopy (SLEEM) with a cathode lens provides improved image resolution at low energies, an enhanced signal of secondary electrons, a completely collected signal of backscattered electrons (BSE) including very low energy electrons that are traditionally abandoned, and plenty of contrast mechanisms not available with fast incident electrons. Below a fuzzy threshold at 50 eV, the inelastic scattering phenomena fade away so the BSE signal strongly dominates and the penetration of primary electrons also increases. At and below hundreds of eV, the BSE signal abandons its dependence on the atomic density of the sample and becomes governed by its crystallinic structure, while at tens and units of eV the electronic structure is what reflects the image signal behavior.From the experimental point of view, it is important to have flat samples with surface unevenness not exceeding tens of m at hundreds of eV and units of m at the lowest energies. It is good practice to cover the sample with a flat cap leveling the equipotential surface. With a primary beam energy of several keV we get, using the sample bias, excellent performance at lower energies, i.e. not only better resolution, but also much higher signal-to-noise ratio and enhanced surface sensitivity. When tuning the landing energy of electrons to what is known as the second critical energy, we get nonconductive samples imaged free of charging artifacts [3]. The dynamical theory of electron diffraction indicates [4], and practice confirms [5], that in the 10 2 eV range the grain contrast of polycrystals substantially increases and even the distribution of residual strains inside grains becomes visible [6]. Below 50 eV, the absorption of hot electrons injected into samples is low enough to allow the electron reflectance in the (00) spot to respond to the local density of empty electron states available in the direction of motion, which provides an alternative method of determining the local crystallographic system and its orientation [7]. After non-zero diffracted rays emerge, flat sur...

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mentioning

confidence: 63%

Scanning Electron Microscopy With Slow Electrons

Frank¹,

Mikmeková²,

Pokorná³

et al. 2013

Microsc Microanal

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“…The morphology of BSCF powders was analyzed by SEM using a FEI Quanta 3D equipment operated at low acceleration voltage (maximum 5 kV) and using the backscatter detector in beam deceleration mode. This SEM mode enables high resolution imaging and high surface sensitivity [22], and it was used in this study to evidence the surface features of the BSCF particles.…”

Section: Methodsmentioning

confidence: 99%

Thermodynamic Stability and Microscopic Behavior of Ba_xSr_1-xCo_1-yFe_yO_3-δ Perovskites

Maxim¹,

Botea‐Petcu²,

Teodorescu³

et al. 2020

Structure Processing Properties Relationships in Stoichiometric and Nonstoichiometric Oxides

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The mixed conducting perovskite-type oxides BaxSr1-xCo1-yFeyO3-δ (BSCF) are intensively studied as potential high-performance solid oxide fuel cell cathode materials. The effect of different compositional variables and oxygen stoichiometry on the structure and thermodynamic stability of the BaxSr1-xCo1-yFeyO3-δ (x = 0.2, 0.4, 0.5, 0.6, 0.8; y = 0.2, 0.4, 0.6, 0.8, 1) perovskite-type compositions were investigated by solid electrolyte electrochemical cells method and scanning electron microscopy (SEM). The thermodynamic quantities represented by the partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressures of oxygen were obtained in the temperature range of 823–1273 K. The in situ change of oxygen stoichiometry and the determination of thermodynamic parameters of the new oxygen-deficient BSCF compositions were studied via coulometric titration technique coupled with electromotive force (EMF) measurements. The effect of A- and B-site dopants concentration correlated to the variation of oxygen stoichiometry on the thermodynamic stability and morphology of the BSCF samples was evidenced.

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“…Today’s scanning electron microscopes can operate in the “cathode lens” mode [ 6 , 7 ] which utilizes a high negative bias on the sample and a strong electric field around the sample. This mode offers a convenient tool for controlling the landing energy of electrons down to units of electronvolts.…”

Section: Introductionmentioning

confidence: 99%

Quantification of STEM Images in High Resolution SEM for Segmented and Pixelated Detectors

et al. 2021

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The segmented semiconductor detectors for transmitted electrons in ultrahigh resolution scanning electron microscopes allow observing samples in various imaging modes. Typically, two standard modes of objective lens, with and without a magnetic field, differ by their resolution. If the beam deceleration mode is selected, then an electrostatic field around the sample is added. The trajectories of transmitted electrons are influenced by the fields below the sample. The goal of this paper is a quantification of measured images and theoretical study of the capability of the detector to collect signal electrons by its individual segments. Comparison of measured and ray-traced simulated data were difficult in the past. This motivated us to present a new method that enables better comparison of the two datasets at the cost of additional measurements, so-called calibration curves. Furthermore, we also analyze the measurements acquired using 2D pixel array detector (PAD) that provide a more detailed angular profile. We demonstrate that the radial profiles of STEM and/or 2D-PAD data are sensitive to material composition. Moreover, scattering processes are affected by thickness of the sample as well. Hence, comparing the two experimental and simulation data can help to estimate composition or the thickness of the sample.

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Scanning Electron Microscopy with Samples in an Electric Field

Cited by 22 publications

References 55 publications

Scanning Electron Microscopy With Slow Electrons

Scanning Electron Microscopy With Slow Electrons

Thermodynamic Stability and Microscopic Behavior of Ba_xSr_1-xCo_1-yFe_yO_3-δ Perovskites

Quantification of STEM Images in High Resolution SEM for Segmented and Pixelated Detectors

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Scanning Electron Microscopy with Samples in an Electric Field

Cited by 22 publications

References 55 publications

Scanning Electron Microscopy With Slow Electrons

Scanning Electron Microscopy With Slow Electrons

Thermodynamic Stability and Microscopic Behavior of BaxSr1-xCo1-yFeyO3-δ Perovskites

Quantification of STEM Images in High Resolution SEM for Segmented and Pixelated Detectors

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Product

Resources

About

Thermodynamic Stability and Microscopic Behavior of Ba_xSr_1-xCo_1-yFe_yO_3-δ Perovskites