Composition determination of semiconductor alloys towards atomic accuracy by HAADF-STEM

Duschek, Lennart; Kükelhan, Pirmin; Beyer, Andreas; Firoozabadi, Saleh; Oelerich, J. O.; Fuchs, Christian; Stolz, W.; Ballabio, Andrea; Isella, Giovanni; Volz, Kerstin

doi:10.1016/j.ultramic.2019.02.009

Cited by 16 publications

(13 citation statements)

References 43 publications

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“…4,31 . Indeed, quantitative HAADF 2,4,6,31,33,34 gives thicknesses of 30, 60, 85, 110 and 130 nm ( ± 5 nm ) that are in excellent agreement with the thicknesses obtained from PACBED within the uncertainty of the methods.…”

Section: Angular Dependencies Of Elastic and Inelastic Scatteringsupporting

confidence: 78%

“…This is achieved by using a dedicated experimental setup where an ultra-fast pixelated camera is mounted behind an energy filter in an aberration-corrected STEM in addition to another setup with a conventional camera behind the energy filter. These two setups are representative for systems which are used for quantitative STEM [1][2][3][4][5][6] . For two well-defined material systems, we demonstrate that inelastic scattering, predominantly the excitation of plasmons, is responsible for a redistribution of low-angle scattering in diffraction space and hence leads to the mismatch between contemporary theories for quasi-elastic scattering and non-energyfiltered STEM.…”

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confidence: 99%

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Influence of plasmon excitations on atomic-resolution quantitative 4D scanning transmission electron microscopy

Beyer

Krause

Robert

et al. 2020

Sci Rep

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Scanning transmission electron microscopy (STEM) allows to gain quantitative information on the atomic-scale structure and composition of materials, satisfying one of todays major needs in the development of novel nanoscale devices. The aim of this study is to quantify the impact of inelastic, i.e. plasmon excitations (PE), on the angular dependence of STEM intensities and answer the question whether these excitations are responsible for a drastic mismatch between experiments and contemporary image simulations observed at scattering angles below $$\sim $$ ∼ 40 mrad. For the two materials silicon and platinum, the angular dependencies of elastic and inelastic scattering are investigated. We utilize energy filtering in two complementary microscopes, which are representative for the systems used for quantitative STEM, to form position-averaged diffraction patterns as well as atomically resolved 4D STEM data sets for different energy ranges. The resulting five-dimensional data are used to elucidate the distinct features in real and momentum space for different energy losses. We find different angular distributions for the elastic and inelastic scattering, resulting in an increased low-angle intensity ($$\sim $$ ∼ 10–40 mrad). The ratio of inelastic/elastic scattering increases with rising sample thickness, while the general shape of the angular dependency is maintained. Moreover, the ratio increases with the distance to an atomic column in the low-angle regime. Since PE are usually neglected in image simulations, consequently the experimental intensity is underestimated at these angles, which especially affects bright field or low-angle annular dark field imaging. The high-angle regime, however, is unaffected. In addition, we find negligible impact of inelastic scattering on first-moment imaging in momentum-resolved STEM, which is important for STEM techniques to measure internal electric fields in functional nanostructures. To resolve the discrepancies between experiment and simulation, we present an adopted simulation scheme including PE. This study highlights the necessity to take into account PE to achieve quantitative agreement between simulation and experiment. Besides solving the fundamental question of missing physics in established simulations, this finally allows for the quantitative evaluation of low-angle scattering, which contains valuable information about the material investigated.

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Section: Angular Dependencies Of Elastic and Inelastic Scatteringsupporting

confidence: 78%

mentioning

confidence: 99%

Influence of plasmon excitations on atomic-resolution quantitative 4D scanning transmission electron microscopy

Beyer

Krause

Robert

et al. 2020

Sci Rep

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“…The MRSTEM characterization was carried out in a double aberration-corrected JEOL JEM 2200FS operating at 200 kV using a semiconvergence angle of 21 mrad, i.e., typical conditions for high resolution STEM (see, e.g., ref 34). This means the diffraction pattern acquired by the pixelated detector is a complex diffraction pattern containing several overlapping disks instead of just the direct beam.…”

Section: ■ Sample Growth and Characterizationmentioning

confidence: 99%

Quantitative Characterization of Nanometer-Scale Electric Fields via Momentum-Resolved STEM

et al. 2021

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Most of today's electronic devices, like solar cells and batteries, are based on nanometer-scale built-in electric fields. Accordingly, characterization of fields at such small scales has become an important task in the optimization of these devices. In this study, with GaAs-based p−n junctions as the example, key characteristics such as doping concentrations, polarity, and the depletion width are derived quantitatively using four-dimensional scanning transmission electron microscopy (4DSTEM). The built-in electric fields are determined by the shift they introduce to the center-of-mass of electron diffraction patterns at subnanometer spatial resolution. The method is applied successfully to characterize two p−n junctions with different doping concentrations. This highlights the potential of this method to directly visualize intentional or unintentional nanoscale electric fields in real-life devices, e.g., batteries, transistors, and solar cells.

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“…In order to quantitatively analyse the chemical composition of Ge in every atomic column, it is necessary to compare the measured images with the complementary contrast simulations obtained from the software package STEMsalabim [32]. The determination of the concentration is explained in detail in [33]. Due to the dependence of the HAADF-STEM intensity on the sample thickness in addition to atomic number, it is necessary to determine the spatial dependence of the sample thickness.…”

Section: Structural Characterizationmentioning

confidence: 99%

Ge/SiGe parabolic quantum wells

Ballabio¹,

Frigerio²,

Firoozabadi³

et al. 2019

J. Phys. D: Appl. Phys.

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Quantum wells with a parabolic confining potentials allows the realization of semiconductor heterostructures mimicking the physical properties of a quantum harmonic oscillator. Here we report the attempt of attaining such parabolic quantum wells (PQWs) within the Ge/SiGe material platform. Multiple PQWS featuring different widths and composition have been epitaxially grown and characterized by means of high-resolution X-ray diffraction and scanning transmission electron microscopy. The compositional profile is seen to deviate slightly from an ideal parabola, but the quantum confined states are almost equally spaced within the valence and conduction band as indicated by photoreflectance measurements and k • p modelling.

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Composition determination of semiconductor alloys towards atomic accuracy by HAADF-STEM

Cited by 16 publications

References 43 publications

Influence of plasmon excitations on atomic-resolution quantitative 4D scanning transmission electron microscopy

Influence of plasmon excitations on atomic-resolution quantitative 4D scanning transmission electron microscopy

Quantitative Characterization of Nanometer-Scale Electric Fields via Momentum-Resolved STEM

Ge/SiGe parabolic quantum wells

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