Optimal ADF STEM imaging parameters for tilt-robust image quantification

MacArthur, Katherine E.; D’Alfonso, Adrian J.; Özkaya, Doğan; Allen, L. J.; Nellist, Peter D.

doi:10.1016/j.ultramic.2015.04.010

Cited by 29 publications

(25 citation statements)

References 34 publications

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“…From the HAADF image, atomic column intensities for Sr and Ti-O columns (I Sr and I Ti-O ) were measured by averaging intensities within a small disk, with a radius of one-fourth of a lattice constant of SrTiO 3 , around each atomic column position. This method has been demonstrated to be a very effective way to obtain quantitative structural information since the integrated intensity is robust to subtle changes in imaging parameters such as defocus, effective source size, convergence angle, image noise, and sample tilt, all of which are difficult to determine experimentally [30,31].…”

Section: Methodsmentioning

confidence: 99%

Direct Observation of Sr Vacancies inSrTiO3by Quantitative Scanning Transmission Electron Microscopy

et al. 2016

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Unveiling the identity, spatial configuration, and microscopic structure of point defects is one of the key challenges in materials science. Here, we demonstrate that quantitative scanning transmission electron microscopy (STEM) can be used to directly observe Sr vacancies in SrTiO 3 and to determine the atom column relaxations around them. By combining recent advances in quantitative STEM, including variableangle, high-angle annular dark-field imaging and rigid registration methods, with frozen phonon multislice image simulations, we identify which Sr columns contain vacancies and quantify the number of vacancies in them. Picometer precision measurements of the surrounding atom column positions show that the nearest-neighbor Ti atoms are displaced away from the Sr vacancies. The results open up a new methodology for studying the microscopic mechanisms by which point defects control materials properties.

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Section: Methodsmentioning

confidence: 99%

Direct Observation of Sr Vacancies inSrTiO3by Quantitative Scanning Transmission Electron Microscopy

et al. 2016

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“…3 and 4, that the probability of error based on the PF of the SCSs is a good approximation for the probability of error when the decision is based on the joint PF of the image pixel intensities. This is a great advantage of atom-counting using HR STEM, since SCSs are a robust measure for many imaging parameters, including defocus, source coherence, convergence angle [10], and also for crystal tilt [26].…”

Section: Results For Image Intensities On a Pixel By Pixel Basismentioning

confidence: 99%

Atom-counting in High Resolution Electron Microscopy:TEM or STEM – That's the question

et al. 2017

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In this work, a recently developed quantitative approach based on the principles of detection theory is used in order to determine the possibilities and limitations of High Resolution Scanning Transmission Electron Microscopy (HR STEM) and HR TEM for atom-counting. So far, HR STEM has been shown to be an appropriate imaging mode to count the number of atoms in a projected atomic column. Recently, it has been demonstrated that HR TEM, when using negative spherical aberration imaging, is suitable for atom-counting as well. The capabilities of both imaging techniques are investigated and compared using the probability of error as a criterion. It is shown that for the same incoming electron dose, HR STEM outperforms HR TEM under common practice standards, i.e. when the decision is based on the probability function of the peak intensities in HR TEM and of the scattering cross-sections in HR STEM. If the atom-counting decision is based on the joint probability function of the image pixel values, the dependence of all image pixel intensities as a function of thickness should be known accurately. Under this assumption, the probability of error may decrease significantly for atom-counting in HR TEM and may, in theory, become lower as compared to HR STEM under the predicted optimal experimental settings. However, the commonly used standard for atom-counting in HR STEM leads to a high performance and has been shown to work in practice.

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“…For example, Mask1 functions appropriately in terms of very thin samples, ranging from 15-40 nm [34] since the investigating atomic column stays unaffected by the surrounding dumbbells in this thickness range [29]. On the other hand, some researchers suggested a Mask that contains the whole analyzing atomic column proving to provide better HAADF quantitative approach in terms of varying convergence angle, magnification, source size and defocus [38], sample associated small mis-tilt [39], aberrations and astigmatism [40] and scan induced noises [41], as long as the probe size does not change with the sample thickness. These characteristics allow possibility analyzing even thicker samples than of Mask1.…”

Section: Implementation Of the Methodsmentioning

confidence: 99%

Modified qHAADF method for atomic column-by-column compositional quantification of semiconductor heterostructures

et al. 2018

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The qHAADF method allows the quantification of the composition at atomic column resolution in semiconductor materials by comparing the HAADF-STEM intensities between a region of interest to a region of the material of known composition. However, the application of this qHAADF approach requires both regions to be differentiable and included in the same micrograph at close proximity. This limits the application of this approach to certain materials and magnifications where this requirement is fulfilled. In this work, we extend the qHAADF method to analyses where the reference region is imaged in a separate micrograph. The validity of this modified method is proved by comparison to the original qHAADF approach using HAADF-STEM simulated images of the semiconductor heterostructure InSb/InAs. Additionally, the methods are applied successfully to experimental images both of a simple InSb/InAs interface and of a complex InSb/GaSb heterostructure, justifying the significance of the modified method over the original method.

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Optimal ADF STEM imaging parameters for tilt-robust image quantification

Cited by 29 publications

References 34 publications

Direct Observation of Sr Vacancies inSrTiO3by Quantitative Scanning Transmission Electron Microscopy

Direct Observation of Sr Vacancies inSrTiO3by Quantitative Scanning Transmission Electron Microscopy

Atom-counting in High Resolution Electron Microscopy:TEM or STEM – That's the question

Modified qHAADF method for atomic column-by-column compositional quantification of semiconductor heterostructures

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