Compositional Analysis with Atomic Column Spatial Resolution by 5th-Order Aberration-Corrected Scanning Transmission Electron Microscopy

Hernández-Maldonado, David; Herrera, M.; Alonso‐González, Pablo; González, Y.; González, L.; Gàzquez, Jaume; Varela, M.; Pennycook, Stephen J.; Guerrero-Lebrero, Maria P.; Pizarro, J.; Galindo, Pedro L.; Molina, S. I.

doi:10.1017/s1431927611000213

Cited by 15 publications

(19 citation statements)

References 12 publications

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“…The procedure to quantify Bi content was similar to the one published in Ref. [28]. In this work, the integrated intensity quotients of every dumbbell ( R ) was calculated as a ratio between the integrated intensity in the group V columns ( I As − Bi ) in the whole image and the mean integrated intensity in the group V columns in the GaAs layer ( I As ), as R = ( I (As − Bi) )/ I As .…”

Section: Resultsmentioning

confidence: 99%

Analysis of Bi Distribution in Epitaxial GaAsBi by Aberration-Corrected HAADF-STEM

et al. 2018

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The Bi content in GaAs/GaAs1 − xBix/GaAs heterostructures grown by molecular beam epitaxy at a substrate temperature close to 340 °C is investigated by aberration-corrected high-angle annular dark-field techniques. The analysis at low magnification of high-angle annular dark-field scanning transmission electron microscopy images, corroborated by EDX analysis, revealed planar defect-free layers and a non-homogeneous Bi distribution at the interfaces and within the GaAsBi layer. At high magnification, the qHAADF analysis confirmed the inhomogeneous distribution and Bi segregation at the GaAsBi/GaAs interface at low Bi flux and distorted dumbbell shape in areas with higher Bi content. At higher Bi flux, the size of the Bi gathering increases leading to roughly equiaxial Bi-rich particles faceted along zinc blende {111} and uniformly dispersed around the matrix and interfaces. FFT analysis checks the coexistence of two phases in some clusters: a rhombohedral pure Bi (rh-Bi) one surrounded by a zinc blende GaAs1 − xBix matrix. Clusters may be affecting to the local lattice relaxation and leading to a partially relaxed GaAsBi/GaAs system, in good agreement with XRD analysis.

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Section: Resultsmentioning

confidence: 99%

Analysis of Bi Distribution in Epitaxial GaAsBi by Aberration-Corrected HAADF-STEM

et al. 2018

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“…Figure 5g shows a magnified dumbbell where the upper and lower columns are the anionic and cationic components, respectively. In order to estimate column-by-column the Sb and In contents, a method similar to the one used in [9,19] was performed. The R values corresponding to each sub-net column, R i , are represented in Figure 5 with colored dots, where higher values (red dots) are associated with atomic columns with higher proportion of heavier elements with respect to the corresponding atomic columns in GaAs.…”

Section: Resultsmentioning

confidence: 99%

Impact of N on the atomic-scale Sb distribution in quaternary GaAsSbN-capped InAs quantum dots

et al. 2012

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The use of GaAsSbN capping layers on InAs/GaAs quantum dots (QDs) has recently been proposed for micro- and optoelectronic applications for their ability to independently tailor electron and hole confinement potentials. However, there is a lack of knowledge about the structural and compositional changes associated with the process of simultaneous Sb and N incorporation. In the present work, we have characterized using transmission electron microscopy techniques the effects of adding N in the GaAsSb/InAs/GaAs QD system. Firstly, strain maps of the regions away from the InAs QDs had revealed a huge reduction of the strain fields with the N incorporation but a higher inhomogeneity, which points to a composition modulation enhancement with the presence of Sb-rich and Sb-poor regions in the range of a few nanometers. On the other hand, the average strain in the QDs and surroundings is also similar in both cases. It could be explained by the accumulation of Sb above the QDs, compensating the tensile strain induced by the N incorporation together with an In-Ga intermixing inhibition. Indeed, compositional maps of column resolution from aberration-corrected Z-contrast images confirmed that the addition of N enhances the preferential deposition of Sb above the InAs QD, giving rise to an undulation of the growth front. As an outcome, the strong redshift in the photoluminescence spectrum of the GaAsSbN sample cannot be attributed only to the N-related reduction of the conduction band offset but also to an enhancement of the effect of Sb on the QD band structure.

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“…In order to being able to compare these experimental results to the simulated images, it is necessary to average the intensity over a significant number of atomic columns. For this, we have used a method for measuring the integrated intensities around each atomic column [29] that has been successfully used previously for the calculation of the composition of different semiconductor materials from experimental HAADF-STEM image [31-32]. In the case of more than one MoS 2 layers, the crystal can be considered as its bulk crystalline structures, in which a layer-stacked of S-Mo-S units are repeated following two main trigonal phases: the first one is a trigonal-prismatic 2H and the second one is a rhombohedral structure, also called 3R-MoS 2 [33-34].…”

Section: Quantitative Analysismentioning

confidence: 99%

Analysis of electron beam damage of exfoliated MoS2 sheets and quantitative HAADF-STEM imaging

et al. 2014

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In this work we examined MoS2 sheets by aberration-corrected scanning transmission electron microscopy (STEM) at three different energies: 80, 120 and 200 kV. Structural damage of the MoS2 sheets has been controlled at 80 kV according a theoretical calculation based on the inelastic scattering of the electrons involved in the interaction electron-matter. The threshold energy for the MoS2 material has been found and experimentally verified in the microscope. At energies higher than the energy threshold we show surface and edge defects produced by the electron beam irradiation. Quantitative analysis at atomic level in the images obtained at 80 kV has been performed using the experimental images and via STEM simulations using SICSTEM software to determine the exact number of MoS2 layers.

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Compositional Analysis with Atomic Column Spatial Resolution by 5th-Order Aberration-Corrected Scanning Transmission Electron Microscopy

Cited by 15 publications

References 12 publications

Analysis of Bi Distribution in Epitaxial GaAsBi by Aberration-Corrected HAADF-STEM

Analysis of Bi Distribution in Epitaxial GaAsBi by Aberration-Corrected HAADF-STEM

Impact of N on the atomic-scale Sb distribution in quaternary GaAsSbN-capped InAs quantum dots

Analysis of electron beam damage of exfoliated MoS2 sheets and quantitative HAADF-STEM imaging

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