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- Persson, Axel R., et al.
(författare)
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Time-resolved compositional mapping during in situ TEM studies
- 2021
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991 .- 1879-2723. ; 222
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Tidskriftsartikel (refereegranskat)abstract
- In situ studies using transmission electron microscopy (TEM) can provide insights to how properties, structures and compositions of nanostructures are affected and evolving when exerted to heat or chemical exposure. While high-resolved imaging can be obtained continuously, at video-framerates of hundreds of frames per second (fps), compositional analysis struggles with time resolution due to the long acquisition times for a reliable analysis. This especially holds true when performing mapping (correlated spatial and compositional information). Hence, transient changes are difficult to resolve using mapping. In this work, the time-resolution of sequential mapping using scanning TEM (STEM) and energy dispersive spectroscopy (EDS) is improved by acquiring spectrum images during short times and filtering the spectroscopic data. The suggested algorithm uses regularization to smooth and prevent overfitting (known from compressed sensing) to fit model spectra to the data. The algorithm is applied on simulations as well as acquisitions of catalyzed crystal growth (nanowires), performed in situ in a specialized environmental TEM (ETEM). The results show the improved temporal resolution, where the compositional progression of the different regions of the nanostructure is revealed, here with a time-resolution as low as 16 s compared to the minutes usually needed for similar analysis.
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| 2. |
- Sjökvist, Robin, et al.
(författare)
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Compositional Correlation between the Nanoparticle and the Growing Au-Assisted InxGa1-xAs Nanowire
- 2021
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 12:31, s. 7590-7595
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Tidskriftsartikel (refereegranskat)abstract
- The nanowire geometry is favorable for the growth of ternary semiconductor materials, because the composition and properties can be tuned freely without substrate lattice matching. To achieve precise control of the composition in ternary semiconductor nanowires, a deeper understanding of the growth is required. One unknown aspect of seeded nanowire growth is how the composition of the catalyst nanoparticle affects the resulting composition of the growing nanowire. We report the first in situ measurements of the nanoparticle and InxGa1-xAs nanowire compositional relationship using an environmental transmission electron microscopy setup. The compositions were measured and correlated during growth, via X-ray energy dispersive spectroscopy. Contrary to predictions from thermodynamic models, the experimental results do not show a miscibility gap. Therefore, we construct a kinetic model that better predicts the compositional trends by suppressing the miscibility gap. The findings imply that compositional control of InxGa1-xAs nanowires is possible across the entire compositional range.
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