Strain, composition and disorder in ADF imaging of semiconductors

Grillo, Vincenzo; Mueller, Knut; Volz, Kerstin; Grieb, Tim; Rosenauer, A.

doi:10.1088/1742-6596/326/1/012006

Cited by 28 publications

(17 citation statements)

References 27 publications

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“…S4). We note that these findings agree with previous reports in which low-angle unfiltered STEM served for qualitative analyses in thick specimen474849 whereas quantitative agreement was found in bright field STEM in thin specimens where the fraction of inelastic intensity is low50. Moreover, energy filtered diffraction patterns at elevated thicknesses agreed with simulations, too515253.…”

Section: Discussionsupporting

confidence: 91%

Materials characterisation by angle-resolved scanning transmission electron microscopy

Müller‐Caspary

Oppermann

Grieb

et al. 2016

Sci Rep

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Solid-state properties such as strain or chemical composition often leave characteristic fingerprints in the angular dependence of electron scattering. Scanning transmission electron microscopy (STEM) is dedicated to probe scattered intensity with atomic resolution, but it drastically lacks angular resolution. Here we report both a setup to exploit the explicit angular dependence of scattered intensity and applications of angle-resolved STEM to semiconductor nanostructures. Our method is applied to measure nitrogen content and specimen thickness in a GaNxAs1−x layer independently at atomic resolution by evaluating two dedicated angular intervals. We demonstrate contrast formation due to strain and composition in a Si- based metal-oxide semiconductor field effect transistor (MOSFET) with GexSi1−x stressors as a function of the angles used for imaging. To shed light on the validity of current theoretical approaches this data is compared with theory, namely the Rutherford approach and contemporary multislice simulations. Inconsistency is found for the Rutherford model in the whole angular range of 16–255 mrad. Contrary, the multislice simulations are applicable for angles larger than 35 mrad whereas a significant mismatch is observed at lower angles. This limitation of established simulations is discussed particularly on the basis of inelastic scattering.

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Section: Discussionsupporting

confidence: 91%

Materials characterisation by angle-resolved scanning transmission electron microscopy

Müller‐Caspary

Oppermann

Grieb

et al. 2016

Sci Rep

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“…Lattice distortions can significantly reduce channeling by virtue of the greater incoherency of the lattice [51]. This results in reduced high-angle scattering since the de-channeled electrons interact more weakly with the atomic nuclei [52, 53]. In turn, lower angle scattering increases since the scattered electron intensity distribution more closely follows the distribution for kinematic scattering [54].…”

Section: Resultsmentioning

confidence: 99%

Oxidation-state sensitive imaging of cerium dioxide by atomic-resolution low-angle annular dark field scanning transmission electron microscopy

et al. 2016

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Low-angle annular dark field (LAADF) scanning transmission electron microscopy (STEM) imaging is presented as a method that is sensitive to the oxidation state of cerium ions in CeO2 nanoparticles. This relationship was validated through electron energy loss spectroscopy (EELS), in situ measurements, as well as multislice image simulations. Static displacements caused by the increased ionic radius of Ce3+ influence the electron channeling process and increase electron scattering to low angles while reducing scatter to high angles. This process manifests itself by reducing the high-angle annular dark field (HAADF) signal intensity while increasing the LAADF signal intensity in close proximity to Ce3+ ions. This technique can supplement STEM-EELS and in so doing, relax the experimental challenges associated with acquiring oxidation state information at high spatial resolutions.

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“…23. By following the approach of Grillo et al 18,19 the LAADF intensity turns out to be proportional to the curvature of the atomic column that, in a QD, is maximum at the QD periphery. The presence of QD compositional gradients, due to In segregation and In-Ga intermixing, could give rise to an ambiguity in the definition of the exact spatial limits of the QD.…”

Section: Resultsmentioning

confidence: 99%

“…The high angle ADF finds a larger application in compositional analysis but this information is somehow mixed with strain effect. 18,19 Here, we use the low angle detection range (LAADF), which is more sensitive to the strain than to the chemical information; the corresponding range is 30 < 2h < 84 mrad. For ensemble QD optical measurements samples were held in a cold finger of a closed-cycle He cryostat, which can be cooled down to 10 K. PL was measured by using a Ti:sapphire mode locked laser at a wavelength of 780 nm.…”

Section: Methodsmentioning

confidence: 99%

The effect of high-In content capping layers on low-density bimodal-sized InAs quantum dots

Trevisi

Suárez

Seravalli

et al. 2013

Journal of Applied Physics

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The structural and morphological features of bimodal-sized InAs/(In)GaAs quantum dots with density in the low 10 9 cm À2 range were analyzed with transmission electron microscopy and atomic force microscopy and were related to their optical properties, investigated with photoluminescence and time-resolved photoluminescence. We show that only the family of small quantum dots (QDs) is able to emit narrow photoluminescence peaks characteristic of single-QD spectra; while the behavior of large QDs is attributed to large strain fields that may induce defects affecting their optical properties, decreasing the optical intensity and broadening the homogeneous linewidth. Then, by using a rate-equation model for the exciton recombination dynamics, we show that thermal population of dark states is inhibited in both QD families capped by high In content InGaAs layers. We discuss this behavior in terms of alloy disorder and increased density of point defects in the InGaAs pseudomorphic layer. V C 2013 AIP Publishing LLC. [http://dx

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Strain, composition and disorder in ADF imaging of semiconductors

Cited by 28 publications

References 27 publications

Materials characterisation by angle-resolved scanning transmission electron microscopy

Materials characterisation by angle-resolved scanning transmission electron microscopy

Oxidation-state sensitive imaging of cerium dioxide by atomic-resolution low-angle annular dark field scanning transmission electron microscopy

The effect of high-In content capping layers on low-density bimodal-sized InAs quantum dots

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