Theory of dynamical electron channeling contrast images of near-surface crystal defects

Picard, Yoosuf N.; Liu, Mincong; Lammatao, Joel; Kamaladasa, Ranga; Graef, Marc De

doi:10.1016/j.ultramic.2014.07.006

Cited by 40 publications

(31 citation statements)

References 36 publications

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“…In order to reveal the different information content of various data visualizations, we analysed a sample of a GaN thin film containing dislocations. This example is also relevant to the important topic of contrast interpretation in SEM‐based dislocation imaging (Wilkinson & Hirsch, ; Picard et al ., ; Naresh‐Kumar et al ., ; Picard et al ., ; Zaefferer & Elhami, ).…”

Section: Resultsmentioning

confidence: 99%

Diffraction effects and inelastic electron transport in angle‐resolved microscopic imaging applications

Winkelmann

Nolze

Vespucci

et al. 2017

Journal of Microscopy

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SummaryWe analyse the signal formation process for scanning electron microscopic imaging applications on crystalline specimens. In accordance with previous investigations, we find nontrivial effects of incident beam diffraction on the backscattered electron distribution in energy and momentum. Specifically, incident beam diffraction causes angular changes of the backscattered electron distribution which we identify as the dominant mechanism underlying pseudocolour orientation imaging using multiple, angle-resolving detectors. Consequently, diffraction effects of the incident beam and their impact on the subsequent coherent and incoherent electron transport need to be taken into account for an in-depth theoretical modelling of the energy-and momentum distribution of electrons backscattered from crystalline sample regions. Our findings have implications for the level of theoretical detail that can be necessary for the interpretation of complex imaging modalities such as electron channelling contrast imaging (ECCI) of defects in crystals. If the solid angle of detection is limited to specific regions of the backscattered electron momentum distribution, the image contrast that is observed in ECCI and similar applications can be strongly affected by incident beam diffraction and topographic effects from the sample surface. As an application, we demonstrate characteristic changes in the resulting images if different properties of the backscattered electron distribution are used for the analysis of a GaN thin film sample containing dislocations.

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Section: Resultsmentioning

confidence: 99%

Diffraction effects and inelastic electron transport in angle‐resolved microscopic imaging applications

Winkelmann

Nolze

Vespucci

et al. 2017

Journal of Microscopy

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“…Theory and application of the ECCI technique were recently reviewed. [20,21] In contrast to the ordinary SEM, it uses signals of backscattered electrons which are influenced by material composition, crystal orientation, and topography of the sample surface. [22] ECCI is also influenced by the lattice orientation relative to the primary beam.…”

Section: Methodsmentioning

confidence: 99%

Morphology of Upper and Lower Bainite with 0.7 Mass Pct C

Yin

Hillert

Borgenstam

2017

Metall Mater Trans A

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There has been an on-going discussion on the difference in formation mechanisms of upper and lower bainite. Various suggestions have been supported by reference to observed morphologies and illustrated with idealized sketches of morphologies. In order to obtain a better basis for discussions about the difference in mechanism, the morphology of bainite in an Fe-C alloy with 0.7 mass pct carbon was now studied in some detail from 823 K to 548 K (550°C to 275°C) at temperature intervals of 50 K or less. The work focused on bainite seen to start from a grain boundary in the plane of polish and showing an advancing tip in the remaining austenite. The results indicate that there is no essential difference with temperature regarding the ferritic skeleton of feathery bainite. The second stage of bainite formation, which involves the formation of both ferrite and cementite, was regarded as a eutectoid transformation and the resulting morphologies were analyzed in terms of two modes, degenerate and cooperative eutectoid transformation. There was no sharp difference between upper and lower bainite. Ways to define the difference were discussed.

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“…The observed channeling contrast depends on the Burgers vector and the line direction of the dislocation as well as the diffraction vector. 19,20 To date, ECCI has been used to study threading dislocations on the surface of metals 21 and various semiconductors such as SiC, 22 GaSb 23 and GaN. 24,25 Moreover, buried misfit dislocations in SiGe/Si 26 and various III/V compound heterostructures 27,28 have been imaged successfully.…”

Section: B: Electron Channeling Contrast Imagingmentioning

confidence: 99%

Non-destructive characterization of extended crystalline defects in confined semiconductor device structures

et al. 2018

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Semiconductor heterostructures are at the heart of most nanoelectronic and photonic devices such as advanced transistors, lasers, light emitting diodes, optical modulators and photo-detectors. However, the performance and reliability of the respective devices are often limited by the presence of crystalline defects which arise from plastic relaxation of misfit strain present in these heterogeneous systems. To date, characterizing the nature and distribution of such defects in 3D nanoscale devices precisely and non-destructively remains a critical metrology challenge. In this paper we demonstrate that electron channeling contrast imaging (ECCI) is capable of analyzing individual dislocations and stacking faults in confined 3D nanostructures, thereby fulfilling the aforementioned requirements. For this purpose we imaged the intensity of electrons backscattered from the sample under test under controlled diffraction conditions using a scanning electron microscope (SEM). In contrast to transmission electron microscopy (TEM) analysis, no electron transparent specimens need to be prepared. This enables a significant reduction of the detection limit (i.e. lowest defect density that can be assessed) as our approach facilitates the analysis of large sampling volumes, thereby providing excellent statistics. We applied the methodology to SiGe nanostructures grown by selective area epitaxy to study in detail how the nature and distribution of crystalline defects are affected by the dimensions of the structure. By comparing our observations with the results obtained using X-ray diffraction, TEM and chemical defect etching, we could verify the validity of the method. Our findings firmly establish that ECCI must be considered the method of choice for analyzing the crystalline quality of 3D semiconductor heterostructures with excellent precision even at low defect densities. As such, the technique aids in better understanding of strain relaxation and defect formation mechanisms at the nanoscale and, moreover, facilitates the development and fabrication of next generation nanoelectronic and photonic devices.

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Theory of dynamical electron channeling contrast images of near-surface crystal defects

Cited by 40 publications

References 36 publications

Diffraction effects and inelastic electron transport in angle‐resolved microscopic imaging applications

Diffraction effects and inelastic electron transport in angle‐resolved microscopic imaging applications

Morphology of Upper and Lower Bainite with 0.7 Mass Pct C

Non-destructive characterization of extended crystalline defects in confined semiconductor device structures

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