Resolving the Burgers vector for individual GaN dislocations by electron channeling contrast imaging

Picard, Yoosuf N.; Twigg, M. E.; Caldwell, Joshua D.; Eddy, Charles R.; Mastro, Michael A.; Holm, R. T.

doi:10.1016/j.scriptamat.2009.06.021

Cited by 46 publications

(33 citation statements)

References 21 publications

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“…Another method to measure the TDI is via x-ray topography; however, the TDD observed is too high for this technique. TD can be observed at this density when using Electron Channeling Contrast Imaging as performed by Picard et al and Carnevale et al 34,35 The average radius of curvature for the commercial HVPE grown GaN substrates is approximately $5 m, leading to a large disparity in vicinality from edge to edge over the substrate (e.g., $0.6 for R C ¼ 5 m for a 50 mm substrate). For comparison, the vicinality of GaN on sapphire is optimized for $0.2 miscut in the m-direction of GaN which corresponds to 0.2 towards a-direction sapphire.…”

Section: Theoretical Model and Discussionmentioning

confidence: 93%

Curvature and bow of bulk GaN substrates

Foronda

Романов

Young

et al. 2016

Journal of Applied Physics

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We investigate the bow of free standing (0001) oriented hydride vapor phase epitaxy grown GaN substrates and demonstrate that their curvature is consistent with a compressive to tensile stress gradient (bottom to top) present in the substrates. The origin of the stress gradient and the curvature is attributed to the correlated inclination of edge threading dislocation (TD) lines away from the [0001] direction. A model is proposed and a relation is derived for bulk GaN substrate curvature dependence on the inclination angle and the density of TDs. The model is used to analyze the curvature for commercially available GaN substrates as determined by high resolution x-ray diffraction. The results show a close correlation between the experimentally determined parameters and those predicted from theoretical model.

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Section: Theoretical Model and Discussionmentioning

confidence: 93%

Curvature and bow of bulk GaN substrates

Foronda

Романов

Young

et al. 2016

Journal of Applied Physics

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“…Starting in 2009, the group of Pickard and co-workers [23][24][25][26] adapted in the last years the ECCI to GaN and SiC films, in order to resolve burgers vector of individual threading dislocations propagating through the film thickness. It is stated by the authors that due to surface relaxations, the g·b criterion cannot be applied.…”

Section: Imaging Of Individual Lattice Defectsmentioning

confidence: 99%

Case studies on the application of high-resolution electron channelling contrast imaging – investigation of defects and defect arrangements in metallic materials

Weidner

Biermann

2015

Philosophical Magazine

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In 1967, Coates discovered the electron channelling contrast of backscattered electrons (BSEs) in scanning electron microscopy, and by this the possibility to investigate arrangements of lattice defects in deformed microstructures of materials. Since that time, a straightforward development of the scanning electron microscopes as well as of the electron channelling contrast technique took place. Nowadays, the performance of scanning electron microscopes is high enough that the resolution of electron channelling contrast imaging (ECCI) micrographs is comparable with conventional bright field transmission electron microscopy (TEM) micrographs. In the first part of the present paper, a historical review on the development of the ECCI technique starting from its discovery more than 45 years ago up to the combination with other advanced methods of scanning electron microscopy like electron backscatter diffraction or high-resolution selected area channelling patterning in the last few years is given. Major important investigations using this technique for the visualization of individual lattice defects like stacking faults (SFs) and dislocations or dislocation arrangements are chronologically summarized. The second part demonstrates that nowadays, ECCI micrographs taken in high-resolution scanning electron microscopes can be called high-resolution ECCI (HR-ECCI). It is shown that the resolution of individual SFs and dislocations in the HR-ECCI micrographs is comparable to that of conventional TEM (about 15 nm defect image width). Furthermore, the paper is demonstrating that HR-ECCI micrographs can be obtained for various types of materials after different mechanical loadings and different grain sizes ranging from large grain size of 500 μm (cast steel) down to less than 2 μm (γ-TiAl).

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“…The ECCI contrast was also predicted to be generated only generally within 5⇠ g (⇠ g is the extinction distance) of the specimen surface [57]. This phenomenon was further confirmed by later experiment work [51] [59].…”

Section: Literature Reviewmentioning

confidence: 54%

“…However, it received less attention than TEM since the resolution is not as high [42] [48]. The limited applications of ECCI have mostly been performed on relatively light materials like Ni, Al, Fe, semi-conductors, etc [49] [50] [51]. The advantages of ECCI are to allow fast examination of a large amount of specimen, especially quantitative measurements of dislocation density.…”

Section: Literature Reviewmentioning

confidence: 99%