Coherent X-ray imaging investigation of macrodefects and micropipes on SiC (original) (raw)
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Contribution of x-ray topography and high-resolution diffraction to the study of defects in SiC
Journal of Physics D: Applied Physics, 2003
A short review is presented of the various synchrotron white beam x-ray topography (SWBXT) imaging techniques developed for characterization of silicon carbide (SiC) crystals and thin films. These techniques, including back-reflection topography, reticulography, transmission topography, and a set of section topography techniques, are demonstrated to be particularly powerful for imaging hollow-core screw dislocations (micropipes) and closed-core threading screw dislocations, as well as other defects, in SiC. The geometrical diffraction mechanism commonly underlying these imaging processes is emphasized for understanding the nature and origins of these defects. Also introduced is the application of SWBXT combined with high-resolution x-ray diffraction techniques to complete characterization of 3C/4H or 3C/6H SiC heterostructures, including polytype identification, 3C variant mapping, and accurate lattice mismatch measurements.
Investigations of Non-Micropipe X-Ray Imaged Crystal Defects in SiC Devices
MRS Proceedings, 2000
This paper updates on-going experimental and theoretical investigations of non-micropipe defects imaged by synchrotron white beam X-ray topography (SWBXT) in SiC devices and epitaxial layers. Computer-based thermal modeling of screw-dislocation related breakdown in SiC diodes has been initiated to gain insights into internal temperature profiles as a function of microplasma power. A preliminary study of epitaxial 4H-and 6H-SiC p + n mesa diodes indicates that very low angle boundaries, whose electrical properties have not previously been reported, do not significantly impact DC I-V properties (forward and reverse) measured at biases less than 70% of the SiC breakdown field. The presence of very small growth pits on the surface of commercial 4H-SiC epitaxial layers, almost undetectable by high magnification optical microscopy, was revealed by atomic force microscopy and found to correspond to the locations of closed core screw dislocations imaged by SWBXT.
X-ray bright-field imaging analyzes crystalline quality and defects of SiC wafers
Journal of Applied Crystallography, 2007
A new variety of the recently developed technique `X-ray bright-field imaging' is presented. In its basic version, this approach simultaneously yields diffraction-based information on lattice distortions and radiographic information on structural inhomogeneities, and is based on the detection of reversed diffraction contrast in transmission images. The new version extends the scope of the technique to the quantitative analysis of crystalline quality parameters such as the lattice plane curvature and mosaic distribution in SiC wafers, and makes it possible to correlate such parameters directly with defect (distortions/inhomogeneities) structures.
Micropipe evolution in silicon carbide
Applied Physics Letters, 2003
Micropipe bundling and twisting in SiC crystals was revealed using synchrotron x-ray phase sensitive radiography. The computer simulation of micropipe evolution during the crystal growth suggests that the bundled and twisted micropipes arise under the influence of stress fields from other neighboring micropipes. The annihilation of twisted dipoles is attributed to their transformation into semiloops. Reactions of micropipe coalescence lead to the generation of micropipes and/or the annihilation of initial micropipes, resulting in the decrease in their average density.
High-resolution electron microscopic studies on a new polytype of SiC and its intergrowth structures
Acta Crystallographica Section B Structural Science, 1984
Tilted-beam two-dimensional lattice images have been used to determine the structure of a new polytype of SiC, viz 411 R, and its intergrowth structures. Initially, the chevron-shaped fringes in a simple structure of 6H were obtained and analysed with the help of computer simulation based on the multislice approach of Cowley & Moodie [Acta Cryst. (1957), 10, 609-619] in order to arrive at optimum experimental conditions. The method was then applied to a high-period polytype 411R and its intergrowth structures. The suitability of this technique for structural investigations is discussed.
In situ X-ray microtomography characterization of damage in SiCf/SiC minicomposites
Composites Science and Technology, 2011
The purpose of the present study is to characterize matrix crack propagation and fiber breaking occurrences within SiC/SiC minicomposite in order to validate later on a multiscale damage model at the local scale. An in-situ X-ray microtomography tensile test was performed at the European Synchrotron Radiation Facility (ESRF, ID19 beamline) in order to obtain 3-dimensional (3D) images at six successive loading levels. Results reveal a slow and discontinuous propagation of matrix cracks, even after the occurrence of matrix crack saturation. A few fiber failures were also observed. However, radiographs of the whole length (14 mm) of the minicomposites under a load and after the failure were more appropriate to get statistical data about fiber breaking. Thus, observations before the ultimate failure revealed only a few fibers breaking homogenously along the minicomposite. In addition, an increase in fiber breaking density in the vicinity of the fatal matrix crack was observed after failure. These experimental results are discussed in regards to assumptions used in usual 1dimensional (1D) models for minicomposites.
International Journal of Materials Research, 2014
This paper is dedicated to the analysis of 3D data of carbon fiber reinforced silicon carbide ceramics. In the production process of C/SiC, a porous carbon preform reinforced with bundles of carbon fibers is infiltrated with liquid silicon at approximately 1 500 8C. The reaction between liquid silicon and carbon creates a layer of silicon carbide while the silicon vanishes almost completely. This material is able to withstand extremely high temperatures and it is extremely tough with respect to fracture. To increase the efficiency of the costly and time consuming production process, methods for monitoring the quality of the material are helpful. For instance, the thickness of the silicon carbide layer is a valuable measure. Moreover, due to different coefficients of thermal expansion of the components, typically cracks appear during the production process. For effective analysis 3D high resolution image data are necessary that can be acquired by synchrotron computed tomography. In a first image processing step, we segment the 3D image data with a convex optimization approach incorporating spatial regularity. Further, we work on the detection of cracks using an eigenvalue analysis of the 3D Hessian matrix determined in each pixel.
Applied Physics Letters, 2007
We demonstrate high-geometrical-resolution imaging of dislocations in 4H-SiC by monochromatic synchrotron topography Í‘but still under the "integrated wave" conditionÍ’. In back-reflection topographs, 1c screw dislocation images are "magnified" to appear as well-defined circular white spots, while basal plane dislocations with opposite edge Burgers vector components exhibit two distinct kinds of contrast features. All the dislocation images are precisely described by ray-tracing simulations. This imaging technique provides an accurate, comprehensive, and nondestructive characterization tool, which is needed by current SiC researchers is used for industrial applications. It also provides a simple picture for understanding the mechanisms underlying synchrotron diffraction imaging of defects.
Journal of Crystal Growth, 2008
A novel non-destructive method to characterize stacking faults (SFs) in 3C-SiC crystals is presented. This method is based on fast X-ray diffraction reciprocal space mapping and can be used qualitatively for routine analysis of 3C-SiC as SFs give rise to a characteristic star-like pattern in reciprocal space whose intensity depends on the SF density. The simulation of the diffusely scattered intensity streaks with an appropriate model also enables one to obtain quantitative results such as SF densities, mosaic domain size and mosaicity. The model is tested with a commercial (0 0 1) 3C-SiC crystal from HAST corporation, and then it is used to analyze SFs in (1 1 1) 3C-SiC crystals grown by continuous feed-physical vapor transport. r