Characterization of Dislocations and Micropipes in 4H n+ SiC Substrates

2008 ◽  
Vol 600-603 ◽  
pp. 333-336 ◽  
Author(s):  
Ping Wu ◽  
Murugesu Yoganathan ◽  
Ilya Zwieback ◽  
Yi Chen ◽  
Michael Dudley
Keyword(s):  
Etch Pits ◽  
Screw Dislocations ◽  
X Ray ◽  
Nitrogen Doped ◽  
Different Types ◽  
History Of ◽  
Density Analysis ◽  
Threading Defects ◽  
Edge Dislocations

Etching of 4H-SiC wafers in molten KOH as a method for micropipe and dislocation density analysis was investigated. The obtained results were correlated with those of the synchrotron white beam x-ray topography. Heavily nitrogen-doped SiC shows a significantly different etching behavior in comparison with the low-doped material. This complicates identification of different types of threading defects. In particular, it is difficult to separate Threading Screw Dislocations (TSD) from Threading Edge Dislocations (TED). Depending on the level of doping and thermal history of the crystal, some of the etch pits emerging due to the 1c screw dislocations can be as large as those due to the micropipes.

Correlation between Surface Morphological Defects and Crystallographic Defects in SiC

2012 ◽  
Vol 717-720 ◽  
pp. 359-362 ◽  
Author(s):  
Tetsuo Hatakeyama ◽  
Kyoichi Ichinoseki ◽  
Hiroshi Yamaguchi ◽  
N. Sugiyama ◽  
Hirofumi Matsuhata
Keyword(s):  
Epitaxial Layers ◽  
Screw Dislocations ◽  
X Ray ◽  
Morphological Defects ◽  
History Of ◽  
Crystallographic Defects ◽  
Micrometer Scale ◽  
Edge Dislocations ◽  
Scale Surface

The origins of certain types of micrometer-scale surface morphological defects on SiC epitaxial layers are clarified using X-ray topography. Two types of surface morphological defects are commonly observed on Si- and C-face epitaxial layers. Relatively large pits (around 4μm×2μm) originate from threading screw dislocations (TSDs). Relatively small pits (around 1.5μm×1μm) originate from threading edge dislocations (TEDs). The shapes and depths of these surface morphological pits depend on the fabrication history of the epitaxial wafers.

scholarly journals Synthesis and Characterization of Clay Polymer Nanocomposites of P(4VP-co-AAm) and Their Application for the Removal of Atrazine

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 721 ◽  
Author(s):  
Jorge A. Ramírez-Gómez ◽  
Javier Illescas ◽  
María del Carmen Díaz-Nava ◽  
Claudia Muro-Urista ◽  
Sonia Martínez-Gallegos ◽  
...  
Keyword(s):  
Polymer Nanocomposites ◽  
Nanocomposite Materials ◽  
Synthesis And Characterization ◽  
Cross Linking ◽  
X Ray Diffraction ◽  
Numerous Species ◽  
X Ray ◽  
Different Types ◽  
Synthesized Materials

Atrazine (ATZ) is an herbicide which is applied to the soil, and its mechanism of action involves the inhibition of photosynthesis. One of its main functions is to control the appearance of weeds in crops, primarily in corn, sorghum, sugar cane, and wheat; however, it is very toxic for numerous species, including humans. Therefore, this work deals with the adsorption of ATZ from aqueous solutions using nanocomposite materials, synthesized with two different types of organo-modified clays. Those were obtained by the free radical polymerization of 4-vinylpyridine (4VP) and acrylamide (AAm) in different stoichiometric ratios, using tetrabutylphosphonium persulfate (TBPPS) as a radical initiator and N,N′-methylenebisacrylamide (BIS) as cross-linking agent. The structural, morphological, and textural characteristics of clays, copolymers, and nanocomposites were determined through different analytical and instrumental techniques, i.e., X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Adsorption kinetics experiments of ATZ were determined with the modified and synthesized materials, and the effect of the ratio between 4VP and AAm moieties on the removal capacities of the obtained nanocomposites was evaluated. Finally, from these sets of experiments, it was demonstrated that the synthesized nanocomposites with higher molar fractions of 4VP obtained the highest removal percentages of ATZ.

scholarly journals X-ray Micro-Tomography as a Method to Distinguish and Characterize Natural and Cultivated Pearls

2021 ◽  
Vol 6 (4) ◽  
pp. 51
Author(s):  
Luisa Vigorelli ◽  
Elisabetta Croce ◽  
Debora Angelici ◽  
Raffaella Navone ◽  
Sabrina Grassini ◽  
...  
Keyword(s):  
Diagnostic Techniques ◽  
X Ray ◽  
Non Invasive ◽  
Heritage Studies ◽  
Different Types ◽  
Micro Tomography ◽  
Invasive Techniques ◽  
Tomographic Analysis ◽  
Private Collections

Digital radiography and computed tomography are two fundamental diagnostic techniques in different fields of research, including cultural heritage studies and gemmology. The application of these physical methods of investigation has gained considerable importance as they are non-invasive techniques. The presented work has been mainly focused on micro-tomographic analysis. The project is concerned with the study of natural and cultivated pearls in order to develop an investigation methodology for the analysis, distinction and characterization of different types of pearls, some of them belonging to different precious jewels from private collections. The investigations, carried out on a total of 22 heterogeneous types of pearls, allowed us to establish their origin (natural or cultivated) or to confirm/deny if a hypothesis was already expressed, and as well to highlight the cultivation methodology used case by case. Furthermore, it was possible to ascertain how large and varied the market for cultured pearls is nowadays and how difficult is, in some particular cases, to ascertain their attribution to a certain origin.

Characterization of Defect Structures in SiC Single Crystals Using Synchrotron X-Ray Topography

1993 ◽  
Vol 307 ◽  
Author(s):  
S. Wang ◽  
M. Dudley ◽  
C. Carter ◽  
D. Asbury ◽  
C. Fazit
Keyword(s):  
Detailed Analysis ◽  
Single Crystals ◽  
Basal Plane ◽  
Defect Structures ◽  
Dislocation Generation ◽  
Screw Dislocations ◽  
X Ray ◽  
White Beam

ABSTRACTSynchrotron white beam X-ray topography has been used to characterize defect structures in 6H-SiC wafers grown on (0001) seeds. Two major types of defects are observed: super screw dislocations approximately perpendicular to the basal plane and dislocation networks lying in the basal plane. The super screw dislocations, which have open cores, are growth dislocations. These dislocations act as sources and/or sinks for the glide dislocation networks. Detailed analysis and discussion of dislocation generation phenomena and Burgers vectors will be presented.

scholarly journals Characteristics of Instrumental Methods to Describe and Assess the Recrystallization Process in Ice Cream Systems

Foods ◽  
2019 ◽  
Vol 8 (4) ◽  
pp. 117 ◽  
Author(s):  
Anna Kamińska-Dwórznicka ◽  
Ewa Gondek ◽  
Sylwia Łaba ◽  
Ewa Jakubczyk ◽  
Katarzyna Samborska
Keyword(s):  
Ice Cream ◽  
Recrystallization Process ◽  
Micro Ct ◽  
Reflectance Measurement ◽  
X Ray ◽  
Different Types ◽  
Types Of Information ◽  
Instrumental Methods ◽  
Focused Beam

Methods of testing and describing the recrystallization process in ice cream systems were characterized. The scope of this study included a description of the recrystallization process and a description and comparison of the following methods: microscopy and image analysis, focused beam reflectance measurement (FBRM), oscillation thermo-rheometry (OTR), nuclear magnetic resonance (NMR), splat-cooling assay, and X-ray microtomography (micro-CT). All the methods presented were suitable for characterization of the recrystallization process, although they provide different types of information, and they should be individually matched to the characteristics of the tested product.

Theoretical Characterization of X-ray Absorption, Emission, and Photoelectron Spectra of Nitrogen Doped along Graphene Edges

2013 ◽  
Vol 117 (3) ◽  
pp. 579-589 ◽  
Author(s):  
Xianlong Wang ◽  
Zhufeng Hou ◽  
Takashi Ikeda ◽  
Masaharu Oshima ◽  
Masa-aki Kakimoto ◽  
...  
Keyword(s):  
Photoelectron Spectra ◽  
X Ray ◽  
Nitrogen Doped ◽  
Theoretical Characterization ◽  
X Ray Absorption

Preparation and Characterization of N Doped TiO2/ Sepiolite Composite Materials

2011 ◽  
Vol 284-286 ◽  
pp. 597-600
Author(s):  
Dai Mei Chen ◽  
Hai Peng Ji ◽  
Jian Xin Wang ◽  
Jian Chen ◽  
Xin Long Luan ◽  
...  
Keyword(s):  
Composite Materials ◽  
Photoelectron Spectroscopy ◽  
Sol Gel ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nitrogen Doped ◽  
Nitrogen Contents ◽  
Scanning Electron ◽  
Oxygen Atoms

Nitrogen doped TiO2/sepiolite composite materials (N-TiO2/sep) with different nitrogen contents were prepared by a sol-gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), respectively. XRD and SEM results showed that anatase-TiO2nanoparticles were distributed homogenously on the surface of sepiolite. XPS revealed that N atoms could incorporate into the lattice of anatase TiO2substituting the oxygen atoms sites of oxygen atoms.

Effect of Surface Polarity on the Conversion of Threading Dislocations in Solution Growth

2013 ◽  
Vol 740-742 ◽  
pp. 15-18 ◽  
Author(s):  
Yuji Yamamoto ◽  
S. Harada ◽  
Kazuaki Seki ◽  
Atsushi Horio ◽  
Takato Mitsuhashi ◽  
...  
Keyword(s):  
Grown Crystal ◽  
The Other ◽  
Solution Growth ◽  
Threading Dislocations ◽  
Surface Polarity ◽  
Screw Dislocations ◽  
X Ray ◽  
Almost All ◽  
Edge Dislocations ◽  
Effect Of Surface

We investigated the dislocation behaviors during the solution growth on Si-face and C-face off-axis 4H-SiC seed crystals by using synchrotron X-ray topography. On Si-face, almost all threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are converted into Frank-type defects and basal plane dislocations (BPDs), respectively. On the other hand, on C-face, TSDs were hardly converted. Some of TEDs were converted to BPDs and BPD-TED reconversion was often occurred. Therefore, to reduce density of threading dislocations in the grown crystal, it is better to use Si-face off-axis seed crystal.

Dislocation Revelation in Highly Doped N-Type 4H-SiC by Molten KOH Etching with Na2O2 Additive

2011 ◽  
Vol 679-680 ◽  
pp. 290-293 ◽  
Author(s):  
Yong Zhao Yao ◽  
Yukari Ishikawa ◽  
Yoshihiro Sugawara ◽  
Hiroaki Saitoh ◽  
Katsunori Danno ◽  
...  
Keyword(s):  
Electron Concentration ◽  
Basal Plane ◽  
Wet Etching ◽  
Etch Pits ◽  
Screw Dislocations ◽  
Edge Dislocations ◽  
Koh Etching

We have proposed a new wet etching recipe using molten KOH and Na2O2 as the etchant (“KN etching”) for dislocation revelation in highly doped n-type 4H-SiC (n+-4H-SiC). Threading screw dislocations (TSDs) and threading edge dislocations (TEDs) have been clearly revealed as hexagonal etch pits differing in pit sizes, and basal plane dislocations (BPDs) as seashell-shaped pits. This new etching recipe has provided a solution to the problem that conventional KOH etching is not effective for dislocation identification in 4H-SiC if the electron concentration is high (>mid-1018 cm-3). We have investigated the effect of SiC off-cut angle on KN etching and it has been shown that the “KN etching” is applicable for the n+-SiC substrate with off-angle from 0o to 8o.

Characterization of Basal Plane Dislocations in 4H-SiC Substrates by Topography Analysis of Threading Edge Dislocations in Epilayers

2010 ◽  
Vol 645-648 ◽  
pp. 303-306 ◽  
Author(s):  
Isaho Kamata ◽  
Masahiro Nagano ◽  
Hidekazu Tsuchida
Keyword(s):  
High Resolution ◽  
Epitaxial Layer ◽  
Basal Plane ◽  
Grazing Incidence ◽  
Size Difference ◽  
Etch Pits ◽  
Burgers Vector ◽  
Vector Direction ◽  
Edge Dislocations

Burgers vector directions of threading edge dislocations (TEDs) in 4H-SiC epitaxial layer are distinguished by grazing incidence high resolution topography. Based on comparison between appearance of KOH etch pits and direction of TED Burgers vector, the size difference of the TED etch pits is found to be dependent on their Burgers vector directions. Examining TEDs in the epilayer by topography, the Burgers vector direction of basal plane dislocations (BPDs) in the substrate is identified. Correspondence between the topography contrast and the sense of a BPD is also investigated.

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