Correlation of Lifetime Mapping of 4H-SiC Epilayers with Structural Defects Using Synchrotron X-Ray Topography

2016 ◽  
Vol 858 ◽  
pp. 297-300 ◽  
Author(s):  
O.Y. Goue ◽  
Yu Yang ◽  
J.Q. Guo ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Carrier Lifetime ◽  
Substrate Surface ◽  
Stacking Faults ◽  
High Density ◽  
Structural Defects ◽  
Middle Region ◽  
X Ray ◽  
Half Loop ◽  
Interfacial Dislocations

Lifetime maps for two 4H-SiC epi-wafers (samples 1 and 2) were recorded using microwave photoconductive decay (μPCD) measurements and correlated with the type and distribution of structural defects mapped by synchrotron X-ray topography (white beam and monochromatic). Sample 1 showed lower lifetime inside one of its higher doped facet regions and along its edges. The low lifetime in the facet region was associated with the presence of a high density of multi-layered Shockley stacking faults (SFs) and low angle grain boundaries (LAGBs). These stacking faults are likely double Shockley stacking faults (DSSFs) and probably nucleated from scratches present on the substrate surface and LAGBs present in that region, propagating during epilayer growth. In contrast, sample 2 showed a reduced carrier lifetime in the middle region associated with a network of interfacial dislocations (IDs) and half loop arrays (HLAs) originating from 3C inclusions that are generated during epilayer growth. Along the edges of both samples, overlapping triangular defects, microcracks and BPD loops lowered lifetime.

Measurement of Critical Thickness for the Formation of Interfacial Dislocations and Half Loop Arrays in 4H-SiC Epilayer via X-Ray Topography

2014 ◽  
Vol 778-780 ◽  
pp. 328-331 ◽  
Author(s):  
Huan Huan Wang ◽  
Fang Zhen Wu ◽  
Michael Dudley ◽  
Balaji Raghothamachar ◽  
Gil Y. Chung ◽  
...  
Keyword(s):  
Basal Plane ◽  
Critical Thickness ◽  
Opposite Sign ◽  
Substrate Surface ◽  
Dislocation Line ◽  
Threading Dislocation ◽  
X Ray ◽  
Half Loop ◽  
Interfacial Dislocations ◽  
Line Direction

Synchrotron X-ray Beam Topography (SWBXT) and KOH etching observations are presented of interfacial dislocations (IDs) and half-loop arrays (HLAs) which can form under certain growth conditions during homoepitaxy of 4H-SiC on off-cut substrates. The HLAs and IDs are observed to form from pairs of opposite sign basal plane dislocations in the substrate which intersect the substrate surface in screw orientation. These dislocations glide in opposite direction in the epilayer once critical thickness has been exceeded. Half-loop arrays are formed at the same time as the screw-type basal plane dislocations (BPDs) side-glide inside the epilayer. From knowledge of the formation mechanism of the HLAs [, if the line of the HLA is extended to intersect the original threading dislocation line direction, then the distance between this intersection point and the ID along the line direction of the original BPD provides a measure of the critical thickness. It is also calculated that the critical thickness in this case is largely determined by the mutual attractive force between the pairs of opposite sign threading BPDs in the substrate. In addition we observed both interfacial dislocations and HLAs generated from: (a) surface sources of BPDs; (b) micropipes; (c) 3C inclusions; and (d) substrate/epilayer interface scratches.

Stacking Faults in SiC Nanowires

2008 ◽  
Vol 8 (7) ◽  
pp. 3504-3510 ◽  
Author(s):  
K. L. Wallis ◽  
M. Wieligor ◽  
T. W. Zerda ◽  
S. Stelmakh ◽  
S. Gierlotka ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Stacking Faults ◽  
Multiwall Carbon Nanotubes ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
Ir Spectrometry ◽  
X Ray ◽  
Sic Nanowires ◽  
Transmission Electron ◽  
Multiwall Carbon

SiC nanowires were obtained by a reaction between vapor silicon and multiwall carbon nanotubes, CNT, in vacuum at 1200 °C. Raman and IR spectrometry, X-ray diffraction and high resolution transmission electron microscopy, HRTEM, were used to characterize properties of SiC nanowires. Morphology and chemical composition of the nanowires was similar for all samples, but concentration of structural defects varied and depended on the origin of CNT. Stacking faults were characterized by HRTEM and Raman spectroscopy, and both techniques provided complementary results. Raman microscopy allowed studying structural defects inside individual nanowires. A thin layer of amorphous silicon carbide was detected on the surface of nanowires.

Single Shockley Stacking Faults in As-Grown 4H-SiC Epilayers

2010 ◽  
Vol 645-648 ◽  
pp. 327-330 ◽  
Author(s):  
Jawad ul Hassan ◽  
Peder Bergman
Keyword(s):  
Temperature Dependence ◽  
Optical Microscopy ◽  
Optical Spectrum ◽  
Carrier Lifetime ◽  
Geometrical Structure ◽  
Stacking Faults ◽  
Stacking Fault ◽  
Structural Defects ◽  
Forward Voltage ◽  
Substrate Interface

An extended structural defects which locally drastically reduces the carrier lifetime, has been observed in as-grown epilayers. A combination of back polishing, etching in molten KOH and optical microscopy revealed the geometrical structure of the stacking fault inside the epilayer. The fault started close to the epi-substrate interface, expanded initially rapidly but changed geometry after some time and reduced in size during further growth. The optical spectrum as well as the temperature dependence from this fault is identical to the emission from the single Shockley stacking faults previously only observed and formed in the bipolar diodes during forward voltage operation.

scholarly journals Suppressing twin formation in Bi2Se3thin films

2014 ◽  
Vol 70 (a1) ◽  
pp. C727-C727
Author(s):  
Nadezda Tarakina ◽  
Steffen Schreyeck ◽  
Martina Luysberg ◽  
Claus Schumacher ◽  
Grzegorz Karczewski ◽  
...  
Keyword(s):  
Thin Films ◽  
Substrate Surface ◽  
High Energy ◽  
Structural Defects ◽  
Complete Suppression ◽  
Lattice Match ◽  
X Ray ◽  
Perfect Lattice ◽  
Scanning Transmission ◽  
Twin Formation

The goal of the present work was to reveal the origin of the formation of different structural defects in Bi2Se3 thin films. We conducted a detailed comparative study of layers grown on InP(111)A and -B terminated flat and rough substrates using reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), X-ray reflectivity (XRR), X-ray diffraction (XRD) and probe-corrected scanning transmission electron microscopy (STEM). This choice of substrate reduces the formation of mosaicity twist sufficiently due to an almost perfect lattice match (0.2%) between InP and Bi2Se3. The use of substrates with different terminations and roughnesses allows the factors that define twin formation to be identified, providing conclusions about how twinning can be controlled and suppressed. In particular we have shown that growth using molecular beam epitaxy on rough Fe-doped InP(111) substrates leads to the formation of high quality thin films, with very low mosaicity twist and with complete suppression of twins in the Bi2Se3 thin films. No extra layer was observed at the interface between the film and the substrate. We also showed that the substrate surface termination (A or B) defines which family of twin domains dominates. The only types of structural defects that remain in the films are antiphase grain boundaries associated with the variation in substrate height. We believe that our study is relevant not only for Bi2Se3 growth but that it also provides essential insight for obtaining monocrystalline A2B3 (A = Bi, Sb; B = Se, Te) chalcogenide thin films and for realizing desirable electrical properties within this class of materials.

scholarly journals Simultaneous X-ray radiography and diffraction topography imaging applied to silicon for defect analysis during melting and crystallization

2019 ◽  
Vol 52 (6) ◽  
pp. 1312-1320 ◽  
Author(s):  
Maike Becker ◽  
Gabrielle Regula ◽  
Guillaume Reinhart ◽  
Elodie Boller ◽  
Jean-Paul Valade ◽  
...  
Keyword(s):  
Synchrotron Radiation ◽  
Grain Boundaries ◽  
Growth Process ◽  
Defect Formation ◽  
Simultaneous Recording ◽  
European Synchrotron Radiation Facility ◽  
Crystal Defects ◽  
Structural Defects ◽  
X Ray

One of the key issues to be resolved to improve the performance of silicon solar cells is to reduce crystalline defect formation and propagation during the growth-process fabrication step. For this purpose, the generation of structural defects such as grain boundaries and dislocations in silicon must be understood and characterized. Here, in situ X-ray diffraction imaging, historically named topography, is combined with radiography imaging to analyse the development of crystal defects before, during and after crystallization. Two individual indirect detector systems are implemented to record simultaneously the crystal structure (topographs) and the solid–liquid morphology evolution (radiographs) at high temperature. This allows for a complete synchronization of the images and for an increased image acquisition rate compared with previous studies that used X-ray sensitive films to record the topographs. The experiments are performed with X-ray synchrotron radiation at beamline ID19 at the European Synchrotron Radiation Facility. In situ observations of the heating, melting, solidification and holding stages of silicon samples are presented, to demonstrate that with the upgraded setup detailed investigations of time-dependent phenomena are now possible. The motion of dislocations is recorded throughout the experiment, so that their interaction with grain boundaries and their multiplication through the activation of Frank–Read sources can be observed. Moreover, the capability to record with two camera-based detectors allows for the study of the relationship between strain distribution, twinning and nucleation events. In conclusion, the simultaneous recording of topographs and radiographs has great potential for further detailed investigations of the interaction and generation of grains and defects that influence the growth process and the final crystalline structure in silicon and other crystalline materials.

High-density stacking faults in a supersaturated nitrided layer on austenitic stainless steel

2016 ◽  
Vol 49 (6) ◽  
pp. 1967-1971 ◽  
Author(s):  
Ke Tong ◽  
Fei Ye ◽  
Honglong Che ◽  
Ming Kai Lei ◽  
Shu Miao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Nitrided Layer ◽  
Stacking Faults ◽  
High Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

The nitrogen-supersaturated phase produced by low-temperature plasma-assisted nitriding of austenitic stainless steel usually contains a high density of stacking faults. However, the stacking fault density observed in previous studies was considerably lower than that determined by fitting the X-ray diffraction pattern. In this work, it has been confirmed by high-resolution transmission electron microscopy that the strip-shaped regions of about 3–25 nm in width observed at relatively low magnification essentially consist of a series of stacking faults on every second {111} atomic plane. A microstructure model of the clustered stacking faults embedded in a face-centred cubic structure was built for these regions. The simulated X-ray diffraction and transmission electron microscopy results based on this model are consistent with the observations.

X-ray Topography Studies of Relaxation during the Homo-Epitaxy of 4H-SiC

2015 ◽  
Vol 1741 ◽  
Author(s):  
H. Wang ◽  
M. Dudley ◽  
J. Zhang ◽  
B. Thomas ◽  
G. Chung ◽  
...  
Keyword(s):  
Substrate Surface ◽  
Strain Relaxation ◽  
Lattice Parameter ◽  
Relaxation Processes ◽  
Radial Temperature ◽  
X Ray ◽  
Before And After ◽  
Half Loop ◽  
Mismatch Stress ◽  
Epilayer Surface

ABSTRACTA review is presented of Synchrotron X-ray Topography and KOH etching studies carried out on n type 4H-SiC offcut substrates before and after homo-epitaxial growth to study defect replication and strain relaxation processes and identify the nucleation sources of both interfacial dislocations (IDs) and half-loop arrays (HLAs) which are known to have a deleterious effect on device performance. We show that these types of defects can nucleate during epilayer growth from: (1) short segments of edge oriented basal plane dislocations (BPDs) in the substrate which are drawn by glide into the epilayer; and (2) segments of half loops of BPD that are attached to the substrate surface prior to growth which also glide into the epilayer. It is shown that the initial motion of the short edge oriented BPD segments that are drawn from the substrate into the epilayer is caused by thermal stress resulting from radial temperature gradients experienced by the wafer whilst in the epi-chamber. This same stress also causes the initial glide of the surface half-loop into the epilayer and through the advancing epilayer surface. These mobile BPD segments provide screw oriented segments that pierce the advancing epilayer surface that initially replicate as the crystal grows. Once critical thickness is reached, according to the Mathews-Blakeslee model [1], these screw segments glide sideways under the action of the mismatch stress leaving IDs and HLAs in their wake. The origin of the mismatch stress is shown to be associated with lattice parameter differences at the growth temperature, arising from the differences in doping concentration between substrate and epilayer.

scholarly journals Effect of multiple laser shock processing on nano-scale microstructure of an aluminum alloy

2018 ◽  
Author(s):  
Simge GencalpIrizalp ◽  
Nursen Saklakoglu
Keyword(s):  
Stacking Faults ◽  
Stacking Fault ◽  
Structural Defects ◽  
Laser Shock ◽  
X Ray Diffraction ◽  
Laser Shock Processing ◽  
Alloy Plate ◽  
X Ray ◽  
Nano Scale ◽  
Shock Processing

In this study, nano-scale microstructural evolution in 6061-T6 alloy after laser shock processing (LSP) were studied. 6061-T6 alloy plate were subjected to multiple LSP. The LSP treated area was characterized by X-ray diffraction and the microstructure of the samples was analyzed by transmission electron microscopy. Focused Ion Beam (FIB) tools were used to prepare TEM samples in precise areas. It was found that even though aluminum had high stacking fault energy, LSP yielded to formation of ultrafine grains and deformation faults such as dislocation cells, stacking faults. The stacking fault probability (PSF) was obtained in LSP-treated alloy using X-Ray diffraction. Deformation induced stacking faults lead to the peak position shifts, broadening and asymmetry of diffraction. XRD analysis and TEM observations revealed significant densities of stacking faults in LSP-treated 6061-T6 alloy. And mechanical properties of LSP-treated alloy were also determined to understand the hardening behavior with high concentration of structural defects.

In-plane crystalline anisotropy of bulk β-Ga2O3

2021 ◽  
Vol 54 (4) ◽  
Author(s):  
Xiaocui Ma ◽  
Rui Xu ◽  
Jianfang Xu ◽  
Leiying Ying ◽  
Yang Mei ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Grain Boundaries ◽  
Bulk Material ◽  
Stacking Faults ◽  
Coherent Scattering ◽  
Limiting Factors ◽  
X Ray Diffraction ◽  
Limited Size ◽  
X Ray ◽  
Crystalline Anisotropy

The anisotropy of X-ray diffraction scanning of (201) β-Ga2O3 bulk material has been investigated. Symmetric rocking curves (RCs) exhibit distinctly different broadening along different azimuths, with a maximum along [102] and a minimum along a direction rotated by 30° from [010]. Williamson–Hall analysis was applied to study possible factors causing the broadening in these RCs, including instrumental factors, mosaic tilt and coherent scattering. It was found that the RC broadening is determined by both isotropic mosaic tilt and anisotropy in the length over which the crystal structure is not disrupted by limiting factors such as grain boundaries or stacking faults, which we term the `lateral limited size'. In this case, the lateral limited size is governed by {200} stacking faults along the [102] direction and grain boundaries along the [010] direction. The result presents a new anisotropy characteristic of (201) β-Ga2O3.

Structure and microstructure evolution during martensitic transformation in wrought Fe–26Mn–0.14C austenitic steel: an effect of cooling rate

2007 ◽  
Vol 40 (2) ◽  
pp. 354-361 ◽  
Author(s):  
P. Sahu ◽  
A. S. Hamada ◽  
S. Ghosh Chowdhury ◽  
L. P. Karjalainen
Keyword(s):  
Grain Boundaries ◽  
Austenitic Steel ◽  
Cooling Rate ◽  
Microstructure Evolution ◽  
Rietveld Method ◽  
Stacking Faults ◽  
Grain Structure ◽  
Austenite Grain Size ◽  
X Ray ◽  
Structure And Microstructure

Structure and microstructure evolution under various cooling rates of a wrought austenitic steel, Fe–26Mn–0.14C (composition in mass %), were studied by the Rietveld method of X-ray diffraction pattern fitting, grain boundary characterization by electron back-scattered diffraction (EBSD) and optical microscopy. Cooling rate, density of stacking faults, and austenite grain size and grain boundaries influence the observed γfcc→ ∊hcptransformation and lead to significant anisotropic X-ray line broadening. Depending on the cooling conditions, the grain boundaries are misoriented at both lower and higher angles. In the ∊-martensites, the dominant planar fault is twins (∼10−3). The austenite grains were found to contain low to moderate density of stacking faults (∼10−4–10−3), which act as efficient nucleation sites of the ∊-martensites. Both X-ray and EBSD analyses estimated negligible twins in the austenite. Approximate average dislocation densities have been estimated and correlated with the grain structure.

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