The expansion of double-Shockley stacking faults (DSFs) in 4H-SiC was investigated by a photoluminescence (PL) imaging technique. To observe DSFs nondestructively, heavily-nitrogen-doped epilayers ...were prepared to be used as specimens and the PL technique was applied for the observation. The size and shape of the DSFs in the epilayer were clearly distinguished in the two dimensional PL images, although it is normally difficult to observe luminescence from DSFs in substrates grown by the sublimation method. The nucleation and expansion of the DSFs were tracked in the course of successive high-temperature annealing. Dislocation velocities of Shockley partials along the edge of the DSFs were evaluated from the PL observations. Activation energy for the dislocation glide was estimated from the temperature dependence of the velocities. The nucleation sites of the DSFs are also discussed.
•DSFs in heavily-nitrogen-doped epilayer were clearly observed in PL images.•Behavior of the DSF during high-temperature annealing was tracked.•Expansion velocity increased as temperature was elevated.•Activation energy for the dislocation glide was obtained.•Mechanical stress and mismatch stress seemed to trigger DSF nucleation.
Formation of Frank-type faults on the basal plane in 4H-SiC{0
0
0
1} epitaxial growth has been investigated by grazing incidence synchrotron reflection X-ray topography and transmission electron ...microscopy. The Frank faults, which are formed by conversion of a 1
c threading screw dislocation (TSD) in the substrate as well as simultaneous generation of a 1
c TSD during epitaxial growth, are confirmed to be created by four Frank partials with a Burgers vector of 1/40
0
0
1 type having the same sign on four different basal planes. The fine features of the X-ray topography contrast are confirmed to reflect the microscopic structure of the Frank faults. A variety of Frank fault formation has been revealed by comparing topography images taken before and after epitaxial growth. The formation mechanism of the Frank faults is discussed based on the evaluated microscopic structures.
Formation of extended defects during 4H-SiC{0
0
0
1} epitaxial growth has been investigated by grazing incidence synchrotron reflection X-ray topography and KOH-defect selective etching analysis. ...Details of the defect topography contrast features are collated with the KOH etched features. Conversion of threading screw dislocations (TSDs) into a defect on the basal plane as well as a carrot defect is tracked by performing topography before and after epitaxial growth. We found simultaneous nucleation of a TSD and a defect on the basal plane during epitaxial growth. The polytype inclusions are confirmed to be transparent in the topography condition. Formation of threading dislocation clusters during epitaxial growth is also investigated.
Topography image variation of threading edge dislocations (TEDs) in 4H-SiC epilayers has been investigated by grazing incidence high-resolution synchrotron topography. Six different images of TEDs ...resulting from an angle between the diffraction vector and the TED Burgers vector were confirmed by correlation between experimental topography images and simulation results. The TED-type distribution, dependent on the direction of the TED Burger vector, was examined on epitaxial wafers, while the spatial distribution of TEDs on a whole 2
in wafer along 1
1
2¯
0 and 1
1¯
0
0 was investigated.
Aims: The lymphatic system is involved in fluid homeostasis of the cardiac interstitium, but lymphangiogenesis in myocardial remodelling has not previously been examined histopathologically. The aim ...was to investigate by D2‐40 immunohistochemistry the sequential changes in lymphatic distribution in the process of myocardial remodelling after myocardial infarction (MI).
Methods and results: Myocardial tissues in various phases of healing after MI were obtained from 40 autopsied hearts. D2‐40+ lymphatic vessel density (LD) and CD34+ blood vessel density (BD) in the lesion were determined. BD decreased with advance of myocardial necrosis, subsequently increased at the early stage of granulation and thereafter decreased with the progression of scar formation. In contrast, lymphatic vessels were not detected in lesions with coagulation necrosis, and newly formed lymphatics first appeared in the early stages of granulation. A subsequent increase in LD was demonstrated in the late stages of granulation, and lymphatics remained up to the scar phase. Vascular endothelial growth factor‐C was consistently expressed in viable cardiomyocytes around the lesion in all of these stages.
Conclusion: In myocardial remodelling after MI, lymphangiogenesis lags behind blood vessel angiogenesis; newly formed lymphatics may be involved mainly in the maturation of fibrosis and scar formation through the drainage of excessive proteins and fluid.
There have been many applications of the Hilbert curve, such as image processing, image compression, computer hologram, etc. The Hilbert curve is a one-to-one mapping between N-dimensional space and ...one-dimensional (l-D) space which preserves point neighborhoods as much as possible. There are several algorithms for N-dimensional Hilbert scanning, such as the Butz algorithm and the Quinqueton algorithm. The Butz algorithm is a mapping function using several bit operations such as shifting, exclusive OR, etc. On the other hand, the Quinqueton algorithm computes all addresses of this curve using recursive functions, but takes time to compute a one to-one mapping correspondence. Both algorithms are complex to compute and both are difficult to implement in hardware. In this paper, we propose a new, simple, nonrecursive algorithm for N-dimensional Hilbert scanning using look-up tables. The merit of our algorithm is that the computation is fast and the implementation is much easier than previous ones.
A vertical radiant-heating reactor has been developed for thick silicon carbide (SiC) epitaxial growth, in which the susceptor and substrates are heated by radiation from the hot wall. The benefit of ...the heating and sample-holding method is demonstrated by improvements in the curvature of crystal bending and FWHM of X-ray
ω-rocking curves followed by epitaxial growth. The typical growth rate is 13–16
μm/h at 1530–1550°C at the susceptor top under reduced pressure as low as 50–70
mbar. Low background doping at low 10
13
cm
−3 (
N
d−
N
a) was achieved, and some of the 4H–SiC epilayers exhibited a high resistivity. We also succeeded in growing a 4H–SiC epilayer over 240
μm-thick with minimal surface roughness. Little sign of impurities was observed by low-temperature photoluminescence (LTPL), and no impurities (Al, B, Ti, V and Cr) exceeding 1×10
14
cm
−3 were found by secondary ion mass spectroscopy (SIMS) for a 150
μm-thick 4H–SiC epilayer. Thickness and doping uniformity along the gas flow of ∼5% and ∼11%, respectively, were obtained for 2-in substrates. Molten KOH etching analysis revealed that some of the micropipes were dissociated into closed core screw dislocations during epitaxial growth. The electrical performance of high-voltage devices was also demonstrated.
Three types of dislocation are seen in homo‐epilayers of SiC grown on 4H‐SiC wafers with an 8° surface offcut: axial screw dislocations, basal plane dislocations propagated into the epilayer at an 8° ...inclination and threading edge dislocations. These types may be imaged by monochromatic synchrotron X‐ray topography in the grazing‐incidence reflection geometry using the 118 reflection. Equations needed to apply the ray‐tracing method of computer simulating X‐ray topographic defect images in this experimental geometry were derived and used to simulate images of all three. Simulations for axial screw dislocations appear as white circles surrounded by narrow dark rings, and those for basal plane dislocations as linear white streaks, both consistent with experimental topographs. Simulations of the threading edge dislocations showed 4 µm wide white ovals with narrow arcs of dark contrast at their ends, inclined relative to the g vector of the topograph according to the sign of their Burgers vector. These images resembled the experimental topographs inasmuch as was possible at the maximum resolution of X‐ray topographs.
First results of the two-dimensionally reconstructed distribution of divertor radiation in JT-60U are presented. Hardware improvements of in-vessel divertor bolometer cameras to withstand severe ...electrical and thermal loads and the development of tomography software have made detailed and visual studies of divertor radiation possible. Line-integrated bolometer signals are successfully mapped onto the JT-60U geometry, indicating characteristic profiles for radiative divertor operation. A unique measurement of the radiating layer width at the target plate independently confirms the results of tomographic analysis. Radiation which is almost uniformly distributed along the separatrix flux line from the inboard to the outboard divertor is identified in the moderate density H-mode. Temporal evolution of radiative collapse due to heavy argon radiation is explored. Difficulties in the reconstruction associated with the local hot spot and neutrals are also discussed.
Potassium bromate (KBrO
3) is a rat renal carcinogen and a major drinking water disinfection by-product in water disinfected with ozone. Clear cell renal tumors, the most common form of human renal ...epithelial neoplasm, are rare in animals but are inducible by KBrO
3 in F344 rats. Detection of cytoplasmic periodic acid-Schiff-positive granules in clear cell tumors, indicative of glycogen accumulation, provides evidence of their biochemical similarity to human counterparts. Mutation in the coding region of the
von Hippel–Lindau (
VHL) gene is frequently detected in human clear cell renal carcinomas. Detection of
VHL mutations in KBrO
3-induced rat renal tumors could enhance the relevancy of these rat renal tumors for human health risk assessment. Formalin-fixed paraffin-embedded control tissues and renal tumors from male F344 rats exposed to KBrO
3 in the drinking water for 2 years were examined microscopically and were microdissected for DNA extraction. The coding sequence and a promoter region of the
VHL gene were examined by polymerase chain reaction-single strand conformation polymorphism and/or DNA sequencing. Two of nine clear cell renal tumors carried the same C to T mutation at the core region of the Sp1 transcription factor binding motif in the
VHL promoter and one of four untreated animals had C to T mutation outside the highly conserved core region. Mutation in the
VHL coding sequence was only detected in one tumor. No
VHL mutations were observed in three chromophilic tumors. KBrO
3-induced rat renal tumors are morphologically similar to their human counterpart but the genetic basis of tumorigenesis is different.
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