Synchrotron White Beam Topography Studies of Screw Dislocations in 6H-Sic Single Crystals

1994 ◽  
Vol 375 ◽  
Author(s):  
S. Wang ◽  
M. Dudley ◽  
C. H. Carter ◽  
V. F. Tsvetkov ◽  
C. Fazi
Keyword(s):  
Single Crystals ◽  
Structural Defects ◽  
Device Performance ◽  
Topographic Image ◽  
X Ray Diffraction ◽  
Screw Dislocations ◽  
X Ray ◽  
White Beam ◽  
Line Defects ◽  
Kinematical Theory

AbstractSynchrotron white beam X-ray topography, along with optical microscopy and scanning electron microscopy, has been used to characterize structural defects which are potentially detrimental to device performance in PVT 6H-SiC single crystals. Line defects running along the [0001] axis, known as “micropipes”, were studied extensively. Detailed analysis of topographic image contrast associated with “micropipes”, based on the kinematical theory of X-ray diffraction, established that the so-called “micropipes” are screw dislocations with large Burgers vectors.

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.

Characterization of structural defects in MLEK grown InP single crystals using synchrotron white beam X-ray topography

1997 ◽  
Vol 174 (1-4) ◽  
pp. 230-237 ◽  
Author(s):  
H. Chung ◽  
W. Si ◽  
M. Dudley ◽  
A. Anselmo ◽  
D.F. Bliss ◽  
...  
Keyword(s):  
Single Crystals ◽  
Structural Defects ◽  
X Ray ◽  
White Beam

XRDT Study of Structural Defects of 6H-SiC Crystals

2005 ◽  
Vol 483-485 ◽  
pp. 311-314 ◽  
Author(s):  
G. Agrosì ◽  
R.A. Fregola ◽  
A. Monno ◽  
Eugenio Scandale ◽  
G. Tempesta
Keyword(s):  
Synchrotron Radiation ◽  
Growth Mechanism ◽  
Radiation Source ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
Screw Dislocations ◽  
X Ray ◽  
Linear Defects ◽  
Parallel Lines ◽  
Micro Channels

X-Ray Diffraction Topography (XRDT) and Optical Microscopy (OM) are adopted to study extended structural defects in 6H-SiC bulky crystals. Topographs are taken by means of White Beam Synchrotron Radiation Source (WB-SRS-XRDT) and by means of monochromatic radiation (MoKα1) with conventional source (Lang method). All studied samples are characterised by the presence of linear defects, dislocations and microchannels, uniformly distributed in the crystal. Such defects draw a net of independent systems of parallel lines, with different orientation and different contrast widths. Micro-channels are parallel to the c axis, whereas dislocations are perpendicular or nearly parallel to the c axis. The last are unit screw dislocations. It has been concluded that the growth mechanism is driven by screw dislocations and that channels results from the coalescence of parallel dislocations.

Determination of Burgers Vector of Screw Dislocations in 6H-SiC Single Crystals by Synchrotron White Beam X-Ray Topography

1996 ◽  
Vol 437 ◽  
Author(s):  
W. Si ◽  
M. Dudley ◽  
C. Carter ◽  
R. Glass ◽  
V. Tsvetkov
Keyword(s):  
Single Crystals ◽  
Dislocation Core ◽  
Line Defect ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
X Ray ◽  
White Beam ◽  
Lattice Planes ◽  
Vector Magnitude

AbstractIndividual screw dislocations along the [0001] axis in 6H-SiC single crystals have been characterized by means of Synchrotron White Beam X-ray Topography (SWBXT). The magnitude of the Burgers vector was determined from: (1) the diameter of circular diffraction-contrast images of dislocations in back-reflection topographs, (2) the width of bi-modal images associated with screw dislocations in transmission topographs, (3) the magnitude of the tilt of the lattice planes on both sides of dislocation core in projection topographs, and (4) also the magnitude of the tilt of the lattice planes in section topographs. All of the four methods showed reasonable consistency. The sense of the Burgers vector can also be deduced from the abovementioned tilt of the lattice planes. Results revealed that in 6H-SiC a variety of screw dislocations can be found with Burgers vector magnitude ranging from 1c to 7c (c is the lattice constant along [0001] axis). This work demonstrates that SWBXT can be used as a quantitative technique for detailed analyses of line defect configurations.

Characterization of Growth Defects in CdZnTe Single Crystals by Synchrotron White Beam X-ray Topography

1995 ◽  
Vol 378 ◽  
Author(s):  
H. Chung ◽  
B. Raghothamachar ◽  
J. Wu ◽  
M. Dudley ◽  
D. J. Larson ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Single Crystals ◽  
Thermal Stresses ◽  
Structural Defects ◽  
Dislocation Slip ◽  
Accelerated Cooling ◽  
Cooling Rates ◽  
X Ray ◽  
Slip Bands ◽  
White Beam

AbstractSynchrotron white beam X-ray topography has been used to characterize structural defects in microgravity grown CdZnTe single crystals. Defects such as dislocations, slip bands, 180° rotation twins, precipitates and subgrain boundaries are observed but their density is much lower than those in crystals grown under normal gravity. The observed results also indicate that the defect structures of the as grown crystals are strongly influenced by cooling rates. X-ray transmission topographs recorded from regions grown at different cooling rates show that the dislocation density in rapidly cooled regions is higher than that in slowly cooled regions. The formation of dislocations is presumably attributed to the thermal stress caused by accelerated cooling rates, which is greater than the critical resolved shear stress. As the cooling rate is accelerated, the magnitude of thermal stress is increased and more dislocations are formed to relieve the accumulated lattice strain. In addition, if the cooling rates are increased further, the accentuated thermal stresses can give rise to more pronounced deformation processes, comprising the formation of dislocation slip bands, as confirmed by the extensive slip bands revealed by the X-ray reflection topographs.

Studies of Interface Demarcation and Structural Defects in Ga Doped Ge Single Crystals Using Synchrotron White Beam X-Ray Topography

1996 ◽  
Vol 437 ◽  
Author(s):  
H. Chung ◽  
B. Raghothamachar ◽  
W. Zhou ◽  
M. Dudley ◽  
D. C. Gillies
Keyword(s):  
Single Crystals ◽  
Reciprocal Lattice ◽  
Dislocation Cell ◽  
Structural Defects ◽  
Interface Plane ◽  
Lattice Vector ◽  
Synchrotron Source ◽  
X Ray ◽  
Correct Orientation ◽  
White Beam

AbstractSynchrotron White Beam X-ray Topography (SWBXT) has been applied to the characterization of marked growth interfaces in Ga doped Ge single crystals. The techniques employed in interface demarcation include modifications of the cold zone temperature, mechanical pulsing and Peltier pulsing. As revealed by our observations, the visibility of growth interfaces is a sensitive function of diffraction conditions. A combination of the correct orientation of the active reciprocal lattice vector with respect to the interface plane and the necessary strain sensitivity controlled by the rocking curve width of the reflection are proved to be important for interface visibility. This can easily be achieved by using synchrotron radiation since the tunability of the synchrotron source provides great flexibility in the choice of proper diffraction conditions. Structural defects such as small-angle tilt boundaries and dislocation cell structures were also observed. The formation mechanism of these defects will be discussed. Direct evidence of dislocations present in the seed crystal propagating into the as-grown crystal through the melt-back interface during crystal growth was also obtained.

Effect of trytophan as dopant on potassium acid phthalate single crystals

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Visible Region ◽  
X Ray Diffraction ◽  
X Ray ◽  
Slow Evaporation Technique ◽  
Absorption Studies ◽  
Evaporation Technique ◽  
Potassium Acid Phthalate ◽  
Acid Phthalate

Optically transparent single crystals of potassium acid phthalate (KAP, 0.5 g) 0.05 g and 0.1 g (1 and 2 mol %) trytophan were grown in aqueous solution by slow evaporation technique at room temperature. Single crystal X- ray diffraction analysis confirmed the changes in the lattice parameters of the doped crystals. The presence of functional groups in the crystal lattice has been determined qualitatively by FTIR analysis. Optical absorption studies revealed that the doped crystals possess very low absorption in the entire visible region. The dielectric constant has been studied as a function of frequency for the doped crystals. The thermal stability was evaluated by TG-DSC analysis.

scholarly journals Some Novel Cobalt Diphenylphosphine Complexes: Synthesis, Characterization, and Behavior in the Polymerization of 1,3-Butadiene

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4067
Author(s):  
Giovanni Ricci ◽  
Giuseppe Leone ◽  
Giorgia Zanchin ◽  
Benedetta Palucci ◽  
Alessandra Forni ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystals ◽  
The Novel ◽  
X Ray Diffraction ◽  
X Ray ◽  
And Behavior

Some novel cobalt diphenylphosphine complexes were synthesized by reacting cobalt(II) chloride with (2-methoxyethyl)diphenylphosphine, (2-methoxyphenyl)diphenylphosphine, and 2-(1,1-dimethylpropyl)-6-(diphenylphosphino)pyridine. Single crystals suitable for X-ray diffraction studies were obtained for the first two complexes, and their crystal structure was determined. The novel compounds were then used in association with methylaluminoxane (MAO) for the polymerization of 1,3-butadiene, and their behavior was compared with that exhibited in the polymerization of the same monomer by the systems CoCl2(PnPrPh2)2/MAO and CoCl2(PPh3)2/MAO. Some significant differences were observed depending on the MAO/Co ratio used, and a plausible interpretation for such a different behavior is proposed.

scholarly journals Growth of sillenite Bi12FeO20 single crystals: structural, thermal, optical, photocatalytic features and first principle calculations

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Durga Sankar Vavilapalli ◽  
Ambrose A. Melvin ◽  
F. Bellarmine ◽  
Ramanjaneyulu Mannam ◽  
Srihari Velaga ◽  
...  
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Photoelectron Spectroscopy ◽  
Diffraction Method ◽  
Lattice Parameter ◽  
First Principle ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Principle Calculations ◽  
Photodegradation Efficiency

AbstractIdeal sillenite type Bi12FeO20 (BFO) micron sized single crystals have been successfully grown via inexpensive hydrothermal method. The refined single crystal X-ray diffraction data reveals cubic Bi12FeO20 structure with single crystal parameters. Occurrence of rare Fe4+ state is identified via X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The lattice parameter (a) and corresponding molar volume (Vm) of Bi12FeO20 have been measured in the temperature range of 30–700 °C by the X-ray diffraction method. The thermal expansion coefficient (α) 3.93 × 10–5 K−1 was calculated from the measured values of the parameters. Electronic structure and density of states are investigated by first principle calculations. Photoelectrochemical measurements on single crystals with bandgap of 2 eV reveal significant photo response. The photoactivity of as grown crystals were further investigated by degrading organic effluents such as Methylene blue (MB) and Congo red (CR) under natural sunlight. BFO showed photodegradation efficiency about 74.23% and 32.10% for degrading MB and CR respectively. Interesting morphology and microstructure of pointed spearhead like BFO crystals provide a new insight in designing and synthesizing multifunctional single crystals.

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