scholarly journals Study on burgers vector of dislocations in KDP (010) faces and screw dislocation growth mechanism of (101) faces

RSC Advances ◽  
2021 ◽  
Vol 11 (14) ◽  
pp. 7897-7902
Author(s):  
Bo Yu ◽  
Longyun Xu ◽  
Shenglai Wang ◽  
Pingping Huang ◽  
Hui Liu ◽  
...  
Keyword(s):  
Screw Dislocation ◽  
Growth Mechanism ◽  
Optical Method ◽  
Kdp Crystal ◽  
Burgers Vector

We modified the conventional etching-optical method to measure dislocation direction in a KDP crystal.

Elastic interaction between a moving screw dislocation and a surface crack

1995 ◽  
Vol 10 (10) ◽  
pp. 2668-2675 ◽  
Author(s):  
Yu-Zen Tsai ◽  
C.T. Hu ◽  
Sanboh Lee
Keyword(s):  
Stress Intensity Factor ◽  
Free Surface ◽  
Screw Dislocation ◽  
Surface Crack ◽  
Crack Surface ◽  
Image Force ◽  
Elastic Interaction ◽  
Burgers Vector ◽  
Opposite Trend ◽  
Dislocation Modeling

A moving screw dislocation near a surface crack was investigated using dislocation modeling. Motion directions parallel (x direction) and perpendicular (y direction) to the crack surface were considered. Due to the free surface, the net Burgers vector inside the crack is zero. After obtaining the dislocation distribution in the crack, we calculated the stress field in the medium. Relative to a static screw dislocation, the magnitude of σyz due to the moving screw dislocation decreases with increasing velocity Vx. Generally, the effect of dislocation shielding on fracture is reduced if the velocity Vx increases. The magnitude of the image force of the dislocation also decreases with increasing velocity Vx. The effect of velocity along the y direction on the stress intensity factor and image force has the opposite trend to that along the x direction. The present result can reduce to a moving dislocation near a semi-infinite crack and a static dislocation near a surface crack.

Spontaneous growth of hexagonal ZrB2 nanoplates driven by a screw dislocation mechanism

CrystEngComm ◽  
2018 ◽  
Vol 20 (47) ◽  
pp. 7637-7641 ◽  
Author(s):  
Da Liu ◽  
Yanhui Chu ◽  
Beilin Ye ◽  
Xiya Zhou
Keyword(s):  
Molten Salt ◽  
Screw Dislocation ◽  
Growth Mechanism ◽  
Reduction Technique ◽  
Dislocation Mechanism ◽  
Spontaneous Growth ◽  
Borothermal Reduction ◽  
First Time

Hexagonal ZrB2 nanoplates had been successfully synthesized by a facile molten-salt assisted borothermal reduction technique based on the screw dislocation growth mechanism for the first time.

Giant Burgers Vector Micropipe-Dislocations in Silicon Carbide Investigated by Atomic Force Microscopy

2006 ◽  
Vol 527-529 ◽  
pp. 435-438
Author(s):  
Etienne Pernot ◽  
J. Härtwig ◽  
Michel Pons ◽  
Roland Madar
Keyword(s):  
Silicon Carbide ◽  
Atomic Force Microscopy ◽  
Screw Dislocation ◽  
Burgers Vector ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Theoretical Predictions ◽  
Kinetic Effects ◽  
Vector Magnitude

Recently, in some silicon carbide single crystals, some micropipes associated with screw dislocation have been observed by X-ray topography and the strain field around them produced images similar to those of screw dislocations with a very large Burgers vector, about 667 nm. The radius of the hole in the centre of the micropipe is less than 10 'm. This value and the theoretical predictions by Frank (about 7.8 mm) using the Burgers vector magnitude show a large discrepancy. In this paper we present Atomic Force Microscopy experiments around this kind of defects. The Burgers vector magnitude of the screw dislocation and the value of the radius have been measured by this technique. Not only one dislocation, but several have been observed around the micropipe. We concluded that it is in better agreement with the Frank theory modified by Cabrera and Levine concerning kinetic effects during the growth.

scholarly journals Screw-Dislocation-Driven Hierarchical Superstructures of Ag-Ag2O-AgO Nanoparticles

Crystals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1084
Author(s):  
Hua Yang ◽  
Jing Ru Zhang ◽  
Wentao Cao ◽  
Jin Zhen ◽  
Ji Hong Wu
Keyword(s):  
Screw Dislocation ◽  
Uv Irradiation ◽  
Growth Mechanism ◽  
Irradiation Time ◽  
Structural Evolution ◽  
Physiochemical Properties ◽  
Promising Strategy ◽  
Photochemical Method ◽  
Step Density ◽  
Average Size

Constructing multi-dimensional hierarchical superstructures has been, for a longtime, regarded as a promising strategy for modifying the physiochemical properties of nanomaterials. Guided by this rule, this work reports the synthesis of hierarchical superstructures of Ag-Ag2O-AgO nanoparticles (HSANs) using a convenient and surfactant-less photochemical method under 254 nm UV-irradiation. The formation of the HSANs superstructures is dominated by screw-dislocation-driven growth mechanism at low supersaturation condition. The structural evolution of the HSANs superstructures has been systematically investigated. The average size of the HSANs superstructures increased with prolonged 254 nm UV-irradiation. The step density on the superstructure surfaces also increased along with the 254 nm UV-irradiation time.

scholarly journals The Properties of Shuffle Screw Dislocations in Semiconductors Silicon and Germanium

2015 ◽  
Vol 9 (1) ◽  
pp. 10-13 ◽  
Author(s):  
Huili Zhang ◽  
Chun Zhang ◽  
Chunhua Zeng ◽  
Lumei Tong
Keyword(s):  
Screw Dislocation ◽  
Peierls Stress ◽  
Diamond Structure ◽  
Screw Dislocations ◽  
Burgers Vector ◽  
Peierls Barrier ◽  
Silicon And Germanium

The dislocation widths, Peierls barriers and Peierls stresses for shuffle screw dislocations in diamond structure crystals, Si and Ge, have been calculated by the improved P-N theory. The widths are about 0.6b, where b is the Burgers vector. The Peierls barrier for shuffle screw dislocation in Si and Ge, is about 3.61~4.61meV/Å and 5.31~13.32meV/Å, respectively. The Peierls stress is about 0.28~0.33GPa and 0.31~0.53GPa, respectively. The calculated Peierls barriers and stresses are likely the results of shuffle screw dislocation with metastable core which is centered on the bond between two atoms.

scholarly journals Screw-Dislocation-Driven Growth Mode in Two Dimensional GaSe on GaAs(001) Substrates Grown by Molecular Beam Epitaxy

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Nhu Quynh Diep ◽  
Cheng-Wei Liu ◽  
Ssu-Kuan Wu ◽  
Wu-Ching Chou ◽  
Sa Hoang Huynh ◽  
...  
Keyword(s):  
Molecular Beam Epitaxy ◽  
Screw Dislocation ◽  
Growth Mechanism ◽  
Molecular Beam ◽  
Second Harmonic ◽  
Three Dimensional ◽  
Molecular Beam Epitaxy Growth ◽  
Initial Growth ◽  
Two Dimensional ◽  
Pretreatment Period

AbstractRegardless of the dissimilarity in the crystal symmetry, the two-dimensional GaSe materials grown on GaAs(001) substrates by molecular beam epitaxy reveal a screw-dislocation-driven growth mechanism. The spiral-pyramidal structure of GaSe multi-layers was typically observed with the majority in ε-phase. Comprehensive investigations on temperature-dependent photoluminescence, Raman scattering, and X-ray diffraction indicated that the structure has been suffered an amount of strain, resulted from the screw-dislocation-driven growth mechanism as well as the stacking disorders between monolayer at the boundaries of the GaSe nanoflakes. In addition, Raman spectra under various wavelength laser excitations explored that the common ε-phase of 2D GaSe grown directly on GaAs can be transformed into the β-phase by introducing a Se-pretreatment period at the initial growth process. This work provides an understanding of molecular beam epitaxy growth of 2D materials on three-dimensional substrates and paves the way to realize future electronic and optoelectronic heterogeneous integrated technology as well as second harmonic generation applications.

First-principles Studies on Optical Absorption of [010] Screw Dislocation in KDP Crystal

CrystEngComm ◽  
2021 ◽  
Author(s):  
Xuanyu Jiang ◽  
Yang Li ◽  
Liening Wei ◽  
Mingxia Xu ◽  
Lisong Zhang ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Screw Dislocation ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Potassium Dihydrogen Phosphate ◽  
Dihydrogen Phosphate ◽  
Total System ◽  
Kdp Crystal ◽  
Potassium Dihydrogen

The structure, total system energies, electronic structures and optical absorption of the [010] screw dislocation in potassium dihydrogen phosphate (KH2PO4, KDP) crystal are investigated in the framework of density functional...

Selective Etching of Micropipes During Initial Homoepitaxial Growth Stage on Nearly On-Axis 4H-SiC Substrates

2006 ◽  
Vol 527-529 ◽  
pp. 207-210
Author(s):  
Wook Bahng ◽  
Hui Jong Cheong ◽  
In Ho Kang ◽  
Sang Cheol Kim ◽  
Ki Hyun Kim ◽  
...  
Keyword(s):  
Screw Dislocation ◽  
Growth Stage ◽  
Growth Behavior ◽  
Selective Etching ◽  
Initial Growth ◽  
Etch Pits ◽  
Burgers Vector ◽  
Homoepitaxial Growth ◽  
Spiral Shape ◽  
Gas Ratio

The initial homoepitaxial growth behavior on nearly on-axis 4H-SiC substrates was investigated. We have observed circular etch pits on the surface of on-axis substrate in the presence of source gases. However, there were no circular etch pits on the surface of off-axis substrates. In addition, the surface etched by H2 gas did not show circular etch pits even on nearly on-axis substrates. The shape of the circular etch pits was similar to spiral one. The initial growth behavior of epilayers was also investigated with various C/Si ratios of source gases (0.6<C/Si<2.0). The circular etch pits were observed independent of the source gas ratio. It implies that the source gases promote the selective etching, while the H2 gas etches SiC defect-independent. The spiral shape of etch pits seems to be produced from the screw dislocation with large burgers vector of micropipes. Therefore, the circular shape etch pits were not observed in an off-axis substrate.

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