scholarly journals Equilibrium shape and dislocation nucleation in strained epitaxial nanoislands

2005 ◽  
Vol 72 (8) ◽  
Author(s):  
J. Jalkanen ◽  
O. Trushin ◽  
E. Granato ◽  
S. C. Ying ◽  
T. Ala-Nissila
Keyword(s):  
Equilibrium Shape ◽  
Dislocation Nucleation

Publisher's Note: Equilibrium shape and dislocation nucleation in strained epitaxial nanoislands [Phys. Rev. B72, 081403(R) (2005)]

2005 ◽  
Vol 72 (8) ◽  
Author(s):  
J. Jalkanen ◽  
O. Trushin ◽  
E. Granato ◽  
S. C. Ying ◽  
T. Ala-Nissila
Keyword(s):  
Equilibrium Shape ◽  
Dislocation Nucleation

HREM observation of dislocations near room temperature fractures in silicon

1988 ◽  
Vol 46 ◽  
pp. 892-893
Author(s):  
M. H. Rhee ◽  
W. A. Coghlan
Keyword(s):  
Cross Section ◽  
Room Temperature ◽  
Single Crystal Silicon ◽  
Dislocation Nucleation ◽  
Back Side ◽  
Ion Milling ◽  
Crystal Silicon ◽  
Flat Surfaces ◽  
Induced Fractures ◽  
Vicker’S Microhardness

Silicon is believed to be an almost perfectly brittle material with cleavage occurring on {111} planes. In such a material at room temperature cleavage is expected to occur prior to any dislocation nucleation. This behavior suggests that cleavage fracture may be used to produce usable flat surfaces. Attempts to show this have failed. Such fractures produced in semiconductor silicon tend to occur on planes of variable orientation resulting in surfaces with a poor surface finish. In order to learn more about the mechanisms involved in fracture of silicon we began a HREM study of hardness indent induced fractures in thin samples of oxidized silicon.Samples of single crystal silicon were oxidized in air for 100 hours at 1000°C. Two pieces of this material were glued together and 500 μm thick cross-section samples were cut from the combined piece. The cross-section samples were indented using a Vicker's microhardness tester to produce cracks. The cracks in the samples were preserved by thinning from the back side using a combination of mechanical grinding and ion milling.

AN ELECTROHYDRODYNAMIC ANALYSIS OF THE EQUILIBRIUM SHAPE AND STABILITY OF STRESSED CONDUCTING FLUIDS : APPLICATION TO LMIS

1986 ◽  
Vol 47 (C7) ◽  
pp. C7-351-C7-358
Author(s):  
M. CHUNG ◽  
P. H. CUTLER ◽  
T. E. FEUCHTWANG ◽  
E. KAZES ◽  
N. M. MISKOVSKY
Keyword(s):  
Equilibrium Shape ◽  
Stressed Conducting ◽  
Conducting Fluids

High-Temperature Synthesis of CdSe-Based Core/Shell, Core/Shell/Shell, and Core/Graded-Shell Nanoplatelets for Stable and Efficient Narrowband Emitters

2019 ◽  
Author(s):  
Aurelio A. Rossinelli ◽  
Henar Rojo ◽  
Aniket S. Mule ◽  
Marianne Aellen ◽  
Ario Cocina ◽  
...  
Keyword(s):  
Quantum Dots ◽  
High Temperature ◽  
Equilibrium Shape ◽  
Size Variation ◽  
Crystal Defects ◽  
Atomic Scale ◽  
Quantum Yields ◽  
Core Shell ◽  
Compositional Gradient ◽  
High Quality

<div>Colloidal semiconductor nanoplatelets exhibit exceptionally narrow photoluminescence spectra. This occurs because samples can be synthesized in which all nanoplatelets share the same atomic-scale thickness. As this dimension sets the emission wavelength, inhomogeneous linewidth broadening due to size variation, which is always present in samples of quasi-spherical nanocrystals (quantum dots), is essentially eliminated. Nanoplatelets thus offer improved, spectrally pure emitters for various applications. Unfortunately, due to their non-equilibrium shape, nanoplatelets also suffer from low photo-, chemical, and thermal stability, which limits their use. Moreover, their poor stability hampers the development of efficient synthesis protocols for adding high-quality protective inorganic shells, which are well known to improve the performance of quantum dots. <br></div><div>Herein, we report a general synthesis approach to highly emissive and stable core/shell nanoplatelets with various shell compositions, including CdSe/ZnS, CdSe/CdS/ZnS, CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S, and CdSe/ZnSe. Motivated by previous work on quantum dots, we find that slow, high-temperature growth of shells containing a compositional gradient reduces strain-induced crystal defects and minimizes the emission linewidth while maintaining good surface passivation and nanocrystal uniformity. Indeed, our best core/shell nanoplatelets (CdSe/Cd<sub>x</sub>Zn<sub>1–x</sub>S) show photoluminescence quantum yields of 90% with linewidths as low as 56 meV (19.5 nm at 655 nm). To confirm the high quality of our different core/shell nanoplatelets for a specific application, we demonstrate their use as gain media in low-threshold ring lasers. More generally, the ability of our synthesis protocol to engineer high-quality shells can help further improve nanoplatelets for optoelectronic devices.</div>

scholarly journals The Strain Rate Sensitivity and Creep Behavior for the Tripler Plane of Potassium Dihydrogen Phosphate Crystal by Nanoindentation

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 369
Author(s):  
Jianhui Mao ◽  
Wenjun Liu ◽  
Dongfang Li ◽  
Chenkai Zhang ◽  
Yi Ma
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Creep Deformation ◽  
Potassium Dihydrogen Phosphate ◽  
Rate Sensitivity ◽  
Dislocation Nucleation ◽  
Machining Process ◽  
Dihydrogen Phosphate ◽  
Potassium Dihydrogen ◽  
Kdp Crystals

As an excellent multifunctional single crystal, potassium dihydrogen phosphate (KDP) is a well-known, difficult-to-process material for its soft-brittle and deliquescent nature. The surface mechanical properties are critical to the machining process; however, the characteristics of deformation behavior for KDP crystals have not been well studied. In this work, the strain rate effect on hardness was investigated on the mechanically polished tripler plane of a KDP crystal relying on nanoindentation technology. By increasing the strain rate from 0.001 to 0.1 s−1, hardness increased from 1.67 to 2.07 GPa. Hence, the strain rate sensitivity was determined as 0.053, and the activation volume of dislocation nucleation was 169 Å3. Based on the constant load-holding method, creep deformation was studied at various holding depths at room temperature. Under the spherical tip, creep deformation could be greatly enhanced with increasing holding depth, which was mainly due to the enlarged holding strain. Under the self-similar Berkovich indenter, creep strain could be reduced at a deeper location. Such an indentation size effect on creep deformation was firstly reported for KDP crystals. The strain rate sensitivity of the steady-state creep flow was estimated, and the creep mechanism was qualitatively discussed.

scholarly journals Dislocation-mediated shear amorphization in boron carbide

2021 ◽  
Vol 7 (8) ◽  
pp. eabc6714 ◽  
Author(s):  
Kolan Madhav Reddy ◽  
Dezhou Guo ◽  
Shuangxi Song ◽  
Chun Cheng ◽  
Jiuhui Han ◽  
...  
Keyword(s):  
Boron Carbide ◽  
Structural Transition ◽  
Activation Volume ◽  
Structural Evolution ◽  
Dislocation Nucleation ◽  
Superhard Materials ◽  
Rate Dependent ◽  
Transmission Electron ◽  
Lower Activation ◽  
Underlying Mechanisms

The failure of superhard materials is often associated with stress-induced amorphization. However, the underlying mechanisms of the structural evolution remain largely unknown. Here, we report the experimental measurements of the onset of shear amorphization in single-crystal boron carbide by nanoindentation and transmission electron microscopy. We verified that rate-dependent loading discontinuity, i.e., pop-in, in nanoindentation load-displacement curves results from the formation of nanosized amorphous bands via shear amorphization. Stochastic analysis of the pop-in events reveals an exceptionally small activation volume, slow nucleation rate, and lower activation energy of the shear amorphization, suggesting that the high-pressure structural transition is activated and initiated by dislocation nucleation. This dislocation-mediated amorphization has important implications in understanding the failure mechanisms of superhard materials at stresses far below their theoretical strengths.

Equilibrium Shape of a Liquid Metal Subject to Electromagnetic Forces

2004 ◽  
Vol 40 (2) ◽  
pp. 585-588 ◽  
Author(s):  
R. Moretti ◽  
S. Dufour ◽  
G. Vinsard ◽  
B. Laporte
Keyword(s):  
Liquid Metal ◽  
Equilibrium Shape ◽  
Electromagnetic Forces

Anisotropic misfit dislocation nucleation in two-dimensional grown InAs/GaAs(001) heterostructures

1998 ◽  
Vol 73 (8) ◽  
pp. 1074-1076 ◽  
Author(s):  
Achim Trampert ◽  
Klaus H. Ploog ◽  
Eric Tournié
Keyword(s):  
Misfit Dislocation ◽  
Dislocation Nucleation ◽  
Two Dimensional

Dislocation nucleation in heteroepitaxial semiconducting films

2009 ◽  
Vol 6 (8) ◽  
pp. 1827-1835 ◽  
Author(s):  
B. Pichaud ◽  
N. Burle ◽  
M. Texier ◽  
C. Alfonso ◽  
M. Gailhanou ◽  
...  
Keyword(s):  
Dislocation Nucleation
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