Evaluation of Dislocation Mobility in Wurtzite Semiconductors

2015 ◽  
Vol 1741 ◽  
Author(s):  
Ichiro Yonenaga
Keyword(s):  
Activation Energy ◽  
Yield Strength ◽  
Basic Mechanism ◽  
Dislocation Motion ◽  
Minimum Length ◽  
Indentation Hardness ◽  
Dislocation Mobility ◽  
Dislocation Energy ◽  
Dislocation Process ◽  
Individual Dislocation

ABSTRACTThe indentation hardness and yield strength of various wurtzite-structured semiconductors, such as AlN, GaN, InN, and ZnO, were summarized together with those of 6H-SiC. From analysis of the data, the activation energy for motion of an individual dislocation was deduced to be 2–2.7 and 0.7–1.2 eV in GaN and ZnO, respectively, and the evaluated activation energy for dislocation motion showed a dependence on the dislocation energy in the minimum length. The results were evaluated in terms of homology and the basic mechanism of the dislocation process. Dislocation motion is thought to be primarily controlled by the atomic bonding character of the semiconductors.

Hydrogen-enhanced dislocation velocities in Ni3Al single crystals

2000 ◽  
Vol 15 (1) ◽  
pp. 7-9 ◽  
Author(s):  
C. B. Jiang ◽  
S. Patu ◽  
Q. Z. Lei ◽  
C. X. Shi
Keyword(s):  
Activation Energy ◽  
Shear Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Dislocation Motion ◽  
Dislocation Velocity ◽  
Dislocation Mobility ◽  
Preliminary Results ◽  
Etch Pit

The average dislocation velocity in hydrogenated Ni3Al single crystals was directly measured as a function of resolved shear stress (RSS) at room temperature (293 K) by the etch-pit technique. It was found that the dislocation velocity with hydrogen is about 5–25 times faster than that without hydrogen for the same RSS, and hydrogen decreases activation energy for dislocation motion in Ni3Al single crystals. The reason hydrogen can enhance dislocation velocity in this compound is briefly discussed. These preliminary results quantitatively provide the first evidence of hydrogen-enhancing dislocation mobility in Ni3Al material.

The contribution of friction stress to the creep behaviour of the nickel-base in situ composite, γ—γ'-Cr 3 C 2

1980 ◽  
Vol 373 (1752) ◽  
pp. 93-109 ◽  
Keyword(s):  
Activation Energy ◽  
Creep Behaviour ◽  
Friction Stress ◽  
Matrix Alloy ◽  
Dislocation Motion ◽  
Self Diffusion ◽  
The Matrix ◽  
Nickel Base ◽  
Distribution Of Stress

Transient creep following stress reductions has been analysed by the method described by McLean (1980) to determine the friction stress σ 0 as a function of temperature and directional solidification conditions for the γ-γ'-Cr 3 Cr 2 in-situ composite and for the γ-γ' matrix alloy. These values of σ 0 are identical to the flow stresses at creep strain rates and can be identified with the sums of the barriers to dislocation motion through the matrix by climb around γ'-particles and Orowan bowing between the carbide fibres. The friction stress and the kinetics of deformation of the composite are determined by the matrix behaviour, whereas its creep strength depends on the distribution of stress between fibre and matrix. When the steady-state creep behaviour of γ-γ'-Cr 3 C 2 is analysed by using the usual power law description in terms of the effective stress σ — σ 0 , rather than the applied stress σ, the stress exponent is ca 4 and the activation energy is similar to the activation energy of self-diffusion for nickel. The results provide strong evidence for the operation of recovery-creep in both the composite and matrix alloys.

Estimations of Activation Energy for Dislocation Mobility in p-GaN

2021 ◽  
Vol 10 (2) ◽  
pp. 026004
Author(s):  
V. I. Orlov ◽  
A.Y. Polyakov ◽  
P. S. Vergeles ◽  
E. B. Yakimov ◽  
Gyu Cheol Kim ◽  
...  
Keyword(s):  
Activation Energy ◽  
Dislocation Mobility

scholarly journals Quantitative tests revealing hydrogen enhanced dislocation motion in α-iron

2021 ◽  
Author(s):  
Long-Chao Huang ◽  
Dengke Chen ◽  
De-Gang Xie ◽  
Suzhi Li ◽  
Ting Zhu ◽  
...  
Keyword(s):  
Hydrogen Embrittlement ◽  
High Strength Steels ◽  
High Strength ◽  
Dislocation Motion ◽  
Atomistic Simulations ◽  
Vacuum Degassing ◽  
Nucleation Barrier ◽  
Free Behavior ◽  
Individual Dislocation ◽  
Energy Transportation

Abstract Hydrogen embrittlement jeopardizes the use of high-strength steels as critical load-bearing components in energy, transportation, and infrastructure applications. However, our understanding of hydrogen embrittlement mechanism is still obstructed by the uncertain knowledge of how hydrogen affects dislocation motion, due to the lack of quantitative experimental evidence. Here, by studying the well-controlled, cyclic, bow-out movements of individual screw dislocations, the key to plastic deformation in α-iron, we find that the critical stress for initiating dislocation motion in a 2 Pa electron-beam-excited H2 atmosphere is 27~43% lower than that under vacuum conditions, proving that hydrogen lubricates screw dislocation motion. Moreover, we find that aside from vacuum degassing, dislocation motion facilitates the de-trapping of hydrogen, allowing the dislocation to regain its hydrogen-free behavior. Atomistic simulations reveal that the observed hydrogen-enhanced dislocation motion arises from the hydrogen-reduced kink nucleation barrier. These findings at individual dislocation level can help hydrogen embrittlement modelling in steels.

Solid Solution Alloy Effects on Microstructure and Indentation Hardness in Pt-Ru Thin Films

2001 ◽  
Vol 673 ◽  
Author(s):  
Seungmin Hyun ◽  
Oliver Kraft ◽  
Richard P. Vinci
Keyword(s):  
Thin Films ◽  
Solid Solution ◽  
Elastic Moduli ◽  
Composition Range ◽  
Dislocation Motion ◽  
Solid Solution Alloy ◽  
Indentation Hardness ◽  
Solid Solution Strengthening ◽  
Si Substrates ◽  
Solution Strengthening

ABSTRACTThe elastic moduli and flow stresses of as-deposited Pt and Pt-Ru solid solution thin films were investigated by the nanoindentation method. The influence of solid solution alloying was explored by depositing Pt-Ru solid solution thin films with various compositions onto Si substrates. The 200 nm films were prepared by DC magnetron cosputtering with a Ru composition range from 0 to 20wt%. As expected, the modulus and the flow stress both increased significantly with an increase in Ru. The experimental results compare favorably to predictions based on a simple dislocation motion model consisting of three strengthening terms: substrate constraint, grain size strengthening and solid solution strengthening.

Atomistic Simulation of kinks for 1/2a Screw Dislocation in Ta

2001 ◽  
Vol 677 ◽  
Author(s):  
Guofeng Wang ◽  
Alejandro Strachan ◽  
Tahir ÇaǦin ◽  
Willam A. Goddard
Keyword(s):  
Activation Energy ◽  
Screw Dislocation ◽  
Formation Energy ◽  
Dislocation Motion ◽  
Migration Energy ◽  
Embedded Atom ◽  
Kink Pair ◽  
Double Kink ◽  
Fixed Boundaries ◽  
Quantum Mechanical Computations

We study the structure and formation energy of kinks in 1/2a<111> screw dislocation in metallic Ta Embedded Atom Model Force Field parameterized using quantum mechanical computations. We studied a/3<112> kinks using a simulation cell containing four dislocations in a quadrupole arrangement. We impose periodic boundary conditions in the directions perpendicular to [111] and fixed boundaries in the [111] direction. We find that two, energetically equivalent, core configurations for the 1/2a<111> dislocation lead to 8 distinguishable single kinks and 16 kink pairs. The different mismatches of core configurations along [111] direction cause variations in kink formation energy. The lowest formation energy of a kink pair is determined to be 0.73 eV. The geometric features of such kink pair have been studied with the help of structural analysis of the atomistic model. We also compare the activation energy for dislocation motion via the double kink mechanism with the activation energy for a rigid dislocation motion from a dipole annihilation simulation. We find that the migration energy for dislocation motion via double kink formation is 0.016 eV/b, which is less than the quarter of the migration energy associated with the kink free motion of a straight dislocation, 0.073 eV/b.

Effect of interfacial reaction on tensile and creep behaviors of aluminum-borate-whisker-reinforced AA6061 composite

2000 ◽  
Vol 15 (12) ◽  
pp. 2714-2729 ◽  
Author(s):  
Z. Y. Ma ◽  
S. C. Tjong ◽  
L. Geng ◽  
Z. G. Wang
Keyword(s):  
Activation Energy ◽  
Yield Strength ◽  
Apparent Activation Energy ◽  
Creep Resistance ◽  
Squeeze Casting ◽  
Cyclic Creep ◽  
Apparent Stress ◽  
Aluminum Borate ◽  
Reinforcing Effect ◽  
Microcrack Initiation

Aluminum-borate (AlBO) whisker-reinforced AA6061 composite fabricated by squeeze casting was subjected to both tensile and creep investigations. The whisker exhibited a significant reinforcing effect on as-extruded AA6061, but not for T6-treated specimen. The yield strength of the composite decreased slightly after T6 treatment. This was caused by the degradation of the whiskers and the microcrack initiation. The incorporation of the AlBO whisker into the AA6061 improved the creep resistance of the alloy by several orders of magnitude. Moreover, the composite exhibited higher values of apparent stress exponent and apparent activation energy for both the static and cyclic creep. Finally, cyclic creep retardation behavior was observed for both reinforced and unreinforced AA6061.

scholarly journals HIGH TEMPERATURE STRENGTH OF COMPOSITE MATERIAL WITH CELL STRUCTURE ON THE BASIS OF Ni3Al INTERMETALLIDIDE

2019 ◽  
Vol 62 (3) ◽  
pp. 228-234
Author(s):  
M. Yu. Belomyttsev ◽  
Tuan An’ Fung
Keyword(s):  
Activation Energy ◽  
Composite Material ◽  
Creep Rate ◽  
Yield Strength ◽  
Nickel Alloy ◽  
Ultimate Strength ◽  
Single Phase ◽  
Cell Structure ◽  
Tungsten Coating ◽  
Self Diffusion

The powder metallurgy method was used to obtain materials in the form of a single-phase alloy based on Ni3Al and in the form of composite material (Ni3Al + W) with cell structure based on it. The structural unit of the composite material was a round granule (grain) with average size of 25 μm from nickel alloy, on which the continuous tungsten coating with thickness of ~0.4 μm was deposited by chemical vapor deposition. Compression tests at room temperature have shown that the yield stress of composite material (Ni3Al + W) with cell structure at temperatures of 20 – 1000 °C is higher than of single-phase Ni3Al-based alloy (up to 1.7 times), but at higher test temperature the yield strength of the composite is compared with the yield strength of the nickel alloy. The specific yield strength (that is, normalized for the density of 7.8 g/cm3 for the alloy and of 9.5 g/cm3 for the compo site) behaves similarly. At the temperature of 1300 °C, single-phase Ni3Al-based alloy exhibits solid-liquid behavior under compression. Creep tests were carried out for compression under vacuum at temperatures of 1000 – 1200 °C. Using the pair and parametric methods of mathematical analysis of creep processes according to Hollomon, regression equations of creep rate, stress and temperature of the test were obtained. The ultimate strength of creep for the given tolerances for steady-state creep rate and inverse values were calculated. It is shown that at all test temperatures the composite material has lower creep rate (up to 7 times) and higher ultimate strength of creep (up to 2.5 times) than the nickel alloy on which it is based. Creep activation energies of the materials studied are determined using the exponential law of coupling of experimental values. The creep activation energy for the nickel alloy found is close to the activation energy of nickel self-diffusion in Ni3Al and materials based on it (230 ÷ 310 kJ/mol), and for the composite – to self-diffusion activation energy of tungsten (503 kJ/mol).

Yield strength and dislocation mobility in plastically deformed ZnSe

2006 ◽  
Vol 376-377 ◽  
pp. 771-774 ◽  
Author(s):  
I. Yonenaga ◽  
K. Watanabe ◽  
S. Itoh ◽  
S. Fujiwara ◽  
K. Yoshino
Keyword(s):  
Yield Strength ◽  
Dislocation Mobility

ENHANCED TENSILE DUCTILITY IN AN ELECTRODEPOSITED CU WITH NANO-SIZED GROWTH TWINS

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2537-2542 ◽  
Author(s):  
GUOYONG WANG ◽  
ZHONGHAO JIANG ◽  
JIANSHE LIAN
Keyword(s):  
Strain Rate ◽  
Activation Volume ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Dislocation Motion ◽  
Lamellar Thickness ◽  
Petch Relation ◽  
Transmission Electron ◽  
Mean Size ◽  
Dislocation Process

A fully dense electrodeposited microcrystalline copper with nano-scale twins was synthesized by electrodeposition. The microstructure of this copper was analyzed X-ray diffractometer (XRD) and by transmission electron microscopy (TEM). The grains of mean size about 2mm were divided by high density of growth twins with mean lamellar thickness of about 90 nm. Tensile tests at different strain rates and room temperature showed that the strength increased from 379 MPa to 458 MPa with strain rate increasing from 10-5 s-1 to 0.1 s-1. The elongations to fracture were in the range of 13.6~15.5%. So this Cu has good combination of strength and ductility. The strengths are much higher than that determined by Hall-Petch relation with the same grain size, which means that twin boundaries are effective in blocking dislocation motion. The strain rate sensitivity and activation volume estimated from the flow stress versus strain curves was 0.016 and 84 b3~69b3, respectively. Such a large activation volume indicates that the deformation of this copper was controlled by dislocation process.

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