Binding of solute atoms to dislocations

Fiore, N.F.; Bauer, Charles L.

doi:10.1016/0079-6425(68)90019-4

Cited by 61 publications

(26 citation statements)

References 35 publications

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“…Since the In atom is larger than the host Ga atom, it is expected that if the In atoms are sufficiently mobile during growth, then they will segregate to the tensile part of the dislocation strain field 18 .…”

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confidence: 99%

“…In the case of a single In atom in GaN, a binding energy can be defined which is the difference in energy between the In atom at an bulk-like site compared to a site close to the dislocation core. If this binding energy is greater than approximately 1-2kT 18 , it is thought that segregation would not occur. Our calculations show that the limiting radius beyond which the binding energy would be too low is approximately 18 Å for an (a+c)-type core, well within our cut-off radius.…”

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confidence: 99%

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Segregation of In to Dislocations in InGaN

et al. 2015

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Dislocations are one-dimensional topological defects which occur frequently in functional thin film materials and which are known to degrade the performance of In x Ga 1-x N-based optoelectronic devices. Here, we show that large local deviations in alloy composition and atomic structure re expected to occur in and around dislocation cores in In x Ga 1-x N alloy thin 2 films. We present energy-dispersive X-ray spectroscopy data supporting this result. The methods presented here are also widely applicable for predicting composition fluctuations associated with strain fields in other inorganic functional material thin films. KEYWORDSDislocations, III-nitrides, Monte Carlo, alloy segregation, atomistic modeling, STEM-EDX MAIN TEXTDislocations are ubiquitous one-dimensional topological defects that are found within thin films of nitride semiconductors, originating at the interface with the substrate, and threading up through the active region of the device before terminating at the crystal surface 1 . These dislocations can severely degrade device efficiencies 2 , and lifetimes 3 and are responsible for a broad range of undesirable behavior such as leakage currents 4 and properties such as reduced internal quantum efficiencies 5 and defect states 6,7,8,9,10 that can act as non-radiative recombination centers. In x Ga 1-x N-based alloy semiconductors are used in light-emitting diodes 11 , laser diodes 12 and solar cells 13 , which can be tuned to emit or absorb respectively over the entire visible spectrum by varying the In composition 14 . In x Ga 1-x N is subject to very high threading dislocation densities of up to 10 11 cm -2 and typically around 10 9 cm -2 when grown by metalorganic vapourphase epitaxy 15 (MOVPE), of which the majority have a-type ('edge') or (a+c)-type ('mixed') Burgers vectors with < 1% 16 being c-type ('screw'). High dislocation densities are associated with short lifetimes in InGaN-based optoelectronic devices 17 . The electronic properties of dislocations are determined by the local bonding in the region of the dislocation core 8 . It is therefore important to determine whether or not there are local differences in the alloy composition near dislocation cores in In x Ga 1-x N. Such composition fluctuations are likely to 3 affect the electronic properties of the dislocations and would therefore affect device performance.Each dislocation is associated with a strain field determined by its Burgers vector. Since the In atom is larger than the host Ga atom, it is expected that if the In atoms are sufficiently mobile during growth, then they will segregate to the tensile part of the dislocation strain field 18 .Previous theoretical work has shown that the extreme case of a pure InN c-type dislocation core in an In x Ga 1-x N alloy is more energetically favorable compared to the equivalent In x Ga 1-x N core 19 , and also that it is favorable for In atoms to bind to a c-type dislocation core in GaN 20 . Due to the sensitivity required to detect small variations in alloy concentration on sh...

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Segregation of In to Dislocations in InGaN

et al. 2015

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“…For an edge dislocation, compressive and tensile strains produce areas that are depleted and enhanced with solute concentration-a "Cottrell atmosphere." 8 Cottrell atmospheres produce timedependent strengthening mechanisms like strain-aging in steels and the Portevin-Le Chatelier effect in aluminum alloys, 9 and the rearrangement of hydrogen from dislocation strain fields affects dislocation interactions. 10 The dislocation core-where the continuum description of the strain fields breaks down-provides the largest distortions in geometry and the attraction of solutes to this region is crucial for solute effects on strength.…”

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Nanoscale hydride formation at dislocations in palladium:Ab initiotheory and inelastic neutron scattering measurements

Trinkle

Heuser

et al. 2011

Phys. Rev. B

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Hydrogen arranges at dislocations in palladium to form nanoscale hydrides, changing the vibrational spectra. An ab initio hydrogen potential energy model versus Pd neighbor distances allows us to predict the vibrational excitations for H from absolute zero up to room temperature adjacent to a partial dislocation and with strain. Using the equilibrium distribution of hydrogen with temperature, we predict excitation spectra to explain new incoherent inelastic neutron-scattering measurements. At 0K, dislocation cores trap H to form nanometer-sized hydrides, while increased temperature dissolves the hydrides and disperses H throughout bulk Pd.

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“…Those models generally employ two mechanisms to describe the yield strength: a strengthening by grain size reduction, the Hall-Petch effect, and the alloying elements' contribution to the material's strength [15,36,37]. Many of those models have used databases with significant amounts of different alloys to employ a linear regression in order to get parameters that determine the effect of alloying elements on the yield strength of the austenitic steel.…”

Section: Methodsmentioning

confidence: 99%

Ab Initio-Based Modelling of the Yield Strength in High-Manganese Steels

Sevsek

Bleck

2018

Metals

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An ab initio-based model for the strength increase by short-range ordering of C-Mn-Al clusters has been developed. The model is based on ab initio calculations of ordering energies. The impact of clusters on the yield strength of high-manganese austenitic steels (HMnS) is highly dependent on the configurational structure of the cells that carbon atoms will position themselves as interstitial atoms. The impact of the alloying elements C, Mn, and Al on the potential and actual increase in yield strength is analyzed. A model for the calculation of yield strengths of HMnS is derived that includes the impact of short-range ordering, grain size refinement, and solid solution strengthening. The model is in good agreement with experimental data and performs better than other models that do not include strengthening by short-range ordering.

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Binding of solute atoms to dislocations

Cited by 61 publications

References 35 publications

Segregation of In to Dislocations in InGaN

Segregation of In to Dislocations in InGaN

Nanoscale hydride formation at dislocations in palladium:Ab initiotheory and inelastic neutron scattering measurements

Ab Initio-Based Modelling of the Yield Strength in High-Manganese Steels

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