A molecular dynamics study of self-diffusion in the cores of screw and edge dislocations in aluminum

Pun, G. P. Purja; Mishin, Y.

doi:10.1016/j.actamat.2009.07.048

Cited by 79 publications

(36 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In materials, crystallographic imperfections such as dislocations often dictate performance and properties. For example, dislocation cores can act as fast diffusion sites [1][2][3][4], mitigate strain and plasticity during structural phase transformations [5][6][7], and govern crystal growth [8][9][10]. Increasingly, Bragg coherent x-ray diffractive imaging (BCDI) is being utilized at synchrotron and x-ray free electron laser [11,12] sources to address this challenge of understanding and optimizing materials properties via tuning of lattice distortions by nondestructively imaging the 3D lattice distortion field under in situ and operando conditions [13][14][15][16][17][18][19].…”

mentioning

confidence: 99%

Accurate, rapid identification of dislocation lines in coherent diffractive imaging via a min-max optimization formulation

2018

View full text Add to dashboard Cite

Defects such as dislocations impact materials properties and their response during external stimuli. Defect engineering has emerged as a possible route to improving the performance of materials over a wide range of applications, including batteries, solar cells, and semiconductors. Imaging these defects in their native operating conditions to establish the structure-function relationship and, ultimately, to improve performance has remained a considerable challenge for both electron-based and x-ray-based imaging techniques. However, the advent of Bragg coherent x-ray diffractive imaging (BCDI) has made possible the 3D imaging of multiple dislocations in nanoparticles ranging in size from 100 nm to1000 nm. While the imaging process succeeds in many cases, nuances in identifying the dislocations has left manual identification as the preferred method. Derivative-based methods are also used, but they can be inaccurate and are computationally inefficient. Here we demonstrate a derivative-free method that is both more accurate and more computationally efficient than either derivativeor human-based methods for identifying 3D dislocation lines in nanocrystal images produced by BCDI. We formulate the problem as a min-max optimization problem and show exceptional accuracy for experimental images. We demonstrate a 260x speedup for a typical experimental dataset with higher accuracy over current methods. We discuss the possibility of using this algorithm as part of a sparsity-based phase retrieval process. We also provide the MATLAB code for use by other researchers.

show abstract

mentioning

confidence: 99%

Accurate, rapid identification of dislocation lines in coherent diffractive imaging via a min-max optimization formulation

2018

View full text Add to dashboard Cite

show abstract

“…6 On the theoretical side, all atomistic simulations have been performed using empirical potentials. For example, the embedded-atom method ͑EAM͒ has been widely employed to study pipe diffusion in Al, 7 Cu, 8 and Al-Mg alloys. 9 However, generally speaking, empirical potentials are less accurate in dealing with phenomena involving bond breaking, bond formation, and charge transfer, etc., which are usually present at a dislocation core during pipe diffusion.…”

mentioning

confidence: 99%

Calculation of fast pipe diffusion along a dislocation stacking fault ribbon

Zhang

Lü

2010

Phys. Rev. B

View full text Add to dashboard Cite

The diffusion of an interstitial Si atom along an edge dislocation in Al is studied by using a quantummechanics/molecular-mechanics coupling method. It is found that the diffusing Si atom follows approximately a sinusoidal trajectory. The diffusion energy barrier along the partial dislocation core is in excellent agreement with the experimental value. We predict that the stacking fault ribbon could provide a fast pathway for diffusion which increases the diffusivity by 6-7 orders of magnitude comparing to the bulk value at 700 K. At the same temperature, the diffusivity along the stacking fault is found to be three to four orders of magnitude greater than that along the partial dislocation core. Dislocation core acts as fast paths for diffusing atoms whose mobility can be orders of magnitude higher than in bulk diffusion and this phenomenon is often referred as "pipe diffusion." By creating a short-circuit pathway, pipe diffusion can affect many kinetic processes in bulk materials, including creep, 1 dynamic-strain aging, 2 and crystallization. 3 In thin films and nanocrystals, pipe diffusion can become even more crucial due to the reduced material dimensions. For example, pipe diffusion can significantly influence oxidation, corrosion, recovery of radiation damage, and electromigration in nanoelectronic devices. 4 Despite its importance, an accurate determination of diffusivity and diffusing mechanism has remained challenging. On the experimental side, owing to the difficulty in tracking atomic motion, very few direct measurements have been reported 5,6 to date. Among them, a recent experiment on Si diffusing in Al stands out. 6 On the theoretical side, all atomistic simulations have been performed using empirical potentials. For example, the embedded-atom method ͑EAM͒ has been widely employed to study pipe diffusion in Al, 7 Cu, 8 and Al-Mg alloys. 9 However, generally speaking, empirical potentials are less accurate in dealing with phenomena involving bond breaking, bond formation, and charge transfer, etc., which are usually present at a dislocation core during pipe diffusion. Moreover, when multiple elements are involved, the empirical potentials such as EAM are even more prone to giving wrong results. On the other hand, although quantum-mechanical simulations are capable of capturing these phenomena, they are often too computationally expensive to deal with dislocations. To the best of our knowledge, there is no literature reporting quantum-mechanical study of pipe diffusion.Previous studies have shown that the quantum-mechanics ͑QM͒/molecular-mechanics ͑MM͒ method can accurately describe the structure of dislocations in Al. 10,11 Motivated by the recent experiment which has observed "giant diffusivity" of Si interstitial pipe diffusion in Al, 6 we have carried out corresponding QM/MM simulations for Si diffusions in an edge dislocation in Al. By combining computational efficiency and accuracy, the present QM/MM method links quantum-mechanical simulations based on the Kohn-Sham density-functional theory ͑K...

show abstract

“…As shown in previous investigations, the threading dislocations serve as short‐circuit diffusion channels and are responsible for the very long distance diffusion . In sample B or sample C, the GaN layer adjacent to the buffer (under the AlN IL) possesses a high concentration of threading dislocations and a high density of vacancies.…”

Section: Resultsmentioning

confidence: 63%

Barrier Strain and Carbon Incorporation‐Engineered Performance Improvements for AlGaN/GaN High Electron Mobility Transistors^**

Luong

Tran

et al. 2014

Chemical Vapor Deposition

View full text Add to dashboard Cite

The improvements in electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) grown using metalorganic (MO)CVD by engineering structure, barrier strain, and unintentional carbon incorporation, are demonstrated in this work. Both normal HEMT structure (with a high temperature (HT) AlN buffer) and advanced HEMT structure (with a highlow-high temperature (HLHT) AlN buffer, and a HT AlN interlayer (IL)) present a breakdown voltage higher than 200 V, while a much smaller breakdown voltage of 17 V is measured on the conventional structure using a low-temperature GaN buffer. The HT AlN IL inserted in the middle of the conventional HEMT structure introduces a reduction in the tension of the AlGaN barrier, which results in an improvement of the surface morphology (0.46 nm). As a consequence, the two-dimensional electron gas (2DEG) mobility increases by remarkable 46% (1900 cm 2 V À1 s À1 ). The HLHT AlN buffer, substituting for the HT AlN buffer, leads to the enhancement of GaN crystalline quality, which contributes to the performance improvement for HEMTs. The advanced HEMT, using both an AlN IL and an HLHT AlN buffer, produces increases in the DC maximum drain current by 35.5% ($680 A mm À1 ), and in the transconductance by 15% (114 mS mm À1 ) in comparison with the normal HEMT with an AlN buffer. The very low leakage current in the advanced HEMTs is caused by optimizing the design of the buffer and modifying growth parameters. Lastly, the reduction of AlGaN barrier tensile strain by inserting the HT AlN IL is promising for an improvement in AlGaN/GaN HEMT reliability.

show abstract

A molecular dynamics study of self-diffusion in the cores of screw and edge dislocations in aluminum

Cited by 79 publications

References 58 publications

Accurate, rapid identification of dislocation lines in coherent diffractive imaging via a min-max optimization formulation

Accurate, rapid identification of dislocation lines in coherent diffractive imaging via a min-max optimization formulation

Calculation of fast pipe diffusion along a dislocation stacking fault ribbon

Barrier Strain and Carbon Incorporation‐Engineered Performance Improvements for AlGaN/GaN High Electron Mobility Transistors^**

Contact Info

Product

Resources

About

A molecular dynamics study of self-diffusion in the cores of screw and edge dislocations in aluminum

Cited by 79 publications

References 58 publications

Accurate, rapid identification of dislocation lines in coherent diffractive imaging via a min-max optimization formulation

Accurate, rapid identification of dislocation lines in coherent diffractive imaging via a min-max optimization formulation

Calculation of fast pipe diffusion along a dislocation stacking fault ribbon

Barrier Strain and Carbon Incorporation‐Engineered Performance Improvements for AlGaN/GaN High Electron Mobility Transistors**

Contact Info

Product

Resources

About

Barrier Strain and Carbon Incorporation‐Engineered Performance Improvements for AlGaN/GaN High Electron Mobility Transistors^**