Dislocation nucleation from surface steps: atomistic simulation in aluminium

AbstractUsing transmission electron microscopy, we have analyzed dislocations in AlN nucleation layers and GaN films grown by metallorganic chemical vapor deposition (MOCVD) on the (0001) surface of epitaxially-grown 4H-SiC mesas with and without steps. For 4H-SiC substrates free of SiC surface steps, half-loop nucleation and glide parallel to the AlN/SiC interfacial plane play the dominant role in strain relief, with no mechanism for generating threading dislocations. In contrast, 4H-SiC mesa surfaces with steps give rise to regions of high stress at the heteroepitaxial interface, thereby providing an environment conducive to the nucleation and growth of threading dislocations, which act to accommodate misfit strain by the tilting of threading edge dislocations.

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Atomistic simulation study on key factors dominating dislocation nucleation from a crack tip in two FCC materials: Cu and Al

International Journal of Solids and Structures ◽

10.1016/j.ijsolstr.2012.07.007 ◽

2012 ◽

Vol 49 (23-24) ◽

pp. 3345-3354 ◽

Cited By ~ 16

Author(s):

Y. Cheng ◽

M.X. Shi ◽

Y.W. Zhang

Keyword(s):

Simulation Study ◽

Atomistic Simulation ◽

Crack Tip ◽

Dislocation Nucleation ◽

Key Factors ◽

Fcc Materials

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Length Scale Effects in Materials Deformation of Nano and Microscale Au Structures

Volume 11: Mechanics of Solids, Structures and Fluids ◽

10.1115/imece2009-12077 ◽

2009 ◽

Author(s):

Jie Lian ◽

Junlan Wang

Keyword(s):

Mechanical Properties ◽

Elastic Modulus ◽

Size Effect ◽

Sample Size ◽

Atomistic Simulation ◽

Scale Effects ◽

Elastic Recovery ◽

Boundary Effect ◽

Dislocation Nucleation ◽

Atomistic Simulations

In this study, intrinsic size effect — strong size dependence of mechanical properties — in materials deformation was investigated by performing atomistic simulation of compression on Au (114) pyramids. Sample boundary effect — inaccurate measurement of mechanical properties when sample size is comparable to the indent size — in nanoindentation was also investigated by performing experiments and atomistic simulations of nanoindentation into nano- and micro-scale Au pillars and bulk Au (001) surfaces. For intrinsic size effect, dislocation nucleation and motions that contribute to size effect were analyzed for studying the materials deformation mechanisms. For sample boundary effect, in both experiments and atomistic simulation, the elastic modulus decreases with increasing indent size over sample size ratio. Significantly different dislocation motions contribute to the lower value of the elastic modulus measured in the pillar indentation. The presence of the free surface would allow the dislocations to annihilate, causing a higher elastic recovery during the unloading of pillar indentation.

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The role of surface steps in the asymmetric surface dislocation nucleation in vicinal heterostructures with compressive and tensile stresses

Surface Science ◽

10.1016/0039-6028(93)90326-f ◽

1993 ◽

Vol 292 (3) ◽

pp. L817-L820 ◽

Cited By ~ 3

Author(s):

Ferenc Riesz

Keyword(s):

Dislocation Nucleation ◽

Tensile Stresses ◽

Surface Steps

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Atomistic Simulations of Dislocations in Confined Volumes

MRS Bulletin ◽

10.1557/mrs2009.50 ◽

2009 ◽

Vol 34 (3) ◽

pp. 184-189 ◽

Cited By ~ 44

Author(s):

P.M. Derlet ◽

P. Gumbsch ◽

R. Hoagland ◽

J. Li ◽

D.L. McDowell ◽

...

Keyword(s):

Molecular Dynamics ◽

Time Scale ◽

Finite Temperature ◽

Atomistic Simulation ◽

Dislocation Nucleation ◽

Atomic Scale ◽

Atomistic Simulations ◽

Complementary Role ◽

Nanocrystalline Structures ◽

Strength And Ductility

AbstractInternal microstructural length scales play a fundamental role in the strength and ductility of a material. Grain boundaries in nanocrystalline structures and heterointerfaces in nanolaminates can restrict dislocation propagation and also act as a source for new dislocations, thereby affecting the detailed dynamics of dislocation-mediated plasticity. Atomistic simulation has played an important and complementary role to experiment in elucidating the nature of the dislocation/interface interaction, demonstrating a diversity of atomic-scale processes covering dislocation nucleation, propagation, absorption, and transmission at interfaces. This article reviews some atomistic simulation work that has made progress in this field and discusses possible strategies in overcoming the inherent time scale challenge of finite temperature molecular dynamics.

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