scholarly journals Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces

2017 ◽  
Vol 121 (19) ◽  
pp. 195301 ◽  
Author(s):  
J. Gruber ◽  
X. W. Zhou ◽  
R. E. Jones ◽  
S. R. Lee ◽  
G. J. Tucker
Keyword(s):  
Molecular Dynamics ◽  
Defect Formation ◽  
Heteroepitaxial Growth ◽  
Ingan Alloys

Characterization of Defect Nucleation and Propagation in Fe2O3+FCC-Al Nanocomposites During Uniaxial Tensile and Compressive Deformations

2006 ◽  
Author(s):  
Vikas Tomar ◽  
Min Zhou
Keyword(s):  
Molecular Dynamics ◽  
Grain Size ◽  
Defect Formation ◽  
Voronoi Tessellation ◽  
Orientation Distribution ◽  
Uniaxial Tensile ◽  
Grain Sizes ◽  
Classical Molecular Dynamics ◽  
Average Grain Size ◽  
Nanocrystalline Structures

The objective of this research is to analyze uniaxial tensile and compressive mechanical deformations of α-Fe2O3 + fcc Al nanoceramic-metal composites using classical molecular dynamics (MD). Specifically, variations in the nucleation and the propagation of defects (such as dislocations and stacking faults etc.) with variation in the nanocomposite phase morphology and their effect on observed tensile and compressive strengths of the nanocomposites are analyzed. For this purpose, a classical molecular dynamics (MD) potential that includes an embedded atom method (EAM) cluster functional, a Morse type pair function, and a second order electrostatic interaction function is developed, see Tomar and Zhou (2004) and Tomar and Zhou (2006b). The nanocrystalline structures (nanocrystalline Al, nanocrystalline Fe2O3 and the nanocomposites with 40% and 60% Al by volume) with average grain sizes of 3.9 nm, 4.7 nm, and 7.2 nm are generated using a combination of the well established Voronoi tessellation method with the Inverse Monte-Carlo method to conform to prescribed log-normal grain size distributions. For comparison purposes, nanocrystalline structures with a specific average grain size have the same grain morphologies and the same grain orientation distribution. MD simulations are performed at the room temperature (300 K). Calculations show that the deformation mechanism is affected by a combination of factors including the fraction of grain boundary (GB) atoms and the electrostatic forces between atoms. The significance of each factor is dependent on the volume fractions of the Al and Fe2O3 phases. Depending on the relative orientations of the two phases at an interface, the contribution of the interface to the defect formation varies. The interfaces have stronger effect in structures with smaller average grain sizes than in structures with larger average grain sizes.

Impact of Molecular Dynamics Simulations on Research and Development of Semiconductor Materials

MRS Advances ◽  
2019 ◽  
Vol 4 (61-62) ◽  
pp. 3381-3398
Author(s):  
Xiaowang Zhou
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Recent Progress ◽  
Defect Formation ◽  
Atomic Scale ◽  
Semiconductor Materials ◽  
Formation Mechanisms ◽  
Graphene Growth ◽  
First Case ◽  
Dynamics Simulations

ABSTRACTAtomic scale defects critically limit performance of semiconductor materials. To improve materials, defect effects and defect formation mechanisms must be understood. In this paper, we demonstrate multiple examples where molecular dynamics simulations have effectively addressed these issues that were not well addressed in prior experiments. In the first case, we report our recent progress on modelling graphene growth, where we found that defects in graphene are created around periphery of islands throughout graphene growth, not just in regions where graphene islands impinge as believed previously. In the second case, we report our recent progress on modelling TlBr, where we discovered that under an electric field, edge dislocations in TlBr migrate in both slip and climb directions. The climb motion ejects extensive vacancies that can cause the rapid aging of the material seen in experiments. In the third case, we discovered that the growth of InGaN films on (0001) surfaces suffers from a serious polymorphism problem that creates enormous amounts of defects. Growth on ($11\bar{2}0$) surfaces, on the other hand, results in single crystalline wurtzite films without any of these defects. In the fourth case, we first used simulations to derive dislocation energies that do not possess any noticeable statistical errors, and then used these error-free methods to discover possible misuse of misfit dislocation theory in past thin film studies. Finally, we highlight the significance of molecular dynamics simulations in reducing defects in the design space of nanostructures.

Molecular Dynamics Simulations to Evaluate the Effect of Applied Strain on Interstitial Cluster Formation and Orientation Under Collision Cascade Damage

2012 ◽  
Author(s):  
Satoshi Miyashiro ◽  
Satoshi Fujita ◽  
Mitsuhiro Itakura ◽  
Taira Okita
Keyword(s):  
Molecular Dynamics ◽  
Defect Formation ◽  
Cluster Formation ◽  
Md Simulations ◽  
Defect Cluster ◽  
Applied Strain ◽  
Collision Cascade ◽  
Defect Clusters ◽  
Dynamics Simulations ◽  
Cascade Damage

We conducted molecular dynamics (MD) simulations to analyze the strain influence on defect formation and orientation. Collision cascade damage was initiated under uniaxial applied strain with a PKA energy of 10 keV. The number of residual defects increased with applied strain because of the enhanced formation of larger defect cluster. We also applied uniaxial strain to the simulation cell which included an interstitial cluster and detected the change in its direction. The probability of a change in the defect cluster direction was significantly higher under strain. Results further showed that the probability of the change in direction is higher with smaller defect clusters, and that it is extremely low with clusters larger than a certain size.

Molecular Dynamics Simulations to Evaluate the Effect of the Difference in Material Properties on Irradiation-Induced Defect Formation Under Applied Strain

2012 ◽  
Author(s):  
Toshihiro Horinouchi ◽  
Satoshi Miyashiro ◽  
Mitsuhiro Itakura ◽  
Taira Okita
Keyword(s):  
Molecular Dynamics ◽  
Defect Formation ◽  
Stacking Fault ◽  
Applied Strain ◽  
Stacking Fault Energy ◽  
Cascade Process ◽  
Defect Production ◽  
Fcc Metals ◽  
The Difference ◽  
Dynamics Simulations

The influence of applied strain on the defect production rate during a cascade process was evaluated for several FCC metals with different Stacking Fault Energy by the method of molecular dynamics. It was found that applied strain increases the number of surviving defects, which is caused by the enhanced formation of larger clusters. It was also found that the number of defects is almost independent of Stacking Fault Energy even under applied strain.

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