Dislocation Nucleation Models From Point Defect Condensations in Silicon and Germanium

1980 ◽  
Vol 2 ◽  
Author(s):  
T.Y. Tan
Keyword(s):  
Point Defect ◽  
Point Defects ◽  
Strain Energy ◽  
Dislocation Nucleation ◽  
Dominant Factor ◽  
Dangling Bonds ◽  
Configurational Energy ◽  
Nucleation Stage ◽  
Partial Dislocations ◽  
Silicon And Germanium

ABSTRACTThe process of dislocation nucleation from point defect condensations in Si(Ge) is discussed. Based on the assumption that during the dislocation nucleation stage, the dominant factor in the configurational energy is the number of dangling bonds per point defect incorporated, rather than the more commonly recognized factor of strain energy, it is possible to model the dislocation nucleation process. In order to minimize the number of dangling bonds, point defects would condense into row configurations elongated in <110>, called intermediate defects (IDC), and then the IDCs would evolute into undissociated 90° edge –, 60°, and Frank partial dislocations.

Instabilities and Point Defects at Step-Free Si(001) and (111) Terraces During High Temperature Annealing

1999 ◽  
Vol 587 ◽  
Author(s):  
Doohan Lee ◽  
Jack M. Blakely
Keyword(s):  
High Temperature ◽  
Point Defect ◽  
Point Defects ◽  
Strain Energy ◽  
Annealing Temperature ◽  
Small Islands ◽  
High Temperature Annealing ◽  
Atomic Steps ◽  
The Stability

AbstractIn this paper we describe observations on the stability of extremely large Si(001) and (111) terraces that are formed by a technique described previously. Following annealing at high temperature and quenching, a series of concentric pits of monoatomic depth are observed with spacing between successive pits of the order of several microns; pits do not form on (111) until the terraces get extremely large. The occurrence of small islands or small pits on the terraces of quenched samples gives information on the majority point defect at the annealing temperature. On (001) samples that are slowly cooled from the annealing temperature, it is observed that pairs of atomic steps have formed on the large terrace; we believe that these result from the tendency of the surface to minimize the strain energy associated with the (2 × 1) reconstruction.

Ab Initio Simulations of the Nucleation of Single-Walled Carbon Nanotubes

2007 ◽  
Vol 121-123 ◽  
pp. 1037-1040 ◽  
Author(s):  
L. Li ◽  
S. Reich ◽  
J. Robertson
Keyword(s):  
Strain Energy ◽  
Single Walled Carbon Nanotubes ◽  
Dangling Bonds ◽  
Bond Energies ◽  
Ab Initio Simulations ◽  
Nucleation Stage ◽  
Carbon Carbon Bonds ◽  
Metallic Catalyst ◽  
Walled Carbon Nanotubes

We investigated the nucleation of SWNTs and the role of metallic catalyst using firstprinciples calculations. To avoid dangling bonds a closed cap forms on a metal surface. 6 pentagonal rings are introduced into the cap, which reduces the strain energy. A unique tube chirality then grows from the cap, which is controlled by the metal lattice at the nucleation stage. We found that chirality of nanotubes affects the bond energies, including dangling bonds, carbon-carbon bonds & carbonmetal bonds.

Detection of a point defect in a silicon single crystal by high-resolution TEM

1995 ◽  
Vol 53 ◽  
pp. 466-467
Author(s):  
M. Awaji
Keyword(s):  
High Resolution ◽  
Single Crystal ◽  
Point Defect ◽  
Point Defects ◽  
Noise Level ◽  
Dark Field ◽  
Silicon Single Crystal ◽  
High Resolution Image ◽  
Dark Field Imaging ◽  
Field Imaging

It is necessary to improve the resolution, brightness and signal-to-noise ratio(s/n) for the detection and identification of point defects in crystals. In order to observe point defects, multi-beam dark-field imaging is one of the useful methods. Though this method can improve resolution and brightness compared with dark-field imaging by diffuse scattering, the problem of s/n still exists. In order to improve the exposure time due to the low intensity of the dark-field image and the low resolution, we discuss in this paper the bright-field high-resolution image and the corresponding subtracted image with reference to a changing noise level, and examine the possibility for in-situ observation, identification and detection of the movement of a point defect produced in the early stage of damage process by high energy electron bombardment.The high-resolution image contrast of a silicon single crystal in the [10] orientation containing a triple divacancy cluster is calculated using the Cowley-Moodie dynamical theory and for a changing gaussian noise level. This divacancy model was deduced from experimental results obtained by electron spin resonance. The calculation condition was for the lMeV Berkeley ARM operated at 800KeV.

scholarly journals Reactivity of fluorographene is triggered by point defects: beyond the perfect 2D world

Nanoscale ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 4696-4707 ◽  
Author(s):  
Miroslav Medveď ◽  
Giorgio Zoppellaro ◽  
Juri Ugolotti ◽  
Dagmar Matochová ◽  
Petr Lazar ◽  
...  
Keyword(s):  
Point Defect ◽  
Point Defects

Understanding the links between nucleophilic/reductive strength of the environment, formation of radicals and point defect characteristics is crucial for achieving control over the functionalization of fluorographene.

Displacement cascade evolution in tungsten with pre-existing helium and hydrogen clusters: a molecular dynamics study

2020 ◽  
Vol 111 (8) ◽  
pp. 698-705
Author(s):  
Mohammad Abu-Shams ◽  
Jeffery Moran ◽  
Ishraq Shabib
Keyword(s):  
Molecular Dynamics ◽  
Point Defect ◽  
Radiation Damage ◽  
Point Defects ◽  
High Energy ◽  
Dynamics Simulation ◽  
Power Relationship ◽  
Hydrogen Clusters ◽  
Displacement Cascades ◽  
Hydrogen Defects

Abstract The effects of radiation damage on bcc tungsten with preexisting helium and hydrogen clusters have been investigated in a high-energy environment via a comprehensive molecular dynamics simulation study. This research determines the interactions of displacement cascades with helium and hydrogen clusters integrated into a tungsten crystal generating point defect statistics. Helium or hydrogen clusters of atoms~0.1% of the total number of atoms have been randomly distributed within the simulation model and primary knock-on-atom (PKA) energies of 2.5, 5, 7.5 and 10 keV have been used to generate displacement cascades. The simulations quantify the extent of radiation damage during a simulated irradiation cycle using the Wigner-Seitz point defect identification technique. The generated point defects in crystals with and without pre-existing helium/hydrogen defects exhibit a power relationship with applied PKA energy. The point defects are classified by their atom type, defect type, and distribution within the irradiated model. The presence of pre-existing helium and hydrogen clusters significantly increases the defects (5 - 15 times versus pure tungsten models). The vacancy composition is primarily tungsten (e. g., ~70% at 2.5 keV) in models with pre-existing helium, but the interstitials are primarily He (e. g., ~89% at 10 keV). On the other hand, models with pre-existing hydrogen have a vacancy composition that is primarily tungsten (more than 90% irrespective of PKA energy), and the interstitial composition is more balanced between tungsten (average 46%) and hydrogen (average 54%) interstitials across the PKA range. The distribution of the atoms reveals that the tungsten point defects prefer to reside close to the position of cascade initiation, but helium or hydrogen defects reside close to the positions where clusters are built.

X-Ray Diffuse Scattering Investigation of Defects in Ion Implanted and Annealed Silicon

1998 ◽  
Vol 524 ◽  
Author(s):  
C. H. Chang ◽  
U. Beck ◽  
T. H. Metzger ◽  
J. R. Patel
Keyword(s):  
Ion Implantation ◽  
Point Defect ◽  
Point Defects ◽  
Diffuse Scattering ◽  
Grazing Incidence ◽  
X Rays ◽  
Scattered Intensity ◽  
X Ray ◽  
Defect Clusters ◽  
Point Defect Clusters

ABSTRACTTo characterize the point defects and point defect clusters introduced by ion implantation and annealing, we have used grazing incidence x-rays to measure the diffuse scattering in the tails of Bragg peaks (Huang Scattering). An analysis of the diffuse scattered intensity will allow us to characterize the nature of point defects or defect clusters introduced by ion implantation. We have also observed unexpected satellite peaks in the diffuse scattered tails. Possible causes for the occurrence of the peaks will be discussed.

scholarly journals Modeling of Point Defects Annihilation in Multilayered Cu/Nb Composites under Irradiation

2016 ◽  
Vol 2016 ◽  
pp. 1-17 ◽  
Author(s):  
Sarah Fadda ◽  
Antonio Mario Locci ◽  
Francesco Delogu
Keyword(s):  
Point Defect ◽  
Point Defects ◽  
Surface Recombination ◽  
Multilayer Composite ◽  
Balance Equations ◽  
General Validity ◽  
Defect Diffusion ◽  
Temperature Radiation ◽  
General Tool

This work focuses on a mathematical modeling of the response to irradiation of a multilayer composite material. Nonstationary balance equations are utilized to account for production, recombination, transport, and annihilation, or removal, of vacancies and interstitials at interfaces. Although the model developed has general validity, Cu/Nb multilayers are used as case study. Layer thickness, temperature, radiation intensity, and surface recombination coefficients were varied systematically to investigate their effect on point defect annihilation processes at interfaces. It is shown that point defect annihilation at interfaces mostly depends on point defect diffusion. The ability of interfaces to remove point defects can be described by a simple map constructed using only two dimensionless parameters, which provides a general tool to estimate the efficiency of vacancy and interstitial removal in multilayer composite materials.

Point Defect Injection Kinetics by N2O Oxidation of Silicon

1997 ◽  
Vol 469 ◽  
Author(s):  
C. Tsamis ◽  
D. N. Kouvatsos ◽  
D. Tsoukalas
Keyword(s):  
Point Defect ◽  
High Temperatures ◽  
Point Defects ◽  
Silicon Substrate ◽  
Oxidation Process ◽  
Stacking Faults ◽  
Defect Injection ◽  
Dry Oxidation ◽  
Kinetics Of

ABSTRACTThe influence of N2O oxidation of silicon on the kinetics of point defects at high temperatures is investigated. Oxidation Stacking Faults (OSF) are used to monitor the interstitials that are generated during the oxidation process. We show that at high temperatures (1050°-1150°C) the supersaturation of self-interstitials in the silicon substrate is enhanced when oxidation is performed in an N2O ambient compared to 100% dry oxidation. This behavior is attributed to the presence of nitrogen at the oxidizing interface. However, at lower temperatures this phenomenon is reversed and oxidation in N2O ambient leads to reduced supersaturation ratios.

Atomistic simulation for configuration evolution and energetic calculation of crack in body-centered-cubic iron

2006 ◽  
Vol 21 (10) ◽  
pp. 2542-2549 ◽  
Author(s):  
Li-Xia Cao ◽  
Chong-Yu Wang
Keyword(s):  
Low Temperatures ◽  
Crack Tip ◽  
Dislocation Nucleation ◽  
Effect Of Temperature ◽  
Body Centered Cubic ◽  
Partial Dislocations ◽  
Higher Temperature ◽  
Crack Blunting ◽  
Increasing Temperature ◽  
Extended Dislocation

The molecular dynamics method has been used to simulate mode I cracking in body-centered-cubic iron. Close attention has been paid to the process of the atomic configuration evolution of the cracks. The simulation shows that at low temperatures, partial dislocations are emitted before the initiation of crack propagation, subsequently forming the stacking faults or multilayer twins on {112} planes, and then brittle cleavage and extended dislocation nucleation are observed at the crack tip accompanied by twin extension. These results are in agreement with the experimental observation that twinning and fracture processes cooperate at low temperatures. Furthermore, an energetics analysis has been made on the deformation behavior observed at the crack tip. The effect of temperature on the fracture process is discussed. At the higher temperature, plastic deformation becomes easier, and crack blunting occurs. With increasing temperature, the fracture resistance increases, and the effect of the lattice trapping can be weakened by thermal activation.

Study of the Location of Implanted Fluorine Atoms in Silicon and Germanium through Their Nuclear Quadrupole Interactions

1996 ◽  
Vol 51 (5-6) ◽  
pp. 560-564 ◽  
Author(s):  
Stacie S. Nunes ◽  
S. Sulaiman ◽  
N. Sahoo ◽  
T. P. Das ◽  
M. Frank ◽  
...  
Keyword(s):  
Minimum Energy ◽  
Wave Functions ◽  
Dangling Bonds ◽  
Hyperfine Parameters ◽  
Frequency Signal ◽  
Crystalline Materials ◽  
Hartree Fock ◽  
Surface Sites ◽  
Nuclear Quadrupole ◽  
Silicon And Germanium

Abstract Time Differential Perturbed Angular Distribution (TDPAD) measurements of the nuclear quadrupole hyperfine parameters for 19F* implanted into amorphous, polycrystalline and crystalline silicon and germanium are reported and reviewed. Two signals are observed in the crystalline materials (≈ 35 and 23 MHz in silicon, ≈ 33 and 27 MHz in germanium) while only one is detected in the amorphous and polycrystalline samples (≈ 22 MHz in silicon, ≈ 27 in germanium). Impurity sites in these materials were modeled using a Hartree-Fock cluster procedure. The Intrabond, Antibond, and Substitutional sites in the bulk were studied in both silicon and germanium. The ATOP and Intrabond Surface sites were also studied in silicon and the results extended to germa-nium. Lattice relaxation effects were incorporated by employing a geometry optimization method to obtain minimum energy configurations for the clusters modelling each site. The electronic wave functions were obtained for each optimized cluster by applying Unresctricted Hartree-Fock theory, and these wave functions were used to calculate the nuclear quadrupole hyperfine parameters at the site of the fluorine nucleus. Comparison of the theoretical hyperfine parameters to the experimental values indicates that 19F* located in the Intrabond and Intrabond surface sites could readily explain the higher frequency signal that has been observed. 19F* in the Antibond and the surface ATOP sites yield hyperfine parameters consistent with the low frequency signal observed in the crystalline materials and the single signal observed in the amorphous (or polycrystalline) materials. Examina-tion of these two sites, in view of other available experimental evidence including the temperature dependence of the TDPAD signals, leads to the conclusion that the lower frequency signal is due to 19F* implants which have come to rest at the site of dangling bonds in the bulk. These dangling bonds are created as a result of damage generated in the individual collision cascades during the implantation process.

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