Ab Initio Pseudopotential Calculations of Carbon Impurities in SI

1996 ◽  
Vol 438 ◽  
Author(s):  
Jing Zhu ◽  
T. Diaz De La Rubia ◽  
Christian Mailhiot
Keyword(s):  
Binding Energy ◽  
Ab Initio ◽  
Crystalline Silicon ◽  
Carbon Diffusion ◽  
Migration Energy ◽  
Interstitial Carbon ◽  
Enhanced Diffusion ◽  
Carbon Impurities ◽  
Pseudopotential Calculations ◽  
Large Binding Energy

AbstractAb initio planewave pseudopotential method is used to study carbon diffusion and pairing in crystalline silicon. The calculation is performed with a 40 Ry planewave cutoff and 2×2×2 special k-point sampling with a supercell of 64 atoms. It is found that substitutional carbon attracts interstitial Si forming a <001> C interstitial with a large binding energy of 1.45 eV. The interstitial carbon is mobile and can migrate with a migration energy of 0.5 eV. The interstitial carbon can bind further to another substitutional carbon forming a substitutional carbon-interstitutional carbon pair with a binding energy of 1.0 eV. This model is used to understand the effect of high C concentration on the transient enhanced diffusion in Si.

Ab Initio Pseudopotential Calculations of Carbon Impurities In SI

1996 ◽  
Vol 439 ◽  
Author(s):  
Jing Zhu ◽  
T. Diaz De La Rubia ◽  
Christian Mailhiot
Keyword(s):  
Binding Energy ◽  
Ab Initio ◽  
Crystalline Silicon ◽  
Carbon Diffusion ◽  
Migration Energy ◽  
Interstitial Carbon ◽  
Enhanced Diffusion ◽  
Carbon Impurities ◽  
Pseudopotential Calculations ◽  
Large Binding Energy

AbstractAb initio planewave pseudopotential method is used to study carbon diffusion and pairing in crystalline silicon. The calculation is performed with a 40 Ry planewave cutoff and 2×2×2 special k-point sampling with a supercell of 64 atoms. It is found that substitutional carbon attracts interstitial Si forming a <001> C interstitial with a large binding energy of 1.45 eV. The interstitial carbon is mobile and can migrate with a migration energy of 0.5 eV. The interstitial carbon can bind further to another substitutional carbon forming a substitutional carbon-interstitutional carbon pair with a binding energy of 1.0 eV. This model is used to understand the effect of high C concentration on the transient enhanced diffusion in Si.

AB Initio Pseudopotential Calculations of Dopant Diffusion in SI

1997 ◽  
Vol 469 ◽  
Author(s):  
Jing Zhu
Keyword(s):  
Ab Initio ◽  
Degrees Of Freedom ◽  
Quantitative Description ◽  
Carbon Diffusion ◽  
Boron Diffusion ◽  
Electron Charge Density ◽  
Numerical Convergence ◽  
Enhanced Diffusion ◽  
Pseudopotential Calculations ◽  
Consistent Treatment

ABSTRACTThe ab initio pseudopotential method is used to study transient-enhanced-diffusion (TED) related processes. The electronic degrees of freedom are included explicitly, together with the fully self-consistent treatment of the electron charge density. A large supercell and a fine k-point mesh are used to ensure numerical convergence. Such method has been demonstrated to give quantitative description of defect energetics. We will show that boron diffusion is significantly enhanced in the presence of the Si interstitial due to the substantial lowering of the migrational barrier through a kick-out mechanism. The resulting mobile boron can also be trapped by another substitutional boron, forming an immobile and electrically inactive two-boron pair. Similarly, carbon diffusion is also enhanced significantly due to the pairing with Si interstitiels. However, carbon binds to Si interstitials much more strongly than boron does, taking away most Si interstitials from boron at sufficiently large carbon concentration, which causes the suppression of the boron TED. We will also show that Fermi level effect plays an important role in both Si intersititial and boron diffusion.

Influence of Carbon on the Diffusion of Interstitials and Boron in Silicon

2000 ◽  
Vol 610 ◽  
Author(s):  
Mark E. Law ◽  
Michelle D. Griglione ◽  
Misty Northridge
Keyword(s):  
Binding Energy ◽  
Carbon Atom ◽  
Ab Initio ◽  
Point Defects ◽  
Initial Conditions ◽  
Carbon Diffusion ◽  
Reaction Rates ◽  
Interstitial Diffusion ◽  
Enhanced Diffusion ◽  
Transient Enhanced Diffusion

AbstractCarbon is a native impurity in Si which is known to trap self-interstitials and decrease their diffusivity. Carbon has also been observed to decrease B transient enhanced diffusion (TED) in Si through these interstitial interactions. Recently it has been proposed that vacancies must also be considered when accounting for the reduction of B TED. We have incorporated both the kick-out mechanism and the Frank-Turnbull (F-T) mechanism in simulations of interstitial diffusion and carbon diffusion, as well as experiments involving B diffusion in B doped superlattices (DSLs) with varying C concentration regions. We have used the binding energy between a carbon atom and a self-interstitial as a basis for the reaction rates for both mechanisms, and have found that an single energy of 2.25 eV best reproduces the results from several experiments, assuming equilibrium initial conditions for both mechanisms and ab-initio equilibrium values for all point defects.

Interactions of Indium, Arsenic and Carbon in Silicon Using the Pseudopotential Technique

2004 ◽  
Vol 810 ◽  
Author(s):  
M. Shishkin ◽  
A. Yan ◽  
M. M. De Souza
Keyword(s):  
Binding Energy ◽  
Ab Initio ◽  
Carbon Diffusion ◽  
The Self ◽  
The Other ◽  
Interstitial Diffusion ◽  
Strong Binding ◽  
Carbon Interstitial ◽  
Indium Diffusion

ABSTRACTFactors limiting the activation of indium in silicon are examined via the ab initio pseudopotential technique. The role of carbon in the enhancement/retardation of activation/diffusion respectively is clarified. It is found that (1) adjacent substitutional indium atoms are deactivated. Only second neighbour sites of indium are activated unlike the case of boron, where all substitutional sites remain activated. (2) Silicon self-interstitials deactivate indium by trapping them on substitutional sites. Carbon, on the other hand, traps such self- interstitials with higher binding energy and prevents them from deactivating indium. (3) Since both indium and carbon diffusion is interstitial mediated, carbon reduces indium diffusion on account of its higher binding energy with the self-interstitial. Moreover, the release of the carbon interstitial is more favourable than the release of the indium interstitial from a carbon-indium pair. Therefore, carbon minimises indium interstitial diffusion. (4) Arsenic enhances de- activation of indium by neutralisation and by strong binding on adjacent substitutional sites. Furthermore since the release of the indium interstitial is more favourable in comparison to the release of the arsenic interstitial from the indium-arsenic pair, indium diffusion is enhanced in the presence of arsenic.

Role of Interstitials in As TED and Clustering in Crystalline Silicon

2005 ◽  
Vol 864 ◽  
Author(s):  
Scott A. Harrison ◽  
Thomas F. Edgar ◽  
Gyeong S. Hwang
Keyword(s):  
Binding Energy ◽  
Density Functional ◽  
Crystalline Silicon ◽  
Experimental Studies ◽  
Diffusion Activation Energy ◽  
Structure Stability ◽  
Energy Structure ◽  
Generalized Gradient ◽  
Enhanced Diffusion ◽  
Transient Enhanced Diffusion

AbstractIn recent years, experimental studies [1-3] have suggested that Si interstitials may play a role in facilitating As transient enhanced diffusion during pn junction formation in silicon. These studies contradict conventional models that assume vacancy-mediated As diffusion. Using density functional theory calculations within the generalized gradient approximation, we have examined the structure, stability, and diffusion of the neutral As-Sii pair. We find the lowest energy structure is comprised of an As and Sii atom pair that is aligned in the [110] direction while sharing a lattice site. We have calculated the binding energy as well as diffusion pathways and barriers for the neutral As-Sii pair. Our results suggest that the neutral As-Sii pair has a binding energy relative to neutral Sii and neutral As of 0.63 eV. We also find an overall diffusion activation energy of 3.3 eV, which is similar to experimental observations for As diffusion and preVious calculations for As-vacancy complex diffusion. These results clearly support that interstitials can contribute significantly to As transient enhanced diffusion, especially in regions where interstitials exist in excess. In addition, interstitial-mediated arsenic diffusion suggests that interstitials may also play a role in arsenic agglomeration.

Ab initio Study of Metal Atoms on SWNT Surface

2001 ◽  
Vol 675 ◽  
Author(s):  
Shu Peng ◽  
Kyeongjae Cho
Keyword(s):  
Carbon Nanotube ◽  
Binding Energy ◽  
Ab Initio ◽  
Diffusion Barrier ◽  
First Principles ◽  
Ab Initio Study ◽  
Single Walled Carbon Nanotube ◽  
Metal Atoms ◽  
Pseudopotential Calculations ◽  
And Diffusion

ABSTRACTInteractions of metal atoms (Al, Ti) with semiconducting single walled carbon nanotube (SWNT) are investigated using first-principles pseudopotential calculations. Six different adsorption configurations for aluminum and titanium atoms are studied. Comparison of the energetics of these metal atoms on (8,0) SWNT surface shows significant differences in binding energy and diffusion barrier. These differences give an insight to explain why most of metal atoms (such as Al) form discrete particles on nanotube while continuous nanowires are obtained by using titanium in the experiment.

Ab-Initio Pseudopotential Calculations of Boron Diffusion in Silicon

1999 ◽  
Vol 568 ◽  
Author(s):  
W. Windl ◽  
M. M. Bunea ◽  
R. Stumpf ◽  
S. T. Dunham ◽  
M. P. Masquelier
Keyword(s):  
Fermi Level ◽  
Ab Initio ◽  
Diffusion Length ◽  
Crystalline Silicon ◽  
Boron Diffusion ◽  
Elastic Band ◽  
Pseudopotential Calculations ◽  
Band Method ◽  
Diffusion Paths ◽  
And Diffusion

ABSTRACTIn this work we investigate boron diffusion as a function of the Fermi-level position in crystalline silicon using ab-initio calculations and the nudged elastic band method to optimize diffusion paths. Based on our results, a new mechanism for B diffusion mediated by Si self-interstitials is proposed. We find a two-step diffusion process for all Fermi-level positions, which suggests a kick-out with a directly following kick-in process without extensive B diffusion on interstitial sites in-between. Our activation energy of 3.47 – 3.75 eV and diffusion-length exponent of -0.55 to -0.18 eV are in excellent agreement with experiment.

Ab initio band theory approach to electron energy loss near edge structures

1988 ◽  
Vol 46 ◽  
pp. 506-507
Author(s):  
Xudong Weng ◽  
O.F. Sankey ◽  
Peter Rez
Keyword(s):  
Ab Initio ◽  
Local Density ◽  
Interpolation Method ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Large Set ◽  
Theory Approach ◽  
Band Theory ◽  
Atomic Orbitals ◽  
Pseudopotential Calculations

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.

Structure and Stability of Grain Boundaries in Molybdenum with Segregated Carbon Impurities

1999 ◽  
Vol 578 ◽  
Author(s):  
R. Janisch ◽  
T. Ochs ◽  
A. Merkle ◽  
C. Elsässer
Keyword(s):  
Ab Initio ◽  
Grain Boundaries ◽  
Density Functional ◽  
Local Density ◽  
Structural Parameters ◽  
Carbide Phases ◽  
Carbon Impurities ◽  
Transmission Electron ◽  
Local Density Functional Theory ◽  
Symmetrical Tilt

AbstractThe segregation of interstitial impurities to symmetrical tilt grain boundaries (STGB) in bodycentered cubic transition metals is studied by means of ab-initio electronic-structure calculations based on the local density functional theory (LDFT). Segregation energies as well as changes in atomic and electronic structures at the ΣE5 (310) [001] STGB in Mo caused by segregated interstitial C atoms are investigated. The results are compared to LDFT data obtained previously for the pure Σ5 (310) [001] STGB in Mo. Energetic stabilities and structural parameters calculated ab initio for several crystalline Molybdenum Carbide phases with cubic, tetragonal or hexagonal symmetries and different compositions, MoCx, are reported and compared to recent high-resolution transmission electron microscopy (HRTEM) observations of MoCx, intergranular films and precipitates formed by C segregation to a Σ5 (310) [001] STGB in a Mo bicrystal.

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