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.

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.

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.

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.

Quantum simulations

2017 ◽  
Author(s):  
Michael P. Allen ◽  
Dominic J. Tildesley
Keyword(s):  
Ab Initio ◽  
Quantum Monte Carlo ◽  
Degrees Of Freedom ◽  
Small Region ◽  
Time Correlation ◽  
Ab Initio Molecular Dynamics ◽  
Classical Dynamics ◽  
Integral Methods ◽  
Quantum Time ◽  
Low Mass

This chapter covers the introduction of quantum mechanics into computer simulation methods. The chapter begins by explaining how electronic degrees of freedom may be handled in an ab initio fashion and how the resulting forces are included in the classical dynamics of the nuclei. The technique for combining the ab initio molecular dynamics of a small region, with classical dynamics or molecular mechanics applied to the surrounding environment, is explained. There is a section on handling quantum degrees of freedom, such as low-mass nuclei, by discretized path integral methods, complete with practical code examples. The problem of calculating quantum time correlation functions is addressed. Ground-state quantum Monte Carlo methods are explained, and the chapter concludes with a forward look to the future development of such techniques particularly to systems that include excited electronic states.

scholarly journals Self- and Dopant Diffusion in Extrinsic Boron Doped Isotopically Controlled Silicon Multilayer Structures

2002 ◽  
Vol 719 ◽  
Author(s):  
Ian D. Sharp ◽  
Hartmut A. Bracht ◽  
Hughes H. Silvestri ◽  
Samuel P. Nicols ◽  
Jeffrey W. Beeman ◽  
...  
Keyword(s):  
Multilayer Structure ◽  
Secondary Ion Mass Spectrometry ◽  
Diffusion Processes ◽  
Quantitative Description ◽  
Multilayer Structures ◽  
Dopant Diffusion ◽  
Enhanced Diffusion ◽  
Self Diffusion ◽  
Boron Doped ◽  
P Type

AbstractIsotopically controlled silicon multilayer structures were used to measure the enhancement of self- and dopant diffusion in extrinsic boron doped silicon. 30Si was used as a tracer through a multilayer structure of alternating natural Si and enriched 28Si layers. Low energy, high resolution secondary ion mass spectrometry (SIMS) allowed for simultaneous measurement of self- and dopant diffusion profiles of samples annealed at temperatures between 850°C and 1100°C. A specially designed ion-implanted amorphous Si surface layer was used as a dopant source to suppress excess defects in the multilayer structure, thereby eliminating transient enhanced diffusion (TED) behavior. Self- and dopant diffusion coefficients, diffusion mechanisms, and native defect charge states were determined from computer-aided modeling, based on differential equations describing the diffusion processes. We present a quantitative description of B diffusion enhanced self-diffusion in silicon and conclude that the diffusion of both B and Si is mainly mediated by neutral and singly positively charged self-interstitials under p-type doping. No significant contribution of vacancies to either B or Si diffusion is observed.

Ab-Initio Calculation for Boron Diffusion in Si/SiGe Strained Layers

2007 ◽  
Vol 51 (96) ◽  
pp. 270
Author(s):  
Young-Kyu KIM ◽  
Kwan-Sun YOON ◽  
Joong-Sik KIM ◽  
Han-Geon KIM ◽  
Taeyoung WON
Keyword(s):  
Ab Initio ◽  
Ab Initio Calculation ◽  
Boron Diffusion ◽  
Strained Layers

Higher-Order Plate Elements for Large Deformation Analysis in Multibody Applications

2016 ◽  
Author(s):  
Henrik Ebel ◽  
Marko K. Matikainen ◽  
Vesa-Ville Hurskainen ◽  
Aki Mikkola
Keyword(s):  
Large Deformation ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Higher Order ◽  
Deformation Analysis ◽  
Numerical Convergence ◽  
Plate Elements ◽  
Negative Effect ◽  
Numerical Performance ◽  
Locking Phenomena

This study introduces higher-order three-dimensional plate elements based on the absolute nodal coordinate formulation (ANCF) for large deformation multibody applications. The introduced elements employ four to eight nodes and the St. Venant-Kirchhoff material law. A newly proposed eight-node element is carefully verified using various numerical experiments intended to discover possible locking phenomena. In the introduced plate elements, the usage of polynomial approximations of second order in all three directions is found to be advantageous in terms of numerical performance. A comparison of the proposed eight-node element to the introduced four-node higher-order plate elements reveals that the usage of in-plane slopes as nodal degrees of freedom has a negative effect on numerical convergence properties in thin-plate use-cases.

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