Atomistic Modeling of Amorphization in Silicon

ABSTRACTWe discuss atomistic simulations of ion implantation and annealing of Si over a wide range of ion dose and substrate temperatures. The DADOS Monte Carlo model has been extended to include the formation of amorphous regions, and this allows simulations of dopant diffusion at high doses. As the dose of ions increases, a continuous amorphous layer may be formed. In that case, most of the excess interstitials generated by the implantation may be swept to the surface as the amorphous layer regrows, instead of diffusing through the crystalline region. This process reduces the amount of transient enhanced diffusion during annealing. This model also reproduces the dynamic annealing during high temperature implants.

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Monte Carlo simulation of Boron diffusion during low energy implantation and high temperature annealing

MRS Proceedings ◽

10.1557/proc-469-335 ◽

1997 ◽

Vol 469 ◽

Cited By ~ 8

Author(s):

M.-J. Caturla ◽

T. Diaz de la Rubia ◽

J. Zhu ◽

M. Johnson

Keyword(s):

Monte Carlo ◽

High Temperature ◽

Kinetic Monte Carlo ◽

Monte Carlo Model ◽

Low Energy ◽

High Temperature Annealing ◽

Boron Diffusion ◽

Enhanced Diffusion ◽

Diffusion Enhancement ◽

High Doses

ABSTRACTWe use a kinetic Monte Carlo model to simulate the implantation of low energy Boron in Silicon, from 0.5 to 1 keV, at high doses, 1015 ions/cm2. The damage produced by each ion is calculated using UT-Marlowe, based on a binary collision approximation. During implantation at room temperature,, silicon self-interstitials, vacancies and boron interstitials are allowed to migrate and interact. The diffusion kinetics of these defects and dopants has been obtained by ab initio calculations as well as Stillinger Weber molecular dynamics. Clustering of both self-interstitials, vacancies and boron atoms is included. We also model the diffusion of the implanted dopants after a high temperature annealing in order to understand the transient enhanced diffusion (TED) phenomenon. We observe two different stages of TED During the first stage vacancies are present in the lattice together with interstitials and the diffusion enhancement is small. The second stage starts after all the vacancies disappear and gives rise to most of the final TED.

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Validation of a Monte Carlo model used for simulating tube current modulation in computed tomography over a wide range of phantom conditions/challenges

Medical Physics ◽

10.1118/1.4887807 ◽

2014 ◽

Vol 41 (11) ◽

pp. 112101 ◽

Cited By ~ 11

Author(s):

Maryam Bostani ◽

Kyle McMillan ◽

John J. DeMarco ◽

Chris H. Cagnon ◽

Michael F. McNitt-Gray

Keyword(s):

Computed Tomography ◽

Monte Carlo ◽

Monte Carlo Model ◽

Tube Current Modulation ◽

Current Modulation ◽

Tube Current ◽

Wide Range

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Linking ab initio Energetics to Experiment: Kinetic Monte Carlo Simulation of Transient Enhanced Diffusion of B in Si

MRS Proceedings ◽

10.1557/proc-538-291 ◽

1998 ◽

Vol 538 ◽

Cited By ~ 1

Author(s):

Silva K. Theiss ◽

M.-J. Caturla ◽

T. Diaz de la Rubia ◽

M.C. Johnson ◽

Ant Uralt ◽

...

Keyword(s):

Experimental Data ◽

Monte Carlo ◽

Ab Initio ◽

Time Scales ◽

First Principles ◽

Kinetic Monte Carlo ◽

Experimental Studies ◽

Enhanced Diffusion ◽

Transient Enhanced Diffusion ◽

Wide Range

AbstractWe have developed a kinetic Monte Carlo (kMC) simulator that links atomic migration and binding energies determined primarily from first principles calculations to macroscopic phenomena and laboratory time scales. Input for the kMC simulation is obtained from a combination of ab initio planewave pseudopotential calculations, molecular dynamics simulations, and experimental data. The simulator is validated against an extensive series of experimental studies of the diffusion of B spikes in self-implanted Si. The implant energy, dose, and dose rate, as well as the detailed thermal history of the sample, are included. Good agreement is obtained with the experimental data for temperatures between 750 and 950°C and times from 15 to 255 s. At 1050°C we predict too little diffusion after 105 s compared to experiment: apparently, some mechanism which is not adequately represented by our model becomes important at this temperature. Below 1050°C, the kMC simulation produces a complete description over macroscopic time scales of the atomic level diffusion and defect reaction phenomena that operate during the anneals. This simulator provides a practical method for predicting technologically interesting phenomena, such as transient enhanced diffusion of B, over a wide range of conditions, using energetics determined from first-principles approaches.

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Modelling FtsZ nucleation, hydrolysis and treadmilling activity with Monte Carlo methods

10.1101/2020.02.25.965095 ◽

2020 ◽

Author(s):

L. Corbin ◽

H.P. Erickson

Keyword(s):

Monte Carlo ◽

Kinetic Parameters ◽

Molecular Mechanisms ◽

Conformational Transition ◽

Average Length ◽

Monte Carlo Model ◽

Wide Range ◽

Ftsz Assembly

ABSTRACTBacterial cell division is tightly coupled to the dynamic behavior of FtsZ, a tubulin homolog. Recent experimental work in vitro and in vivo has attributed FtsZ’s assembly dynamics to treadmilling, where subunits add to the bottom and dissociate from the top of protofilaments. However, the molecular mechanisms producing treadmilling have yet to be characterized and quantified. We have developed a Monte Carlo model for FtsZ assembly that explains treadmilling and assembly nucleation by the same mechanisms. A key element of the model is a conformational change from R (relaxed), which is highly favored for monomers, to T (tense), which is favored for subunits in a protofilament. This model was created in MATLAB. Kinetic parameters were converted to probabilities of execution during single, small time steps, and these were used to stochastically determine FtsZ dynamics. Our model is able to accurately describe the results of several in vitro and in vivo studies for a variety of FtsZ flavors. With standard conditions, the model FtsZ polymerized and produced protofilaments that treadmilled at 28 nm/s, hydrolyzed GTP at 2.8 to 4.2 GTP min-1 FtsZ-1, and had an average length of 25 to 54 subunits, all similar to experimental results. Adding a bottom capper resulted in shorter protofilaments and higher GTPase, similar to the effect of the known the bottom capper protein MciZ. The model could match nucleation kinetics of several flavors of FtsZ using the same parameters as treadmilling and varying only the R to T transition of monomers.SIGNIFICANCEFtsZ assembly dynamics are now known to be governed by treadmilling, where subunits add to the bottom and dissociate from the top of protofilaments. We have generated a Monte Carlo model of treadmilling based on (a) a conformational transition of FtsZ subunits between two states, and (b) stochastic GTP hydrolysis. Importantly, the nucleation of new protofilaments is explained by the same mechanisms as treadmilling. We have determined kinetic parameters that match a wide range of experimental data. The model is available to users for their own in silico experiments.

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Atomistic Simulations of Damage Evolution in Silicon

MRS Proceedings ◽

10.1557/proc-568-135 ◽

1999 ◽

Vol 568 ◽

Cited By ~ 2

Author(s):

Marius M. Buneat ◽

Pavel Fastenko ◽

Scott T. Dunham

Keyword(s):

Molecular Dynamics ◽

Monte Carlo ◽

Long Range ◽

Tight Binding ◽

Atomistic Simulations ◽

Spatial Correlations ◽

Range Interaction ◽

Lattice Monte Carlo ◽

Long Range Interactions ◽

High Doses

ABSTRACTWe have studied the damage annealing process using kinetic lattice Monte Carlo (KLMC) and molecular dynamics (MD) with initial damage distribution from Monte Carlo ion implant simulations. MD calculations find a long range interstitial vacancy interaction, as also seen in previous tight-binding molecular dynamics (TBMD) simulations.1 The influence of the long range interaction as well as the initial spatial correlations present in the implant damage are then analyzed with KLMC in the form of corrections to the +1 model. We find that both long range interactions and the initial spatial correlations are significant at low doses, while the effects disappear at high doses.

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A COMBINED P1 AND MONTE CARLO MODEL FOR MULTIDIMENSIONAL RADIATIVE TRANSFER PROBLEMS IN SCATTERING MEDIA

Computational Thermal Sciences An International Journal ◽

10.1615/computthermalscien.v2.i6.60 ◽

2010 ◽

Vol 2 (6) ◽

pp. 549-560 ◽

Cited By ~ 10

Author(s):

Wojciech Lipinski ◽

Leonid A. Dombrovsky

Keyword(s):

Monte Carlo ◽

Radiative Transfer ◽

Monte Carlo Model ◽

Scattering Media ◽

Transfer Problems

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Monte Carlo calculation of the energy parameters and spatial distribution of the cathodic arc ions while passing through the macro-particles filters

International Journal of Computational Physics Series ◽

10.29167/a1i1p30-34 ◽

2018 ◽

Vol 1 (1) ◽

pp. 30-34 ◽

Cited By ~ 2

Author(s):

Alexey Chernogor ◽

Igor Blinkov ◽

Alexey Volkhonskiy

Keyword(s):

Magnetic Field ◽

Mass Transfer ◽

Monte Carlo ◽

Monte Carlo Calculation ◽

Inhomogeneous Magnetic Field ◽

Flow Energy ◽

Wide Range ◽

Field Concentrator ◽

Cathodic Arc ◽

The Magnetic Field

The flow, energy distribution and concentrations profiles of Ti ions in cathodic arc are studied by test particle Monte Carlo simulations with considering the mass transfer through the macro-particles filters with inhomogeneous magnetic field. The loss of ions due to their deposition on filter walls was calculated as a function of electric current and number of turns in the coil. The magnetic field concentrator that arises in the bending region of the filters leads to increase the loss of the ions component of cathodic arc. The ions loss up to 80 % of their energy resulted by the paired elastic collisions which correspond to the experimental results. The ion fluxes arriving at the surface of the substrates during planetary rotating of them opposite the evaporators mounted to each other at an angle of 120° characterized by the wide range of mutual overlapping.

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