Atomistic Simulations of Epitaxial Regrowth of As-doped Silicon

2008 ◽  
Vol 1070 ◽  
Author(s):  
Joo Chul Yoon ◽  
Scott Dunham
Keyword(s):  
Crystalline Silicon ◽  
Solid Phase ◽  
Nearest Neighbors ◽  
Surface Region ◽  
Md Simulations ◽  
Atomistic Simulations ◽  
Dual Function ◽  
Crystalline Region ◽  
Kinetics Of ◽  
Si Ion Implantation

ABSTRACTWe conducted molecular dynamics (MD) simulations of solid phase epitaxial growth of As-doped Si using a Tersoff potential characterized via comparison to DFT calculations, including energies of AsnV clusters. The Si:As systems were initialized by amorphizing the surface region of crystalline silicon via Si ion implantation and/or selective melting. The remaining crystalline region provides dual function of controlling temperature in system without perturbing regrowth and providing seed for recrystallization. After recrystallization, isolated As atoms occupy substitutional sites, with the average number of nearest neighbors for As changing from about 3.3 in amorphous Si to 4 after crystallization. We observe V incorporation associated with high As concentrations. A small fraction of isolated As atoms have associated vacancies, while vacancies are incorporated in the majority of cases in which there are sites with two As neighbors. These observations are consistent with our previous model developed to explain kinetics of As shallow junction formation which assumed V incorporation at sites with 2 or more As nearest neighbors to account for experimental data.

Amorphisation, Crystallisation And Related Phenomena In Silicon

1985 ◽  
Vol 51 ◽  
Author(s):  
J.S. Williams
Keyword(s):  
Epitaxial Growth ◽  
Crystalline Silicon ◽  
Solid Phase ◽  
Ion Beam ◽  
Ion Bombardment ◽  
Heavy Ion ◽  
Impurity Effects ◽  
Surface Layers ◽  
Random Nucleation ◽  
Kinetics Of

ABSTRACTThis review examines recently observed phenomena associated with amorphisation and crystallisation of silicon under ion bombardment and furnace annealing. Ideally, heavy ion damage should completely amorphise the silicon surface layers so that the underlying crystal can provide a perfect template for subsequent epitaxial growth. However, in practise the ion bombardment and annealing behaviour can be decidedly more complex. During ion bombardment of silicon, several correlated processes can take place depending on the target temperature and the precise bombardment conditions. These processes include: defect production; amorphisation; diffusion and segregation of defects and impurities; and ion-beam-induced (epitaxial) crystallisation. During subsequent heat treatment, amorphous layers can exhibit anomalous impurity diffusion and precipitation effects, nucleation of random crystallites, and solid phase epitaxial growth. In addition, the kinetics of the epitaxial growth process are sensitive to the type and state of implanted impurities present in the silicon. The competition between random nucleation and epitaxy is also dominated by impurity effects. Finally, correlations between all of these phenomena provide i) considerable insight into impurity and defect behaviour in amorphous and crystalline silicon, and ii) a better understanding of the amorphous to crystalline phase transition, including mechanisms of solid phase epitaxial growth.

scholarly journals Cyclic Photoisomerization of Azobenzene in Atomistic Simulations: Modeling the Effect of Light on Columnar Aggregates of Azo Stars

Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7674
Author(s):  
Markus Koch ◽  
Marina Saphiannikova ◽  
Olga Guskova
Keyword(s):  
Molecular Mechanisms ◽  
Driving Forces ◽  
Computational Study ◽  
Morphological Changes ◽  
Md Simulations ◽  
Atomistic Simulations ◽  
Experimental Works ◽  
New Interpretation ◽  
Kinetics Of ◽  
Supramolecular Aggregates

This computational study investigates the influence of light on supramolecular aggregates of three-arm azobenzene stars. Every star contains three azobenzene (azo) moieties, each able to undergo reversible photoisomerization. In solution, the azo stars build column-shaped supramolecular aggregates. Previous experimental works report severe morphological changes of these aggregates under UV–Vis light. However, the underlying molecular mechanisms are still debated. Here we aim to elucidate how light affects the structure and stability of the columnar stacks on the molecular scale. The system is investigated using fully atomistic molecular dynamics (MD) simulations. To implement the effects of light, we first developed a stochastic model of the cyclic photoisomerization of azobenzene. This model reproduces the collective photoisomerization kinetics of the azo stars in good agreement with theory and previous experiments. We then apply light of various intensities and wavelengths on an equilibrated columnar stack of azo stars in water. The simulations indicate that the aggregate does not break into separate fragments upon light irradiation. Instead, the stack develops defects in the form of molecular shifts and reorientations and, as a result, it eventually loses its columnar shape. The mechanism and driving forces behind this order–disorder structural transition are clarified based on the simulations. In the end, we provide a new interpretation of the experimentally observed morphological changes.

Thermodynamics and Kinetics of Melting and Growth of Crystalline Silicon Clusters

1998 ◽  
Vol 536 ◽  
Author(s):  
P. Keblinski
Keyword(s):  
Melting Temperature ◽  
Cluster Size ◽  
Crystalline Silicon ◽  
Md Simulations ◽  
Silicon Clusters ◽  
Homoepitaxial Growth ◽  
Thermodynamics And Kinetics ◽  
Three Body ◽  
Body Potential ◽  
Kinetics Of

AbstractMolecular-dynamics (MD) simulations and the Stillinger-Weber three-body potential are used to study the growth and stability of silicon clusters of diameters from 2 to 5 nm embedded in the melt. Our simulations show that the melting temperature of such nano-clusters is lower than the bulk melting temperature by an amount proportional to the inverse of the cluster size. We also show that the nature of the kinetics of such small Si clusters is essentially the same as that of the homoepitaxial growth. In particular, we show that the mobility of the highly-curved crystalliquid interface is controlled by diffusion in the adjacent melt, and is characterized by the same activation energy.

scholarly journals Ion Implantation and Annealing of SrTiO3 and CaTiO3

1987 ◽  
Vol 93 ◽  
Author(s):  
C. W. White ◽  
L. A. Boatner ◽  
J. Rankin ◽  
M. J. Aziz
Keyword(s):  
Ion Implantation ◽  
Solid Phase ◽  
Surface Region ◽  
Single Crystal Substrate ◽  
Recrystallization Process ◽  
Near Surface ◽  
Ion Channeling ◽  
Implantation Damage ◽  
Crystal Substrate ◽  
Kinetics Of

ABSTRACTIon implantation damage and thermal annealing results are presented for single crystals of SrTiO3 and CaTiO3. The near-surface region of both of these materials can be made amorphous by low doses (∼1015/cm2 ) of heavy ions (Pb at 540 keV). During annealing, the amorphous implanted region crystallizes epitaxially on the underlying single-crystal substrate. The kinetics of this solid-phase epitaxial recrystallization process have been measured by employing ion channeling techniques.

Formation of Nanocrystalline Silicon in Tin-Doped Amorphous Silicon Films

2020 ◽  
Vol 65 (3) ◽  
pp. 236
Author(s):  
R. M. Rudenko ◽  
O. O. Voitsihovska ◽  
V. V. Voitovych ◽  
M. M. Kras’ko ◽  
A. G. Kolosyuk ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Crystalline Silicon ◽  
Solid Phase ◽  
Nanocrystalline Silicon ◽  
Recrystallization Temperature ◽  
Nanocrystalline Phase ◽  
Silicon Phase ◽  
Silicon Nanocrystallites ◽  
Lower Temperature ◽  
Two Stages

The process of crystalline silicon phase formation in tin-doped amorphous silicon (a-SiSn) films has been studied. The inclusions of metallic tin are shown to play a key role in the crystallization of researched a-SiSn specimens with Sn contents of 1–10 at% at temperatures of 300–500 ∘C. The crystallization process can conditionally be divided into two stages. At the first stage, the formation of metallic tin inclusions occurs in the bulk of as-precipitated films owing to the diffusion of tin atoms in the amorphous silicon matrix. At the second stage, the formation of the nanocrystalline phase of silicon occurs as a result of the motion of silicon atoms from the amorphous phase to the crystalline one through the formed metallic tin inclusions. The presence of the latter ensures the formation of silicon crystallites at a much lower temperature than the solid-phase recrystallization temperature (about 750 ∘C). A possibility for a relation to exist between the sizes of growing silicon nanocrystallites and metallic tin inclusions favoring the formation of nanocrystallites has been analyzed.

scholarly journals Thermodynamics and kinetics of the amyloid-β peptide revealed by Markov state models based on MD data in agreement with experiment

2021 ◽  
Author(s):  
Arghadwip Paul ◽  
Suman Samantray ◽  
Marco Anteghini ◽  
Mohammed Khaled ◽  
Birgit Strodel
Keyword(s):  
Amyloid Β ◽  
Md Simulations ◽  
Amyloid Β Peptide ◽  
Intrinsically Disordered ◽  
Thermodynamics And Kinetics ◽  
Markov State ◽  
Markov State Models ◽  
State Models ◽  
Kinetics Of

The convergence of MD simulations is tested using varying measures for the intrinsically disordered amyloid-β peptide (Aβ). Markov state models show that 20–30 μs of MD is needed to reliably reproduce the thermodynamics and kinetics of Aβ.

scholarly journals A Study of the Impact of Graphite on the Kinetics of SPS in Nano- and Submicron WC-10%Co Powder Compositions

Ceramics ◽  
2021 ◽  
Vol 4 (2) ◽  
pp. 331-363
Author(s):  
Eugeniy Lantcev ◽  
Aleksey Nokhrin ◽  
Nataliya Malekhonova ◽  
Maksim Boldin ◽  
Vladimir Chuvil'deev ◽  
...  
Keyword(s):  
Activation Energy ◽  
Solid Phase ◽  
Continuous Heating ◽  
Diffusion Creep ◽  
Hard Alloys ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
The Impact ◽  
Kinetics Of

This study investigates the impact of carbon on the kinetics of the spark plasma sintering (SPS) of nano- and submicron powders WC-10wt.%Co. Carbon, in the form of graphite, was introduced into powders by mixing. The activation energy of solid-phase sintering was determined for the conditions of isothermal and continuous heating. It has been demonstrated that increasing the carbon content leads to a decrease in the fraction of η-phase particles and a shift of the shrinkage curve towards lower heating temperatures. It has been established that increasing the graphite content in nano- and submicron powders has no significant effect on the SPS activation energy for “mid-range” heating temperatures, QS(I). The value of QS(I) is close to the activation energy of grain-boundary diffusion in cobalt. It has been demonstrated that increasing the content of graphite leads to a significant decrease in the SPS activation energy, QS(II), for “higher-range” heating temperatures due to lower concentration of tungsten atoms in cobalt-based γ-phase. It has been established that the sintering kinetics of fine-grained WC-Co hard alloys is limited by the intensity of diffusion creep of cobalt (Coble creep).

Effect of maturity of Napier grass (Pennisetum purpureum) hay on intake, digestibility, and rumen dynamics when given to zebu bulls

2000 ◽  
Vol 2000 ◽  
pp. 144-144
Author(s):  
A.J. Ayala-Burgos ◽  
F.D.DeB. Hovell ◽  
R.M. Godoy ◽  
Hamana S. Saidén ◽  
R. López ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Solid Phase ◽  
Napier Grass ◽  
Pennisetum Purpureum ◽  
Ad Libitum ◽  
The Tropics ◽  
Kinetics Of

Cattle in the tropics mostly depend on pastures. During dry periods the forage available is usually mature, constraining both intake and digestion. These constraints need to be understood, for intake and digestibility define productivity. Intake depends on the rumen space made available by fermentation and outflow. Markers such as PEG (liquid phase), and chromium mordanted fibre (solid phase) can be used to measure rumen volume and outflow, but have limitations. The objective of this experiment was to measure intake, digestibility, and rumen kinetics of cattle fed ad libitum forages with very different degradation characteristics, and also to compare rumen volumes measured with markers with those obtained by manual emptying.

Kinetics of silicon nitride crystallization in N+-implanted silicon

1989 ◽  
Vol 4 (2) ◽  
pp. 394-398 ◽  
Author(s):  
V. S. Kaushik ◽  
A. K. Datye ◽  
D. L. Kendall ◽  
B. Martinez-Tovar ◽  
D. S. Simons ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Amorphous Silicon ◽  
Crystalline Silicon ◽  
Wafer Surface ◽  
Amorphous Silicon Nitride ◽  
Silicon Lattice ◽  
Nitrogen Ions ◽  
The Mean ◽  
Nitride Layers ◽  
Kinetics Of

Implantation of nitrogen at 150 KeV and a dose of 1 ⊠ 1018/cm2 into (110) silicon results in the formation of an amorphized layer at the mean ion range, and a deeper tail of nitrogen ions. Annealing studies show that the amorphized layer recrystallizes into a continuous polycrystalline Si3N4 layer after annealing for 1 h at 1200 °C. In contrast, the deeper nitrogen fraction forms discrete precipitates (located 1μm below the wafer surface) in less than 1 min at this temperature. The arcal density of these precipitates is 5 ⊠ 107/cm2 compared with a nuclei density of 1.6 ⊠ 105/cm2 in the amorphized layer at comparable annealing times. These data suggest that the nucleation step limits the recrystallization rate of amorphous silicon nitride to form continuous buried nitride layers. The nitrogen located within the damaged crystalline silicon lattice precipitates very rapidly, yielding semicoherent crystallites of β–Si3N4.

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