Investigation of helium interstitials aggregation in silicon: Why bubbles formation by a self-trapping mechanism does not work

Pizzagalli, Laurent; David, Marie‐Laure; Charaf-Eddin, Azzam

doi:10.1016/j.nimb.2014.12.002

Cited by 8 publications

(9 citation statements)

References 20 publications

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“…Second, the expansion of V n He p clusters is accompanied by a decrease of their number, in agreement with the intended growth behaviour. At last, it is noteworthy that pure helium aggregates are not found, as expected [25].…”

Section: A Typical Scenariosupporting

confidence: 74%

Influence of helium on the nucleation and growth of bubbles in silicon: a multiscale modelling study

Pizzagalli¹,

Dérès²,

David³

et al. 2019

J. Phys. D: Appl. Phys.

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The formation and growth of helium-filled cavities in silicon have been investigated using both molecular dynamics simulations and rate equation cluster dynamics calculations. This multiscale approach allowed us to identify atomic scale mechanisms involved in nucleation and early growth steps, and to follow their dynamics over experimental timescales. We especially focus our analyses on the influence of helium. Our results first suggest that both Ostwald ripening and migration-coalescence mechanisms are jointly activated during bubble growth. We also discover that an original mechanism, based on the splitting of bubbles, could have a significant contribution. Overall, helium atoms are found to delay growth, proportionally to their concentration. This can be clearly observed at the nanosecond timescale. However, for longer timescales, cluster dynamics calculations also reveal periods of accelerated growth for specific helium concentrations. Finally, it is determined that the main effect of Si interstitials is to impede bubble growth, due to an early recombination with vacancies.

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Section: A Typical Scenariosupporting

confidence: 74%

Influence of helium on the nucleation and growth of bubbles in silicon: a multiscale modelling study

Pizzagalli¹,

Dérès²,

David³

et al. 2019

J. Phys. D: Appl. Phys.

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“…Concerning the He-He MEAM parametrization, the attractive part was fitted on the Tang and Toennies potential [62], while the repulsive one was fitted on first-principles calculations [51]. Preliminary calculations using the potential showed that it predicts no clustering of helium interstitials in silicon, in accordance with first-principles calculations [63].…”

Section: Simulation Detailsmentioning

confidence: 73%

“…Note that this is not an unrealistic hypothesis because not all implanted helium atoms are necessarily located inside the bubbles. Here we consider single interstitial helium atoms, since it has recently been shown that helium clustering is not favored in silicon [63]. To estimate this effect on the final density, we investigated a d 0 = 6.5 nm bubble in a (9.8 nm) 3 supercell in order to include an interaction between bubbles.…”

Section: Influence Of Interstitial Atomsmentioning

confidence: 99%

Properties of helium bubbles in covalent systems at the nanoscale: A combined numerical and experimental study

Dérès¹,

David²,

Alix³

et al. 2017

Phys. Rev. B

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The properties of nanometric-sized helium bubbles in silicon have been investigated using both spatially resolved electron-energy-loss spectroscopy combined with a recently developed method, and molecular-dynamics simulations. The experiments allowed for an accurate determination of size, aspect ratio, and helium density for a large number of single bubbles, whose diameters ranged from 6 to 20 nm. Very high helium densities, from 60 to 180 He nm −3 , have been measured depending on the conditions, in stark contrast with previous investigations of helium bubbles in metal with similar sizes. To supplement experiments on a smaller scale, and to obtain insights into the silicon matrix state, atomistic calculations have been performed for helium bubbles in the diameter range 1-13 nm. Molecular-dynamics simulations revealed that the maximum attainable helium density is critically related to the strength of the silicon matrix, which tends to yield by amorphization at the highest density levels. Calculations give helium density values for isolated single bubbles that are typically lower than measurements. However, excellent agreement is recovered when the interactions between bubbles and the presence of helium interstitials in the matrix are taken into account. Both experiments and numerical simulations suggest that the Laplace-Young law cannot be used to predict helium density in nanometric-sized bubbles in a covalent material such as silicon.

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“…Each symbol corresponds to a calculation, whereas dashed lines are drawn to show trends. In red is also reported the formation energy variation corresponding to helium interstitial aggregation in the pristine silicon bulk . The inset graph represents the same information, but now normalized with respect to the number of vacancies along the two axis.…”

Section: Resultsmentioning

confidence: 99%

“…Theoretical investigations revealed that in the undefected cubic diamond lattice, an interstitial helium atom is located in tetrahedral sites and diffuses through hexagonal sites . It has also been shown that helium interstitials do not easily cluster , thus highlighting the pivotal role of vacancies in the initial stages of helium bubbles formation. Much less information is available regarding the aggregation of helium atoms and vacancies.…”

Section: Introductionmentioning

confidence: 97%

Density functional theory calculations of helium clustering in mono‐, di‐, and hexa‐vacancy in silicon

Pizzagalli

David

Dérès

2017

Physica Status Solidi (a)

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Combining classical molecular dynamics and first-principles DFT calculations, we perfom an extensive investigation of low energy configurations for He n V m complexes in silicon. The optimal helium fillings are hence determined for V 1 , V 2 , and V 6 (figure on the right), and the structures formed by helium atoms arrangements in the vacancy defect are analyzed. For V 1 and V 2 , the He atoms structure is mainly controled by the host silicon matrix, whereas a high density helium packing is obtained for V 6 . For the latter, we estimate a helium density of about 170 He nm −3 in the center of the hexa-vacancy at the optimal helium filling.Relaxed structures obtained from DFT calculations for configurations with the lowest formation energies: (a) He 14 V 1 , (b) He 20 V 2 , and (c) He 40 V 6 .

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Investigation of helium interstitials aggregation in silicon: Why bubbles formation by a self-trapping mechanism does not work

Cited by 8 publications

References 20 publications

Influence of helium on the nucleation and growth of bubbles in silicon: a multiscale modelling study

Influence of helium on the nucleation and growth of bubbles in silicon: a multiscale modelling study

Properties of helium bubbles in covalent systems at the nanoscale: A combined numerical and experimental study

Density functional theory calculations of helium clustering in mono‐, di‐, and hexa‐vacancy in silicon

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