Migration of noble gas atoms in interaction with vacancies in silicon

Abstract

First principles calculations in combination with the nudged elastic band method have been performed in order to determine the mobility properties of various noble gas species (He, Ne, Ar, Kr, and Xe) in silicon, a model semiconducting material. We focussed on single impurity, in interstitial configuration or forming a complex with a mono-or a di-vacancy, since the latter are known to be present and to play a key role in the formation of extended defects like bubbles or platelets. We determined several migration mechanisms and associated activation energies and have discussed these results in relation to available experiments. In particular, conflicting measured values of the migration energy of helium are explained by the present calculations. We also predict that helium diffuses solely as an interstitial, while an opposite behaviour is found for heavier species such as Ar, Kr, and Xe, with the prevailing role of complexes in that case. Finally, our calculations indicate that extended defects evolution by Ostwald ripening is possible for helium and maybe neon, but is rather unlikely for heavier noble gas species.

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

“…Other possible interactions concern Si interstitials and He atoms. Previous investigations showed that the interaction between helium interstitials in silicon is weak and can be safely neglected [20]. We also assume that the combined aggregation of helium and Si interstitials does not play a significant role in the formation of helium bubbles.…”

“…After 22 ps, the decrease of the amount of V n seen in figure 1(d), is correlated to the increase of V n He p clusters, and is obviously due to the transformation of V n to V n He p by capturing one or more He atoms. A single helium atom is indeed less mobile than V 1 , with a migration energy of 0.68 eV [20], but enough to diffuse during the short MD time span. In contrast with V n , the mean size of V n He p aggregates continuously increases during the simulation.…”

“…However, the insertion of the helium atom into vacancy aggregates is energetically favourable, starting with the di-vacancy. The lowest energy diffusion path corresponds to the helium interstitial migrating through an hexagonal site, with an activation energy of about 0.6-0.8 eV [19,20]. Another well established quantity, both exper imentally [6,21,22] and theoretically [23], is the energy equal to 1.7-1.8 eV that is required for the helium atom to effuse out of well formed bubbles.…”

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

“…In semiconductors, fewer works are available, and typically focus on helium in silicon or in silicon carbide. 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.…”