Interaction of sodium atoms with stacking faults in silicon with different Fermi levels

Abstract

Variation in the formation energy of stacking faults (SFs) with the contamination of Na atoms was examined in Si crystals with different Fermi levels. Na atoms agglomerated at SFs under an electronic interaction, reducing the SF formation energy. The energy decreased with the decrease of the Fermi level: it was reduced by more than 10 mJ/m 2 in p-type Si, whereas it was barely reduced in n-type Si. Owing to the energy reduction, Na atoms agglomerating at SFs in p-type Si are stable compared with those in n-type Si, and this hypothesis was supported by ab initio calculations.

Segregation mechanism of arsenic dopants at grain boundaries in silicon

“…We hypothesize that As atoms would prefer to segregate at 5-membered rings via anisotropic bond distortions spontaneously introduced so as to lower the donor level, as Jahn-Teller distortions, even when the sites are unfavourable to segregate from an elastic point of view. Similar segregation characteristics can be observed for other donors such as phosphorus [15,59,62], antimony [45] and sodium [63].…”

Insight into segregation sites for oxygen impurities at grain boundaries in silicon

“…7,16) Since oxygen atoms are neutral interstitials that exist at bond-centered sites in the Si lattice, they do not induce complicated electronic effects (extended carrier behaviors around impurity ions, or drastic configurational changes of impurity atoms to localize such carriers). [17][18][19][20] Thus, it is hypothesized that the origin of the segregation is elastic interactions rather than electronic interactions. 15) Under this hypothesis, the three-dimensional (3D) distribution of oxygen atoms segregated at a dislocation is compared with the strain field around the dislocation's core, and it is seen that oxygen atoms segregate at bond-centered sites under tensile stresses above about 2 GPa.…”

Second-stage potential-induced degradation of n-type front-emitter crystalline silicon photovoltaic modules and its recovery

“…Ohno et al have demonstrated that the Nadecorated stacking faults in undoped or n-type Si are much less stable than those in p-type Si. 41) The Na atoms in the stacking faults existing in the depletion region of the p + -n junction can thus be removed more easily than those in the p + region during the recovery process. We speculate that Na ions may be partly or completely diffused out from the stacking faults in the depletion region, whereas Na-decorated stacking faults may remain in the p region.…”