| Summary: | Three-dimensional distribution of arsenic (As) dopants at Σ3{111}, Σ9{221}, Σ9{114}, and Σ9{111}/{115} grain boundaries (GBs) in silicon (Si) is examined by correlative analytical methods using atom probe tomography (APT) combined with low-temperature focused ion beam (LT-FIB), scanning transmission electron microscopy, and ab initio calculations. Σ3{111} GBs, consisting of only 6-membered rings with small bond distortions, do not exhibit an apparent As segregation. Meanwhile, it is hypothesized that As atoms would segregate at 5-membered rings in the other GBs via anisotropic bond distortions spontaneously introduced so as to lower the donor level, as Jahn-Teller distortions. In addition, APT combined with LT-FIB suggests preferential As segregation around stretched $$\left\langle {1\overline 1 0} \right\rangle $$ bonds reconstructed in Σ9{114} and Σ9{111}/{115} GBs, that are inevitably introduced in the $$\left\langle {1\overline 1 0} \right\rangle $$ tilt GBs with the tilt angle larger than 70.5°. It is hypothesized that As atoms would form As dimers at stretched $$\left\langle {1\overline 1 0} \right\rangle $$ bonds and the adjacent $$\langle 111\rangle $$ bonds, due to the tendency of As with five valence electrons to form a three-coordinated configuration, which is efficiently attained by an As dimer of a long length. This work provides important insights into As segregation at GBs; it is mainly determined by electronic interactions depending on the characteristics of valence electrons of As atoms, as well as on local bond distortions at GBs, via anisotropic bond distortions and dimerization.
|
|---|