Heterogeneous twinning during directional solidification of multi-crystalline silicon

Abstract

Heterogeneous twinning nucleation from the wall or gas interface during directional solidification of silicon have been modelled, and further used to clarify the details of twining observed in situ in X-ray synchrotron imaging experiments [1]. It is found that the heterogeneous twinning from the wall/grains or wall/gas/grain trijunctions requires much lower undercoolings leading to much higher twinning probability. The lower attachment energy and the contact area are the key factors for the heterogeneous nucleation of twins.

Strain building and correlation with grain nucleation during silicon growth

“…Larger facet angles relatively to the wall are calculated for the left {111} facet in Figure 7 so that it has a lower contact area with the crucible wall. Finally, both low attachment energy and lower contact area concur to a higher twining probability of 8 x 10 -7 on the left facet (facet 1 in reference [40]) compared to the a twinning probability of 8 x 10 -8 on the right facet (facet 2 in reference [40]). Thus, according to this model, the left {111} facet (Grain V in Figure 7) is the most thermodynamically favourable for the nucleation of a new grain.…”

“…As seen above, the nucleation of the purple grain VI occurs on the left {111} facet of the grain boundary groove. The attachment energy and the contact area are the key factors for the heterogeneous nucleation of twins as modelled by Jhang et al [40]. This model was specifically applied to the particular experiment described here and to the grain boundary groove in Figure 7 (Case 1, model 1.1 in [40]).…”

“…The attachment energy and the contact area are the key factors for the heterogeneous nucleation of twins as modelled by Jhang et al [40]. This model was specifically applied to the particular experiment described here and to the grain boundary groove in Figure 7 (Case 1, model 1.1 in [40]). For both facets, the attaching energy of a twin at the level of the crucible wall/Grain IV/Grain V is negative so that twinning is thermodynamically favourable for the experimentally measured undercooling of about 0.4 K [29].…”

X-ray Based in Situ Investigation of Silicon Growth Mechanism Dynamics—Application to Grain and Defect Formation

“…A 3D model was proposed by Jhang et al [86] to determine the nucleation probability at the level of {111} facets. This model was specifically applied to several of our experimental cases.…”

“…These measurements confirm that the undercooling measured in grain boundary grooves and at the edges are sufficient for twin nucleation on the {111} facets. A 3D model was proposed by Jhang et al [86] to determine the nucleation probability at the level of {111} facets. This model was specifically applied to several of our experimental cases.…”