High Temperature Annealing of Bent Multicrystalline Silicon Rods

Dislocation etch-pit structures on multicrystalline silicon rods deformed at 900°C in four-point bending were studied prior to and after a high-temperature annealing. After deformation, the majority of the dislocation etch-pits were aligned along traces of {111} planes. Certain localized areas revealed network structures, where etch-pit arrays deviated in the range of 2-10° from the {111} plane traces. After annealing at 1350°C for 12h, a marked change in dislocation density and structure which varied from grain to grain was observed. Some grains showed incomplete polygonized structures, with notable irregularities and Y-junctions. The results were compared with observations on as-cast industrial multicrystalline silicon wafers for solar cells, where similar incomplete polygonized structures can be found.