Atomic-level characterization of crystal defects in a polycrystalline silicon-diamond structure

Electronic-grade polycrystalline silicon of large size holds a crucial position in the semiconductor industry due to its extensive application prospects. This study aims to fill the gap in the atomic-level characterization of crystal defects within polycrystalline silicon. By employing focused ion beam technology for sample preparation and combining advanced scanning electron microscopy-electron backscatter diffraction technology with aberration-corrected transmission electron microscopy, we have uncovered that the silicon core of the polycrystalline silicon exhibits a single crystal structure and dense twinning within the polycrystalline matrix. These twins predominantly originate at grain boundaries and extend into the grains, forming on the {111} densely packed planes. At the atomic level, twin boundaries consist of atomically misaligned stacking faults. Moreover, we have observed atomic-scale distortions and the formation of additional stacking faults at dislocations within the twin boundaries, indicating significant atomic rearrangement. Interfaces composed of dislocations can cause twin boundaries to undergo near-vertical torsion, while coherent twin boundaries can induce slip in incoherent interfaces. Beyond being predominantly composed of dislocations, coherent twin boundaries also facilitate the formation of incoherent interfaces through transitions across the twin boundaries. These findings have critical implications for the development of polycrystalline silicon solar cells and provide a theoretical foundation for improving the quality of polycrystalline silicon.